Project description:Growth factors selectively activate calcium signaling pathways in the cell nucleus, which in turn regulate gene transcription and other intra-nuclear events, but the specific way this is accomplished is not entirely understood. The present study shows that growth factors increase inositol 1,4,5-trisphosphate (IP3) in the nucleus, which in turn releases calcium from intranuclear IP3 receptors (ITPRs), which then leads to transient assembly of an actin nucleoskeleton that associates with intranuclear MYH9. Mass spectrometry suggests that much of the MYH9 cargo consists of components of the gene transcription machinery, while chromatin immunoprecipitation identified a number of specific genes that associate with the myosin in response to stimulation with growth factors. Together, these findings suggest that growth factors initiate gene transcription by transiently assembling an actin nucleoskeleton that works with MYH9 to bring specific genes to the transcription machinery.
Project description:Lysosome dysfunction has been widely implicated in many models of neurodegeneration, but much less is understood of its involvement during brain development in health and disease. Hereditary spastic paraplegia caused by mutations in the SPG11 gene is a neurodevelopmental and neurodegenerative disorder characterized by lysosome dysfunction. We identify here lysosomal accumulation of calcium in SPG11 cellular models. We show that alteration of lysosomal calcium reduced proliferation of neural progenitor cells and diminished apical tight junctions in early human cortical development, modeled using organoids derived from induced pluripotent stem cells. The phenotypes were corrected by modulating the lysosomal calcium channel TRPML1 using the drug ML-SA1. We performed RNA-sequencing in control and SPG11 organoids, either untreated or treated with ML-SA1 to identify pathways linking lysosomal dysfunction to proliferation of neural progenitor cells