Dr. Renz is a postdoctoral- and fellowship-trained specialist in gynecologic oncology. He is an instructor of Gynecologic Oncology in the Department of Obstetrics & Gynecology at Stanford University School of Medicine and a member of the Stanford Cancer Institute.
Dr. Renz is an expert in both clinical care and basic science research. He provides exceptional and empathetic care for each patient and excels in cancer cell biology and molecular imaging.
His research addresses clinically relevant questions that he confronts every day with patients. For example, he has used advanced molecular imaging tools to characterize the proteins that enable tumor cells to metastasize.
Prior to joining Stanford Medicine, Dr. Renz was a postdoctoral fellow at the National Institutes of Health in the Cell Biology and Metabolism Program. In that role, he focused on developing new live-cell microscopy techniques that resolve single molecules and on applying these tools to address principal molecular mechanisms of disease. During his residency at the Albert Einstein College of Medicine in the Bronx, he served as an adjunct scientist to the National Institutes of Health, committed to providing medical care to underserved communities.
He has presented the findings of his research at the Annual Meeting of the Biophysical Society and the American Society for Cell Biology, among other professional organizations. His research has been published in peer-reviewed journals including Cell, Nature Methods, and Proceedings of the National Academy of Science (PNAS).
Dr. Renz is the lead author of the book Synopsis of Key Trials in Gynecologic Oncology and the chapters “Cancer Genetics” and “Targeted and Immunotherapy” in the textbook Gynecologic Oncology. He is also a reviewer for publications including Proceedings of the National Academy of Sciences, Nature Scientific Reports, Molecular Biology of the Cell, and Journal of Cell Science.
Dr. Renz has won awards for excellence in clinical care from the American Association of Gynecologic Laparoscopists and Albert Einstein College of Medicine. Stanford University School of Medicine and Albert Einstein College of Medicine have both recognized him for excellence in teaching.
Dr. Renz is a member of the American College of Obstetrics and Gynecology, Society of Gynecological Oncology, American Society of Cell Biology, and Biophysical Society.
- Gynecologic Oncology
- Obstetrics and Gynecology
Honors & Awards
Elected Member, Alpha Omega Alpha (2020)
Resident Teaching Award, Stanford University School of Medicine (2020)
Award for Excellence in Scientific Research, Montefiore Medical Center/ Albert Einstein College, Bronx (2017)
Lewis Award for Excellence in Labor Management, Montefiore Medical Center/ Albert Einstein College, Bronx (2017)
Outstanding Senior Resident Teacher of Junior Residents Award, Montefiore Medical Center/ Albert Einstein College, Bronx (2017)
Recognition of Excellence in Minimally Invasive Gynecology, American Association of Gynecologic Laparoscopists (AAGL) (2017)
Medical Student Teaching Award, Medical School at the Albert Einstein College, Bronx (2016)
Award for Compassion and Excellence in Outpatient Management, Montefiore Medical Center/ Albert Einstein College, Bronx (2015)
Award for Excellence as Junior Resident, Montefiore Medical Center, Albert Einstein College, Bronx (2014)
Award for Best Doctoral Thesis 2008, Faculty of Medicine at Heinrich-Heine University Dusseldorf (2009)
Charles Trey Memorial Post-Doctoral Research Award, American Liver Foundation (2009)
Postdoctoral Fellow, German Research Foundation (DFG) and National Institutes of Health (2008-2012)
Art and Science Fellow, Akademie Schloss Solitude (2008)
Doctoral Fellow, German Academic Scholarship Foundation (2005-2007)
Master Pupil with Professor Markus Lüpertz, Academy of Fine Arts (2002)
Student Fellow, German Academic Scholarship Foundation (2001-2005)
Fellowship: Stanford University Gynecologic Oncology Fellowship (2020) CA
Residency: Albert Einstein Medical Center Obstetrics and Gynecology Residency (2017) NY
Medical Education: University of Dusseldorf (2005) Germany
Clinical Fellow, Stanford University School of Medicine, Gynecologic Oncology (2020)
Resident Physician, Albert Einstein College of Medicine Bronx, Obstetrics and Gynecology (2017)
Postdoctoral Fellow, National Institutes of Health Bethesda, Biophysics/ Cell Biology (2012)
Ph.D., German Cancer Research Center Heidelberg, Biophysics/ Cancer Research (2008)
M.D., Heinrich-Heine University Dusseldorf, Medicine (2005)
Academy Letter (Diploma), Academy of Fine Arts Dusseldorf, Fine Arts/ Painting (2003)
Current Research and Scholarly Interests
I am interested in cell motility and molecular dynamics. I believe that intra- and intercellular molecular dynamics, compartmentalization, and complex formation may differentiate disease from normal beyond the expression level of proteins and may constitute relevant pathomechanisms. The tools I am using are quantitative fluorescence live-cell microscopy on the ensemble and single-molecule level. I aim to bridge direct patient care and basic research.
