A novel SMAD family protein, SMAD9 is involved in follicular initiation and changes egg yield of geese via synonymous mutations in exon1 and intron2.

Elevation of egg performance is vital to goose farming. Many poultry scientists are seeking for efficient molecular genetic markers associated with egg yield. In this study, mRNA differential display was adopted to investigate gene expression profiling in the follicular development of goose. For the first time, a novel SMAD family protein SMAD9 (EST CJ111007) was found to be involved in follicular initiation and used to be a candidate gene. Functional regions analysis of Smad9 indicated that SMAD9 protein is highly conserved in MH1 and MH2 domains, and the connection area is highly variable region. 6 pairs of primers (p1-p6) were designed to detect the SNPs of Smad9 by PCR-SSCP method. The results revealed that polymorphisms were discovered in the PCR products amplified with P1 primers in exon1 and P3 primers in intron2. In Smad9 exon1, 5 genotypes were found: FK, FF, JJ, JK and KK, including 2 SNPs: 243 bp G -- A, 309 bp T -- G, the mutations did not result in amino acid mutations; In intron2, 3 genotypes were found: AA, BB and AB, only 1 SNP (C -- T). The annual egg yield of FK genotype geese or allele gene A in intron2 are significantly more than those of other genotypes on the average (p < 0.05). Taken together, it is suggested that Smad9 is a promising candidate gene affecting egg performance in goose.