Variants in SART3 cause a novel spliceosomopathy characterised by failure of testis development and neuronal defects

Squamous cell carcinoma antigen recognized by T cells 3 (SART3) is an RNA binding protein that regulates a diverse array of biological processes, including recycling small nuclear ribonucleic acids (snRNAs) back to the spliceosome. Here we describe nine individuals from six independent families with a multisystem disorder, characterised by intellectual disability, developmental delay, brain anomalies and 46, XY-specific gonadal dysgenesis, who harbour recessive variants in the SART3 gene. Knockdown of the fly orthologue of SART3, Rnp4f, demonstrates a conserved role in neuronal and testicular development. Human induced pluripotent stem cells (iPSCs) carrying patient SART3 variants have disrupted neuronal and gonadal differentiation in vitro. These iPSCs have significant disruption to multiple signalling pathways and complexes, including spliceosome components and mRNA splicing. We propose that biallelic variants in the SART3 gene underlie a novel spliceosomopathy characterised by neuronal defects and testicular dysgenesis.