Severe complications in a child with achondroplasia and two FGFR3 mutations on the same allele

Department of Clinical Genetics, University Medical Center Groningen, University of Groningen, The Netherlands.
American Journal of Medical Genetics Part A (Impact Factor: 2.16). 02/2006; 140(3):284-90. DOI: 10.1002/ajmg.a.31084
Source: PubMed


We describe a unique case of achondroplasia with associated complications, including severe respiratory problems. Molecular analysis of the fibroblast growth factor receptor type 3 (FGFR3) gene in this patient showed the common p.G380R mutation and a second novel p.L377R mutation. An allele-specific PCR demonstrated that these mutations were on the same allele (cis). Both mutations were not present in the parents and appear to have occurred de novo. To our knowledge, this is the first report in the literature on an achondroplasia patient with two FGFR3 mutations on the same allele.

8 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: In classical achondroplasia (Ach), a glycine residue is replaced by an arginine at codon 380 in exon 10 of the fibroblast growth factor receptor 3 gene (FGFR3). Here we report on a mother and daughter with hypochondroplasia (Hch) caused by a new heterozygous double mutation (1138_1139GG > AA) at the same codon 380, but encoding a lysine instead of the usual arginine. Previous functional assays of these codon 380 amino acid substitutions demonstrated a lesser activation of receptor signaling by lysine compared to arginine [Webster and Donoghue, 1996; EMBO J 15:520-527]. This could explain the milder phenotype observed in our patients. Several other rare double mutations were previously described in both FGFR2 and FGFR3 and interpreted as resulting from positive selection of spermatogonial cells owing to gain-of-function in the encoded protein [Goriely et al., 2005; Proc Natl Acad Sci USA 102:6051-6056]. The present case contributes additional support for this hypothesis.
    No preview · Article · Feb 2007 · American Journal of Medical Genetics Part A
  • [Show abstract] [Hide abstract]
    ABSTRACT: Thanatophoric dysplasia is a lethal chondrodysplasia caused by heterozygous fibroblast growth factor receptor 3 (FGFR3) missense mutations. Mutations have been identified in several domains of the receptor. The most frequent mutations (p.R248C, p.S249C, p.Y373C) create a cysteine residue within the extracellular domain, whereas the others eliminate the termination codon (p.X807R, p.X807C, p.X807G, p.X807S, p.X807W). Here, we report a unique patient with thanatophoric dysplasia and a double de novo FGFR3 mutation, located on the same allele, (c.[1620C>A;1454A>G]), which corresponds to p.[N540K;Q485R]. The p.N540K mutation is associated with 60% of patients with hypochondroplasia and the p.Q485R mutation is a novel mutation located in a highly conserved domain of FGFRs. Evidence for the structural impact of the two concurrent missense mutations was achieved using protein alignments and three-dimensional structural prediction, in agreement with our modeling of the FGFR3 structure. In this patient with thanatophoric dysplasia, we conclude that the presence of the double FGFR3 missense mutation on the same allele alters the receptor structure, holding the receptor in its fully activated state, thus leading to lethal chondrodysplasia.
    No preview · Article · Jun 2009 · American Journal of Medical Genetics Part A
  • [Show abstract] [Hide abstract]
    ABSTRACT: Data from diverse organisms suggests that transient hypermutability is a general mutational mechanism with the potential to generate multiple synchronous mutations, a phenomenon probably best exemplified by closely spaced multiple mutations (CSMMs). Here we have attempted to extend the concept of transient hypermutability from somatic cells to the germline, using human inherited disease-causing multiple mutations as a model system. Employing stringent criteria for data inclusion, we have retrospectively identified numerous potential examples of pathogenic CSMMs that exhibit marked similarities to the CSMMs reported in other systems. These examples include (1) eight multiple mutations, each comprising three or more components within a sequence tract of <100 bp; (2) three possible instances of "mutation showers"; and (3) numerous highly informative "homocoordinate" mutations. Using the proportion of CpG substitution as a crude indicator of the relative likelihood of transient hypermutability, we present evidence to suggest that CSMMs comprising at least one pair of mutations separated by < or =100 bp may constitute signatures of transient hypermutability in human genes. Although this analysis extends the generality of the concept of transient hypermutability and provides new insights into what may be considered a novel mechanism of mutagenesis underlying human inherited disease, it has raised serious concerns regarding current practices in mutation screening.
    No preview · Article · Oct 2009 · Human Mutation
Show more