The heterozygous Pro250Arg substitution mutation in fibroblast growth factor 
receptor 3 (FGFR3), which increases ligand-dependent signalling, is the most 
common genetic cause of craniosynostosis in humans and defines Muenke syndrome. 
Since FGF signalling plays dosage-sensitive roles in the differentiation of the 
auditory sensory epithelium, we evaluated hearing in a large group of Muenke 
syndrome subjects, as well as in the corresponding mouse model (Fgfr3(P244R)). 
The Muenke syndrome cohort showed significant, but incompletely penetrant, 
predominantly low-frequency sensorineural hearing loss, and the Fgfr3(P244R) 
mice showed dominant, fully penetrant hearing loss that was more severe than 
that in Muenke syndrome individuals, but had the same pattern of relative 
high-frequency sparing. The mouse hearing loss correlated with an alteration in 
the fate of supporting cells (Deiters'-to-pillar cells) along the entire length 
of the cochlear duct, with the most extreme abnormalities found at the apical or 
low-frequency end. In addition, there was excess outer hair cell development in 
the apical region. We conclude that low-frequency sensorineural hearing loss is 
a characteristic feature of Muenke syndrome and that the genetically equivalent 
mouse provides an excellent model that could be useful in testing hearing loss 
therapies aimed at manipulating the levels of FGF signalling in the inner ear.