8368 Functional Evaluation Of Novel CYP21A2 Variants: Expanding The Genetic Basis Of Non-classic CAH

Abstract Disclosure: A. Matveeva: None. Y. Xu: None. V. Tardy-Guidollet: None. A.V. Pandey: None. Introduction: Congenital adrenal hyperplasia (CAH) comprises a group of autosomal recessive genetic disorders affecting the production of glucocorticoids, mineralocorticoids, and gonadocorticoids. In approximately 95% of cases, CAH results from a deficiency in CYP21A2. A Non-Classic form of CAH (NC-CAH) arises when CYP21A2 activity decreases to 20-50% of the normal level, occurring at an estimated frequency of 1 in 200 - 1000 individuals. The clinical picture is characterized by the accumulation of androgen precursors, causing hirsutism, acne, metabolic syndrome, menstrual irregularities, infertility in females, and androgenic alopecia, oligospermia in males. Methods: We selected mutations from CYP21A2 sequence data of patients with NC-CAH symptoms admitted to CHU Lyon, France (L49V, A81T, R125G, I161T, L199F, L289H, L289F, V306D, L462P). Additional variants were selected from the SNP databases (dbSNP, gnomAD, ClinVar) based on a high frequency in humans (H393Q, P387L, T201A, S203G S274Y, S494N, R76K, Leu10del). All variants underwent in silico assessment considering evolutionary, structural, and functional aspects (ConSurf, Predict SNP2, CADD, DANN, FATHMM, FunSeq2, GWAVA, PANTHER, SNPs&GO, PhD-SNP, SIFT, SNAP, Meta-SNP, Polyphen2, HDIV, DUET). The CYP21A2 proteins carrying the mutations were overexpressed in HEK 293T cells. We evaluated CYP21A2 enzyme activities by measuring the conversion of 14C-Progesterone into 11-deoxycortisol by thin layer chromatography and autoradiography. Samples were tested in duplicates, using the activity of WT CYP21A2 as a control. Results: Computational analysis revealed that A81T, R125G, I161T, and L289H substitutions significantly impair protein structure, while other variants showed moderate effects. Except for L199F, all patient-derived variants exhibited reduced 21-hydroxylase (CYP21A2) activity associated with NC-CAH phenotypes. Variants from databases did not demonstrate a significant loss of function related to CAH. Conclusion: In this study we investigate the pathogenicity of uncharacterized CYP21A2 variants in relation to non-classic congenital adrenal hyperplasia (NC-CAH), contributing to a better understanding of associated phenotypes. The findings, particularly the identification of novel mutations and the assessment of their impact on CYP21A2 activity, hold promise for improving diagnosis and treatment strategies aimed at mitigating severe outcomes of NC-CAH, such as miscarriages or irreversible alopecia. It also raises awareness among heterozygous carriers, assisting in family planning and medical decisions. Presentation: 6/1/2024