Biology subjects

Mertz, J. L.

Publications and source records attributed to Mertz, J. L..

4 recordsLinked to original sources

bioRxiv2020

Single-Cell Transcriptomic Analysis Reveals Molecular Diversity of Human Oligodendrocyte Progenitor Cells

Injury and loss of oligodendrocytes can cause demyelinating diseases such as multiple sclerosis. To improve our understanding of oligodendrocyte development, which could facilitate development of remyelination-based treatment strategies, we performed single-cell-transcriptomic-analysis of developing human oligodendrocyte-precursor-cells (hOPCs). We engineered knock-in hESC-reporter lines in which an Identification-and-Purification tag is expressed under control of the endogenous, OPC-specific, PDGFR promoter, and performed time-course single-cell-RNA-sequencing of purified hOPCs. Our analysis uncovered marked transcriptional heterogeneity of PDGFR+ hOPCs and identified regulatory genes and networks that control their differentiation and myelination competence. Pseudotime trajectory analysis revealed two distinct trajectories for the development of oligodendrocytes vs astrocytes from hOPCs. We also identified novel transcription factors and other genes that developing hOPCs potentially use to choose between oligodendrocyte vs astrocyte lineages. In addition, pathway enrichment analysis followed by pharmacological intervention of those pathways confirm that mTOR and cholesterol biosynthesis signaling pathways are involved in maturation of oligodendrocytes from hOPCs.

neuroscience↗

bioRxiv2020

Structural engraftment and topographic spacing of transplanted human stem cell-derived retinal ganglion cells

Retinal ganglion cell (RGC) replacement and optic nerve regeneration hold potential for restoring vision lost to optic neuropathy. Following transplantation, RGCs must integrate into the neuroretinal circuitry in order to receive afferent visual signals for processing and transmission to central targets. To date, the efficiency of RGC retinal integration following transplantation has been limited. We sought to characterize spontaneous interactions between transplanted human embryonic stem cell-derived RGCs and the recipient mature mammalian retina, and to identify and overcome barriers to the structural integration of transplanted neurons. Using an in vitro model system, following transplantation directly onto the inner surface of organotypic mouse retinal explants, human RGC somas form compact clusters and extend bundled neurites that remain superficial to the neural retinal tissue, hindering any potential for afferent synaptogenesis. To enhance integration, we explored methods to increase the cellular permeability of the internal limiting membrane (ILM). Digestion of extracellular matrix components using proteolytic enzymes was titrated to achieve disruption of the ILM while minimizing retinal toxicity and preserving endogenous retinal glial reactivity. Such ILM disruption is associated with dispersion rather than clustering of transplanted RGC bodies and neurites, and with a marked increase in transplanted RGC neurite extension into retinal parenchyma. The ILM appears to be a barrier to afferent retinal connectivity by transplanted RGCs and its circumvention may be necessary for successful functional RGC replacement through transplantation.

neuroscience↗

bioRxiv2020

Comparison of three glycoproteomic methods for the analysis of CHO cells treated with 1,3,4-O-Bu3ManNAc

Comprehensive analysis of the glycoproteome is critical due to the widespread importance of this post-translational modification to protein function, and difficult because of the tremendous complexity it exhibits. Here we compared three glycoproteomic analysis methods, a recently described chemoenzymatic glycoproteome analysis methods, N-linked glycans and glycosite containing peptides (NGAG), Solid-phase extraction of N-linked glycoproteins (SPEG), and hydrophilic interaction liquid chromatography (HILIC), for the analysis of N-linked glycosites of Chinese hamster ovarian (CHO) cells treated with 1,3,4-O-Bu3ManNAc. The NGAG protocol resulted in substantially increased glycosite identifications over both SPEG and HILIC. Interestingly, while the glycosites identified by SPEG and HILIC overlapped strongly, NGAG identified many glycosites not observed in either of the other two methods. Further, utilizing the enhanced intact glycopeptide identification afforded by the NGAG workflow, we also found that of the sugar analog 1,3,4-O-Bu3ManNAc increases sialylation of proteins secreted by CHO cells, including an ectopically expressed human proteins.

biochemistry↗

bioRxiv2020

Proteomic and phosphoproteomic analysis identifies novel liver-related signaling in retinal pigment epithelial cells during epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is associated with several potentially blinding retinal diseases. Proteomic and phosphoproteomic studies were performed on human pluripotent stem cell-derived RPE (hPSC-RPE) monolayers to better understand the pathways mediating RPE EMT. EMT was induced by enzymatic dissociation or by co-treatment with transforming growth factor beta (TGF{beta}) and tumor necrosis factor alpha (TNF; TGNF). The global and phosphoproteomes were analyzed at 1 hr post EMT induction to capture early events in kinase/phosphatase signaling cascades and at 12 hrs to define early changes in protein abundance. Pathway enrichment analysis revealed that TGNF and Dissociation rapidly perturbed signaling in many of the same pathways, with striking similarity in the phosphoproteome at 1 hr. Surprisingly, functions related to liver cell proliferation and hyperplasia were strongly enriched in the phosphosites altered by both treatments at 1 hr and in protein abundance changes at 12 hrs. Hepatocyte Growth Factor-cMET signaling exhibited the strongest overall enrichment in both treatments. These signaling pathways may serve as suitable targets for the development of therapeutic strategies for the inhibition of RPE EMT, and thus progression of several debilitating visual diseases.

cell biology↗