title: Genetic effects of polymorphisms in candidate genes and the QTL region on chicken age at first egg.
abstract: BACKGROUND
  The age at first egg (AFE), an important indicator for sexual maturation in female chickens, is controlled by polygenes. Based on our knowledge of reproductive physiology, 6 genes including gonadotrophin releasing hormone-I (GnRH-I), neuropeptide Y (NPY), dopamine D2 receptor (DRD2), vasoactive intestinal polypeptide (VIP), VIP receptor-1 (VIPR-1), and prolactin (PRL), were selected as candidates for influencing AFE. Additionally, the region between ADL0201 and MCW0241 of chromosome Z was chosen as the candidate QTL region according to some QTL databases. The objective of the present study was to investigate the effects of mutations in candidate genes and the QTL region on chicken AFE.
  
  
  RESULTS
  Marker-trait association analysis of 8 mutations in those 6 genes in a Chinese native population found a highly significant association (P < 0.01) between G840327C of the GnRH-I gene with AFE, and it remained significant even with Bonferroni correction. Based on the results of the 2-tailed χ2 test, mutations T32742394C, T32742468C, G32742603A, and C33379782T in the candidate QTL region of chromosome Z were selected for marker-trait association analysis. The haplotypes of T32742394C and T32742468C were significantly associated (P < 0.05) with AFE. Bioinformatics analysis indicated that T32742394C and T32742468C were located in the intron region of the SH3-domain GRB2-like 2 (SH3GL2) gene, which appeared to be associated in the endocytosis and development of the oocyte.
  
  
  CONCLUSIONS
  This study found that G840327C of the GnRH-I gene and the haplotypes of T32742394C-T32742468C of the SH3GL2 gene were associated with the chicken AFE.
authors.affiliation: Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong, China.
authors.forename: Haiping
authors.initials: H
authors.lastname: Xu
authors.forename: Hua
authors.initials: H
authors.lastname: Zeng
authors.forename: Chenglong
authors.initials: C
authors.lastname: Luo
authors.forename: Dexiang
authors.initials: D
authors.lastname: Zhang
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Liang
authors.initials: L
authors.lastname: Sun
authors.forename: Lishan
authors.initials: L
authors.lastname: Yang
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Nie
authors.forename: Xiquan
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics; D009154:Mutation; D011110:Polymorphism, Genetic; D040641:Quantitative Trait Loci / Q000235:genetics*; D012741:Sexual Maturation / Q000235:genetics*
chemical_list: D007987:Gonadotropin-Releasing Hormone