Recurrent Mutation of the Gene Encoding sequestosome 1 (SQSTM1/p62) in Paget Disease of Bone

Abstract

Paget disease of bone (PDB) is a common disorder characterized by focal and disorganized increases of bone turnover. Genetic factors are important in the pathogenesis of PDB. We and others recently mapped the third locus associated with the disorder, PDB3, at 5q35-qter. In the present study, by use of 24 French Canadian families and 112 unrelated subjects with PDB, the PDB3 locus was confined to approximately 300 kb. Within this interval, two disease-related haplotype signatures were observed in 11 families and 18 unrelated patients. This region encoded the ubiquitin-binding protein sequestosome 1 (SQSTM1/p62), which is a candidate gene for PDB because of its association with the NF-kappaB pathway. Screening SQSTM1/p62 for mutations led to the identification of a recurrent nonconservative change (P392L) flanking the ubiquitin-associated domain (UBA) (position 394-440) of the protein that was not present in 291 control individuals. Our data demonstrate that two independent mutational events at the same position in SQSTM1/p62 caused PDB in a high proportion of French Canadian patients.

SQSTM1 gene analysis and gene-environment interaction in Paget's disease of bone

“…This percentage is comparable with the results of mutational analysis studies performed in other countries, such as Great Britain (13.9%), France (12.8%), and Canada (19.8%). (8,9,11,17) Consistent with previous findings, the prevalence of mutations was highest (36.9%) in patients with a clear family history. Since we were not able to clinically exclude the presence of PDB in all first-degree relatives of recruited patients, we cannot exclude that a proportion of patients reporting no family history and thus classified as sporadic patients may have familial PDB.…”

“…Consistent with previous studies in different populations, (8,22,30,31) the H 1 (916T-976A-2503C-2687T) and H 2 (916C-976G-2503T-2687G) haplotypes accounted for the largest proportion of patients (94.3%) and controls (91.5%). The remaining patients were accounted for by six rare haplotypes with individual frequencies of between 0.2% and 3.6%.…”

“…Moreover, we also observed two H 1 -H 1 homozygous patients carrying the P392L mutation, suggesting that the same mutation has occurred independently at least twice, as observed previously in the French-Canadian population. (8,22) An increased prevalence of the H 2 haplotype also was seen in patients with the M404V mutation, whereas the Y383X mutation was carried with the H 2 haplotype in all patients. This also strongly supports the presence of a founder effect for this mutation.…”

“…All the remaining exons and intron-exon boundaries of SQSTM1 also were screened in familial PDB patients who did not show mutations in exons 7 and 8. To analyze the genetic background of mutated patients, we genotyped four single-nucleotide polymorphisms (SNPs) located in exon 6 (C916T, G976A) and the 3' untranslated region of SQSTM1 (C2503T, T2687G) as performed in previous studies. (8,22,30,31) The software program PHASE was used to reconstruct haplotypes (www.stat.washington.edu/stephens/).…”

“…(7) In 2002, Laurin and colleagues identified a recurrent C!T transition at position þ1215 leading to a proline-to-leucine substitution at codon 392 (P392L) on the SQSTM1 gene (within the 5q35 PDB3 locus) as a cause of PDB in about 50% and 20% of familial and sporadic French-Canadian patients, respectively. (8) This gene encodes the p62/sequestosome 1 protein, which acts as a scaffold protein in the NFkB pathway as well as an intermediate protein in the proteosomal degradation of polyubiquitinated proteins. The same P392L mutation was identified subsequently in familial and sporadic PDB subjects from different countries.…”