Molecular characterization and identification of a novel polymorphism of 200 bp indel associated with age at first egg of the promoter region in chicken follicle-stimulating hormone receptor (FSHR) gene.

Follicle-stimulating hormone receptor (FSHR) plays an important role in animal follicular development. Polymorphisms in FSHR promoter region likely impact transcription and follicle growth and maturation. In this study, a fragment of ~1.9 kb of cFSHR promoter for Zang, Xianju, Lohmann Brown, Jining Bairi and Wenchang breeds (line) was obtained. Totally 49 variations were revealed, of which 39 are single nucleotide substitutions, one is nucleotide substitution of (TTG) to (CAC) and nine are indels. Polymorphism at -874 site (a 200 bp indel mutation) was identified, and their effects on egg production traits as well as gene expression were analyzed. At this site, allele I(+) was dominant in Lohmann Brown and Xinyang Brown (a synthetic egg-laying line) lines, but very rare in three Chinese indigenous chicken breeds, namely Jining Bairi, Wenchang, Zang and one synthetic boiler line (Luqin). In Xinyang Brown population, the polymorphism was associated with age at first egg (AFE) (P < 0.05) and its effect on egg number at 37 weeks of age (E37) and egg number at 57 weeks of age (E57) was not significantly different (P > 0.05). The cFSHR mRNA level was not significantly different between three genotypes in small white and small yellow follicles of Xinyang Brown hens, however, allele I(+) tends to increase cFSHR transcription.