Variants affecting diverse domains of MEPE are associated with two distinct bone disorders, a craniofacial bone defect and otosclerosis

Genet Med. 2019 May;21(5):1199-1208. doi: 10.1038/s41436-018-0300-5. Epub 2018 Oct 5.

Abstract

Purpose: To characterize new molecular factors implicated in a hereditary congenital facial paresis (HCFP) family and otosclerosis.

Methods: We performed exome sequencing in a four-generation family presenting nonprogressive HCFP and mixed hearing loss (HL). MEPE was analyzed using either Sanger sequencing or molecular inversion probes combined with massive parallel sequencing in 89 otosclerosis families, 1604 unrelated affected subjects, and 1538 unscreened controls.

Results: Exome sequencing in the HCFP family led to the identification of a rare segregating heterozygous frameshift variant p.(Gln425Lysfs*38) in MEPE. As the HL phenotype in this family resembled otosclerosis, we performed variant burden and variance components analyses in a large otosclerosis cohort and demonstrated that nonsense and frameshift MEPE variants were significantly enriched in affected subjects (p = 0.0006-0.0060).

Conclusion: MEPE exerts its function in bone homeostasis by two domains, an RGD and an acidic serine aspartate-rich MEPE-associated (ASARM) motif inhibiting respectively bone resorption and mineralization. All variants associated with otosclerosis are predicted to result in nonsense mediated decay or an ASARM-and-RGD-truncated MEPE. The HCFP variant is predicted to produce an ASARM-truncated MEPE with an intact RGD motif. This difference in effect on the protein corresponds with the presumed pathophysiology of both diseases, and provides a plausible molecular explanation for the distinct phenotypic outcome.

Keywords: MEPE; craniofacial bone disorder; hearing loss; hereditary congenital facial paresis; otosclerosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bone and Bones / metabolism
  • Extracellular Matrix Proteins / genetics*
  • Extracellular Matrix Proteins / metabolism
  • Facial Paralysis / congenital*
  • Facial Paralysis / etiology
  • Facial Paralysis / genetics
  • Facial Paralysis / metabolism
  • Family
  • Female
  • Genetic Diseases, X-Linked / genetics
  • Genetic Variation / genetics
  • Glycoproteins / genetics*
  • Glycoproteins / metabolism
  • Hearing Loss / genetics
  • Heterozygote
  • Humans
  • Male
  • Otosclerosis / genetics*
  • Pedigree
  • Phenotype
  • Phosphoproteins / genetics*
  • Phosphoproteins / metabolism
  • Whole Exome Sequencing / methods

Substances

  • Extracellular Matrix Proteins
  • Glycoproteins
  • MEPE protein, human
  • Phosphoproteins

Supplementary concepts

  • Facial paresis, hereditary, congenital