The effect of palmitate supplementation on gene expression profile in proliferating myoblasts.

High-fat diet, exposure to saturated fatty acids, or the presence of adipocytes in myoblast microenvironment affects skeletal muscle growth and function. The aim of the present study was to investigate the effect of palmitate supplementation on transcriptomic profile of mouse C2C12 myoblasts. Global gene expression was evaluated using whole mouse genome oligonucleotide microarrays, and the results were validated through qPCR. A total of 4047 genes were identified as differentially expressed, including 3492 downregulated and 555 upregulated genes, during a 48-h exposure to palmitate (0.1 mmol/l). Functional classification showed the involvement of these genes in several processes which regulate cell growth. In conclusion, the addition of palmitate modifies the expression of genes associated with (1) myoblast responsiveness to hormones and growth factors, (2) cytokine and growth factor expression, and (3) regulation of cell-cell and cell-matrix communication. Such alterations can affect myoblast growth and differentiation; however, further studies in this field are required.

Characterization of microRNA profile in mammary tissue of dairy and beef breed heifers.

MicroRNAs (miRNAs) are small non-coding RNAs that participate in the regulation of gene expression. Their role during mammary gland development is still largely unknown. In this study, we performed a microarray analysis to identify miRNAs associated with high mammogenic potential of the bovine mammary gland. We identified 54 significantly differentially expressed miRNAs between the mammary tissue of dairy (Holstein-Friesian, HF) and beef (Limousin, LM) postpubertal heifers. Fifty-two miRNAs had higher expression in the mammary tissue of LM heifers. The expression of the top candidate miRNAs (bta-miR-10b, bta-miR-29b, bta-miR-101, bta-miR-375, bta-miR-2285t, bta-miR-146b, bta-let7b, bta-miR-107, bta-miR-1434-3p) identified in the microarray experiment was additionally evaluated by qPCR. Enrichment analyses for targeted genes revealed that the major differences between miRNA expression in the mammary gland of HF versus LM were associated with the regulation of signalling pathways that are crucial for mammary gland development, such as TGF-beta, insulin, WNT and inflammatory pathways. Moreover, a number of genes potentially targeted by significantly differentially expressed miRNAs were associated with the activity of mammary stem cells. These data indicate that the high developmental potential of the mammary gland in dairy cattle, leading to high milk productivity, depends also on a specific miRNA expression pattern.

Transcriptional background of beef marbling - novel genes implicated in intramuscular fat deposition.

The purpose of this study was to identify novel marbling-related genes by comparison of the global gene expression in semitendinosus muscle of 15-month-old Limousin (LIM), Holstein-Friesian (HF) and Hereford (HER) bulls. Muscle of LIM was lean with low intramuscular fat (IMF) content (0.53%) unlike the marbled muscles of HER and HF characterized by higher amounts of IMF (1.10 and 0.81%, respectively). The comparison of muscle transcriptional profile between marbled and lean beef revealed significant differences in expression of 144 genes, presumably involved in consecutive stages of adipose tissue development, such as preadipocyte proliferation and differentiation, adipocyte maturation, lipid filling and lipid metabolism leading to increased IMF deposition and marbling development. Correlation coefficients and regression analysis for nine of them (gadd45a, pias3, ccrn4l, diras3, pou5f1, hoxa9, atp2a2 and pim1) validated by real-time qPCR confirmed their moderate-high correlation with IMF% and explained up to 70.5% of the total variability in IMF deposition in the bulls.

The transcriptomic signature of myostatin inhibitory influence on the differentiation of mouse C2C12 myoblasts.

GDF8 (myostatin) is a unique cytokine strongly affecting the skeletal muscle phenotype in human and animals. The aim of the present study was to elucidate the molecular mechanism of myostatin influence on the differentiation of mouse C2C12 myoblasts, using the global-transcriptome analysis with the DNA microarray technique. Treatment with exogenous GDF8 strongly affected the growth and development of C2C12 mouse myoblasts. This was manifested by the inhibition of proliferation and differentiation as well as the impairment of cell fusion. DNA microarray analysis revealed 778 genes regulated by GDF8 in differentiating myoblasts (436 down-regulated and 235 up-regulated). Ontological analysis revealed their involvement in 17 types of biological processes, 10 types of molecular functions and 68 different signalling pathways. The effect of GDF8 was mainly mediated by the disruption of the cell cycle, calcium and insulin signalling pathways and expression of cytoskeletal and muscle specific proteins. The identified key-genes that could play a role as GDF8 targets in differentiating myoblasts are: Mef2, Hgf, Ilbl, Itgb1, Edn1, Ppargc1a.

Transcriptional pattern of TGF-beta1 inhibitory effect on mouse C2C12 myoblasts differentiation.

The aim of the present study was to define the effect of TGF-beta1 on C2C12 myoblasts myogenesis. TGF-beta1 together with its receptor is a negative auto-paracrine regulator of myogenesis, which influences the proliferation, differentiation, and functions of muscle cells. TGF-beta1 exerts highly significant inhibitory effect on differentiation of C2C12 mouse myoblasts manifested by the impairment of cell fusion and very low expression of myosin heavy chain. The study of differentiating C2C12 mouse myoblasts treated with TGF-beta1 revealed 502 genes (436 down-regulated and 66 up-regulated) with statistically different expression. TGF-beta1-regulated genes were identified to be involved in 29 biological processes, 29 molecular functions groups and 59 pathways. The strongest inhibiting effect of TGF-beta1 was observed in the cadherin and Wnt pathways. The key-genes that could play the role of TGF-beta1 targets during myoblasts differentiation was identified such as: Max, Creb1, Ccna2, Bax, MdfL, Tef, Tubg1, Cxcl5, Rho, Calca and Lgals4.