Biology subjects

Sayed, A.

Publications and source records attributed to Sayed, A..

4 recordsLinked to original sources

bioRxiv2023

NMDA receptors regulate neural progenitor cell proliferation and maturation in the zebrafish forebrain.

Developmental neurogenesis is a tightly regulated spatiotemporal process with its dysregulation implicated in neurodevelopmental disorders. NMDA receptors are glutamate-gated ion channels that are widely expressed in the early nervous system, yet their contribution to neurogenesis is poorly understood. Notably, a variety of mutations in genes encoding NMDA receptor subunits are associated with neurodevelopmental disorders. To rigorously define the role of NMDA receptors in developmental neurogenesis, we used a mutant zebrafish line (grin1-/-) that lacks all NMDA receptors yet survives to 10 days post-fertilization, offering the opportunity to study post-embryonic neurodevelopment in the absence of NMDA receptors. Focusing on the forebrain, we find that these fish have a progressive supernumerary neuron phenotype confined to the telencephalon at the end of embryonic neurogenesis, but which extends to all forebrain regions during postembryonic neurogenesis. This enhanced neuron population does not arise directly from increased numbers or mitotic activity of radial glia cells, the principal neural stem cells. Rather, it stems from a lack of timely maturation of transit-amplifying neuroblasts into post-mitotic neurons, as indicated by a decrease in expression of the ontogenetically-expressed chloride transporter, KCC2. Pharmacological blockade with MK-801 recapitulates the grin1-/- supernumerary neuron phenotype, indicating a requirement for ionotropic signaling. Thus, NMDA receptors are required for suppression of indirect, transit amplifying cell-driven neurogenesis by promoting maturational termination of mitosis. Loss of suppression results in neuronal overpopulation that can fundamentally change brain circuitry and may be a key factor in pathogenesis of neurodevelopmental disorders caused by NMDA receptor dysfunction.

neuroscience↗

bioRxiv2021

Hypoxia promotes a perinatal-like progenitor state in the adult murine epicardium

The epicardium is a reservoir of progenitors that give rise to coronary vasculature and stroma during development and mediates cardiac vascular repair in lower vertebrates. However, its role as a source of progenitors in the adult mammalian heart remains unclear due to lack of clear lineage markers and single-cell culture systems to elucidate epicardial progeny cell fate. We found that in vivo exposure of mice to physiological hypoxia induced adult epicardial cells to re-enter the cell cycle and to express a subset of developmental genes. Multiplex transcriptional profiling revealed a lineage relationship between epicardial cells and smooth muscle, stromal, and endothelial fates, and that physiological hypoxia promoted an endothelial cell fate. In vitro analyses of purified epicardial cells showed that cell growth and subsequent differentiation is dependent upon hypoxia, and that resident epicardial cells retain progenitor identity in the adult mammalian heart with self-renewal and multilineage differentiation potential. These results point to a source of progenitor cells in the adult heart that can promote heart revascularization, providing an invaluable in vitro model for further studies.

cell biology↗

bioRxiv2021

Fibroadipogenic Progenitors contribute to microvascular repair during skeletal muscle regeneration

Skeletal muscle injury results in a disruption of the muscle bed vascular network. A local source of vascular progenitors during muscle regeneration has not been clearly identified. Fibroadipogenic progenitors (FAPs) are required for proper regeneration, however they can also directly contribute to fibrotic and fatty infiltration in response to chronic muscle injury and muscle disease. We show here that acute muscle injury leads to hypoxia and glucose deprivation, triggering FAP proliferation and differentiation into endothelial cells in vitro and in vivo. In response to glucose deprivation, FAPs down regulate fibrotic and fat associated genes and acquire an endothelial cell fate, which is dependent upon mTORC2-HIF2-eNOS pathway. These findings bring new insights into the mechanisms of vascular regeneration during muscle regeneration and define a highly plastic resident progenitor population that responds to oxygen/glucose-deprivation induced cell stress by promoting an endothelial cell fate.

cell biology↗

bioRxiv2021

Amelioration of hemophilia B through CRISPR/Cas9 induced homology-independent targeted integration

Site-specific integration of exogenous gene through genome editing is a promising strategy for gene therapy. However, homology-directed repair (HDR) only occurring in proliferating cells is inefficient especially in vivo. To investigate the efficacy of Cas9-induced homology-independent targeted integration (HITI) strategy for gene therapy, a rat hemophilia B model was generated and employed. Through HITI, a DNA sequence encoding the last exon of rat Albumin (rAlb) gene fused with a high-specific-activity Factor IX variant (R338L) using T2A, was inserted into the last intron of rAlb via recombinant adeno-associated viral (rAAV). The knock-in efficiency reached up to 3.66% determined by ddPCR. The clotting time was reduced to normal level 4 weeks after treatment, and the circulating FIX level was gradually increased up to 52% of normal during 9 months even after partial hepatectomy, demonstrating the amelioration of hemophilia. Through PEM-seq, no significant off-targeting effect was detected. Moreover, this study provides a promising therapeutic approach for hereditary diseases.

bioengineering↗