Spatiotemporal Expression of IRS-1 During Brain Development and its Role in Neural Stem Cell Differentiation

Insulin receptor substrate 1 (IRS-1) is a key mediator of insulin signaling linked to focal cortical dysplasia. While previous studies have primarily focused on IRS-1 in peripheral tissues, its function in the central nervous system has remained largely unexplored. This study aimed to investigate the spatiotemporal expression patterns of IRS-1 protein in mouse cerebral cortex and human brain organoids, along with its role in neural development. In mice, Irs-1 expression was consistent throughout brain development, with notable localization in the ventricular/subventricular zone during early gestation and later in the outer cerebral cortex. In human brain organoids, IRS-1 was primarily found in rosette structures initially, shifting to the outer cortical layer as they matured. Knockdown of Irs-1 at embryonic day 14.5 via in-utero electroporation impaired neuronal migration, resulting in more neurons remaining in the intermediate zone compared to controls. Moreover, SH-SY5Y cells treated with isotretinoin exhibited a significant decrease in IRS-1 protein expression during maturation. RNA sequencing indicates an upregulation of neurodevelopment-related genes alongside a downregulation of the IRS-1. These findings underscore the significance of IRS-1 in brain development, particularly regarding neuronal migration and differentiation.