Whole exome sequencing links dental tumor to an autosomal-dominant mutation in ANO5 gene associated with gnathodiaphyseal dysplasia and muscle dystrophies

Abstract

Tumors of the jaws may represent different human disorders and frequently associate with pathologic bone fractures. In this report, we analyzed two affected siblings from a family of Russian origin, with a history of dental tumors of the jaws, in correspondence to original clinical diagnosis of cementoma consistent with gigantiform cementoma (GC, OMIM: 137575). Whole exome sequencing revealed the heterozygous missense mutation c.1067G > A (p.Cys356Tyr) in ANO5 gene in these patients. To date, autosomal-dominant mutations have been described in the ANO5 gene for gnathodiaphyseal dysplasia (GDD, OMIM: 166260), and multiple recessive mutations have been described in the gene for muscle dystrophies (OMIM: 613319, 611307); the same amino acid (Cys) at the position 356 is mutated in GDD. These genetic data and similar clinical phenotypes demonstrate that the GC and GDD likely represent the same type of bone pathology. Our data illustrate the significance of mutations in single amino-acid position for particular bone tissue pathology. Modifying role of genetic variations in another gene on the severity of the monogenic trait pathology is also suggested. Finally, we propose the model explaining the tissue-specific manifestation of clinically distant bone and muscle diseases linked to mutations in one gene.

Figure 1. Family examined in this study.

(a) Family with cementoma and repeated bone fractures. (b,c) Clinical phenotypes of two brothers (III-1 and III-2) include fragility and deformation of tubular bone. The detailed clinical descriptions of facial tumors overlapped with familial gigantiform cementoma (OMIM: 137575) were made previously. The affected siblings and their unaffected father were used for genetic analysis. The mother (II-2) that was unavailable for the study had an operation on cementoma lower jaw, but had no GDD clinical diagnosis in her medical history. No limbs deformation were expressed in the mother. The probands’ uncle (II-1) and grandfather (I-1) had repeated bone fractures (see. Material and Methods).

Figure 2. Genetic analysis of the family.

(a) Sanger sequence chromatograms of ANO5 are shown for one affected individual (MUT) and unaffected father (WT). The arrow indicates the heterozygous mutation at the position c.1067G > A (p.Cys356Tyr) of ANO5 gene in the affected individual. (b) Genomic sequence chromatograms of COL5A1 identified two heterozygous mutations in the COL5A1 gene (designated by arrows) in the affected brothers, which were inherited from their father (shown on the chromatogram).

Figure 3

Amino-acid sequence alignment of ANO5 with (a) paralogous human proteins and (b) orthologous proteins. Conserved cysteine residues are marked by asterisks and the p.356Cys position of ANO5 is boxed.

Figure 4. Predicted structure and helices topology of wild-type and mutant human ANO5 protein based on Phyre2 prediction.

(a,d) Transmembrane domains in wild type ANO5. (b) Monomer ANO5 structure. (c) ANO5 subunit in dimer structure. Both loops with p.Cys356 and the area which change its predicted structure (loss of TMD predicted structure) are marked by red. (e) p.Cys356 mutations change the structure of region between 8 and 10 TMD. (f) Cysteine residuaes p.Cys520, p.Cys572, p.Cys601, p.Cys606 (blue) is located close to p.Thr513 (magenta) in predicted protein structure. (g) The largest pockets were detected by the fpocket2 program^, in the loop between 1^st and 2^nd TMDs of ANO5. Green helixes are alpha helixes, blue arrows are beta strands. Yellow boxes indicate the amino acids involved in the pocket formation. No large pockets were predicted for wild-type protein structure.

Figure 5. 3D alignment of predicted structures of the wild-type ANO5 protein (cyan) and p.Ile513 mutant form (gold) revealed the differences in the extracellular loops (indicated by arrows).