A Novel Single-Nucleotide Polymorphism in <i>W</i><i>NT4</i> Promoter Affects Its Transcription and Response to FSH in Chicken Follicles.

The signaling pathway of the wingless-type mouse mammary tumor virus integration site (Wnt) plays an important role in ovarian and follicular development. In our previous study, <i>W</i><i>NT4</i> was shown to be involved in the selection and development of chicken follicles by upregulating the expression of follicle-stimulating hormone receptors (<i>FSHR</i>), stimulating the proliferation of follicular granulosa cells, and increasing the secretion of steroidal hormones. FSH also stimulates the expression of <i>WNT4</i>. To further explore the molecular mechanism by which FSH upregulates <i>W</i><i>NT4</i> and characterize the cis-elements regulating <i>W</i><i>NT4</i> transcription, in this study, we determined the critical regulatory regions affecting chicken <i>W</i><i>NT4</i> transcription. We then identified a single-nucleotide polymorphism (SNP) in this region, and finally analyzed the associations of the SNP with chicken production traits. The results showed that the 5' regulatory region from -3354 to -2689 of <i>W</i><i>NT4</i> had the strongest activity and greatest response to FSH stimulation, and we identified one SNP site in this segment, -3015 (G &amp;gt; C), as affecting the binding of NFAT5 (nuclear factor of activated T cells 5) and respones to FSH stimulation. When G was replaced with C at this site, it eliminated the NFAT5 binding. The mRNA level of <i>WNT4</i> in small yellow follicles of chickens with genotype GG was significantly higher than that of the other two genotypes. Moreover, this locus was found to be significantly associated with comb length in hens. Individuals with the genotype CC had longer combs. Collectively, these data suggested that SNP-3015 (G &amp;gt; C) is involved in the regulation of <i>W</i><i>NT4</i> gene expression by responding FSH and affecting the binding of NFAT5 and that it is associated with chicken comb length. The current results provide a reference for further revealing the response mechanism between WNT and FSH.