Abstract
Large White, an introduced European pig breed, and Meishan, a Chinese indigenous pig breed, were hybridized directly and reciprocally and a total of 260 pigs, including purebreds, Large White and Meishan, and their hybrids, White×Meishan (LM) and Meishan×Large White (ML) pigs, were bred in our laboratory. The mRNA differential display PCR (DD-PCR) was used to detect the age-dependent changes of differential gene expression in backfat tissue between hybrids and parents. Some measures were taken to reduce the false positives in our experiment. Among the total of 2,686 bands obtained, 1,952 bands (about 72.67%) were reproducible and eight patterns (fifteen kinds) of gene expression were observed. The percentage of differentially expressed genes between hybrids and parents is 56.86% at the age of four months and 57.71% at the age of six months. This indicated that the differences of gene expression between hybrids and their parents were very obvious. U-test was used to compare the patterns of gene expression between the age of four and six months, and results showed that bands occurring in only one hybrid and bands displayed in one hybrid and one parent were significantly different at p<0.05, and bands visualized in only two hybrids were significantly different at p<0.01. These indicated that differential gene expression between hybrids and parents changed at different ages. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 5 : 682-685)
Highlights
Fat tissue was the main location saving up fat, which could store energy, maintain animal heat, protect vital organisms, lighten physical pressure and secreted many cytokines and cytokine-likes such as leptin (Luheshi et al, 1999), TNF-α (Kern et al, 1995), IL-6 (Yumoto et al, 1999), adiponectin (Yamauchi et al, 2001) and so on
Eight patterns of gene expression were observed at both four and six months old (Figure 2), which included: (1) bands occurring in only parents (1001); (2) bands occurring in only one parent (0001 and 1000); (3) bands observed in parents and one hybrid (1101 and 1011); (4) bands occurring in only one hybrid (0100 and 0010); (5) bands visualized in only hybrids (0110); (6) bands occurring in one hybrid and one parent (1010, 0101, 1100 and 0011); (7) bands occurring in hybrids and one parent (1110 and 0111) and (8) bands detected in both hybrids and parents (1111)
The key problems of this technique were the reproducibility of display PCR and the high percentage of false positive
Summary
Fat tissue was the main location saving up fat, which could store energy, maintain animal heat, protect vital organisms, lighten physical pressure and secreted many cytokines and cytokine-likes such as leptin (Luheshi et al, 1999), TNF-α (tumor necrosis factor alpha) (Kern et al, 1995), IL-6 (interleukin-6) (Yumoto et al, 1999), adiponectin (Yamauchi et al, 2001) and so on. The increase of cell number was found at forepart before and after birth in adipose tissue, cell volume increased basically. The increase of lipocyte volume was very quick at the age of four months but became slow after the age of six months in pigs. It would be very meaningful that pigs at the age of four and six months were selected to detect the agedependant changes of differential gene expression. There are significant phenotypic variance between Chinese indigenous pigs and introduced pigs. Chinese pigs have higher prolificacy and superior meat quality, but lower growth rate and higher fat ratio compared to the introduced pigs (Mo et al, 2003). Many pig breeders have crossed indigenous pig breeds with European pig breeds to develop new pig breeds that have superior performance compared to their parents.
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