Altered RNA-processing provides a mechanistic framework delineating human sex reversal associated with pathogenic variants in the RNA-helicase DHX37

Recurrent heterozygous missense variants in the highly conserved RNA-helicase DHX37, which is required for ribosome biogenesis, are a frequent cause of 46,XY sex-reversal or testis regression syndrome. How these missense variants specifically disrupt testis formation is unknown. Here, we demonstrate that mutant DHX37 proteins retain their ATPase activity and are not associated with stabilization of cellular {beta}-catenin. Transfection of DHX37 p.R674Q mutant protein in an in-vitro cellular model recapitulating human Sertoli cell formation, showed a reduced activation of pro-testis genes compared to the WT protein. The expression of a DHX37 mutant protein in in-vitro derived human Sertoli-like cells (iSLCs) was also associated with global changes in gene expression, predicted to impact basic cellular functions. To define RNA transcripts interacting with either the WT or a mutant (p.R674Q) protein, we combined HyperTRIBE and single-cell full-length RNA-sequencing approaches using iSLCs. Gene ontology analysis indicated that transcripts targeted by WT DHX37 were primarily associated with cytoskeleton organization, including cell motility and cell adhesion. However, in contrast transcripts targeted by the mutated DHX37 protein, were not only associated with cytoskeleton organization but also with protein degradation and cell death. These data provide mechanistic framework that may explain how variants in the DHX37 protein can result in 46,XY sex-reversal through altered RNA networks that are required for the formation and maintenance of the supporting cell lineages of the human testis.