Vulvar sarcoma outcomes by histologic subtype: a Surveillance, Epidemiology, and End Results (SEER) database review.
International journal of gynecological cancer : official journal of the International Gynecological Cancer Society
Vulvar cancers account for 5% of all gynecologic malignancies; only 1%-3% of those vulvar cancers are primary vulvar sarcomas. Given the rarity of vulvar sarcomas, outcome data specific to histopathologic subtypes are sparse. The aim of this study was to identify clinical and pathologic factors of primary vulvar sarcomas that are associated with survival and may inform treatment decisions.The Surveillance, Epidemiology, and End Results (SEER) database was searched for women diagnosed with vulvar sarcoma between 1973 and 2018. We identified 315 patients and reviewed their demographic, clinicopathologic, surgical, and survival information. Statistical analyses included χ2 and t-tests, Kaplan-Meier survival, and Cox regression analyses.The most common histopathologies of vulvar sarcomas were dermatofibrosarcomas (85/315, 27%) and leiomyosarcomas (72/315, 22.9%). Rhabdomyosarcomas (18/315, 5.7%), liposarcomas (16/315, 5.1%), and malignant fibrous histiocytomas (16/315, 5.1%) were less frequent. The majority of patients underwent surgery (292/315, 92.7%), which included lymph node dissections in 21.6% (63/292). Survival and lymph node involvement varied significantly with histologic subtype. The 5-year disease-specific survival for dermatofibrosarcomas, liposarcomas, and fibrosarcomas was 100% and only 60.3% and 62.5% for malignant fibrous histiocytomas and rhabdomyosarcomas, respectively. None of the patients with (dermato)fibrosarcomas, liposarcomas, or leiomyosarcomas had positive lymph nodes, in contrast to rhabdomyosarcomas and malignant fibrous histiocytomas with 77.8% and 40% positive lymph nodes, respectively. The 5-year disease-specific survival for women with positive lymph nodes was 0%.Vulvar sarcomas are heterogeneous with survival highly dependent on the histopathologic subtype. While surgical excision is the mainstay of treatment for all vulvar sarcomas, staging lymphadenectomy should be deferred for (dermato)fibrosarcomas, liposarcomas, and leiomyosarcomas as there were no cases of lymph nodes metastases.
View details for DOI 10.1136/ijgc-2020-001516
View details for PubMedID 32641392
In invasion assays, the breast cancer cell nucleus leads the way.
BMC research notes
2020; 13 (1): 480
Cancer cell metastasis determines disease prognosis. During cancer cell metastasis, the cancer cell and the cancer cell nucleus have to undergo extreme shape changes. To monitor shape changes of cancer cells and cancer cell nuclei and the positioning of the cancer cell nucleus during cancer cell invasion, a customized invasion assay with 8-μm pores and reconstituted basal membrane was imaged using fluorescence live-cell microscopy.The observed cells changed their shape from a distinct fibroblast-like spindle shape to an amoeboid shape without polarization immediately after the passage through an 8-μm pore of the invasion assay. During the process of invasion, the cancer cell centered the cancer cell nucleus over the 8-μm pore, and cancer cell nucleus and adjacent cytoplasmic areas moved first through such a pore. Seemingly testing if the largest and least deformable organelle may fit, the cancer cell nucleus led the way through the porous membrane of the invasion assay.
View details for DOI 10.1186/s13104-020-05314-9
View details for PubMedID 33046121
- Biologic, Targeted, and Immune Therapy Berek and Hacker's Gynecologic Oncology Lippincott Williams & Wilkins (LWW). 2020; 7th: 36–59
- Cancer Genetics Berek and Hacker's Gynecologic Oncology Lippincott Williams & Wilkins (LWW). 2020; 7th: 2–22
Long-term outcome of postmenopausal women with proliferative endometrium on endometrial sampling.
