Modifier variant of METTL13 suppresses human GAB1–associated profound deafness
Rizwan Yousaf, … , Thomas B. Friedman, Saima Riazuddin
Rizwan Yousaf, … , Thomas B. Friedman, Saima Riazuddin
Published February 6, 2018
Citation Information: J Clin Invest. 2018;128(4):1509-1522. https://doi.org/10.1172/JCI97350.
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Research Article Genetics Otology

Modifier variant of METTL13 suppresses human GAB1–associated profound deafness

Abstract

A modifier variant can abrogate the risk of a monogenic disorder. DFNM1 is a locus on chromosome 1 encoding a dominant suppressor of human DFNB26 recessive, profound deafness. Here, we report that DFNB26 is associated with a substitution (p.Gly116Glu) in the pleckstrin homology domain of GRB2-associated binding protein 1 (GAB1), an essential scaffold in the MET proto-oncogene, receptor tyrosine kinase/HGF (MET/HGF) pathway. A dominant substitution (p.Arg544Gln) of METTL13, encoding a predicted methyltransferase, is the DFNM1 suppressor of GAB1-associated deafness. In zebrafish, human METTL13 mRNA harboring the modifier allele rescued the GAB1-associated morphant phenotype. In mice, GAB1 and METTL13 colocalized in auditory sensory neurons, and METTL13 coimmunoprecipitated with GAB1 and SPRY2, indicating at least a tripartite complex. Expression of MET-signaling genes in human lymphoblastoid cells of individuals homozygous for p.Gly116Glu GAB1 revealed dysregulation of HGF, MET, SHP2, and SPRY2, all of which have reported variants associated with deafness. However, SPRY2 was not dysregulated in normal-hearing humans homozygous for both the GAB1 DFNB26 deafness variant and the dominant METTL13 deafness suppressor, indicating a plausible mechanism of suppression. Identification of METTL13-based modification of MET signaling offers a potential therapeutic strategy for a wide range of associated hearing disorders. Furthermore, MET signaling is essential for diverse functions in many tissues including the inner ear. Therefore, identification of the modifier of MET signaling is likely to have broad clinical implications.

Authors

Rizwan Yousaf, Zubair M. Ahmed, Arnaud P.J. Giese, Robert J. Morell, Ayala Lagziel, Alain Dabdoub, Edward R. Wilcox, Sheikh Riazuddin, Thomas B. Friedman, Saima Riazuddin

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Figure 2

The human METTL13 modifier variant suppresses the effect of the GAB1 variant in vivo.

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The human METTL13 modifier variant suppresses the effect of the GAB1 var...
(A and B) Expression in zebrafish embryos of WT gab1 and mettl13 mRNA normalized against expression of gapdh. Expression of gab1 and mettl13 mRNA was easily detectable during early development (up to 12 hours), but subsequently declined. (C–J) RNA ISH of gab1 and mettl13 in whole zebrafish embryos at 48 hours post fertilization (hpf) shows expression in many tissues, but especially in the brain region and the developing inner ear (arrowheads). (K) Lateral views of normal and gab1 morphants. MO suppression of gab1 resulted in developmental defects that were divided into 3 classes. Class I: defect in eye formation; class II: delayed development with embryos stalled at the budding stage; class III: marked developmental delay with embryos arrested at 50% epiboly to late epiboly. (L) In vivo rescue assay of gab1 MO with human mRNA. Coinjection of 1 ng WT human GAB1 mRNA with zebrafish gab1 mRNA translation–blocking MO resulted in significant rescue at the 10- to 12-somite stage, whereas mRNA encoding the hypomorphic p.Gly116Glu variant resulted in partial rescue. Coinjection of human full-length METTL13 mRNA encoding the p.Arg544Gln-suppressor variant of DFNB26 deafness along with GAB1 mutant mRNA and gab1 MO significantly attenuated the phenotype at the 10- to 12-somite stage, while the WT human METTL13 mRNA did not. The number of embryos phenotyped for each experiment is shown. ***P < 0.005, by 1-way ANOVA for rescue versus gab1 MO normal and severe (class III) morphants.