Abstract
This study was to screen, verify and apply molecular markers of candidate genes (FREM1 and PTPRM) related to eyelid defect, which may facilitate establishment of autosexing strains of Huoyan goose. Using 150 1-d-old Huoyan geese containing 100 with colobomus eyelid and 50 with normal eyelid, 6 and 3 polymorphic loci single nucleotide polymorphisms (SNPs) were identified in the 1-kb upstream sequences of FREM1 transcript 1 and transcript 2, respectively. All identified SNPs showed significant association with the colobomus eyelid trait (P < 0.05). To further investigate the regulatory effects of these SNPs, dual-luciferase reporter assays in goose primary hepatocytes and myocytes confirmed that mutations at SNP2 locus (c.-385 A > T) in transcript 1 and SNP3 locus (c.-714 A > G) in transcript 2 significantly enhanced or suppressed FREM1 expression, respectively (P < 0.05). Subsequently, bioinformatics analysis predicted that SNP2 was located within the binding sequence of Pou1f1, and that SNP3 was located within the binding sequence of CUX2. Treatment with 1 μmol/L dexamethasone (drug for Poulf1) induced FREM1 expression (P < 0.05), and treatment with 75 μg/mL rifampicin (drug for CUX2) suppressed FREM1 expression (P < 0.05). Furthermore, quantitative real-time PCR analysis revealed that female Huoyan geese with either the normal eyelid or wild type genotype exhibited significantly higher FREM1 expression in both eyelid and liver tissues of than those with the colobomus eyelid or mutant genotype, respectively (P < 0.05). Based on the key polymorphic locus in FREM1 identified in this study, combined with previously discovered key locus in PTPRM, marker-assisted selection led to an increase in the colobomus eyelid rate, reaching 97.03 % in 303 offspring. In conclusion, the findings strongly support FREM1 and PTPRM as causative genes for the colobomus eyelid trait; the obtained molecular markers can significantly improve the selection efficiency; mutations at the key SNP loci in the upstream sequences of FREM1 can alter its expression by affecting the binding affinity of the putative transcription factors, Pou1f1 and CUX2.