Genetic alterations in SUPT6H are associated with neurodevelopmental disorders

Genetic variants affecting the RNA polymerase II complex have been associated with various neurodevelopmental disorders (NDDs). SUPT6H, an RNA polymerase II-associated elongation factor and a histone chaperone, plays a critical role in transcriptional regulation. However, the contribution of SUPT6H variants to human NDDs and the phenotypic consequences of its loss-of-function in vivo remain unexplored. Here, we analyzed 18 published sporadic single-nucleotide variants (SNVs) of SUPT6H associated with human developmental disorders. Molecular modeling suggests that these variants are likely deleterious, leading to loss of function. Consistent with this, homozygous or heterozygous Supt6 null mice exhibit embryonic lethality, underscoring its essential role during development. To investigate the postnatal consequences of Supt6 deficiency, we generated conditional Supt6 knockout (KO) mice with targeted deletion in parvalbumin-expressing GABAergic interneurons (cKO^PV). Homozygous Supt6 cKO^PV mice displayed motor defects and behavioral seizures, whereas heterozygous counterparts exhibited behavioral phenotypes relevant to neuropsychiatric disorders despite normal motor activity. Notably, both heterozygous and homozygous Supt6 cKO^PV mice showed a significant reduction in parvalbumin-expressing neurons compared to wild-type controls. These findings establish a direct link between Supt6 loss-of-function and neurodevelopmental phenotypes, highlighting its critical role in maintaining interneuron populations and neural circuit integrity. Altogether, our results suggest that deleterious SUPT6H variants may contribute to the etiology of NDDs, providing valuable insights into its function and potential as a therapeutic target.