American journal of obstetrics and gynecology
Proliferative endometrium has been reported in 15% of endometrial biopsies of women aged 50 years and older. Contrary to endometrial hyperplasia, proliferative endometrium has not been associated with the risk of endometrial cancer.This study aimed to report on the long-term outcome of postmenopausal women who received a diagnosis of proliferative endometrium.This is a retrospective cohort study of 1808 women aged 55 years and older who underwent endometrial sampling between January 1997 and December 2008. Outcome data were available through February 2018. Women with a proliferative endometrium were compared with those with an atrophic endometrium for future development of endometrial hyperplasia or cancer. A subanalysis was performed for those who presented with postmenopausal bleeding. Uni- and multivariable logistic regression analyses were used to assess for confounders.In this study, 297 women (16.4%) received a diagnosis of proliferative endometrium. Furthermore, 962 women met the inclusion criteria. Among those women, 278 had a proliferative endometrium, and 684 had an atrophic endometrium. Women with a proliferative endometrium were younger (61.2 vs 64.5 years; P<.0001) and had a higher body mass index (33.9 vs 30.6 kg/m2; P<.0001). More African American women had a proliferative endometrium. Both groups had a similar length of surveillance (11.9 vs 11.5 years; P=.27). Women with a proliferative endometrium had a higher risk of developing endometrial hyperplasia or cancer (11.9% vs 2.9%; P<.0001), any endometrial cancer (5.8% vs 1.8%; P=.002), atypical endometrial hyperplasia (2.2% vs 0.4%; P=.02), and nonatypical endometrial hyperplasia (2.0% vs 0.7%; P=.001). The risk of developing endometrial cancer and endometrial hyperplasia remained similar after excluding cases on hormonal replacement therapy (12.2% vs 3%; P=.001). On logistic regression analysis, proliferative endometrium histology (odds ratio, 3.89; 95% confidence interval, 2.03-7.49; P<.0001), age >60 years (odds ratio, 1.98; 95% confidence interval, 1.03-3.82; P=.04), and body mass index >35 kg/m2 (odds ratio, 2.3; 95% confidence interval, 1.09-4.83; P<.0001) remained significant risk factors for progression to cancer.One of the 6 postmenopausal women who underwent endometrial sampling had a proliferative endometrium. Furthermore, 11.9% of women developed endometrial hyperplasia or cancer, a 4-fold greater incidence than women with an atrophic endometrium. The findings of this study suggest that long-term monitoring is warranted for women with postmenopausal bleeding and a proliferative endometrium histology. Further studies are needed to examine if a treatment is required to negate the risk of unopposed estrogen.
View details for DOI 10.1016/j.ajog.2020.06.045
View details for PubMedID 32640199
Dissecting Oligomeric States with Photoactivated Localization Microscopy: A Numerical Model.
Cytometry. Part A : the journal of the International Society for Analytical Cytology
Although photoactivated localization microscopy offers the potential to interrogate protein interactions in the physiological environment of a cell, uncertainties in the detection efficiency of photoactivatable proteins lead to complications with data interpretation. Here, we present a numerical model that provides probabilities to detect neighboring molecules dependent on their oligomerization status, density, detection efficiency, and radius, and can be used to assess oligomeric states or detection efficiencies of two molecular species. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.
View details for DOI 10.1002/cyto.a.24167
View details for PubMedID 32558006
The role of asymptomatic screening in the detection of recurrent ovarian cancer.
Gynecologic oncology reports
2020; 33: 100595
To investigate the utility of asymptomatic screening, including CA-125, imaging, and pelvic exam, in the diagnosis and management of recurrent ovarian cancer.Women with ovarian cancer whose cancer recurred after remission were categorized by first method that their provider suspected disease recurrence: CA-125, imaging, symptoms, or physical exam. Differences in clinicopathologic, primary treatment characteristics, and outcomes data including secondary cytoreductive surgery (SCS) outcome and overall survival (OS) were collected.102 patients were identified at our institution from 2003 to 2015. 20 recurrences were detected by symptoms, while 62 recurrences were diagnosed first by asymptomatic rise in CA-125, 5 by pelvic exam, and 15 by imaging in the absence of known exam abnormality or rise in CA-125.Mean time to recurrence was 18.9 months, and median survival was 45.8 months. These did not vary by recurrence detection method (all p > 0.4). Patients whose disease was detected by CA-125 were less likely to undergo SCS than those detected by other means (21.7% vs. 35.0%, p = 0.007). In addition to the 5 patients whose recurrence was detected primarily by pelvic exam, an additional 10 (total n = 15) patients had an abnormal pelvic exam at time of diagnosis of recurrence.Recurrence detection method was not associated with differing rates of survival or optimal SCS, however those patients detected by CA-125 were less likely to undergo SCS. The pelvic exam was a useful tool for detecting a significant proportion of recurrences.
