Genomewide search in familial Paget disease of bone shows evidence of genetic heterogeneity with candidate loci on chromosomes 2q36, 10p13, and 5q35

Abstract

Paget disease of bone (PDB) is a common disorder characterized by focal abnormalities of increased and disorganized bone turnover. Genetic factors are important in the pathogenesis of PDB, and previous studies have shown that the PDB-like bone dysplasia familial expansile osteolysis is caused by activating mutations in the TNFRSF11A gene that encodes receptor activator of nuclear factor kappa B (RANK); however, linkage studies, coupled with mutation screening, have excluded involvement of RANK in the vast majority of patients with PDB. To identify other candidate loci for PDB, we conducted a genomewide search in 319 individuals, from 62 kindreds with familial PDB, who were predominantly of British descent. The pattern of inheritance in the study group as a whole was consistent with autosomal dominant transmission of the disease. Parametric multipoint linkage analysis, under a model of heterogeneity, identified three chromosomal regions with LOD scores above the threshold for suggestive linkage. These were on chromosomes 2q36 (LOD score 2.7 at 218.24 cM), 5q35 (LOD score 3.0 at 189.63 cM), and 10p13 (LOD score 2.6 at 41.43 cM). For each of these loci, formal heterogeneity testing with HOMOG supported a model of linkage with heterogeneity, as opposed to no linkage or linkage with homogeneity. Two-point linkage analysis with a series of markers from the 5q35 region in another large kindred with autosomal dominant familial PDB also supported linkage to the candidate region with a maximum LOD score of 3.47 at D5S2034 (187.8 cM). These data indicate the presence of several susceptibility loci for PDB and identify a strong candidate locus for the disease, on chromosome 5q35.

Figure 1

Candidate loci for familial PDB identified by genomewide search. Data are shown from chromosomes 2, 5, and 10, where maximized LOD scores yielded values ⩾1.9, under a model of heterogeneity. The position of selected markers spanning the regions of interest are indicated.

Figure 2

Pedigree structure and haplotypes spanning the 5q35 region in an extended U.S. kindred with familial PDB. A haplotype shared by most affected members of the kindred is boxed. Blackened symbols denote affected individuals, and unblackened symbols denote unaffected individuals. Unblackened symbols that contain a question mark indicate individuals whose diagnosis was unclear.