All Publications


  • The COVID-19 Pandemic as an Opportunity for Operational Innovation at 2 Student-Run Free Clinics. Journal of primary care & community health Ruiz Colón, G. D., Mulaney, B. n., Reed, R. E., Ha, S. K., Yuan, V. n., Liu, X. n., Cao, S. n., Ambati, V. S., Hernandez, B. n., Cáceres, W. n., Charon, M. n., Singh, B. n. ; 12: 2150132721993631

    Abstract

    The onset of the COVID-19 pandemic and subsequent county shelter-in-place order forced the Cardinal Free Clinics (CFCs), Stanford University's 2 student-run free clinics, to close in March 2020. As student-run free clinics adhering to university-guided COVID policies, we have not been able to see patients in person since March of 2020. However, the closure of our in-person operations provided our student management team with an opportunity to innovate. In consultation with Stanford's Telehealth team and educators, we rapidly developed a telehealth clinic model for our patients. We adapted available telehealth guidelines to meet our patient care needs and educational objectives, which manifested in 3 key innovations: reconfigured clinic operations, an evidence-based social needs screen to more effectively assess and address social needs alongside medical needs, and a new telehealth training module for student volunteers. After 6 months of piloting our telehealth services, we believe that these changes have made our services and operations more robust and provided benefit to both our patients and volunteers. Despite an uncertain and evolving public health landscape, we are confident that these developments will strengthen the future operations of the CFCs.

    View details for DOI 10.1177/2150132721993631

    View details for PubMedID 33615883

  • The MEK5-ERK5 kinase axis controls lipid metabolism in small cell lung cancer. Cancer research Cristea, S., Coles, G. L., Hornburg, D., Gershkovitz, M., Arand, J., Cao, S., Sen, T., Williamson, S. C., Kim, J. W., Drainas, A. P., He, A., Le Cam, L., Byers, L. A., Snyder, M. P., Contrepois, K., Sage, J. 2020

    Abstract

    Small cell lung cancer (SCLC) is an aggressive form of lung cancer with dismal survival rates. While kinases often play key roles driving tumorigenesis, there are strikingly few kinases known to promote the development of SCLC. Here we investigated the contribution of the MAP kinase module MEK5/ERK5 to SCLC growth. MEK5 and ERK5 were required for optimal survival and expansion of SCLC cell lines in vitro and in vivo. Transcriptomics analyses identified a role for the MEK5-ERK5 axis in the metabolism of SCLC cells, including lipid metabolism. In-depth lipidomics analyses showed that loss of MEK5/ERK5 perturbs several lipid metabolism pathways, including the mevalonate pathway that controls cholesterol synthesis. Notably, depletion of MEK5/ERK5 sensitized SCLC cells to pharmacological inhibition of the mevalonate pathway by statins. These data identify a new MEK5-ERK5-lipid metabolism axis that promotes the growth of SCLC.

    View details for DOI 10.1158/0008-5472.CAN-19-1027

    View details for PubMedID 31969375

  • Mammalian Hbs1L deficiency causes congenital anomalies and developmental delay associated with Pelota depletion and 80S monosome accumulation PLOS GENETICS O'Connell, A. E., Gerashchenko, M. V., O'Donohue, M., Rosen, S. M., Huntzinger, E., Gleeson, D., Galli, A., Ryder, E., Cao, S., Murphy, Q., Kazerounian, S., Morton, S. U., Schmitz-Abe, K., Gladyshev, V. N., Gleizes, P., Seraphin, B., Agrawal, P. B. 2019; 15 (2): e1007917

