The Expression Of POSTN And PDGFRL Genes In Ovarian Follicles And Association Of Their Polymophism With Egg Production Traits In Hens

The periostin(POSTN, PN) gene, also known as periosteal proteins, it was originally named as osteoblast-specific factor 2(OSF-2). POSTN was originally cloned from mouse osteoblasts, and the gene involved in the collection, adhesion and migration of cells. It is the important cell growth factor. In recent years, it has been shown that a high level of periostin protein was detected in the human ovary, and be implicated in regulation of ovarian development. Platelet-derived growth factor receptor-like(PDGFRL), since this gene encodes a protein with significant sequence similarity to the ligand binding domain of PDGFR-?, so called platelet-derived growth factor receptor protein. It has been found that this gene product may function as a tumor suppressor, and involved in PDGF regulation network of signaling pathways. In the present study, we explored the temporal and spatial expression of POSTN and PDGFRL gene in the follicle development from the level of mRNA and protein level using semi-quantitative RT-PCR and immunohistochemistry, respectively. The SNPs were identified within the candidate genes using the PCR-single strand conformation polymorphism(PCR-SSCP) method, and then associated with the egg production traits. The aim of this work is to provide a potential genetic molecular marker able to facilitate improved egg production traits. The results are as following:(1) The results of semi-quantitative RT-PCR shown that POSTN and PDGFRL genes mRNA are expressed highly in various-sized prehierarchical and preovulatory follicles in 150-day-old Hy-Line Brown hens, and with a significant differences in different grade follicles by semi-quantitative RT-PCR. The expression level of POSTN mRNA in 5-6 mm prehierarchichal follicles was significantly high than F1(P?0.05), other follicles were not significant. It indicated that POSTN gene was implicated primarily in regulation of hen prehierarchical follicles development. The expression of POSTN gene mRNA were gradually decline with the follicles differentiation. The expression of PDGFRL gene mRNA progressive increased and then deceased with the follicles development,with higher expression in the period closed to hierarchic process.The transcripts of PDGFRL gene have a higher expression in F5 level of hen follicles, which compared with stroma?4-5 mm?6-7 mm?F4?F2?F1(P?0.05),other follicles were not significant(P>0.05). It showed that PDGFRL gene may be involved in the follicular hierarchic process.(2) The results of immunohistochemistry demonstrated that POSTN and PDGFRL proteins were predominately expressed in oocytes and stroma cells of follicles which diameter was less than 4 mm in 150-day-old Hy-Line Brown hens,while did not express in the follicles membrane layer. With the development of follicles, POSTN protein positive signal was detected in granlosa, and PDGFRL protein was detected in the cytoplasm of granlosa in prehierarchical follicles. The location of these two genes manifested that they participate in the regulation of follicular development through some autocrine or paracrine pathway.(3) The results of PCR-SSCP and correlation analysis shown that SNP A2727 T transversion in intron 2 of POSTN gene was found. For the SNP A2727 T, a total of 360 Dagu hens were classified as AA and AB genotypes, the AA genotype was significantly correlated with higher hen-housed egg production(HHEP) at 43, 57 and 66 weeks(wks) of age and with a higher egg weight(EW) at 30 wks than AB genotype(P < 0.05), and this SNP explains a large percentage of the additive genetic variance for the HHEP. Two transitions, SNPs G6761 A and A6839 G in exon 2 of PDGFRL gene were detected. For the two linked SNPs(G6761A and A6839G) in the PDGFRL fragment, the hens were typed into TT, TC and CC genotypes. The TT genotype was correlated with higher HHEP at 57 and 66 wks of age than CC genotype, while genotype CC associated with the highest body weight and EW at 30 and 43 wks than the other genotypes(P < 0.05), and a large percentage of the additive variance was explained by the two linked SNPs for its significant association with the traits, respectively. Furthermore, five haplotypes were reconstructed based on these SNPs, with the AATT haplotype associated with the highest HHEP at 43 to 66 wks of age and higher EW at 30 wks(P < 0.05). Collectively, these SNPs identified in this study might be used as a potential molecular marker favorable to genetic improvement of egg productivity in chicken breeding.