Optimizing care for MRKH patients: From malformation screening to uterus transplantation eligibility.

INTRODUCTION: Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome with utero-vaginal aplasia is the most severe form of the Müllerian duct anomalies and can be associated with extra-genital abnormalities such as renal or skeletal anomalies, hearing loss, or cardiac defects. The past two decades have witnessed significant advances both in understanding the etiologies of MRKH and in the development of fertility treatments such as uterine transplantation. The present work aimed to determine the rate of women with MRKH syndrome who underwent optimal initial management (after comprehensive malformation assessment) and to establish the rate of patients eligible for uterine transplantation (i.e., those with a vaginal length ≥7 cm without reconstruction using a bowel segment, and an anti-Müllerian hormone level >1.5 ng/mL before 35 years). MATERIAL AND METHODS: Cohort study of 85 women with MRKH syndrome consulting in our tertiary center. RESULTS: 62.4% of women with MRKH syndrome had an exhaustive malformative evaluation according to the French guidelines (Protocole National de Diagnostic et de Soin [PNDS]), of which 76.5% had associated malformations (MRKH type II). Pedigree, when available, showed a family history of infertility or a urogenital tract spectrum anomaly in 60% of cases. Concerning the uterine transplantation selection criteria, when evaluated, 22.6% of women had an anti-Müllerian hormone level <1.5 ng/mL and 36% a vaginal length <7 cm. On the 21 women with complete evaluation of both primary and secondary outcomes, 14 of them would be eligible for a uterine transplantation program at the time of consultation according to the main inclusion criteria of uterine transplantation program. CONCLUSIONS: Women with MRKH syndrome are often inadequately explored for associated malformations. Early assessment and monitoring of the ovarian reserve is key for fertility preservation, especially in the era of uterine transplantation.

STAG3 homozygous missense variant causes primary ovarian insufficiency and male non-obstructive azoospermia.

Infertility, a global problem affecting up to 15% of couples, can have varied causes ranging from natural ageing to the pathological development or function of the reproductive organs. One form of female infertility is premature ovarian insufficiency (POI), affecting up to 1 in 100 women and characterised by amenorrhoea and elevated FSH before the age of 40. POI can have a genetic basis, with over 50 causative genes identified. Non-obstructive azoospermia (NOA), a form of male infertility characterised by the absence of sperm in semen, has an incidence of 1% and is similarly heterogeneous. The genetic basis of male and female infertility is poorly understood with the majority of cases having no known cause. Here, we study a case of familial infertility including a proband with POI and her brother with NOA. We performed whole-exome sequencing (WES) and identified a homozygous STAG3 missense variant that segregated with infertility. STAG3 encodes a component of the meiosis cohesin complex required for sister chromatid separation. We report the first pathogenic homozygous missense variant in STAG3 and the first STAG3 variant associated with both male and female infertility. We also demonstrate limitations of WES for the analysis of homologous DNA sequences, with this variant being ambiguous or missed by independent WES protocols and its homozygosity only being established via long-range nested PCR.

Gene Editing Corrects In Vitro a G > A GLB1 Transition from a GM1 Gangliosidosis Patient.

Ganglioside-monosialic acid (GM1) gangliosidosis, a rare autosomal recessive disorder, is frequently caused by deleterious single nucleotide variants (SNVs) in GLB1 gene. These variants result in reduced ß-galactosidase (ß-gal) activity, leading to neurodegeneration associated with premature death. Currently, no effective therapy for GM1 gangliosidosis is available. Three ongoing clinical trials aim to deliver a functional copy of the GLB1 gene to stop disease progression. In this study, we show that 41% of GLB1 pathogenic SNVs can be replaced by adenine base editors (ABEs). Our results demonstrate that ABE efficiently corrects the pathogenic allele in patient-derived fibroblasts, restoring therapeutic levels of ß-gal activity. Off-target DNA analysis did not detect off-target editing activity in treated patient's cells, except a bystander edit without consequences on ß-gal activity based on 3D structure bioinformatics predictions. Altogether, our results suggest that gene editing might be an alternative strategy to cure GM1 gangliosidosis.

Meiotic genes in premature ovarian insufficiency: variants in HROB and REC8 as likely genetic causes.

Premature ovarian insufficiency (POI), affecting 1 in 100 women, is characterised by loss of ovarian function associated with elevated gonadotropin, before the age of 40. In addition to infertility, patients face increased risk of comorbidities such as heart disease, osteoporosis, cancer and/or early mortality. We used whole exome sequencing to identify the genetic cause of POI in seven women. Each had biallelic candidate variants in genes with a primary role in DNA damage repair and/or meiosis. This includes two genes, REC8 and HROB, not previously associated with autosomal recessive POI. REC8 encodes a component of the cohesin complex and HROB encodes a factor that recruits MCM8/9 for DNA damage repair. In silico analyses, combined with concordant mouse model phenotypes support these as new genetic causes of POI. We also identified novel variants in MCM8, NUP107, STAG3 and HFM1 and a known variant in POF1B. Our study highlights the pivotal role of meiosis in ovarian function. We identify novel variants, consolidate the pathogenicity of variants previously considered of unknown significance, and propose HROB and REC8 variants as new genetic causes while exploring their link to pathogenesis.