View details for DOI 10.1016/j.gore.2020.100595
View details for PubMedID 32548232
View details for PubMedCentralID PMC7286959
Long-term outcome of postmenopausal women with non-atypical endometrial hyperplasia on endometrial sampling.
Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology
OBJECTIVE: To assess the long-term outcome of post-menopausal women diagnosed with non-atypical endometrial hyperplasia (NEH).METHODS: It is a retrospective study of women aged 55 and older who underwent endometrial sampling in our large academic medical center between 1997 and 2008. Women diagnosed with NEH were included in the study group and were compared to women diagnosed with atrophic endometrium on endometrial sampling. Outcome data was obtained through February 2018. The main outcomes were the risk of progression to endometrial carcinoma and the risk of persistent endometrial hyperplasia (EH). Logistic regression was used to identify covariates that remained significant risk factors for cancer progression.RESULTS: 1808 women aged 55 and older underwent endometrial sampling during the study period. The median surveillance time was 10.0years. 73 women were found to have NEH and they were compared to 742 women with atrophic endometrium (AE). When compared to women with AE, women with NEH had a significantly higher BMI (33.9 vs. 30.6, p=0.01), a higher rate of progression to type 1 endometrial cancer and persistent endometrial hyperplasia (8.2% vs. 0.8%, p<0.0001 and 21.9% vs 0.7% respectively, p<0.0001). They also had a higher rate of progression to all types of uterine cancer or persistent hyperplasia (32.9% vs 3.4%, p<0.0001). Women with NEH also had significantly higher rate of future surgical intervention (50.7% vs 15.4%, p<0.0001) and future hysterectomy (34.3% vs. 9.6%, p<0.0001). On logistic regression analysis, NEH, BMI>35, thick endometrium on ultrasound and diabetes remained significant risk factors for progression to cancer.CONCLUSIONS: Postmenopausal women with NEH are at significant risk for persistent endometrial hyperplasia (EH) and progression to uterine cancer, at higher rates than rates previously reported. Guidelines for the appropriate management of postmenopausal women with NEH are needed to decrease the rate of persistent disease or progression to cancer. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/uog.20421
View details for PubMedID 31389091
Immediate intraoperative sentinel lymph node analysis by frozen section is predictive of lymph node metastasis in endometrial cancer.
Journal of robotic surgery
Sentinel lymph nodes sampling (SLN) in endometrial cancer is being evaluated as a means to gather prognostic information about lymphatic metastasis while avoiding the morbidity associated with complete lymphadenectomy. SLN ultrastaging has been advocated to identify low-volume metastases, but its value remains uncertain. This study aims to evaluate a pathological protocol for the immediate intraoperative SLN work-up using H&E staining alone. In this retrospective single-center study, patients received standardized cervical injection of indocyanine green, SLN mapping followed by pelvic lymphadenectomy with or without para-aortic lymphadenectomy. SLNs were entirely frozen, multiple H&E stained sections prepared and evaluated intraoperatively. No immunohistochemistry was performed. SLN results were compared with the complete lymphadenectomy specimen. Over 3.5 years, 90 patients were identified who underwent SLN mapping and subsequent complete pelvic lymphadenectomy. At least one SLN was detected in 79 (88%) patients. The median number of SLNs removed was 2.0. Para-aortic SLNs were detected in 7%. Final pathology showed 67% Type I tumors, 76% locally confined. The mean number of lymph nodes removed during complete lymphadenectomy was 21. In this series, only 6 patients had lymph node metastases. 5/6 were identified by the described SLN approach resulting in 83.3% sensitivity and a negative predictive value of 98.7%. Our approach permits immediate intraoperative results and helps guide the primary surgery. The immediate SLN work-up using frozen sections showed both high accuracy and negative predictive value. The comparably lower sensitivity may be related to the low number of patients with positive lymph nodes (7.6%).
View details for PubMedID 30687881
How to Quantify the Fraction of Photoactivated Fluorescent Proteins in Bulk and in Live Cells.
Journal of visualized experiments : JoVE
Photoactivatable and -convertible fluorescent proteins (PA-FPs) have been used in fluorescence live-cell microscopy for analyzing the dynamics of cells and protein ensembles. Thus far, no method has been available to quantify in bulk and in live cells how many of the PA-FPs expressed are photoactivated to fluoresce. Here, we present a protocol involving internal rulers, i.e., genetically coupled spectrally distinct (photoactivatable) fluorescent proteins, to ratiometrically quantify the fraction of all PA-FPs expressed in a cell that are switched on to be fluorescent. Using this protocol, we show that different modes of photoactivation yielded different photoactivation efficiencies. Short high-power photoactivation with a confocal laser scanning microscope (CLSM) resulted in up to four times lower photoactivation efficiency than hundreds of low-level exposures applied by CLSM or a short pulse applied by widefield illumination. While the protocol has been exemplified here for (PA-)GFP and (PA-)Cherry, it can in principle be applied to any spectrally distinct photoactivatable or photoconvertible fluorescent protein pair and any experimental set-up.
