Mutations in the gene encoding fibroblast growth factor receptor-3 in achondroplasia

Abstract

Achondroplasia, the most common cause of chondrodysplasia in man (1 in 15,000 live births), is a condition of unknown origin characterized by short-limbed dwarfism and macrocephaly. More than 90% of cases are sporadic and there is an increased paternal age at the time of conception of affected individuals, suggesting that de novo mutations are of paternal origin. Affected individuals are fertile and achondroplasia is transmitted as a fully penetrant autosomal dominant trait, accounting for rare familial forms of the disease (10%). In contrast, homozygous achondroplasia is usually lethal in the neonatal period and affects 25% of the offspring of matings between heterozygous achondroplasia parents. The gene responsible for achondroplasia has been mapped to chromosome 4p16.3 (refs 7, 8); the genetic interval encompassing the disease gene contains a member of the fibroblast-growth-factor receptor (FGFR3) family which is expressed in articular chondrocytes. Here we report the finding of recurrent missense mutations in a CpG doublet of the transmembrane domain of the FGFR3 protein (glycine substituted with arginine at residue 380, G380R) in 17 sporadic cases and 6 unrelated familial forms of achondroplasia. We show that the mutant genotype segregates with the disease in these families. Thus it appears that recurrent mutations of a single amino acid in the transmembrane domain of the FGFR3 protein account for all cases (23/23) of achondroplasia in our series.

Activation of FGF receptors by mutations in the transmembrane domain

“…While the original stimulus for this investigation resulted from the ®nding of a remarkably conserved mutation (Gly 380?Arg) in the FGFR-3 transmembrane region in ACH (Rousseau et al, 1994;Shiang et al, 1994), we were interested in extending these studies to another FGF receptor, namely FGFR-2 mainly for the following reasons: (1) to ascertain whether the e ect of similar mutations resulted in the same phenotype in two of the FGF receptors; (2) because other mutations associated with dominant skeletal disorders had been detected in FGFR-2 (Muenke and Schell, 1995); (3) to overcome the problems associated with studying changes in thè weak' signaling potential of FGFR-3. As observed by others (Ornitz and Leder, 1992;Chellaiah et al, 1994;Wang et al, 1994), this receptor seems to posssess a weak kinase activity, and is unable to generate a strong mitogenic signal when expressed in receptor-negative cells.…”

“…Developmental abnormalities are associated with knock-out of the FGF-4 and FGF-3 genes as well as of FGFR-1 (Mansour et al, 1993;Deng et al, 1994;Yamaguchi et al, 1994;Feldman et al, 1995) and targeting of dominant-negative receptor molecules to various organs in transgenic mice also results in a variety of defects in development Peters et al, 1994;Mima et al, 1995;Campochiaro et al, 1996). A remarkably conserved mutation at a guanosine nucleotide at position 1138 of FGFR-3 has been shown to be associated with achondroplasia (ACH), a human autosomal dominant trait whose classic features include rhizomelic dwar®sm, macrocephaly and other skeletal abnormalities (Rousseau et al, 1994;Shiang et al, 1994). This mutation substitutes Gly 380 with Arg in the transmembrane region of the receptor.…”

Predominance of the mutation at 1138 of the cDNA for the fibroblast growth factor receptor 3 in Japanese patients with achondroplasia

“…braneous domain of the fibroblast growth factor receptor 3 (FGFR3), which is mapped to 4p16.3, were found in patients with ACH (Rousseau et al, 1994;Shiang et al, 1994). Interestingly, more than 90~ of the mutations were G to A substitutions at 1138 resulting in glycine to arginine conversion at residue 380.…”

“…Interestingly, more than 90~ of the mutations were G to A substitutions at 1138 resulting in glycine to arginine conversion at residue 380. According to one of the most recent report (Mulvihil, 1995), the G380R substitution account for 193 of 194 identified cases, five of which are due to G to C substitution at 1138, yet several unidentified mutations are left to be disclosed (Shiang et al, 1994;Rousseau et al, 1994;Bellus et al, 1995). It is quite exceptional to have a unique mutation with a great predominance in such a popular genetic disorder.…”

“…All of them were considered as sporadic cases and none of them was suspected to be an ACH homozygote. The sequence for the transmembrane region of the FGFR3 was amplified by polymerase chain reaction (PCR) using the following primers (Rousseau et al, 1994); the forward primer: 5'-TGACGAGGCGGGCAGTG-3' and the backward primer: 5'-AGCGGGAAGCGGGAGAT-3'. Genomic DNA (200 ng), which was extracted from leukocytes, was incubated (94~ for 40 sec, 52~ for 20 sec, 72~ for 20 sec/30 cycles) with 50 mM KC1, 10 mM Tris-HC1, pH8.3, 1.5 mM MgC12, 25 pmol primers, 10~ DMSO, 200 ~M of each deoxynucleotide triphosphate, 0.5 U Taq polymerase in 50 ~1 of total reaction.…”