Sex-specific mechanisms of cortical circuit dysfunction in a mouse ASD model

Increasing evidence indicates that Autism Spectrum Disorder (ASD) is manifests differently in males and females behaviorally and affects brain function and connectivity differently between sexes. There has been little known of how ASD genes affect the female brain on a cellular and microcircuit level. During the previous grant period we discovered that deletion of the ASD-risk gene, Pten (Phosphatase and tensin homolog deleted on chromosome 10), in neocortical pyramidal neurons (NSEPten KO) resulted in robust hyperexcitability of local neocortical circuits in female, but not male, mice, observed as prolonged, spontaneous persistent activity states (UP states). We also demonstrated that circuit hyperexcitability in NSEPten KO mice is mediated by enhanced signaling of metabotropic glutamate receptor 5 (mGluR5) and estrogen receptor α (ERα) to ERK and de novo protein synthesis selectively in Pten deleted female neurons. Pten deleted Layer 5 cortical neurons have a female-specific increase in mGluR5 levels and mGluR5-driven protein synthesis. In addition, mGluR5-ERα complexes are elevated in female cortex and genetic reduction of ERα in Pten KO cortical neurons rescues circuit excitability, protein synthesis and enhanced neuron size selectively in females. Abnormal timing and hyperexcitability of neocortical circuits in female NSEPten KO mice are associated with deficits in temporal processing of sensory stimuli and social behaviors as well as mGluR5-dependent seizures. Female-specific cortical hyperexcitability and mGluR5-dependent seizures are also observed in a human disease relevant mouse model, germline Pten+/- mice. Our results demonstrate sex-specific dysfunction of developing cortical circuits with loss of function of a high-confidence ASD-risk gene. Importantly, we demonstrate a distinct, female-specific dysfunction of mGluR5- ERα signaling pathways that drive excitability. For the Phase 2 extension of this work, we propose to determine the female-specific, Pten-regulated cellular and molecular alterations in cortical neurons that give rise to hyperexcitability of circuits. In Aim 1, we will determine the sex-specific, mGluR5 and ERα -regulated neuronal and synaptic properties in L5 PTEN KO neurons. In Aim 2 we will determine the sex- specific, PTEN-regulated ribosome- associated transcripts in L5 cortical neurons and their regulation by mGluR5 and ERα. Our results reveal sex-specific and estrus cycle-dependent deficits in sensory-processing in Pten loss of function models. In Aim 3 we will determine if a reduction in mGluR5 or ERα function corrects these sensory processing deficits and in Aim 4, we will examine the role of estrogen and estrus cycle in dysfunction of developing and mature cortical circuits and in vivo resting and sensory-driven EEG phenotypes in Pten loss of function models. Results of these aims are expected to provide knowledge of the sex-specific mechanisms by which ASD-risk genes regulate the development and function of sensory cortical circuits and affect sensory processing.