Isolation, characterization, and expression analysis of FGF5 isoforms in cashmere goat

Abstract

Fibroblast growth factor 5 (FGF5) is a secreted signaling protein which has been proved to inhibits hair growth and induces catagen in mouse hair follicle in vivo. Shaanbei white cashmere goat (SWCG), a unique genetic resource in China, was used as the subject in this study. The cDNA of FGF5 of SWCG (cgFGF5) was firstly cloned. The length of the open reading frame (ORF) in cgFGF5 was 813bp, encoding a protein of 270 amino acid residues. Our results showed that the cgFGF5 gene expressed one alternative variant, designated as cgFGF5s, which was derived from the cgFGF5 complete transcript via alternative splicing (AS). Analyses of the putative proteins sequences revealed that the same signal peptide was identified in the two transcripts, and the cleavage site was between position 20th and 21st of amino acid residues. A basic FGF domain, which is a characteristic domain of FGFs family, was found in the predictive cgFGF5, but not in the acquired cgFGF5s sequence. Homologous comparison with various species indicated that cgFGF5 gene implied good evolutional conservation in sequence. Analysis using real-time PCR showed that cgFGF5 and cgFGF5s mRNA were both detected in the 12 tissues examined (heart, subcutaneous fat, liver, muscle, spleen, brain, skin, kidney, rumen, large intestine, small intestine and lung). High expression levels of cgFGF5 mRNA were detected in brain, rumen and skin; while cgFGF5s mRNA was highly expressed in subcutaneous fat, heart and skin. In addition, the temporal expression analysis showed that expression of the two transcripts varied throughout hair growth cycle of cashmere goat: mRNA expression of cgFGF5 peaked at telogen; cgFGF5s peaked at catagen, and the lowest level of expressions were both observed at anagen. Results from the present study suggested that FGF5 gene may play a crucial role in cashmere goat hair growth cycle. This study is the first research to provide the primary foundational evidence for further insight into the role of cashmere goat FGF5 gene.