Abstract
Intramuscular fat (IMF) is an important trait influencing meat quality, and preadipocyte differentiation is a key factor affecting IMF deposition. Here we compared the transcriptome profiles of porcine intramuscular and subcutaneous preadipocytes during differentiation to gain insight into specific molecular and cellular events associated with intramuscular stromal vascular cell (MSVC) differentiation. RNA-Seq was used to screen for differentially expressed genes (DEGs) during the in vitro differentiation of MSVC and subcutaneous stromal vascular cell (ASVC) on days 0, 2 and 4. A total of 985 DEGs were identified during ASVC differentiation and 1469 DEGs during MSVC differentiation. Among these DEGs, 409 genes were specifically expressed during ASVC differentiation, 893 genes were specifically expressed during MSVC differentiation, and 576 DEGs were co-expressed during ASVC and MSVC differentiation. The expression profiles of DEGs during ASVC or MSVC differentiation were determined by cluster analysis based on Short Time-series Expression Miner (STEM). Four significant STEM profiles (profiles 1, 4, 5, and 14) were determined during ASVC differentiation, and four significant STEM profiles (profiles 1, 4, 11, and 14) were determined during MSVC differentiation. Gene ontology (GO) analysis indicated that DEGs related to adipocyte differentiation were identified to be significantly enriched in both adipose and muscle profile 14. In addition, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of DEGs in adipose profile 14 and muscle profiles 11 and 14 (STEM clustered them into one cluster) showed that the PPAR signaling pathway was significantly enriched in these profiles and four signaling pathways were specifically enriched in muscle profiles 11 and 14. Furthermore, analysis of transcription factor binding sites (TFBS) in the gene set revealed two over-represented transcription factors (NR3C4 and NR3C1), which were specifically significantly enriched in the promoter regions of genes within muscle gene expression profiles 11 and 14.
Highlights
The deposition of intramuscular fat in pigs significantly contributes to meat quality, including juiciness, flavor, and tenderness[1]
To identify gene expression changes during porcine ASVC and MSVC differentiation and to compare whether the change is origin specific, an Illumina HiSeq 2000 sequencing experiment was carried out during the adipogenic differentiation of stromal vascular (SV) cells isolated from porcine longissimus dorsi muscle (LM) and subcutaneous adipose tissue (SAT)
Preadipocytes derived from different fat depots appear to have distinct adipogenic potential [5], which may be an intrinsic factor causing the different number of differentially expressed genes (DEGs) and expressed genes during the adipogenic differentiation of ASCV and MSVC
Summary
The deposition of intramuscular fat in pigs significantly contributes to meat quality, including juiciness, flavor, and tenderness[1]. To meet the increasing demand of consumers for high-quality pork, a main goal of animal scientists worldwide is to improve IMF content. The increase of adipose tissue mass is a result of adipocyte hyperplasia (increase in number) and hypertrophy (increase in size) [2], but the ratio between the two processes varies among depots [3]. Previous study has suggested that IMF deposition appeared to mainly depend on hyperplasia [4]. To increase the IMF content, the potential factors influencing intramuscular adipocyte hyperplasia that occurs via the differentiation of preadipocytes into adipocytes should be investigated. Preadipocytes in different fat depots appear to have distinct adipogenic potential [5]. The tissue-specific molecular regulatory mechanisms underlying intramuscular preadipocyte differentiation remain unclear
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