Rosane Oliveira

Multisite haplotype on cattle chromosome 3 is associated with quantitative trait locus effects on lactation traits

The goal of this study was to identify candidate genes and DNA polymorphisms for quantitative trait loci (QTL) affecting milk yield (MY), fat yield (FY), and protein yield (PY) previously mapped to bovine chromosome 3 (BTA3). To accomplish this, 373 half-siblings sired by three bulls previously shown to be segregating for lactation trait QTL, and 263 additional sires in the U.S. Dairy Bull DNA Repository (DBDR) were genotyped for 2,500 SNPs within a 16.3 Mbp QTL critical region on BTA3. Targeted resequencing of ∼1.8 Mbp within the QTL critical region of one of the QTL heterozygous sires identified additional polymorphisms useful for association studies. Twenty-three single nucleotide polymorphisms (SNPs) within a fine-mapped region were associated with effects on breeding values for MY, FY, or PY in DBDR sires, of which five SNPs were in strong linkage disequilibrium in the population. This multisite haplotype included SNPs located within exons or promoters of four tightly linked genes: RAP1A, ADORA3, OVGP1, and C3H1orf88. An SNP within RAP1A showed strong evidence of a recent selective sweep based on integrated haplotype score and was also associated with breeding value for PY. Because of its known function in alveolar lumen formation in the mammary gland, RAP1A is thus a strong candidate gene for QTL effects on lactation traits. Our results provide a detailed assessment of a QTL region that will be a useful guide for complex traits analysis in humans and other noninbred species.

Changes in WNT signaling-related gene expression associated with development and cloning in bovine extra-embryonic and endometrial tissues during the peri-implantation period

We determined if somatic cell nuclear transfer (SCNT) cloning is associated with WNT‐related gene expression in cattle development, and if the expression of genes in the WNT pathway changes during the peri‐implantation period. Extra‐embryonic and endometrial tissues were collected at gestation days 18 and 34 (d18, d34). WNT5A, FZD4, FZD5, LRP5, CTNNB1, GNAI2, KDM1A, BCL2L1, and SFRP1 transcripts were localized in extra‐embryonic tissue, whereas SFRP1 and DKK1 were localized in the endometrium. There were no differences in the localization of these transcripts in extra‐embryonic tissue or endometrium from SCNT or artificial insemination (AI) pregnancies. Expression levels of WNT5A were 11‐fold greater in the allantois of SCNT than AI samples. In the trophoblast, expression of WNT5A, FZD5, CTNNB1, and DKK1 increased significantly from d18 to d34, whereas expression of KDM1A and SFRP1 decreased, indicating that implantation is associated with major changes in WNT signaling. SCNT was associated with altered WNT5A expression in trophoblasts, with levels increasing 2.3‐fold more in AI than SCNT conceptuses from d18 to d34. In the allantois, expression of WNT5A increased 6.3‐fold more in SCNT than AI conceptuses from d18 to d34. Endometrial tissue expression levels of the genes tested did not differ between AI or SCNT pregnancies, although expression of individual genes showed variation across developmental stages. Our results demonstrate that SCNT is associated with altered expression of specific WNT‐related genes in extra‐embryonic tissue in a time‐ and tissue‐specific manner. The pattern of gene expression in the WNT pathway suggests that noncanonical WNT signal transduction is important for implantation of cattle conceptuses. Mol. Reprod. Dev. 80: 977–987, 2013.