Xavier Gaeta MD PhD

All Publications

• A small molecule screen to identify regulators of let-7 targets SCIENTIFIC REPORTS Cinkornpumin, J., Roos, M., Nguyen, L., Liu, X., Gaeta, X., Lin, S., Chan, D. N., Liu, A., Gregory, R. I., Jung, M., Chute, J., Zhu, H., Lowry, W. E. 2017; 7: 15973

  Abstract

  The let-7 family of miRNAs has been shown to be crucial in many aspects of biology, from the regulation of developmental timing to cancer. The available methods to regulate this family of miRNAs have so far been mostly genetic and therefore not easily performed experimentally. Here, we describe a small molecule screen designed to identify regulators of let-7 targets in human cells. In particular, we focused our efforts on the identification of small molecules that could suppress let-7 targets, as these could serve to potentially intercede in tumors driven by loss of let-7 activity. After screening through roughly 36,000 compounds, we identified a class of phosphodiesterase inhibitors that suppress let-7 targets. These compounds stimulate cAMP levels and raise mature let-7 levels to suppress let-7 target genes in multiple cancer cell lines such as HMGA2 and MYC. As a result, these compounds also show growth inhibitory activity on cancer cells.

  View details for DOI 10.1038/s41598-017-16258-9

  View details for Web of Science ID 000415983600061

  View details for PubMedID 29162914

  View details for PubMedCentralID PMC5698460

• Defining Transcriptional Regulatory Mechanisms for Primary let-7 miRNAs PLOS ONE Gaeta, X., Le, L., Lin, Y., Xie, Y., Lowry, W. E. 2017; 12 (1): e0169237

  Abstract

  The let-7 family of miRNAs have been shown to control developmental timing in organisms from C. elegans to humans; their function in several essential cell processes throughout development is also well conserved. Numerous studies have defined several steps of post-transcriptional regulation of let-7 production; from pri-miRNA through pre-miRNA, to the mature miRNA that targets endogenous mRNAs for degradation or translational inhibition. Less-well defined are modes of transcriptional regulation of the pri-miRNAs for let-7. let-7 pri-miRNAs are expressed in polycistronic fashion, in long transcripts newly annotated based on chromatin-associated RNA-sequencing. Upon differentiation, we found that some let-7 pri-miRNAs are regulated at the transcriptional level, while others appear to be constitutively transcribed. Using the Epigenetic Roadmap database, we further annotated regulatory elements of each polycistron identified putative promoters and enhancers. Probing these regulatory elements for transcription factor binding sites identified factors that regulate transcription of let-7 in both promoter and enhancer regions, and identified novel regulatory mechanisms for this important class of miRNAs.

  View details for DOI 10.1371/journal.pone.0169237

  View details for Web of Science ID 000391621500038

  View details for PubMedID 28052101

  View details for PubMedCentralID PMC5215532

• Glycolytic Metabolism Plays a Functional Role in Regulating Human Pluripotent Stem Cell State CELL STEM CELL Gu, W., Gaeta, X., Sahakyan, A., Chan, A. B., Hong, C. S., Kim, R., Braas, D., Plath, K., Lowry, W. E., Christofk, H. R. 2016; 19 (4): 476–90

  Abstract

  The rate of glycolytic metabolism changes during differentiation of human embryonic stem cells (hESCs) and reprogramming of somatic cells to pluripotency. However, the functional contribution of glycolytic metabolism to the pluripotent state is unclear. Here we show that naive hESCs exhibit increased glycolytic flux, MYC transcriptional activity, and nuclear N-MYC localization relative to primed hESCs. This status is consistent with the inner cell mass of human blastocysts, where MYC transcriptional activity is higher than in primed hESCs and nuclear N-MYC levels are elevated. Reduction of glycolysis decreases self-renewal of naive hESCs and feeder-free primed hESCs, but not primed hESCs grown in feeder-supported conditions. Reduction of glycolysis in feeder-free primed hESCs also enhances neural specification. These findings reveal associations between glycolytic metabolism and human naive pluripotency and differences in the metabolism of feeder-/feeder-free cultured hESCs. They may also suggest methods for regulating self-renewal and initial cell fate specification of hESCs.

  View details for DOI 10.1016/j.stem.2016.08.008

  View details for Web of Science ID 000389473800011

  View details for PubMedID 27618217

  View details for PubMedCentralID PMC5055460

• Identifying gene expression modules that define human cell fates STEM CELL RESEARCH Germanguz, I., Listgarten, J., Cinkornpumin, J., Solomon, A., Gaeta, X., Lowry, W. E. 2016; 16 (3): 712-724

  Abstract

  Using a compendium of cell-state-specific gene expression data, we identified genes that uniquely define cell states, including those thought to represent various developmental stages. Our analysis sheds light on human cell fate through the identification of core genes that are altered over several developmental milestones, and across regional specification. Here we present cell-type specific gene expression data for 17 distinct cell states and demonstrate that these modules of genes can in fact define cell fate. Lastly, we introduce a web-based database to disseminate the results.