    Abstract

    Hbs1 has been established as a central component of the cell's translational quality control pathways in both yeast and prokaryotic models; however, the functional characteristics of its human ortholog (Hbs1L) have not been well-defined. We recently reported a novel human phenotype resulting from a mutation in the critical coding region of the HBS1L gene characterized by facial dysmorphism, severe growth restriction, axial hypotonia, global developmental delay and retinal pigmentary deposits. Here we further characterize downstream effects of the human HBS1L mutation. HBS1L has three transcripts in humans, and RT-PCR demonstrated reduced mRNA levels corresponding with transcripts V1 and V2 whereas V3 expression was unchanged. Western blot analyses revealed Hbs1L protein was absent in the patient cells. Additionally, polysome profiling revealed an abnormal aggregation of 80S monosomes in patient cells under baseline conditions. RNA and ribosomal sequencing demonstrated an increased translation efficiency of ribosomal RNA in Hbs1L-deficient fibroblasts, suggesting that there may be a compensatory increase in ribosome translation to accommodate the increased 80S monosome levels. This enhanced translation was accompanied by upregulation of mTOR and 4-EBP protein expression, suggesting an mTOR-dependent phenomenon. Furthermore, lack of Hbs1L caused depletion of Pelota protein in both patient cells and mouse tissues, while PELO mRNA levels were unaffected. Inhibition of proteasomal function partially restored Pelota expression in human Hbs1L-deficient cells. We also describe a mouse model harboring a knockdown mutation in the murine Hbs1l gene that shared several of the phenotypic elements observed in the Hbs1L-deficient human including facial dysmorphism, growth restriction and retinal deposits. The Hbs1lKO mice similarly demonstrate diminished Pelota levels that were rescued by proteasome inhibition.

    View details for DOI 10.1371/journal.pgen.1007917

    View details for Web of Science ID 000459970100019

    View details for PubMedID 30707697

    View details for PubMedCentralID PMC6373978

  • Novel founder intronic variant in SLC39A14 in two families causing Manganism and potential treatment strategies MOLECULAR GENETICS AND METABOLISM Rodan, L. H., Hauptman, M., D'Gama, A. M., Qualls, A. E., Cao, S., Tuschl, K., Al-Jasmi, F., Hertecant, J., Hayflick, S. J., Wessling-Resnick, M., Yang, E. T., Berry, G. T., Gropman, A., Woolf, A. D., Agrawal, P. B. 2018; 124 (2): 161-167

    Abstract

    Congenital disorders of manganese metabolism are rare occurrences in children, and medical management of these disorders is complex and challenging. Homozygous exonic mutations in the manganese transporter SLC39A14 have recently been associated with a pediatric-onset neurodegenerative disorder characterized by brain manganese accumulation and clinical signs of manganese neurotoxicity, including parkinsonism-dystonia. We performed whole exome sequencing on DNA samples from two unrelated female children from the United Arab Emirates with progressive movement disorder and brain mineralization, identified a novel homozygous intronic mutation in SLC39A14 in both children, and demonstrated that the mutation leads to aberrant splicing. Both children had consistently elevated serum manganese levels and were diagnosed with SLC39A14-associated manganism. Over a four-year period, we utilized a multidisciplinary management approach for Patient 1 combining decreased manganese dietary intake and chelation with symptomatic management of dystonia. Our treatment strategy appeared to slow disease progression, but did not lead to a cure or reversal of already established deficits. Clinicians should consider testing for noncoding mutations in the diagnosis of congenital disorders of manganese metabolism and utilizing multidisciplinary approaches in the management of these disorders.

    View details for DOI 10.1016/j.ymgme.2018.04.002

    View details for Web of Science ID 000435426900009

    View details for PubMedID 29685658

    View details for PubMedCentralID PMC5976541

  • SPEG-deficient skeletal muscles exhibit abnormal triad and defective calcium handling HUMAN MOLECULAR GENETICS Huntoon, V., Widrick, J. J., Sanchez, C., Rosen, S. M., Kutchukian, C., Cao, S., Pierson, C. R., Liu, X., Perrella, M. A., Beggs, A. H., Jacquemond, V., Agrawal, P. B. 2018; 27 (9): 1608-1617

