A recurrent mutation in bone morphogenetic proteins-2-inducible kinase gene is associated with developmental dysplasia of the hip

Abstract

Developmental dysplasia of the hip (DDH) is a complex disorder of the hip joint affecting 1-5‰ of newborns. While genetic influence on DDH has been long known, DDH has not been ascribed to any specific genetic event. The present study reported on variants contributing to DDH susceptibility in a family with four individuals affected across three generations. Whole-exome sequencing was performed in three affected and two unaffected individuals of a pedigree with DDH. Candidate variants were confirmed by Sanger sequencing and then validated in available family members and 37 sporadic DDH patients. Two novel heterozygous, inframe mutations causing multi-nucleotide substitution polymorphisms (c.1432_1440delCAGCAGCAG corresponding with p.Gln478_480del and c.1440_1441insCAG corresponding with p.Gln480ins) in exon 11 of chromosome 4 in bone morphogenetic proteins-2-inducible kinase (BMP2K) were identified; these were found in members of the pedigree affected by DDH and in the unaffected grandmother of the proband, who was deemed to be the carrier of potential mutations, but not in the unaffected normal control saunt of the proband. These two variants shared the same genomic coordinate but with different types of mutation in BMP2K. BMP2K is known to be associated with bone and cartridge development and heterozygous mutations were found to be present in 4/4 (100%) of the affected family members, 4/15 (26.7%) of the unaffected family members and 0/7 (0%) of the unaffected unrelated family members. Genotyping of 37 unrelated, sporadic DDH patients showed that three cases were positive for the BMP2K c.1432_1440delCAGCAGCAG variants (8.12%). These findings provided strong evidence for the role of BMP2K variants in causing DDH and demonstrated that the combination of pedigree information and next-generation sequencing is an effective method for identifying pathogenic sites associated with DDH.

Keywords: developmental dysplasia of the hip; susceptibility-inducing mutation; whole-exome sequencing.

Figure 1.

Pedigree assessed in the present study and members of the pedigree carrying BMP2K mutations. Filled in symbols denote individuals with DDH. Symbols with a backslash denote individuals that have died. Asterisks indicate individuals whose DNA samples were retrieved. Five members of the family, which are marked with ‘exome’, were recruited for whole-exome sequencing analysis. The main proband of the study is indicated by an arrow. ‘insCAG’ indicates individuals with c.1440_1441insCAG mutation and ‘delCAGCAGCAG’ indicates individuals with c.1432_1440delCAGCAGCAG mutation. DDH, developmental dysplasia of the hip; Ins, insertion; del, deletion.

Figure 2.

Filtering strategy of susceptibility variants. Numbers of variants are shown in the boxes. SNP, single-nucleotide polymorphism; SIFT, sorting intolerant from tolerant; NHLBI, National Heart, Lung and Blood Institute.

Figure 3.

Mutation analysis in subjects with BMP2K mutations. (A) c.1432_1440delCAGCAGCAG and c.1440_1441insCAG mutations in exon 11 of BMP2K in the pedigree as determined by whole-exome sequencing (top one for II7, III10 and IV6 in the pedigree, middle one for III3 in the pedigree, separately) compared to the control (bottom one for III2 in the pedigree). (B) The c.1432_1440delCAGCAGCAG mutation in BMP2K was validated by Sanger sequencing in three unrelated sporadic cases of developmental dysplasia of the hip (top three) compared to one control (bottom one). The mutated nucleotide is indicated by an arrow.