  View details for DOI 10.1016/j.scr.2016.04.008

  View details for Web of Science ID 000377416900022

  View details for PubMedID 27108395

  View details for PubMedCentralID PMC4903895

• Defining the Role of Oxygen Tension in Human Neural Progenitor Fate STEM CELL REPORTS Xie, Y., Zhang, J., Lin, Y., Gaeta, X., Meng, X., Wisidagama, D. R., Cinkornpumin, J., Koehler, C. M., Malone, C. S., Teitell, M. A., Lowry, W. E. 2014; 3 (5): 743–57

  Abstract

  Hypoxia augments human embryonic stem cell (hESC) self-renewal via hypoxia-inducible factor 2α-activated OCT4 transcription. Hypoxia also increases the efficiency of reprogramming differentiated cells to a pluripotent-like state. Combined, these findings suggest that low O2 tension would impair the purposeful differentiation of pluripotent stem cells. Here, we show that low O2 tension and hypoxia-inducible factor (HIF) activity instead promote appropriate hESC differentiation. Through gain- and loss-of-function studies, we implicate O2 tension as a modifier of a key cell fate decision, namely whether neural progenitors differentiate toward neurons or glia. Furthermore, our data show that even transient changes in O2 concentration can affect cell fate through HIF by regulating the activity of MYC, a regulator of LIN28/let-7 that is critical for fate decisions in the neural lineage. We also identify key small molecules that can take advantage of this pathway to quickly and efficiently promote the development of mature cell types.

  View details for DOI 10.1016/j.stemcr.2014.09.021

  View details for Web of Science ID 000345118600007

  View details for PubMedID 25418722

  View details for PubMedCentralID PMC4235163

• let-7 miRNAs Can Act through Notch to Regulate Human Gliogenesis STEM CELL REPORTS Patterson, M., Gaeta, X., Loo, K., Edwards, M., Smale, S., Cinkornpumin, J., Xie, Y., Listgarten, J., Azghadi, S., Douglass, S. M., Pellegrini, M., Lowry, W. E. 2014; 3 (5): 758-773

  Abstract

  It is clear that neural differentiation from human pluripotent stem cells generates cells that are developmentally immature. Here, we show that the let-7 plays a functional role in the developmental decision making of human neural progenitors, controlling whether these cells make neurons or glia. Through gain- and loss-of-function studies on both tissue and pluripotent derived cells, our data show that let-7 specifically regulates decision making in this context by regulation of a key chromatin-associated protein, HMGA2. Furthermore, we provide evidence that the let-7/HMGA2 circuit acts on HES5, a NOTCH effector and well-established node that regulates fate decisions in the nervous system. These data link the let-7 circuit to NOTCH signaling and suggest that this interaction serves to regulate human developmental progression.

  View details for DOI 10.1016/j.stemcr.2014.08.015

  View details for Web of Science ID 000345118600008

  View details for PubMedID 25316189

  View details for PubMedCentralID PMC4235151

• Sequential addition of reprogramming factors improves efficiency NATURE CELL BIOLOGY Gaeta, X., Xie, Y., Lowry, W. E. 2013; 15 (7): 725-727

  Abstract

  Addition of a specific set of transcription factors reprograms somatic cell nuclei to a pluripotent state. Sequential addition of these factors, rather than the simultaneous exposure used in standard protocols, improves reprogramming efficiency. This sequential method favours a transition through a state with enhanced mesenchymal characteristics before driving an epithelial transformation on the way to the pluripotent state.

  View details for DOI 10.1038/ncb2800

  View details for Web of Science ID 000321181400004

  View details for PubMedID 23817236

  View details for PubMedCentralID PMC5842428

• The CCR2/CCL2 Interaction Mediates the Transendothelial Recruitment of Intravascularly Delivered Neural Stem Cells to the Ischemic Brain STROKE Andres, R. H., Choi, R., Pendharkar, A. V., Gaeta, X., Wang, N., Nathan, J. K., Chua, J. Y., Lee, S. W., Palmer, T. D., Steinberg, G. K., Guzman, R. 2011; 42 (10): 2923-U387