View details for PubMedID 30663670
Synopsis of Key Gynecologic Oncology Trials
CRC Press. 2019
View details for DOI 10.1201/9780429200199
Sentinel lymph node biopsies in endometrial cancer - practice patterns among Gynecologic Oncologists in the United States.
Journal of minimally invasive gynecology
To evaluate practice patterns among gynecologic oncologists with regards to sentinel lymph node injection and biopsy in endometrial cancer.Observational study with no control group.Active members of the Society of Gynecologic Oncology.After IRB approval, we performed an online survey amongst active members of the Society of Gynecologic Oncology. Members were contacted via email and their answers anonymously captured. Study data were collected using REDCap.318 of 1216 listed members completed the online survey, The majority of respondents (82.7%) perform sentinel lymph node sampling for endometrial cancer staging. Most technical aspects of sentinel lymph node sampling were consistently applied by the vast majority of respondents, including the choice of indocyanine green (ICG) as lymphatic tracer (97.3%) and its injection into the cervix (100%). Other technical aspects of sentinel lymph node sampling, such as the depth of injection, varied amongst respondents. While 50.9% of the respondents perform an intraoperative assessment of the uterus by frozen section, only 17.9% assess sentinel lymph nodes by frozen section and/or touch prep. Some of the respondents' approaches are based on limited data, including (i) the use of sentinel lymph node injection and biopsy for high-risk histologies (performed by 69 - 75% of the respondents dependent upon the histology), (ii) omitting side-specific completion lymphadenectomy in the absence of sentinel node mapping (in up to 57.8%) or (iii) when lymph node metastases are present (in 39.9%).In summary, despite the growing use of sentinel lymph node injection and biopsy in endometrial cancer, practice patterns vary considerably among providers sampled by this survey. Some of the decisions are based on limited evidence and, in some instances, deviate from current published guidelines.
View details for PubMedID 30980995
Cytoplasmic self-organization established by internal lipid membranes in the interplay with either actin or microtubules
View details for DOI 10.1101/506436
Robotic Olympics: A novel robotic surgical training experience for residents in an obstetrics and gynecology residency program
View details for DOI 10.7287/peerj.preprints.3510v2
Internal rulers to assess fluorescent protein photoactivation efficiency.
Cytometry. Part A : the journal of the International Society for Analytical Cytology
Photoactivatable fluorescent proteins (PA-FPs) have been widely used to assess the dynamics of cell biological processes. In addition, PA-FPs enabled single-molecule based super-resolution imaging (photoactivated localization microscopy) and thereby provided unprecedented structural insight. For the lack of tools, however, the fraction of PA-FPs that is, actually being switched on to fluoresce, that is, the photoactivation efficiency, has been difficult to assess. Uncertainty about photoactivation efficiency has hampered an understanding of the absolute amount of PA-FPs, that is, being examined. Here, we present internal rulers to assess photoactivation efficiencies of photoactivatable proteins. These internal rulers comprise a PA-FP that is genetically directly coupled to a spectrally distinct always-on fluorescent protein. Thus, these fluorescent proteins will be expressed in the bacterial and mammalian cell in a one-to-one ratio. With these tools, we describe photoactivation efficiencies of PA-GFP and PA-Cherry in intensity-based ratiometric ensemble studies and on the single-molecule level. In ratiometric ensemble studies, we show that photoactivation efficiency depends on how the PA-FPs are exposed to 405 nm light. Using a laser-scanning microscope, hundreds of iterative low-level exposures are up to four times more efficient than a short high-power exposure. Using wide-field illumination, photoactivation was similarly efficient and instantaneous. These findings suggest that the repetitive or stochastic exposure to photons of 405 nm light results in more efficient photoactivation than a continuous flow of photons. Because of the differential photoactivation efficiency, it is crucial to assess photoactivation efficiency for any given experimental set-up. The tools we provide can be applied to any genetically encoded photoactivatable protein. Determination of photoactivation efficiency is essential for an understanding of absolute molecule numbers in ensemble studies and, most importantly, quantitative superresolution imaging. © 2017 International Society for Advancement of Cytometry.