    Abstract

    Centronuclear myopathies (CNM) are a subtype of congenital myopathies (CM) characterized by skeletal muscle weakness and an increase in the number of central myonuclei. We have previously identified three CNM probands, two with associated dilated cardiomyopathy, carrying striated preferentially expressed gene (SPEG) mutations. Currently, the role of SPEG in skeletal muscle function is unclear as constitutive SPEG-deficient mice developed severe dilated cardiomyopathy and died in utero. We have generated a conditional Speg-KO mouse model and excised Speg by crosses with striated muscle-specific cre-expressing mice (MCK-Cre). The resulting litters had a delay in Speg excision consistent with cre expression starting in early postnatal life and, therefore, an extended lifespan up to a few months. KO mice were significantly smaller and weaker than their littermate-matched controls. Histopathological skeletal muscle analysis revealed smaller myofibers, marked fiber-size variability, and poor integrity and low number of triads. Further, SPEG-deficient muscle fibers were weaker by physiological and in vitro studies and exhibited abnormal Ca2+ handling and excitation-contraction (E-C) coupling. Overall, SPEG deficiency in skeletal muscle is associated with fewer and abnormal triads, and defective calcium handling and excitation-contraction coupling, suggesting that therapies targeting calcium signaling may be beneficial in such patients.

    View details for DOI 10.1093/hmg/ddy068

    View details for Web of Science ID 000431882900009

    View details for PubMedID 29474540

    View details for PubMedCentralID PMC5905626

  • Homozygous EEF1A2 mutation causes dilated cardiomyopathy, failure to thrive, global developmental delay, epilepsy and early death HUMAN MOLECULAR GENETICS Cao, S., Smith, L. L., Padilla-Lopez, S. R., Guida, B. S., Blume, E., Shi, J., Morton, S. U., Brownstein, C. A., Beggs, A. H., Kruer, M. C., Agrawal, P. B. 2017; 26 (18): 3545-3552

    Abstract

    Eukaryotic elongation factor 1A (EEF1A), is encoded by two distinct isoforms, EEF1A1 and EEF1A2; whereas EEF1A1 is expressed almost ubiquitously, EEF1A2 expression is limited such that it is only detectable in skeletal muscle, heart, brain and spinal cord. Currently, the role of EEF1A2 in normal cardiac development and function is unclear. There have been several reports linking de novo dominant EEF1A2 mutations to neurological issues in humans. We report a pair of siblings carrying a homozygous missense mutation p.P333L in EEF1A2 who exhibited global developmental delay, failure to thrive, dilated cardiomyopathy and epilepsy, ultimately leading to death in early childhood. A third sibling also died of a similar presentation, but DNA was unavailable to confirm the mutation. Functional genomic analysis was performed in S. cerevisiae and zebrafish. In S. cerevisiae, there was no evidence for a dominant-negative effect. Previously identified putative de novo mutations failed to complement yeast strains lacking the EEF1A ortholog showing a major growth defect. In contrast, the introduction of the mutation seen in our family led to a milder growth defect. To evaluate its function in zebrafish, we knocked down eef1a2 expression using translation blocking and splice-site interfering morpholinos. EEF1A2-deficient zebrafish had skeletal muscle weakness, cardiac failure and small heads. Human EEF1A2 wild-type mRNA successfully rescued the morphant phenotype, but mutant RNA did not. Overall, EEF1A2 appears to be critical for normal heart function in humans, and its deficiency results in clinical abnormalities in neurologic function as well as in skeletal and cardiac muscle defects.

    View details for DOI 10.1093/hmg/ddx239

    View details for Web of Science ID 000409091200008

    View details for PubMedID 28911200

    View details for PubMedCentralID PMC5886049

  • Time Course and Size of Blood Brain Barrier Opening in a Mouse Model of Blast-Induced Traumatic Brain Injury JOURNAL OF NEUROTRAUMA Hue, C. D., Cho, F. S., Cao, S., Nicholls, R. E., Vogel, E. W., Sibindi, C., Arancio, O., Bass, C., Meaney, D. F., Morrison, B. 2016; 33 (13): 1202-+