  Abstract

  The inflammatory response is a critical component of ischemic stroke. In addition to its physiological role, the mechanisms behind transendothelial recruitment of immune cells also offer a unique therapeutic opportunity for translational stem cell therapies. Recent reports have demonstrated homing of neural stem cells (NSC) into the injured brain areas after intravascular delivery. However, the mechanisms underlying the process of transendothelial recruitment remain largely unknown. Here we describe the critical role of the chemokine CCL2 and its receptor CCR2 in targeted homing of NSC after ischemia.Twenty-four hours after induction of stroke using the hypoxia-ischemia model in mice CCR2+/+ and CCR2-/- reporter NSC were intra-arterially delivered. Histology and bioluminescence imaging were used to investigate NSC homing to the ischemic brain. Functional outcome was assessed with the horizontal ladder test.Using NSC isolated from CCR2+/+ and CCR2-/- mice, we show that receptor deficiency significantly impaired transendothelial diapedesis specifically in response to CCL2. Accordingly, wild-type NSC injected into CCL2-/- mice exhibited significantly decreased homing. Bioluminescence imaging showed robust recruitment of CCR2+/+ cells within 6 hours after transplantation in contrast to CCR2-/- cells. Mice receiving CCR2+/+ grafts after ischemic injury showed a significantly improved recovery of neurological deficits as compared to animals with transplantation of CCR2-/- NSC.The CCL2/CCR2 interaction is critical for transendothelial recruitment of intravascularly delivered NSC in response to ischemic injury. This finding could have significant implications in advancing minimally invasive intravascular therapeutics for regenerative medicine or cell-based drug delivery systems for central nervous system diseases.

  View details for DOI 10.1161/STROKEAHA.110.606368

  View details for PubMedID 21836091

• Intra-arterial injection of neural stem cells using a microneedle technique does not cause microembolic strokes JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM Chua, J. Y., Pendharkar, A. V., Wang, N., Choi, R., Andres, R. H., Gaeta, X., Zhang, J., Moseley, M. E., Guzman, R. 2011; 31 (5): 1263-1271

  Abstract

  Intra-arterial (IA) injection represents an experimental avenue for minimally invasive delivery of stem cells to the injured brain. It has however been reported that IA injection of stem cells carries the risk of reduction in cerebral blood flow (CBF) and microstrokes. Here we evaluate the safety of IA neural progenitor cell (NPC) delivery to the brain. Cerebral blood flow of rats was monitored during IA injection of single cell suspensions of NPCs after stroke. Animals received 1 × 10(6) NPCs either injected via a microneedle (microneedle group) into the patent common carotid artery (CCA) or via a catheter into the proximally ligated CCA (catheter group). Controls included saline-only injections and cell injections into non-stroked sham animals. Cerebral blood flow in the microneedle group remained at baseline, whereas in the catheter group a persistent (15 minutes) decrease to 78% of baseline occurred (P<0.001). In non-stroked controls, NPCs injected via the catheter method resulted in higher levels of Iba-1-positive inflammatory cells (P=0.003), higher numbers of degenerating neurons as seen in Fluoro-Jade C staining (P<0.0001) and ischemic changes on diffusion weighted imaging. With an appropriate technique, reduction in CBF and microstrokes do not occur with IA transplantation of NPCs.

  View details for DOI 10.1038/jcbfm.2010.213

  View details for PubMedID 21157474

• Biodistribution of Neural Stem Cells After Intravascular Therapy for Hypoxic-Ischemia STROKE Pendharkar, A. V., Chua, J. Y., Andres, R. H., Wang, N., Gaeta, X., Wang, H., De, A., Choi, R., Chen, S., Rutt, B. K., Gambhir, S. S., Guzman, R. 2010; 41 (9): 2064-2070

  Abstract

  Intravascular transplantation of neural stem cells represents a minimally invasive therapeutic approach for the treatment of central nervous system diseases. The cellular biodistribution after intravascular injection needs to be analyzed to determine the ideal delivery modality. We studied the biodistribution and efficiency of targeted central nervous system delivery comparing intravenous and intra-arterial (IA) administration of neural stem cells after brain ischemia.Mouse neural stem cells were transduced with a firefly luciferase reporter gene for bioluminescence imaging (BLI). Hypoxic-ischemia was induced in adult mice and reporter neural stem cells were transplanted IA or intravenous at 24 hours after brain ischemia. In vivo BLI was used to track transplanted cells up to 2 weeks after transplantation and ex vivo BLI was used to determine single organ biodistribution.Immediately after transplantation, BLI signal from the brain was 12 times higher in IA versus intravenous injected animals (P<0.0001). After IA injection, 69% of the total luciferase activity arose from the brain early after transplantation and 93% at 1 week. After intravenous injection, 94% of the BLI signal was detected in the lungs (P=0.004) followed by an overall 94% signal loss at 1 week, indicating lack of cell survival outside the brain. Ex vivo single organ analysis showed a significantly higher BLI signal in the brain than in the lungs, liver, and kidneys at 1 week (P<0.0001) and 2 weeks in IA (P=0.007).IA transplantation results in superior delivery and sustained presence of neural stem cells in the ischemic brain in comparison to intravenous infusion.

  View details for DOI 10.1161/STROKEAHA.109.575993

  View details for PubMedID 20616329

• Intracarotid delivery of CD49d FACS sorted neural stem cells enhances angiogenesis and improves functional outcome after experimental stroke Guzman, R., Angeles, A., Choo, K., Gaeta, X., Cote, J., Cheshier, S., Steinberg, G. K. LIPPINCOTT WILLIAMS & WILKINS. 2008: 540

  View details for Web of Science ID 000252726100112