View details for PubMedID 29286574
Simultaneous Endometrial Aspiration and Sonohysterography for the Evaluation of Endometrial Pathology in Women Aged 50 Years and Older
OBSTETRICS AND GYNECOLOGY
2015; 125 (2): 414-423
To evaluate the performance of simultaneous endometrial aspiration at the time of sonohysterography for screening postmenopausal women at risk for endometrial cancer.A retrospective cohort study of women older than 50 years who underwent saline-infusion sonohysterography for the evaluation of their endometrium. On completion of imaging, the remaining intracavitary saline and endometrial tissue were aspirated through the saline-infusion sonohysterography catheter and submitted for pathologic evaluation. Based on the clinical, pathologic, and ultrasonographic results, the patients underwent surgical treatment with hysteroscopy, hysterectomy, or clinical observation. Follow-up results and outcomes were collected using electronic medical records. Sensitivity, specificity, and predictive values of saline-infusion sonohysterography, endometrial aspiration, and combined approaches for endometrial aspiration and sonohysterography were assessed.Six hundred three patients underwent endometrial aspiration at the time of sonohysterography. Endometrial tissue was present in 567 (94.0%) and outcome data were available for 540 (89.5%). In 194 (35.9%) patients, final pathology was obtained by surgical intervention. The remaining 346 (64.1%) patients were monitored for at least 6 months. Thirty patients (5.6%) had cancer or endometrial hyperplasia. A sequential model, in which endometrial aspiration was done only for positive saline-infusion sonohysterography findings, yielded sensitivity of 86.7% (95% confidence interval [CI] 69-96%) and specificity of 100% (95% CI 99-100%) for detecting endometrial hyperplasia or cancer (area under the curve 0.93). Considering proliferative endometrium as abnormal endometrial aspiration reduced specificity to 88.3% (95% CI 85-91%, P<.01) without significant increase in sensitivity (100%, 95% CI 88-100%, P=.13).The high sensitivity and specificity of the sequential endometrial aspiration at the time of sonohysterography make this approach a useful and reliable screening algorithm for detecting endometrial cancer or hyperplasia in postmenopausal women at risk. Endometrial aspiration at the time of sonohysterography should be considered as an initial one-stop endometrial evaluation in this population.
View details for DOI 10.1097/AOG.0000000000000631
View details for Web of Science ID 000348595500021
View details for PubMedID 25568988
Probing the Stochastic, Motor-Driven Properties of the Cytoplasm Using Force Spectrum Microscopy
2014; 158 (4): 822-832
Molecular motors in cells typically produce highly directed motion; however, the aggregate, incoherent effect of all active processes also creates randomly fluctuating forces, which drive diffusive-like, nonthermal motion. Here, we introduce force-spectrum-microscopy (FSM) to directly quantify random forces within the cytoplasm of cells and thereby probe stochastic motor activity. This technique combines measurements of the random motion of probe particles with independent micromechanical measurements of the cytoplasm to quantify the spectrum of force fluctuations. Using FSM, we show that force fluctuations substantially enhance intracellular movement of small and large components. The fluctuations are three times larger in malignant cells than in their benign counterparts. We further demonstrate that vimentin acts globally to anchor organelles against randomly fluctuating forces in the cytoplasm, with no effect on their magnitude. Thus, FSM has broad applications for understanding the cytoplasm and its intracellular processes in relation to cell physiology in healthy and diseased states.
View details for DOI 10.1016/j.cell.2014.06.051
View details for Web of Science ID 000340944700013
View details for PubMedID 25126787
- Optical highlighters: Applications to cell biology The Fluorescent Protein Revolution CRC Press, Taylor and Francis. 2014
Fluorescence microscopy-A historical and technical perspective
CYTOMETRY PART A
2013; 83 (9): 767-779
For a little more than a century, fluorescence microscopy has been an essential source of major discoveries in cell biology. Recent developments improved both visualization and quantification by fluorescence microscopy imaging and established a methodology of fluorescence microscopy. By outlining basic principles and their historical development, I seek to provide insight into and understanding of the ever-growing tools of fluorescence microscopy. Thereby, this synopsis may help the interested researcher to choose a fluorescence microscopic method capable of addressing a specific scientific question.
