ESPE Abstracts (2021) 94 P1-49

Sex Endocrinology and Gonads A

Biallelic PPP2R3C mutations are associated with partial and complete gonadal dysgenesis in 46,XY and 46,XX individuals

Dilek Cicek1, Nick Warr2, Gozde Yesil3, Hatice Kocak Eker4, Firdevs Bas5, Sukran Poyrazoglu5, Feyza Darendeliler5, Gul Direk1, Nihal Hatipoglu1, Mehmet Eltan6, Busra Gurpinar Tosun6, Sare Betul Kaygusuz6, Tuba Seven Menevse6, Serap Turan6, Abdullah Bereket6, Andy Greenfield2 & Tulay Guran6


1Erciyes University, School of Medicine, Department of Paediatric Endocrinology and Diabetes, Kayseri, Turkey; 2Mammalian Genetics Unit, Medical Research Council Harwell Institute, Harwell, Oxfordshire, United Kingdom; 3Istanbul University, School of Medicine, Department of Medical Genetics, Istanbul, Turkey; 4Konya Training and Research Hospital, Department of Medical Genetics, Konya, Turkey; 5Istanbul University, School of Medicine, Department of Pediatric Endocrinology and Diabetes, Istanbul, Turkey; 6Marmara University, School of Medicine, Department of Paediatric Endocrinology and Diabetes, Istanbul, Turkey

Context: PPP2R3C encodes the B”gamma regulatory subunit of the protein phosphatase 2A (PP2A), which is a serine/threonine phosphatase involved in the phospho-regulation processes of mammalian cells. We have recently reported homozygous and heterozygous mutations in PPP2R3C in patients with syndromic 46,XY complete gonadal dysgenesis (MEGD syndrome) and impaired spermatogenesis, respectively. In this study, we have further investigated the role of PPP2R3C in the etiology of gonadal dysgenesis.

Method: We sequenced the PPP2R3C gene in four new patients from four unrelated families. The clinical, laboratory and molecular characteristics were investigated. We have also determined the requirement for Ppp2r3c in mice using CRISPR/Cas9 genome editing.

Results: We have identified a homozygous c.578T>C (p.L193S) PPP2R3C variant in one 46,XX girl with primary gonadal insufficiency, 2 girls with 46,XY complete gonadal dysgenesis, and one undervirilized boy with 46,XY partial gonadal dysgenesis. The patients with complete gonadal dysgenesis had low gonadal and adrenal androgens, low AMH and high FSH and LH concentrations. All patients manifested characteristic features of MEGD syndrome (typical facial gestalt, low birth weight, myopathy, rod and cone dystrophy, anal atresia, omphalocele, sensorineural hearing loss, dry and scaly skin, skeletal abnormalities, renal agenesis, and neuromotor delay). We then generated mice (C57BL6/N) lacking functional Ppp2r3c by using CRISPR/Cas9 genome editing to delete an 1100 bp segment encoding a critical early exon. Heterozygotes for the deletion allele appeared overtly normal and fertile. Timed mates between heterozygous animals were used to generate homozygotes at 14.5 days post coitum (dpc) in order to allow inspection of the fetal gonads after the sex-determining period. However, genotyping revealed that no homozygous animals were detected at this stage. Inspection of embryos at earlier stages (9.5 dpc and 8.5 dpc) revealed evidence of dead embryos. Genotyping indicated that this material was derived exclusively from homozygous embryos. We conclude that loss of function of Ppp2r3c is not compatible with viability in mice and results in embryonic death from 7.5 dpc or earlier.

Conclusion: Our data indicate essential roles for PPP2R3C in mouse and human development. Germline homozygous mutations in human PPP2R3C are associated with distinctive syndromic gonadal dysgenesis of varying severity in both 46,XY and 46,XX individuals.