The goal of this proposal is to identify how abnormalities of brain development in monogenic disorders involving the PI3K-mTOR pathway (e.g., tuberous sclerosis complex [TSC]) lead to alterations in circuit and in information processing. TSC is a classical disorder of the mTOR signaling pathway due to second-hit somatic mutations in TSC1 or TSC2 leading to mTOR hyperactivity and developmental malformations associated with seizures and neurological deficits. 50-60% of children with TSC have severe cognitive deficits and autism accompanied with abnormal sensory processing. Published work from our lab identified a combination of molecular and cellular alterations in murine neurons with hyperactive mTOR. These alterations include neuron misplacement and dysmorphogenesis that are conserved across cortical regions and between mice and humans. However, the impact of these defects on circuit formation and information processing, and the dependence on mTOR and downstream pathways at the circuit level remain unclear. Here, we propose to use the mouse barrel cortex as a well-established model system to start addressing the link between neuronal abnormalities and alterations in circuitry and sensory processing. Building from our previous findings, we hypothesize that dysmorphogenesis of layer (L) 4 barrel cortex neurons in TSC contributes to mTOR-dependent abnormalities in circuitry, functional connectivity, and sensory responses. We have the following two aims: (1) To test the hypothesis that mTOR hyperactivity in L4 neurons alters barrel circuitry and functional connectivity. (2) To test the hypothesis that reducing mTOR activity during a brief critical window and normalizing two downstream pathways prevent abnormalities in circuit and sensory responses in TSC condition. To address these aims, we will use in utero electroporation to express RhebCA and generate humanized Tsc1 mutations using CRISPR/Cas9 in L4 neurons of the barrel cortex.
Fifty to sixty percent of children with the neurodevelopmental disorder, tuberous sclerosis complex (TSC), have severe cognitive deficits and autism accompanied with abnormal sensory processing. This proposal aims at understanding how diseased neurons in individuals with TSC lead to defects in circuit formation and sensory information processing. We will also examine whether a transient treatment with rapamycin is sufficient to rescue alterations in the circuitry and sensory responses.