View details for DOI 10.1002/cyto.a.22295
View details for Web of Science ID 000323480200003
View details for PubMedID 23585290
Plasticity of the asialoglycoprotein receptor deciphered by ensemble FRET imaging and single-molecule counting PALM imaging
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (44): E2989-E2997
The stoichiometry and composition of membrane protein receptors are critical to their function. However, the inability to assess receptor subunit stoichiometry in situ has hampered efforts to relate receptor structures to functional states. Here, we address this problem for the asialoglycoprotein receptor using ensemble FRET imaging, analytical modeling, and single-molecule counting with photoactivated localization microscopy (PALM). We show that the two subunits of asialoglycoprotein receptor [rat hepatic lectin 1 (RHL1) and RHL2] can assemble into both homo- and hetero-oligomeric complexes, displaying three forms with distinct ligand specificities that coexist on the plasma membrane: higher-order homo-oligomers of RHL1, higher-order hetero-oligomers of RHL1 and RHL2 with two-to-one stoichiometry, and the homo-dimer RHL2 with little tendency to further homo-oligomerize. Levels of these complexes can be modulated in the plasma membrane by exogenous ligands. Thus, even a simple two-subunit receptor can exhibit remarkable plasticity in structure, and consequently function, underscoring the importance of deciphering oligomerization in single cells at the single-molecule level.
View details for DOI 10.1073/pnas.1211753109
View details for Web of Science ID 000311149900008
View details for PubMedID 23043115
Multiscale diffusion in the mitotic Drosophila melanogaster syncytial blastoderm
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (22): 8588-8593
Despite the fundamental importance of diffusion for embryonic morphogen gradient formation in the early Drosophila melanogaster embryo, there remains controversy regarding both the extent and the rate of diffusion of well-characterized morphogens. Furthermore, the recent observation of diffusional "compartmentalization" has suggested that diffusion may in fact be nonideal and mediated by an as-yet-unidentified mechanism. Here, we characterize the effects of the geometry of the early syncytial Drosophila embryo on the effective diffusivity of cytoplasmic proteins. Our results demonstrate that the presence of transient mitotic membrane furrows results in a multiscale diffusion effect that has a significant impact on effective diffusion rates across the embryo. Using a combination of live-cell experiments and computational modeling, we characterize these effects and relate effective bulk diffusion rates to instantaneous diffusion coefficients throughout the syncytial blastoderm nuclear cycle phase of the early embryo. This multiscale effect may be related to the effect of interphase nuclei on effective diffusion, and thus we propose that an as-yet-unidentified role of syncytial membrane furrows is to temporally regulate bulk embryonic diffusion rates to balance the multiscale effect of interphase nuclei, which ultimately stabilizes the shapes of various morphogen gradients.
View details for DOI 10.1073/pnas.1204270109
View details for Web of Science ID 000304881700050
View details for PubMedID 22592793
Probing protein heterogeneity in the plasma membrane using PALM and pair correlation analysis
2011; 8 (11): 969-975
Photoactivated localization microscopy (PALM) is a powerful approach for investigating protein organization, yet tools for quantitative, spatial analysis of PALM datasets are largely missing. Combining pair-correlation analysis with PALM (PC-PALM), we provide a method to analyze complex patterns of protein organization across the plasma membrane without determination of absolute protein numbers. The approach uses an algorithm to distinguish a single protein with multiple appearances from clusters of proteins. This enables quantification of different parameters of spatial organization, including the presence of protein clusters, their size, density and abundance in the plasma membrane. Using this method, we demonstrate distinct nanoscale organization of plasma-membrane proteins with different membrane anchoring and lipid partitioning characteristics in COS-7 cells, and show dramatic changes in glycosylphosphatidylinositol (GPI)-anchored protein arrangement under varying perturbations. PC-PALM is thus an effective tool with broad applicability for analysis of protein heterogeneity and function, adaptable to other single-molecule strategies.
View details for DOI 10.1038/NMETH.1704
View details for Web of Science ID 000296891800022
View details for PubMedID 21926998
Bright Monomeric Photoactivatable Red Fluorescent Protein for Two-Color Super-Resolution sptPALM of Live Cells
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2010; 132 (18): 6481-6491
Rapidly emerging techniques of super-resolution single-molecule microscopy of living cells rely on the continued development of genetically encoded photoactivatable fluorescent proteins. On the basis of monomeric TagRFP, we have developed a photoactivatable TagRFP protein that is initially dark but becomes red fluorescent after violet light irradiation. Compared to other monomeric dark-to-red photoactivatable proteins including PAmCherry, PATagRFP has substantially higher molecular brightness, better pH stability, substantially less sensitivity to blue light, and better photostability in both ensemble and single-molecule modes. Spectroscopic analysis suggests that PATagRFP photoactivation is a two-step photochemical process involving sequential one-photon absorbance by two distinct chromophore forms. True monomeric behavior, absence of green fluorescence, and single-molecule performance in live cells make PATagRFP an excellent protein tag for two-color imaging techniques, including conventional diffraction-limited photoactivation microscopy, super-resolution photoactivated localization microscopy (PALM), and single particle tracking PALM (sptPALM) of living cells. Two-color sptPALM imaging was demonstrated using several PATagRFP tagged transmembrane proteins together with PAGFP-tagged clathrin light chain. Analysis of the resulting sptPALM images revealed that single-molecule transmembrane proteins, which are internalized into a cell via endocytosis, colocalize in space and time with plasma membrane domains enriched in clathrin light-chain molecules.
