The GTPase Activating Rap/RanGAP Domain-Like 1 Gene Is Associated with Chicken Reproductive Traits

BACKGROUND: Abundant evidence indicates that chicken reproduction is strictly regulated by the hypothalamic-pituitary-gonad (HPG) axis, and the genes included in the HPG axis have been studied extensively. However, the question remains as to whether any other genes outside of the HPG system are involved in regulating chicken reproduction. The present study was aimed to identify, on a genome-wide level, novel genes associated with chicken reproductive traits. METHODOLOGY/PRINCIPAL FINDING: Suppressive subtractive hybridization (SSH), genome-wide association study (GWAS), and gene-centric GWAS were used to identify novel genes underlying chicken reproduction. Single marker-trait association analysis with a large population and allelic frequency spectrum analysis were used to confirm the effects of candidate genes. Using two full-sib Ningdu Sanhuang (NDH) chickens, GARNL1 was identified as a candidate gene involved in chicken broodiness by SSH analysis. Its expression levels in the hypothalamus and pituitary were significantly higher in brooding chickens than in non-brooding chickens. GWAS analysis with a NDH two tail sample showed that 2802 SNPs were significantly associated with egg number at 300 d of age (EN300). Among the 2802 SNPs, 2 SNPs composed a block overlapping the GARNL1 gene. The gene-centric GWAS analysis with another two tail sample of NDH showed that GARNL1 was strongly associated with EN300 and age at first egg (AFE). Single marker-trait association analysis in 1301 female NDH chickens confirmed that variation in this gene was related to EN300 and AFE. The allelic frequency spectrum of the SNP rs15700989 among 5 different populations supported the above associations. Western blotting, RT-PCR, and qPCR were used to analyze alternative splicing of the GARNL1 gene. RT-PCR detected 5 transcripts and revealed that the transcript, which has a 141 bp insertion, was expressed in a tissue-specific manner. CONCLUSIONS/SIGNIFICANCE: Our findings demonstrate that the GARNL1 gene contributes to chicken reproductive traits

Prior experience with photostimulation enhances photo-induced reproductive response in female house finches

In vertebrates, reproductive output often increases with age. Unlike older birds, first-year photoperiodic birds lack experience with the reproductively stimulatory effects of long day lengths (photostimulation). We examined whether age-related differences in annual reproductive development could be partially attributed to previous experience with photostimulation in the photoperiodic house finch (Carpodacus mexicanus). By manipulating photoperiod, we generated 2 groups of first-year females: a photo-experienced group that underwent 1 photoperiodically induced cycle of gonadal development and regression and a photo-naïve group exposed to long days since hatch. We transferred both groups from long to short days and then photostimulated and exposed them to male birdsong prior to sacrifice. Following concurrent photostimulation, both groups exhibited similar plasma luteinizing hormone surges and hypothalamic vasoactive intestinal polypeptide immunoreactivity. In contrast, hypothalamic gonadotropin-releasing hormone immunoreactivity and circulating vitellogenin levels were higher in photo-experienced birds, and yolk deposition occurred in only 2 females, both of which were photo-experienced. Our results demonstrate that photo-experience enhances some aspects of early photo-induced reproductive development and raise the hypothesis that photo-experience may account for at least some age-related variation in reproductive output