Inherited Missense Mutation Occurring in Arginine76 of the SRY Gene Does Not Account for Familial 46, XY Sex Reversal

NR5A1/SF-1 Collaborates with Inhibin α and the Androgen Receptor

Steroidogenic factor 1 (SF-1) is a nuclear receptor that regulates steroidogenesis and reproductive development. NR5A1/SF-1 variants are associated with a broad spectrum of phenotypes across individuals with disorders of sex development (DSDs). Oligogenic inheritance has been suggested as an explanation. SF-1 interacts with numerous partners. Here, we investigated a constellation of gene variants identified in a 46,XY severely undervirilized individual carrying an ACMG-categorized 'pathogenic' NR5A1/SF-1 variant in comparison to the healthy carrier father. Candidate genes were revealed by whole exome sequencing, and pathogenicity was predicted by different in silico tools. We found variants in NR1H2 and INHA associated with steroidogenesis, sex development, and reproduction. The identified variants were tested in cell models. Novel SF-1 and NR1H2 binding sites in the AR and INHA gene promoters were found. Transactivation studies showed that wild-type NR5A1/SF-1 regulates INHA and AR gene expression, while the NR5A1/SF-1 variant had decreased transcriptional activity. NR1H2 was found to regulate AR gene transcription; however, the NR1H2 variant showed normal activity. This study expands the NR5A1/SF-1 network of interacting partners, while not solving the exact interplay of different variants that might be involved in revealing the observed DSD phenotype. It also illustrates that understanding complex genetics in DSDs is challenging.

In-frame deletion of SMC5 related with the phenotype of primordial dwarfism, chromosomal instability and insulin resistance

BACKGROUND

SMC5/6 complex plays a vital role in maintaining genome stability, yet the relationship with human diseases has not been described.

METHODS

SMC5 variation was identified through whole-exome sequencing (WES) and verified by Sanger sequencing. Immunoprecipitation, cytogenetic analysis, fluorescence activated cell sorting (FACS) and electron microscopy were used to elucidate the cellular consequences of patient's cells. smc5 knockout (KO) zebrafish and Smc5K371del knock-in mouse models were generated by CRISPR-Cas9. RNA-seq, quantitative real-time PCR (qPCR), western blot, microquantitative computed tomography (microCT) and histology were used to explore phenotypic characteristics and potential mechanisms of the animal models. The effects of Smc5 knockdown on mitotic clonal expansion (MCE) during adipogenesis were investigated through Oil Red O staining, proliferation and apoptosis assays in vitro.

RESULTS

We identified a homozygous in-frame deletion of Arg372 in SMC5, one of the core subunits of the SMC5/6 complex, from an adult patient with microcephalic primordial dwarfism, chromosomal instability and insulin resistance. SMC5 mutation disrupted its interaction with its interacting protein NSMCE2, leading to defects in DNA repair and chromosomal instability in patient fibroblasts. Smc5 KO zebrafish showed microcephaly, short length and disturbed glucose metabolism. Smc5 depletion triggers a p53-related apoptosis, as concomitant deletion of the p53 rescued growth defects phenotype in zebrafish. An smc5K371del knock-in mouse model exhibited high mortality, severe growth restriction and fat loss. In 3T3-L1 cells, the knockdown of smc5 results in impaired MCE, a crucial step in adipogenesis. This finding implies that defective cell survival and differentiation is an important mechanism linking growth disorders and metabolic homeostasis imbalance.