ESPE Abstracts

Background: Primary ovarian failure is (POF) characterised by primary amenorrhoea or early menopause in females. Minichromosome maintenance 10 (MCM10) is a gene involved in DNA damage repair, DNA replication and chromatin formation has received attention as a potential genetic etiology for neoplastic disease. Drosophila with mutated MCM10 have subfertility and dysfunction in female germline development. In humans, biallelic mutations of the MCM10 causes NK cell deficiency.

Objective and clinical phenotype: To elucidate the etiology of POF in an Ethiopian 17y old female, from a nonconsanguineous family presenting with absence of spontaneous pubertal development and primary amenorrhea. The Karyotype was 46,XX and gonadotrophins were elevated (LH – 22.7IU/l FSH – 53.7IU/l). Pelvic MRI detected a small uterus, but no ovaries could be seen.

Methods and results: Whole exome sequencing, revealed the patient to have a novel homozygous mutation in the MCM10 gene: c.T1553C, p.F518S. The healthy parents and sister were heterozygous for this mutation. AA F518 is highly conserved among species. Structure analysis revealed that MCM10 works in a hexamer and that the mutation (F-S transition) destabilizes DNA binding and the secondary structure in its region. Chromosomal breakage assays on patient derived B-cells using DNA damage agent Mitomycin C (300mM) resulted with increased number of breaks per cell, (3.08±0.46 vs 1.90±0.35, P=0.005) when compared to unrelated control. DNA combing assays performed on patient derived fibroblasts showed slower progression of the replication fork when compared to control (2.55±0.06 vs. 2.09±0.04 Kbp/min, P=5X10-11).

Conclusions: The novel MCM10 p.F518S mutation cause increase rate of chromosomal breakage and slower progression of the replication fork, p.F518S thereby compromising meiosis and oocyte formation in humans resulting in ovarian dysgenesis. As such, MCM10 a component of the pre-replication complex, is crucial for gonadal development and maintenance in females. When mutated MCM10 is shown here to be a novel genetic etiology for ovarian dysgenesis. These findings re-emphasize the importance of meiosis, homologous recombination and normal DNA damage repair mechanism in ovariogenesis.