Abstract
Backfat thickness is one of the most important traits of commercially raised pigs. Meishan pigs are renowned for having thicker backfat than Landrace pigs. To examine the genetic factors responsible for the differences, we first produced female crossbred pig lines by mating Landrace (L) × Large White (W) × Duroc (D) females (LWD) with Landrace (L) or Meishan (M) boars (i.e., LWD × L = LWDL for Landrace offspring and LWD × M = LWDM for the Meishan offspring). We confirmed that LWDM pigs indeed had a thicker backfat than LWDL pigs. Next, we performed gene expression microarray analysis in both genetic lines to examine differentially expressed genes (DEGs) in energy metabolism-related tissues, subcutaneous adipose (fat), liver, and longissimus dorsi muscle tissues. We analyzed the annotation of DEGs (2-fold cutoff) to functionally categorize them by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. The number of DEGs in muscle tissues of both lines was much less than that in fat and liver tissues, indicating that DEGs in muscle tissues may not contribute much to differences in backfat thickness. In contrast, several genes related to muscle (in fat tissue) and lipid metabolism (in liver tissue) were more upregulated in LWDM pigs than LWDL pigs, indicating that those DEGs might be responsible for differences in backfat thickness. The different genome-wide gene expression profiles in the fat, liver, and muscle tissues between genetic lines can provide useful information for pig breeders.
Highlights
Genetic improvements in physiological characteristics related to productivity and quality of meat is an economically important subject matter to livestock producers
At 12 days of age, LWDL pigs were significantly heavier than the LWDM pigs
In the fat of LWDL sucklings, the AGT, fibroblast growth factor 2 (FGF2), and platelet-derived growth factor receptor alpha (PDGFRA) genes were upregulated. Because these genes are reported to affect adipocyte differentiation [32,33,34,35], these findings suggest that these upregulated genes, by affecting adipocyte differentiation, might be involved in promoting thinner backfat in LWDL pigs than in LWDM pigs
Summary
Genetic improvements in physiological characteristics related to productivity and quality of meat is an economically important subject matter to livestock producers. The study of genetic factors regulating the development of subcutaneous adipose tissues has been intensively investigated [1,2,3]. More than 3,600 quantitative trait loci (QTLs) associated with fat-related phenotypes have been reported in pigs [4]. The integration of QTL information and associated physiological information, such as regulation of adipocyte differentiation, would be useful for determining responsive genes in QTL regions [6, 7]. We have investigated genomewide gene expression profiles during the adipocyte differentiation of a PSPA cell line, derived from a clonal preadipocyte cell line established from porcine subcutaneous tissues [8], using DNA microarray analysis [9]. The study revealed that several differentially expressed genes identified during adipocyte differentiation co-localized to previously detected fat-related QTL regions, which suggests that these genes are candidates for fat-related QTL regions
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