    Abstract

    An increasing number of studies have reported blood-brain barrier (BBB) dysfunction after blast-induced traumatic brain injury (bTBI). Despite this evidence, there is limited quantitative understanding of the extent of BBB opening and the time course of damage after blast injury. In addition, many studies do not report kinematic parameters of head motion, making it difficult to separate contributions of primary and tertiary blast-loading. Detailed characterization of blast-induced BBB damage may hold important implications for serum constituents that may potentially cross the compromised barrier and contribute to neurotoxicity, neuroinflammation, and persistent neurologic deficits. Using an in vivo bTBI model, systemic administration of sodium fluorescein (NaFl; 376 Da), Evans blue (EB; 69 kDa when bound to serum albumin), and dextrans (3-500 kDa) was used to estimate the pore size of BBB opening and the time required for recovery. Exposure to blast with 272 ± 6 kPa peak overpressure, 0.69 ± 0.01 ms duration, and 65 ± 1 kPa*ms impulse resulted in significant acute extravasation of NaFl, 3 kDa dextran, and EB. However, there was no significant acute extravasation of 70 kDa or 500 kDa dextrans, and minimal to no extravasation of NaFl, dextrans, or EB 1 day after exposure. This study presents a detailed analysis of the time course and pore size of BBB opening after bTBI, supported by a characterization of kinematic parameters associated with blast-induced head motion.

    View details for DOI 10.1089/neu.2015.4067

    View details for Web of Science ID 000378336200386

    View details for PubMedID 26414212

  • Clinical heterogeneity associated with KCNA1 mutations include cataplexy and nonataxic presentations NEUROGENETICS Brownstein, C. A., Beggs, A. H., Rodan, L., Shi, J., Towne, M. C., Pelletier, R., Cao, S., Rosenberg, P. A., Urion, D. K., Picker, J., Tan, W., Agrawal, P. B. 2016; 17 (1): 11-16

    Abstract

    Mutations in the KCNA1 gene are known to cause episodic ataxia/myokymia syndrome type 1 (EA1). Here, we describe two families with unique presentations who were enrolled in an IRB-approved study, extensively phenotyped, and whole exome sequencing (WES) performed. Family 1 had a diagnosis of isolated cataplexy triggered by sudden physical exertion in multiple affected individuals with heterogeneous neurological findings. All enrolled affected members carried a KCNA1 c.941T>C (p.I314T) mutation. Family 2 had an 8-year-old patient with muscle spasms with rigidity for whom WES revealed a previously reported heterozygous missense mutation in KCNA1 c.677C>G (p.T226R), confirming the diagnosis of EA1 without ataxia. WES identified variants in KCNA1 that explain both phenotypes expanding the phenotypic spectrum of diseases associated with mutations of this gene. KCNA1 mutations should be considered in patients of all ages with episodic neurological phenotypes, even when ataxia is not present. This is an example of the power of genomic approaches to identify pathogenic mutations in unsuspected genes responsible for heterogeneous diseases.

    View details for DOI 10.1007/s10048-015-0460-2

    View details for Web of Science ID 000367695300002

    View details for PubMedID 26395884

    View details for PubMedCentralID PMC4911217

  • Dexamethasone potentiates in vitro blood-brain barrier recovery after primary blast injury by glucocorticoid receptor-mediated upregulation of ZO-1 tight junction protein JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM Hue, C. D., Cho, F. S., Cao, S., Bass, C., Meaney, D. F., Morrison, B. 2015; 35 (7): 1191-1198

    Abstract

    Owing to the frequent incidence of blast-induced traumatic brain injury (bTBI) in recent military conflicts, there is an urgent need to develop effective therapies for bTBI-related pathologies. Blood-brain barrier (BBB) breakdown has been reported to occur after primary blast exposure, making restoration of BBB function and integrity a promising therapeutic target. We tested the hypothesis that treatment with dexamethasone (DEX) after primary blast injury potentiates recovery of an in vitro BBB model consisting of mouse brain endothelial cells (bEnd.3). DEX treatment resulted in complete recovery of transendothelial electrical resistance and hydraulic conductivity 1 day after injury, compared with 3 days for vehicle-treated injured cultures. Administration of RU486 (mifepristone) inhibited effects of DEX, confirming that barrier restoration was mediated by glucocorticoid receptor signaling. Potentiated recovery with DEX treatment was accompanied by stronger zonula occludens (ZO)-1 tight junction immunostaining and expression, suggesting that increased ZO-1 expression was a structural correlate to BBB recovery after blast. Interestingly, augmented ZO-1 protein expression was associated with specific upregulation of the α(+) isoform but not the α(-) isoform. This is the first study to provide a mechanistic basis for potentiated functional recovery of an in vitro BBB model because of glucocorticoid treatment after primary blast injury.

