The Expression Of Chicken PAPPA And PAPPA2 Genes In Follicular Tissues And Their Correlation With Egg Production Traits In Hens

Egg production is one of the most important economic traits in chicken,which is affected by light,temperature,nutrition and other factors.It has been shown that the growth and development of follicle is a complex process regulated by multiple genes and multiple hormones.Our previous study showed that PAPPA gene may be closely related to follicular growth and development.Pappalysin?PAPPA?,mRNA fragment length is 10998 bp in size,located in chicken chromosome 17,encoding a protein of chicken pregnancy associated plasma protein,also known as the crested 1.PAPPA gene contains 22 exons and 1627 amino acids in the chicken genome.PAPPA was originally found to be produced by the secretion of placental tissue,which was later found to be secreted by different types of cells.PAPPA is an essential biomarker when screening for chromosomal abnormalities.In 1974,PAPPA was isolated from the serum of pregnant women for the first time.PAPPA plays an important role in regulating the growth and development of follicle,and plays a role in the selection of dominant follicle and the survival of corpus luteum.PAPPA2?XM₄26627.4?mRNA gene fragment length is 7556 bp,located in chicken chromosome 8,called pappus element 2,PAPPA is two PAPPA2 is different from the non covalent dimer,1496 amino acids in chicken,composed of 22 exons of translation.PAPPA2 is a protease of insulin like growth factor binding protein 5,and is a potential biomarker,which has 1496 amino acids in chicken and is translated by the 22 exons.Recently,it has been found that the single nucleotide polymorphism of PAPPA2 gene plays an important role in the reproduction of cattle.In addition,studies have shown that the expression of PAPPA2 gene in placenta is the highest in placenta during pregnancy.PAPPA2 has a certain effect on the endothelial and trophoblast cells of the embryo,and the differentiation of fetal and trophoblast cells.It can be inferred that PAPPA2 gene may play an important role in the regulation of follicular development.However,there are no reports about the specific biological and molecular mechanisms of PAPPA2 gene on the growth and development of follicle.This study used 150 day old Hy-Line Brown layers of ovarian tissue as test materials,detection and analysis of genes in follicles at different developmental stages in theexperiment by RT-PCR from the mRNA levels of PAPPA and PAPPA2 gene transcriptions,and then in situ hybridization and immunohistochemical method inthe analysis of PAPPA gene mRNA and PAPPA2 protein levels,in order to express the characteristics of space-time process of inquiry PAPPA,PAPPA2 gene in the chicken follicular growth and development in depth,suggesting that these two genes in follicle specific regulatory role in the development of the regulatory mechanism and provide a molecular basis.This study to analyze the polymorphism of two candidate genes of PCR-SSCP technology and analyzed their correlation with egg production traits of Chinese Dagu chickens,in order to select potential the genetic markers associated with egg production traits.The experimental results are as follows:Through the RT-PCR test of 150 day old Hy-Line layers in the ovary of PAPPA and the expression level of PAPPA2 genes of mRNA,the results showed that PAPPA gene mRNA in chicken follicles expressed in various levels and higher expression of PAPPA2 gene and the relative expression of mRNA were not high.The mRNA expression levels of PAPPA and PAPPA2 were significantly different in all grades of follicles?P < 0.05?.The mRNA expression of chicken PAPPA gene in the stroma was significantly higher than that of F2 follicles?P < 0.05?,while the mRNA expression of chicken PAPPA2 gene in the stroma was significantly higher than that of F3?P < 0.05?.Chicken PAPPA and PAPPA2 genes might play an important role in regulating the development of chicken follicles.The expression of PAPPAgene was detected by in situ hybridization?ISH?in the first grade of the chicken,and then the expression of PAPPA2 protein in the first grade follicle was detected by immunohistochemistry.The results showed that chicken PAPPA and PAPPA2 had positive signals in the oocytes and granulosa cells of the first grade follicles.It can be concluded that the PAPPA and PAPPA2 protein molecules of the mRNA gene may be involved in the regulation of follicular development in the course of the development of the first class of follicles.The polymorphism of PAPPA and PAPPA2 genes in Chinese Dagu chickens detection results by using the PCR-SSCP technology,the PAPPA gene in 3`-untranslated region?UTR?detected three genotypes AA,AB and BB,the allele frequency of A was higher than that of allele B and genotype AA and AB frequency was higher than BB the genotype frequency?P<0.05?and was the dominant genotype.In the PAPPA2 gene in 3`-UTR detected two genotypes TC and CC genotype,TC genotype was the dominant genotype and C allele frequency was higher than the frequency of allele T?P<0.05?.PAPPA and PAPPA2 genotypes associated with egg production traits analysis results showed that there were significant in PAPPA gene BB genotype at 30,43,and 57 week old egg production and egg weight at 43 weeks of age?P<0.05?,there is a significant correlation of PAPPA2 gene TC genotype in Dagu chicken total yield and performance traits?P<0.05?.