Transrational regulation in neurogenesis driven by shift in cortical stiffness

초록

The mechanical properties of the extracellular microenvironment, including its stiffness, play a crucial role in the differentiation of stem cells. Although previous studies have demonstrated that the developing brain exhibits spatiotemporal diversity in stiffness (Iwashita et al, Development, 2014), it remains unclear how neural stem cells sense the stiffness of their microenvironment and alter their fate towards specific neural lineages at molecular resolution in vivo. To uncover this issue, we performed a reconstitution assay combined with RNA-Seq using brain-stiffness-mimicking gels established by our group from tilapia skin collagen (Iwashita et al, Scientific Reports, 2019). Neural stem cells derived from mouse embryonic brains were cultured on “Soft” and “Hard” gels reproducing local tissue stiffness in the developing brain. By bioinformatics analysis, we identified ER stress pathway gene “ppp1r15b”, differentially expressing between “Soft” versus “Hard” conditions in the differentiated neurons derived from neural stem cells. Intriguingly, ppp1r15b is a causative gene of microcephaly. To investigate its functions, we analyzed the expression pattern of the neural-specific marker, Ctip2 (expressing in layer V) and Satb2 (expressing in layer II/III). Gain-of-function and Loss-of-function analysis in vivo resulted in the shift of expressing pattern of Ctip2 and Satb2 during neural differentiation. ER stress pathway inhibitor analysis in vitro induced the differences in the expression pattern of Ctip2 and Satb2 as similar as in vivo. Our results suggested that the ER stress pathway responds to brain stiffness during brain development.