Transcriptome Study On The Molecular Mechanism Of Curly Coat Phenotype In Chinese Tan Sheep

Tan sheep (Ovis aries), one of the Chinese indigenous breeds, distributes in Ningxia and its adjacent areas. The breed originated from Mongolian sheep amd is hardy and well adapted to a dry, cold and windy environment. It is renowned not only for its excellent meat, but also for the production of high quality pelts. The lamb pelts from Tan sheep are characterized by a natural white color and a lustrous curly fleece. The curly fleece appears when Tan lambs are one month old. After processing, the lamb pelts with curly fleece tend to be thin and light weight, which are well suited for the production of fur coats, carpets, furniture covering, and various forms of handicrafts. However, this unique phenotype disappears gradually with age and the mechanisms behind the phenomenon are still unclearthe. We did experiments below based on the background of Tan lamb curly fleece.1) We identificatified differential expressed genes between adult and lamb Tan sheep by RNA-Seq. In this study, the skin transcriptome data was used for shedding some lights on this issue. In total30,081transcripts including described transcripts and transfrags were identified. The pathway analysis of top100most highly expressed transcripts, which includes TCHH and keratin gene family members, such as KRT25, KRT5, KRT71, KRTI4and others, showed pathways known to be relevant to hair/fleece development and function.37differentially expressed transcripts were detected at two different physiological ages (one-month-old with curly fleece and48-month-old without curly fleece). Subsequent gene ontology analysis showed that a number of genes related to hair/fleece development and showed differential expression between the two physiological stages, the differentially expressed genes (SPINK4, KRTl, ESRa, EphA3, ASIP and GPR110) were confirmed by qPCR analysis. Further pathway analysis of alternative splices tended to be enriched in Notch, VEGF, Wnt, MAPK and some other hair/fleece development related signaling pathways, and some enriched pathways were specifically found in a single physiological stage. We deduced that the differences existed in expressed transcripts, splice isoforms and pathway between two different physiological stages, which might constitute the major reasons for explaining the trait evolvement of curly fleece in Chinese Tan sheep. This study provides some clues for elucidating the molecular mechanism of fleece change with age in Chinese Tan sheep, as well as supplying some potential values for understanding human hair disorder and texture changes.2) The KRT71is one of the highly expressed genes in transcriptome of four samples, which specifically expressed in the IRS (inner root sheath), particular in Henle and Huxley layers of the hair follicle in IRS. Based on clues metioned above and previous data from suppression subtractive hybridization, we cloned and analyzed KRT71gene. KRT71gene has been associated with the curly coat phenotype of animals. The complete cDNA sequence of one ovine gene—KRT71was amplified using rapid amplification of cDNA ends method. The sequence analyses of this novel gene revealed that the sheep KRT71gene encodes a protein of525amino acids which has high homology with the keratin71of other mammal species. Analysis of promoter characters and transcript factors biding site of this gene supply key role for further study. The tissue expression profile analyses indicated that the ovine KRT71gene is generally but differently expressed in the detected tissues including spleen, muscle, skin, stomach, kidney, lung, liver and heart. And the relative expression of KRT71by qRT-PCR was different at Tan sheep with age. Furthermore, the promoter of KRT71gene was conserved at2.2kb before transcription start site among species, and had some conserved transcription factor binding site families. And the CCAAT box might have some important function in regulating the differential expression of KRT71in Tan sheep skin tissues at different stages. The cloning and character analysis of the sheep KRT71gene will probably provide molecular basis for associating KRT71gene with curly fleece phenotype of Tan sheep, as well as other animals with curly coat.