Microarray analysis reveals genes and functional networks relevant to the predisposition to inverted teats in pigs1

Abstract

The inverted teat defect is characterized by the failure of teats to protrude from the udder surface and has a negative effect on the economic efficiency of pig production. The inverted teat defect is influenced by genetic factors, but the number and identity of relevant genes are unknown. In this study, we compared the mRNA expression of teat tissues from unaffected pigs and affected pigs by using microarrays. Simultaneously, 24,123 probe sets were screened, of which some 15,000 had present calls and were analyzed for differential expression between mesenchymal and epithelial tissue of 3 categories of teats (i.e., normal teats of unaffected and affected animals, and inverted teats of the latter). Differential expression was more pronounced in epithelial than in mesenchymal tissue, and the comparisons among the 3 categories of teats showed that local processes at the side of the affected area as well as processes taking place at the level of the organ contribute to the development of inverted teats. Genes related to biofunctions of cell maintenance, proliferation, differentiation, and replacement; organismal, organ, and tissue development; genetic information and nucleic acid processing; and cell-to-cell signaling and interaction were differentially expressed, depending on the teat phenotype and the status of the animal as affected or unaffected. In particular, genes encoding members of canonical pathways of growth factor signaling were highlighted. Complementary to previous real-time quantitative reverse-transcription PCR experiments showing upregulation of growth factors (epidermal growth factor, fibroblast growth factor, hepatocyte growth factor, platelet-derived growth factor, vascular endothelial growth factor) and their receptors in the inverted teat, here it is shown that the abundance of transcripts encoding subordinated proteins (acid phosphatase 1, soluble; activating transcription factor 2; casein kinase 2, α 1 polypeptide; casein kinase 2, α prime polypeptide; actinin, α 2; and Homo sapiens growth factor receptor-bound protein 2) within the growth factor signaling pathways are also affected. Tuning of the expression of genes of these pathways balances the differentiation and proliferation of epithelial and mesenchymal teat tissue and finally affects the shape and structure of the teats.

Epigenetics and developmental programming of welfare and production traits in farm animals

“…As for cattle and sheep, mammary gland development in the pig is initiated during the early stages of fetal development (from around Day 23 of gestation), and involves intricate signalling between the epithelial cells of the mammary buds, which go on to form milk lines, and the surrounding mesenchymal cells; molecular details for this species are only just coming to light (Chomwisarutkun et al 2012). However, other than the aforementioned effect of fetal sex ratio on teat number in gilts, the authors are unaware of any studies that have investigated in utero programming of mammary gland development in this species.…”

Identification of novel candidate genes for the inverted teat defect in sows using a genome-wide marker panel

“…There have been only a few studies on genetic markers for the inverted teat defect or other teat abnormalities in pigs. Quantitative trait loci (QTLs) have previously been reported on different chromosomes for inverted teats (Jonas et al 2008) and for extremely small teats (Sato et al 2006), while expression studies were performed for the inverted teat (Chomwisarutkun et al 2012a, b, 2013). The region identified on chromosome 2 overlapped to both the previous linkage studies (Jonas et al 2008; Sato et al 2006) and the expression study (Chomwisarutkun et al 2012b).…”

“…Quantitative trait loci (QTLs) have previously been reported on different chromosomes for inverted teats (Jonas et al 2008) and for extremely small teats (Sato et al 2006), while expression studies were performed for the inverted teat (Chomwisarutkun et al 2012a, b, 2013). The region identified on chromosome 2 overlapped to both the previous linkage studies (Jonas et al 2008; Sato et al 2006) and the expression study (Chomwisarutkun et al 2012b). Results from a previous study did also present a suggestive QTL in a commercial pig lines for the region on chromosome 10 (Jonas et al 2008), as most of our identified loci did also not exceed the significance threshold.…”

“…While the QTL identified using pigs from an experimental population did reach the significance threshold, this QTL was in another position on the same chromosome (Jonas et al 2008). However, gene expression differences between tissue from inverted and normal teats of affected sows and between inverted and normal teats of affected and normal sows were observed in the same regions on chromosome 10 (Chomwisarutkun et al 2012b). The results on chromosome 18 did confirmed regions identified in previous linkage studies, while the differentially expressed genes were identified in different regions on that chromosome.…”

“…Presently, only a few studies have focused on the identification of genetic regions associated with this trait, using linkage and expression analysis (Chomwisarutkun et al 2012a, b; Jonas et al 2008). A number of candidate genes had been tested, including parathyroid hormone-like hormone gene ( PTHLH ) and its receptor ( PTHR1 ), which have been suggested as possible regulators for inverted teats (Tetzlaff et al 2009).…”