Expression of MEGAP mRNA during embryonic development.

Mental retardation (MR) affects up to two percent of the population and is usually accompanied by impaired learning and memory. MR is frequently associated with mutations of genes involved in Rho signal transduction cascades. Rho signal transduction pathways regulate axonal and dendritic growth during embryonic development and morphological adaptations of dendritic spines during synaptic plasticity in adult neurons. The MEGAP/SRGAP3 protein is part of the Rho signal transduction cascades. Mutation of MEGAP (Mental disorder associated GTPase-activating protein) gene is present in some patients who have MR, ataxia and monosomy for the distal portion of the short arm of chromosome 3. Here, we investigated the pattern of mouse MEGAP mRNA expression during embryonic development. Mouse embryos and brain sections from stage E10 to adults were analysed by in-situ hybridisation for MEGAP transcript in whole-mount and in brain sections. We demonstrate here robust expression of MEGAP mRNA in the whole central nervous system of E10 embryos. At E12, we also detected MEGAP in dorsal root ganglia. This pattern narrows in adult animals into an expression mainly in hippocampus and cortex. Our findings support the presumed role of MEGAP in Rho-associated MR.