Cholesterol as a synaptogenic factor involved in the development of proper synaptic structure in an hiPSC-derived neurons model of Rett syndrome

Astrocytes role is to provide support to neurons both metabolically and functionally. Most importantly, during neuronal development astrocytes provide synaptogenic factors among with cholesterol is of paramount importance. In Rett syndrome the lack of MeCP2 function induces astrocytes to either secrete synaptotoxic factors and lack in the production of trophic molecules. Previous work from our laboratory showed an increased release of IL-6 from Mecp2-KO astrocytes with detrimental effects1, now we are investigating the effect of the lack of cholesterol production on synapses maturation. Evidence from primary cell culture showed a deregulation of genes involved in cholesterol metabolisms in astrocytes, biochemical investigations were inconclusive about the altered cholesterol production and release in the culture medium from astrocytes depending on the expression of their MeCP2 allele, thus pinpointing that the mechanism could be different from the secretion per se. Nonetheless, functional data support a defective role of cholesterol in Mecp2-KO astrocytes as stated by analysis of synapses maturation in term of Synapsin1/2 and Shank2 puncta presence and their colocalization, an indication of synapses maturity. Taking advantage of an engineered iPSC line able to differentiate in glutamatergic neurons by doxyciclin-induced Neurogenin2 expression2 we are investigating deficiency in synapse formation and eventual cholesterol role in this process comparing CRISPR-Cas9-edited MECP2-KO and isogenic control iPSCs.