Sex determination (SD) is embryonic initiation of differentiation as either male or female, that is controlled by mutually antagonistic, but poorly characterized regulatory networks which canalize development down one pathway, whilst actively repressing the other (Capel, 2017). Errors in SD result in disorders in sex development (DSD), a complex group of rare congenital conditions with discordant chromosomal, gonadal or anatomical sex. Using whole exome sequencing, we identified frequent pathogenic variants in DHX37 associated with 46,XY DSD (McElreavey et al., 2020).
DHX37 is an evolutionarily conserved, ubiquitously expressed RNA helicase involved in ribosome biogenesis in eukaryotic cells (Boneberg et al., 2019). Evidence in support of specific biological functions for DHX37, independent of its role in ribosome biogenesis, are indicated by both zebrafish studies (Hirata et al., 2013) and human genome wide screens to identify factors that modulate human T cell function (Liu et al., 2022).
How variants in DHX37 cause 46,XY DSD is unclear. The variants associated with DSD are predicted to be deleterious for the protein function. However, our preliminary data suggests to the contrary. We hypothesize a gain of function by DHX37 variants, that disrupt determination/maintenance of testicular tissue during development. To understand this, we have cloned DHX37 upstream of the RNA-editing enzyme, ADAR, catalytic domain. ADAR deaminates adenosines to inosines, which are recognized as guanosine. We have also introduced DSD causing variants of DHX37 in these constructs and transfected them in the in-vitro derived Sertoli cells (Gonen et al., in press). This project proposes to use RNA-sequencing to identify and compare the RNA targets of the WT and mutants DHX37 in these in-vitro Sertoli-like cells. This will allow us to understand the role of DHX37 in human testicular development and the molecular events associated with sex-reversal in the patients with DHX37 variants.