    View details for DOI 10.1038/jcbfm.2015.38

    View details for Web of Science ID 000357137500018

    View details for PubMedID 25757751

    View details for PubMedCentralID PMC4640274

  • Repeated Primary Blast Injury Causes Delayed Recovery, but not Additive Disruption, in an In Vitro Blood-Brain Barrier Model JOURNAL OF NEUROTRAUMA Hue, C. D., Cao, S., Bass, C., Meaney, D. F., Morrison, B. 2014; 31 (10): 951-960

    Abstract

    Recent studies have demonstrated increased susceptibility to breakdown of the cerebral vasculature associated with repetitive traumatic brain injury. We hypothesized that exposure to two consecutive blast injuries would result in exacerbated damage to an in vitro model of the blood-brain barrier (BBB) compared with exposure to a single blast of the same severity. Contrary to our hypothesis, however, repeated mild or moderate primary blast delivered with a 24 or 72 h interval between injuries did not significantly exacerbate reductions in transendothelial electrical resistance (TEER) across a brain endothelial monolayer compared with sister cultures receiving a single exposure of the same intensity. Permeability of the barrier to a range of different-sized solutes remained unaltered after single and repeated blast, supporting that the effects of repeated blast on BBB integrity were not additive. Single blast exposure significantly reduced immunostaining of ZO-1 and claudin-5 tight junction proteins, but subsequent exposure did not cause additional damage to tight junctions. Although repeated blast did not further reduce TEER, the second exposure delayed TEER recovery in BBB cultures. Similarly, recovery of hydraulic conductivity through the BBB was delayed by a second exposure. Extending the interinjury interval to 72 h, the effects of multiple injuries on the BBB were found to be independent given sufficient recovery time between consecutive exposures. Careful investigation of the effects of repeated blast on the BBB will help identify injury levels and a temporal window of vulnerability associated with BBB dysfunction, ultimately leading to improved strategies for protecting warfighters against repeated blast-induced disruption of the cerebral vasculature.

    View details for DOI 10.1089/neu.2013.3149

    View details for Web of Science ID 000335863200007

    View details for PubMedID 24372353

  • Blood-Brain Barrier Dysfunction after Primary Blast Injury in vitro JOURNAL OF NEUROTRAUMA Hue, C. D., Cao, S., Haider, S. F., Vo, K. V., Effgen, G. B., Vogel, E., Panzer, M. B., Bass, C., Meaney, D. F., Morrison, B. 2013; 30 (19): 1652-1663

    Abstract

    The incidence of blast-induced traumatic brain injury (bTBI) has increased substantially in recent military conflicts. However, the consequences of bTBI on the blood-brain barrier (BBB), a specialized cerebrovascular structure essential for brain homeostasis, remain unknown. In this study, we utilized a shock tube driven by compressed gas to generate operationally relevant, ideal pressure profiles consistent with improvised explosive devices (IEDs). By multiple measures, the barrier function of an in vitro BBB model was disrupted following exposure to a range of controlled blast loading conditions. Trans-endothelial electrical resistance (TEER) decreased acutely in a dose-dependent manner that was most strongly correlated with impulse, as opposed to peak overpressure or duration. Significantly increased hydraulic conductivity and solute permeability post-injury further confirmed acute alterations in barrier function. Compromised ZO-1 immunostaining identified a structural basis for BBB breakdown. After blast exposure, TEER remained significantly depressed 2 days post-injury, followed by spontaneous recovery to pre-injury control levels at day 3. This study is the first to report immediate disruption of an in vitro BBB model following primary blast exposure, which may be important for the development of novel helmet designs to help mitigate the effects of blast on the BBB.

    View details for DOI 10.1089/neu.2012.2773

    View details for Web of Science ID 000325146800006

    View details for PubMedID 23581482