Oral Virtual Presentation (Virtual only) ESA-SRB-ANZBMS 2021

A biallelic variant in MRPL50 is associated with syndromic premature ovarian insufficiency in twin sisters (#32)

Shabnam Bakhshalizadeh 1 2 , Rajini Sreenivasan 1 2 , Katrina M. Bell 3 , Nicole Siddall 4 , Franca Casagranda 4 , Sadishkumar Kamalanathan 5 , Daniella H. Hock 6 , Jocelyn Van den bergen 1 , Gorjana Robevska 1 , Katie Ayers 1 2 , David A. Stroud 6 , David R. Thorburn 2 7 , Gary R. Hime 4 , Andrew H. Sinclair 1 2 , Elena J. Tucker 1 2
  1. Murdoch Children's Research Institute, Melbourne, VIC, Australia
  2. Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia
  3. Bioinformatic Methods, Murdoch Children's Research Institute, Melbourne, VIC, Australia
  4. Department of Anatomy and Physiology, University of Melbourne, Melbourne, VIC, Australia
  5. Department of Endocrinology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry 605006, India
  6. Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
  7. Brain and Mitochondrial Research Group, Murdoch Children’s Research Institute, Melbourne, VIC, Australia

Premature ovarian insufficiency (POI) is a common cause of infertility in young women. POI is associated with menstrual disturbance (primary or secondary amenorrhea) with elevated gonadotropins before the age of 40 and affects up to 1 in 100 women. This condition is highly heterogeneous with over 50 causative genes known so far, however, these explain only a minority of cases. Using whole exome sequencing, we identified an MRPL50 homozygous missense variant (c.335T>A; p.Val112Asp) shared by twin sisters presenting with POI, sensorineural hearing loss, kidney and heart dysfunction. The identified variant is rare, affects a highly conserved residue and is predicted to be detrimental via in silico analyses.  MRPL50 encodes a component of the mitochondrial ribosomal large subunit. Using quantitative proteomics on patient fibroblasts, we demonstrated a loss of MRPL50 protein and an associated destabilisation of the large subunit of the mitochondrial ribosome while the small subunit was preserved. The mitochondrial ribosome is responsible for the translation of subunits of the mitochondrial oxidative phosphorylation machinery, and we found patient fibroblasts have a mild but significant decrease in mitochondrial complex I. These data support a biochemical phenotype associated with MRPL50 variants. To validate the association of the MRPL50 variants with the clinical phenotype, we are using RNAi and CRISPR-Cas9 mediated technology to generate knockdown and knockout/knockin Drosophila melanogaster disease models for our MRPL50 variant, which affects a well-conserved residue in flies. Preliminary data indicate that flies with MRPL50 knockdown have disrupted ovarian development/function. We will continue to monitor MRPL50 fly models for fertility, ovarian morphology and the development of both germline and somatic cells in ovaries. In conclusion, we have shown that a MRPL50 missense variant destabilises the mitochondrial ribosome and leads to syndromic POI in humans. Our findings highlight the role of mitochondria in the development and function of human ovaries.