View details for DOI 10.1021/ja100906g
View details for Web of Science ID 000277445400039
View details for PubMedID 20394363
Dynamics of the CapG actin-binding protein in the cell nucleus studied by FRAP and FCS
2008; 16 (3): 427-437
FRAP (fluorescence recovery after photobleaching) and FCS (fluorescence correlation spectroscopy) are spectroscopic methods for monitoring the dynamic distribution of proteins inside the nucleus of living cells. As an example we report our studies on the intracellular mobility of the actin-binding protein CapG in live breast cancer cells. This Gelsolin-related protein is a putative oncogene. It appears to be overexpressed especially in metastasizing breast cancer. Furthermore, the CapG protein is known to be involved in the motility control of non-muscle benign cells. Its increased expression triggers an increase in cell motility of benign cells. Thus it can be expected that in cancer cells overexpressing the CapG protein, motility, invasiveness and metastasis might be particularly promoted. Since the nuclear CapG fraction seems to be pivotal to the increase in cell motility, we focused our studies on the CapG mobility in cell nuclei of live breast cancer cells. Using FCS and FRAP we showed that the eGFP-tagged CapG is monomeric and characterized its diffusional properties on the microsecond to minute timescale. This information about the mobility and compartmentalization of CapG might help to provide insight into its function within the cell nucleus and give clues about its altered cellular function in malignant dedifferentiation.
View details for DOI 10.1007/s10577-008-1234-6
View details for Web of Science ID 000255680800007
View details for PubMedID 18461482
Invasive breast cancer cells exhibit increased mobility of the actin-binding protein CapG
INTERNATIONAL JOURNAL OF CANCER
2008; 122 (7): 1476-1482
The CapG protein, a Gelsolin-related actin-binding protein, is expressed at higher levels in breast cancer, especially in metastasizing breast cancer, than in normal breast epithelium. Furthermore, it is known that an increased expression of the CapG protein triggers an increase in cell motility. According to in vitro experiments, it was supposed that it is the nuclear fraction of the protein, which causes the increase in cell motility. Here, we examined the dynamical distribution of the CapG protein within the living cell, i.e. the import of the CapG protein into the nucleus. The nuclear import kinetics of invasive, metastasizing breast cancer cells were compared to the import kinetics of non-neoplastic cells similar to normal breast epithelium. FRAP kinetics showed a highly significant increase in the recovery of photobleached CapG-eGFP in the cancer cells, so that a differentiation of invasive, metastasizing cells and non-invasive, non-metastasizing cells on the basis of transport processes of the CapG protein between the nucleus and the cytoplasm seems to be possible. Comprehension of the mobility and compartmentalization of the CapG protein in normal and in cancer cells in vivo could constitute a new basis to characterize the invasiveness and metastasizing potential of breast cancer.
View details for DOI 10.1002/ijc.23215
View details for Web of Science ID 000253441100004
View details for PubMedID 18059028
Intrazelluläre Mobilität und Funktion des CapG-Proteins: eine Analyse anhand lebender neoplastischer und nichtneoplastischer Brustepithelzellen
The CapG protein, a Gelsolin related actin-binding protein, is overexpressed in breast cancer, especially in metastasizing breast cancer. The CapG protein is known to be involved in the control of motility of non-muscle cells. Its increased expression is described to trigger an increase in cell motility of benign cells. Thus it can be expected that in cancer cells, which overexpress the CapG protein, motility, invasiveness and metastasizing are especially promoted. In this work it was achieved via fluorescence labeling of the CapG protein to visualize the dynamics of cellular processes as migration and invasiveness and to analyze the kinetics of the intracellular distribution of the CapG protein. Differences of the intracellular mobility of CapG between non-neoplastic and neoplastic breast epithelial cells could be demonstrated, correlations of increased tumor cell motility and accelerated intracellular CapG mobility revealed and a causal context of CapG expression and distribution on one hand and invasiveness and metastasizing on the other could be made probable, so that a differentiation of tumor cells applying kinetic analysis of single live cells seems to be possible.http://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=7471