Impatto delle 16p11.2 Copy Number Variants sull'espansione e il differenziamento dei progenitori della corteccia cerebrale

Neurodevelopmental Disorders (NDDs) encompass a broad spectrum of clinical conditions affecting cognitive, behavioral, and motor functions. These include attention deficit hyperactivity disorder (ADHD), autism spectrum disorders (ASD), intellectual disabilities, Epilepsy, and Schizophrenia. The etiology of these disorders is complex and multifactorial, with a strong genetic component. Among the key genetic risk factors, Copy Number Variants (CNVs), which involve deletions or duplications of DNA segments, have been significantly associated with several neurodevelopmental conditions, especially due to their impact on critical developmental processes in the cerebral cortex. A particularly relevant CNV is the 16p11.2 region, which has been implicated in ASD, intellectual disability, and other neuropsychiatric abnormalities. Alterations in this locus can differentially affect brain development and plasticity depending on whether a deletion or duplication occurs. My thesis investigates the impact of 16p11.2 CNVs on the proliferation and differentiation of neural progenitors during cortical development, with a focus on the medial cortex of E14.5 mouse embryos, a critical stage of corticogenesis characterized by both symmetric proliferative and asymmetric neurogenic divisions. Using fluorescent and brightfield immunohistochemistry, we analyzed key markers of cortical progenitor populations: Pax6 (radial glial cells), Tbr2 (intermediate progenitors), Cyclin D1 (G1 phase progression), and Ki67 (active proliferation). Marker expression was quantified across different cortical layers (ventricular zone, subventricular zone), and statistical analyses were conducted to compare wild-type, deletion, and duplication groups. Our findings indicate that the 16p11.2 microdeletion is associated with a reduction in Pax6+ progenitors in the ventricular zone and a significant decrease in Tbr2+ cells in the subventricular zone. Pax6/Tbr2 double-positive cells- likely representing a transitional progenitor state4were reduced and abnormally distributed, particularly in deletion models. Cyclin D1 expression appeared reduced and shifted toward the deeper ventricular zone in deletion models, suggesting a prolonged G1 phase that could affect progenitor cell cycle progression. In duplication models, Cyclin D1 was diffusely decreased across the VZ/SVZ and into the intermediate zone, indicating a general reduction in cell cycle activity. Ki67 analysis revealed increased expression and broader distribution in deletion models, suggesting extended proliferative activity, while a general decrease in Ki67+ cells was observed in duplications, pointing to reduced proliferative capacity. These results demonstrate that 16p11.2 CNVs disrupt early neurogenic processes by altering cell cycle dynamics and progenitor differentiation. Such disruptions may have long-term consequences for cortical architecture, particularly for the production and integration of glutamatergic neurons, the principal excitatory neuronal population. Impaired generation of these neurons could contribute to excitation/inhibition imbalances a hallmark of ASD, schizophrenia, and other psychiatric disorders. Aberrant cortical development may also compromise circuit formation and higher cognitive functions such as attention, memory, and emotional regulation, with possible implications for adult brain function. Unraveling the cellular and molecular mechanisms underlying these changes is essential to developing early diagnostic tools and therapeutic strategies aimed at preventing irreversible neurobiological damage in neurodevelopmental disorders.