Investigating the role of HERC2 and HERC2/UBE3A synergy towards the pathogenesis of Dup15q syndrome

Dup15q syndrome is a neurodevelopmental disorder caused by extra copies of the maternal chromosome 15q11.2-13.1 region, characterized by hypotonia, motor delays, epilepsy, and autism spectrum disorder (ASD). Current models of disease pathogenesis focus largely on UBE3A, a maternally expressed gene located within the duplicated region. While increased UBE3A gene dosage has been implicated in Dup15q syndrome, clinical observation of patients with isolated UBE3A microduplications and murine models replicating UBE3A overexpression demonstrate that elevated UBE3A levels alone are insufficient to fully explain disease pathology. HERC2, a protein encoded by another gene within the 15q11.2-13.1 region, has emerged as a potential contributor to disease pathology due to its ability to interact with UBE3A. This study investigates whether HERC2 modulates UBE3A function in a mouse model of HERC2 overexpression. In this study, I demonstrate that transgenic HERC2 protein is functional and retains the ability to interact with endogenous UBE3A through co-immunoprecipitation (co-IP). To assess whether this interaction facilitates potential regulation, I examined whether changes in HERC2 gene dosage affect UBE3A protein abundance and vice versa. Our results indicate that, while HERC2In addition, to evaluate the potential consequences of HERC2 overexpression on UBE3A activity, I quantified three previously identified UBE3A substrates; UBE3A, UCHL5, and UBLCP1, where I due to HERC2 overexpression. Although these findings suggest that HERC2 can interact with UBE3A in vitro, and UBE3A is a potential regulator of HERC2, the results likewise demonstrate limited impact of their interaction on target UBE3A substrates. Future experimentation using proteomic approaches to identify additional UBE3A substrates, followed by similar substrate analysis, may provide further insights into the molecular mechanisms underlying the HERC2-UBE3A interaction and the molecular mechanisms underlying Dup15q syndrome. Ultimately, this study holds strong clinical relevance in identifying other players in Dup15q syndrome, informing therapeutic strategies to improve existing disease treatment.