title: A missense mutation in Fgfr1 causes ear and skull defects in hush puppy mice.
abstract: The hush puppy mouse mutant has been shown previously to have skull and outer, middle, and inner ear defects, and an increase in hearing threshold. The fibroblast growth factor receptor 1 (Fgfr1) gene is located in the region of chromosome 8 containing the mutation. Sequencing of the gene in hush puppy heterozygotes revealed a missense mutation in the kinase domain of the protein (W691R). Homozygotes were found to die during development, at approximately embryonic day 8.5, and displayed a phenotype similar to null mutants. Reverse transcription PCR indicated a decrease in Fgfr1 transcript in heterozygotes and homozygotes. Generation of a construct containing the mutation allowed the function of the mutated receptor to be studied. Immunocytochemistry showed that the mutant receptor protein was present at the cell membrane, suggesting normal expression and trafficking. Measurements of changes in intracellular calcium concentration showed that the mutated receptor could not activate the IP(3) pathway, in contrast to the wild-type receptor, nor could it initiate activation of the Ras/MAP kinase pathway. Thus, the hush puppy mutation in fibroblast growth factor receptor 1 appears to cause a loss of receptor function. The mutant protein appears to have a dominant negative effect, which could be due to it dimerising with the wild-type protein and inhibiting its activity, thus further reducing the levels of functional protein. A dominant modifier, Mhspy, which reduces the effect of the hush puppy mutation on pinna and stapes development, has been mapped to the distal end of chromosome 7 and may show imprinting.
authors.affiliation: Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Calvert
authors.forename: Skarlatos G
authors.initials: SG
authors.lastname: Dedos
authors.forename: Kelvin
authors.initials: K
authors.lastname: Hawker
authors.forename: Michelle
authors.initials: M
authors.lastname: Fleming
authors.forename: Morag A
authors.initials: MA
authors.lastname: Lewis
authors.forename: Karen P
authors.initials: KP
authors.lastname: Steel
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D004423:Ear / Q000002:abnormalities*; D007150:Immunohistochemistry; D051379:Mice; D008817:Mice, Mutant Strains / Q000235:genetics*; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics*; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012886:Skull / Q000002:abnormalities*
chemical_list: C496349:Fgfr1 protein, mouse; D051496:Receptor, Fibroblast Growth Factor, Type 1; D002118:Calcium