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Earlier studies demonstrated that knock-out of fibroblast growth factor 5 gene (FGF5) resulted in long hairs in the mice.FGF5S, a shorter polypeptide with FGF5 antagonizing activity translated from alternatively spliced mRNA, was subsequently verified that it could suppress the activity of FGF5.In order to investigate the structure of sheep FGF5 gene and evaluate its function in wool growth, FGF5 and an alternative splicing isoform of FGF5 which named FGF5s were firstly cloned from Xinjiang Merino sheep by RT-PCR and Rapid Amplification of cDNA Ends (RACE).The open reading frame (ORF) of FGF5 cDNA in sheep was 813bp in length, encoding 270 amino acids, while the ORF of FGF5s cDNA was 378bp in length, encoding 125 amino acids.Western blot analysis showed that recombinant expression of FGF5 and FGF5s protein band of approximately 30kDa and 15 kDa, consistent with the expected results.Then the transgenic sheep were generated by microinjection of recombinant lentivirus particles carrying sheep rFGF5s into periviteline space of zygote.Total of 20 transgenic lambs were identified from 23 offspring by PCR and Southern Blot.The copies of integrants varied from 2 to 11 among different individuals.Up to now, 12 transgenic sheep are still living and were used for the following studies.Significant increase of foreign FGF5s expression in transgenic sheep was observed by qRT-PCR and western blot compared to non-transgenic sheep.While the other quality of wool characteristic, including fiber diameter, crimp, staple strength, appear identical to that of non-transgenic sheep, the only obvious different phenotype in these one-year-old transgenic sheep is the length of wool that is about 15% longer than that of non-transgenic sheep.These findings provide evidence that the antagonized FGF5s might be a promising candidate gene for promoting wool growth.Further studies still have been conducting to reveal its involvement in wool growth.