Characterization of the CYP11A1 Nonsynonymous Variant p.E314K in Children Presenting With Adrenal Insufficiency.

Context: Cholesterol side-chain cleavage enzyme (P450scc), encoded by CYP11A1, catalyzes the first step of steroidogenesis. Complete P450scc deficiency leads to primary adrenal insufficiency (PAI) and 46,XY disordered sexual development. Partial impairment can cause variable adrenal and gonadal dysfunction. Objective: Our aim was to evaluate the effects of the CYP11A1 variant p.E314K, identified in patients with PAI, specifically on P450scc enzyme stability and function. Patients and Methods: We studied four boys from two unrelated families presenting with PAI during childhood (3.6 to 9 years old). All patients were compound heterozygous for c.940G>A (p.E314K), a CYP11A1 nonsynonymous variant likely to be pathogenic by some but not all in silico prediction models, and c.835delA (p.I79Yfs*10), a known pathogenic variant. HEK293T cells were transfected with wild type (WT) and p.E314K mutant vectors, and a cycloheximide chase assay was performed to analyze protein stability. Pregnenolone production was assayed from cells expressing WT and p.E314K-F2 fusion proteins. Results: Two boys experienced spontaneous puberty but then developed evidence of primary gonadal failure at 14 and 18 years old. Two boys had testicular adrenal rest tumor (TART), detected by ultrasound at ages 8.6 and 16 years. Compared with WT, mutant protein synthesis was reduced (P = 0.0006) with increased protein turnover, and mutant P450scc half-life was decreased by ~50%. p.E314K mutant P450scc retained 60% of WT enzymatic activity (P = 0.007). Conclusions: The CYP11A1 p.E314K variant impairs P450scc stability and is a possible cause of PAI in childhood. Pathogenic CYP11A1 variants potentially affect both adrenal and gonadal function, and male patients may develop TART.