Biology subjects

Fazal, S. V.

Publications and source records attributed to Fazal, S. V..

5 recordsLinked to original sources

bioRxiv2024

The immunological profile of RC17 hESC-derived dopaminergic neural progenitor cells in vitro: implications for the STEM-PD clinical trial.

Parkinsons Disease involves the progressive loss of dopaminergic neurons (DAn), prompting clinical trials replacing cell loss with neural grafts. This includes the transplantation of pluripotent stem cell-derived DAn progenitor cells (NPC) currently under investigation in the STEM-PD trial. To determine the likelihood of immune rejection post-grafting, we characterised the immunogenicity of the STEM-PD product (RC17-hESC-derived NPCs), comparing them to human foetal ventral mesencephalic tissue (hfVM) previously tested in trials, including our own TRANSEURO trial. Despite MHC-Class I expression, upregulated by proinflammatory cytokines, no immune response to NPCs was detected in vitro. Instead, they were immunosuppressive. Transcriptomic analysis revealed similarities between RC17-NPCs and hfVM, both strongly upregulating antigen processing and presentation pathways in response to IFN{gamma}. Furthermore, immunosuppressant mycophenolate mofetil detrimentally affected NPC survival and differentiation in vitro. Overall, our data suggest that aggressive immunosuppression is not required following hESC-NPC transplantation and that caution should be exercised when selecting the immunosuppressive regimen.

neuroscience↗

bioRxiv2023

Thermosensitivity of translation underlies the mammalian nocturnal-diurnal switch

Early mammals were nocturnal until the Cretaceous-Paleogene extinction enabled diurnal niche expansion. Diurnality evolved multiple times independently, but the mechanisms driving this shift remain unclear. We identify a conserved cell-intrinsic signal inversion that facilitates the transition from nocturnality to diurnality. Diurnal and nocturnal mammalian cells respond oppositely to temperature and osmotic cycles, mirroring species activity patterns. Cells exhibit differential global responses to temperature changes, including the phosphoproteome and protein synthesis. mTOR signaling is identified as a central mediator of this inversion, with diurnal mammals converging on modifications to mTOR and WNK pathways during evolution. Reducing mTOR activity induces nocturnal-to-diurnal shifting at cellular, tissue, and organismal levels. Therefore, the mTOR pathway is a cellular nexus that integrates energetic state and environmental signals to determine activity niche.

cell biology↗

bioRxiv2023

Distinct axo-protective and axo-destructive roles for Schwann cells after injury in a novel compartmentalised mouse myelinating coculture system.

Myelinating Schwann cell (SC)- dorsal root ganglion (DRG) neuron cocultures have been an important technique over the last four decades in understanding cell-cell signalling and interactions during peripheral nervous system (PNS) myelination, injury, and regeneration. While methods using rat SCs and rat DRG neurons are commonplace, there are no established protocols in the field describing the use of mouse SCs with mouse DRG neurons in dissociated myelinating cocultures. There is a great need for such a protocol as this would allow the use of cells from many different transgenic mouse lines. Here we describe a protocol to coculture dissociated mouse SCs and DRG neurons and induce robust myelination. Use of microfluidic chambers permits fluidic isolation for drug treatments, allows cultures to be axotomised to study injury responses, and cells can readily be transfected with lentiviruses to permit live imaging. We used this model to quantify the rate of degeneration after traumatic axotomy in the presence and absence of myelinating SCs and axon aligned SCs that were not induced to myelinate. We find that SCs, irrespective of myelination status, are axo-protective and delay axon degeneration early on. At later time points after injury, we use live imaging of cocultures to show that once axonal degeneration has commenced SCs break up, ingest, and clear axonal debris. Summary statementA novel compartmentalised dissociated mouse myelinating SC-DRG coculture system reveals distinct axo-protective and axo-destructive phases of Schwann cells on axon integrity after trauma.

neuroscience↗

bioRxiv2022

SARM1 detection in oligodendrocytes but not Schwann cells though sarm1/Sarm1 deletion does not perturb CNS nor PNS myelination in zebrafish and mice.

SARM1 is a central regulator of programmed axon death and is required to initiate axon self-destruction after traumatic and toxic insults to the nervous system. Abnormal activation of this axon degeneration pathway is increasingly recognized as a contributor to human neurological disease and SARM1 knockdown or inhibition has become an attractive therapeutic strategy to preserve axon loss in a variety of disorders of the peripheral and central nervous system. Despite this, it remains unknown whether Sarm1/SARM1 is present in myelinating glia and whether it plays a role in myelination in the PNS or CNS. It is important to answer these questions to understand whether future therapies inhibiting SARM1 function may have unintended deleterious impacts on myelination. Here we show that Sarm1 mRNA is present in oligodendrocytes in zebrafish but only detectable at low levels in Schwann cells in both zebrafish and mice. We find SARM1 protein is readily detectable in murine oligodendrocytes in vitro and in vivo and activation of endogenous SARM1 in oligodendrocytes induces cell death. In contrast, SARM1 protein is not detectable in Schwann cells and satellite glia in the adult murine nervous system. Cultured Schwann cells contain negligible functional SARM1 and are insensitive to specific SARM1 activators. Using zebrafish and mouse Sarm1 mutants, we show that SARM1 is not required for initiation of myelination nor myelin sheath maintenance by oligodendrocytes and Schwann cells. Thus, strategies to inhibit SARM1 function in the nervous system to treat neurological disease are unlikely to perturb myelination in humans. Main PointsO_LISARM1 protein is detectable in oligodendrocytes but not in Schwann cells C_LIO_LIOligodendrocytes but not Schwann cells die in response to endogenous SARM1 activation C_LIO_LICNS nor PNS myelination, in zebrafish and mice, is hindered by loss of sarm1/Sarm1 C_LI

neuroscience↗

bioRxiv2020

Failures of nerve regeneration caused by aging or chronic denervation are rescued by restoring Schwann cell c-Jun

After nerve injury, myelin and Remak Schwann cells reprogram to repair cells specialized for regeneration. Normally providing strong regenerative support, these cells fail in aging animals, and during the chronic denervation that results from the slow growth of axons. This impairs axonal regeneration and causes a significant clinical problem. In mice, we find that repair cells express reduced c-Jun protein as the regenerative support provided by these cells declines in aging animals and during chronic denervation. In both cases, genetically restoring Schwann cell c-Jun levels restores regeneration to that in controls. We identify potential gene candidates mediating this effect and implicate Shh in the control of Schwann cell c-Jun levels. This establishes that a common mechanism, reduced c-Jun in Schwann cells, regulates the success and failure of nerve repair both during aging and chronic denervation. This provides a molecular framework for addressing important clinical problems, and suggests molecular pathways that can be targeted to promote repair in the PNS.

neuroscience↗