Three-generation pedigrees, in which the founders were Meishan and Large White purebred pigs, were used to identify QTL for female reproductive performance. The Chinese Meishan is one of the most prolific pig breeds known, farrowing up to five more piglets per litter than the European commercial Large White breed. However, the Meishan is not commercially viable in Europe due to its poor growth rate and high carcass fat content. Therefore, including the beneficial alleles from the Meishan into the Large White breed is of commercial relevance. QTL for ovulation rate, teat number, age at puberty and uterine capacity have been mapped to chromosome 8 (SSC8) in earlier studies. The aim of this study was to focus specifically on SSC8 and to identify and test candidate genes for the QTL. The genotypes of twenty markers on SSC8 were combined with data collected on the reproductive performance of 220 F2 females. QTL for the related traits of litter size and prenatal survival were identified at the distal end of the q arm. The beneficial alleles at these QTL seem to be from the Meishan. The QTL for prenatal survival was defined as a region of about 30 cM and therefore contains many positional candidate genes, but only a few of these have been mapped in pigs. Human chromosome 4 (HSA4) shares extensive homology to SSC8. A gene map of SSC8 was developed by radiation hybrid mapping in order to align the human genome sequence of HSA4 with the QTL and thus identify comparative positional candidate genes. The resulting comparative map revealed extensive conservation of synteny and gene order. One positional candidate gene, secreted phosphoprotein 1 (<i>SPP1</i>), is also a physiological candidate gene as the protein is involved in porcine embryo implantation and maintenance of pregnancy. A copy of <i>SPP1 </i>(~10 kb) from both Meishan and Large White origin was sequenced to identify candidate causal variation. A total of 97 variants, including single nucleotide polymorphisms (SNPs) and indels, were found. Three of the SNPs would result in non-synonymous amino acid changes. For one of these SNPs the Meishan allele encodes a serine, which would be phosphorylated and the Large White allele encodes a proline, which would not. To test whether the variation at this particular locus resulted in differences in litter sizes, the SNP was genotyped over 2974 pigs of varying breed origin. No association was identified between genotypes at this locus and litter size.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653425 |
| Date | January 2003 |
| Creators | King, Annemarie H. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12376 |
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