Characterization of the Natural History of Microduplication Syndrome 7q11.23

Plain-language summary

7q11.23 duplication syndrome (7q duplication syndrome/7DUP) is caused by a microduplication of the 7q11.23 chromosomal region, encompassing 26-28 genes, including the GTF2I gene. This syndrome, often considered as a "mirror" phenotype of Williams-Beuren syndrome (WBS), is characterized by a wide range of neurodevelopmental impairments, including a neurodevelopmental disorder (NDD), autism spectrum disorders (ASD), selective mutism, mild dysmorphic features, and aortic dilation. Notably, one of the core clinical features of 7DUP is socialization impairment, which varies in severity across individuals. The GTF2I gene, identified as critical in the pathogenesis of both WBS and 7DUP, exhibits opposite expression patterns in the two syndromes, with reduced expression in WBS and overexpression in 7DUP. The gene's dysregulation in 7DUP plays a pivotal role in the pathogenesis of the associated NDD and social deficits. Despite progress in characterizing the genetic underpinnings of 7DUP, there remains a critical gap in understanding the developmental trajectory of socialization impairments in affected individuals, especially during their transition through different developmental stages, from early childhood to adulthood. Recent advancements in the study of neuronal models derived from induced pluripotent stem cells (iPSCs) and brain organoids have shed light on the molecular mechanisms driving 7DUP-related NDDs. Histone deacetylase inhibitors (HDAC inhibitors), which have been widely used in oncology, have shown promising preliminary results in reducing abnormal GTF2I expression in glutamatergic neurons differentiated from 7DUP patient-derived iPSCs. Preclinical studies in mouse models further demonstrated that these drugs can ameliorate socialization deficits, highlighting their therapeutic potential in addressing the core neurodevelopmental challenges in 7DUP. However, despite these advancements, no longitudinal clinical studies have characterized the developmental trajectory of socialization impairments in 7DUP patients. Understanding this trajectory is critical, as it can inform the timing and potential impact of therapeutic interventions, such as HDAC inhibitors. Given the complexity and variability of the 7DUP phenotype, a comprehensive clinical characterization of socialization impairments across the lifespan is essential to improve diagnostic accuracy, optimize intervention strategies, and ultimately improve patient outcomes. The aim of this research is to characterize the developmental trajectory of socialization impairments in patients with 7DUP, from early childhood through adulthood. By identifying patterns of socialization difficulties, this innovative study will allow to efficiently prepare future therapeutic trials, by specifying the phenotype of the patients, and by determining the most relevant outcome measures, taking into account, on one hand, their neurodevelopmental involvement and, on the other hand, the type of experimental design to be used in the context of rare diseases.

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