Effect of Inorganic Dietary Selenium Supplementation on Selenoprotein and Lipid Metabolism Gene Expression Patterns in Liver and Loin Muscle of Growing Lambs.

Effect of selenium (Se) supplementation on the selenoprotein and lipid metabolism gene expression patterns in ruminants, especially in lambs is not yet fully understood. The aim of study was to evaluate the effect of Se supplementation on the messenger RNA (mRNA) expression patterns of selected selenoproteins and genes related to lipid metabolism in growing lambs. The experiment was conducted on 48 Polish Merino lambs divided into two groups (n = 24): control (C)-lambs fed with a basal diet (BD) with no Se supplementation, and supplemented (S)-lambs fed with a BD, supplemented with 0.5 mg Se/kg as sodium selenate for 8 weeks. Expression of 12 selenoproteins and six genes related to lipid metabolism was analyzed in the liver and longissimus dorsi (LD) muscle of growing lambs by qPCR. Significant differences were found in the expression of GPX1, GPX2, SEPM, SEPW1, SEP15, SEPGS2, and TXNRD1 in the liver, and GPX1, SEPP1, SEPN1, SEPW1, SEP15, and MSRB1 in the LD muscle between S and C lambs. Se supplementation mainly upregulated SEPW1, SEP15 (P < 0.001; P < 0.01) mRNA expression in the liver, and GPX1, SEPP1, SEPN1, SEPW1 (P < 0.001; P < 0.01) in the muscle of S group. On the other hand, significant decrease in GPX2 (P < 0.01), SEPM (P < 0.001), and SEPHS2 (P < 0.01) mRNA expression levels were observed in the liver of S group of lambs. Se supplementation did not affect PON1, LXRα, and PPARα mRNA expression levels, but a significant increase in mRNA levels of APOE and LPL in the LD muscle (P < 0.05) as well as LPL (P < 0.05) in the liver were noticed in the group of Se supplemented lambs. Our study confirmed that, in lambs, similarly to other species, mRNA expression patterns of several selenoproteins highly depend on dietary Se levels, and their expression is ruled by hierarchical principles and tissue-specific mechanisms. Moreover, the study showed that changes Se intake leads to different levels of genes expression related with lipid metabolism.

Promoter variant-dependent mRNA expression of the MEF2A in longissimus dorsi muscle in cattle.

The myocyte enhancer factor 2A (MEF2A) gene encodes a member of the myocyte enhancer factor 2 (MEF2) protein family that is involved in vertebrate skeletal, cardiac, and smooth muscle development and differentiation during myogenesis. According to recent studies, MEF2 genes might be major regulators of postnatal skeletal muscle growth; thus, they are considered to be important, novel candidates for muscle development and body growth in farm animals. The aim of the present study was to search for polymorphisms in the bovine MEF2A gene and analyze their effect on the MEF2A mRNA expression level in the longissimus dorsi muscle of Polish Holstein-Fresian cattle. In total, 4094 bp of the whole coding sequence and the promoter region of MEF2A were re-sequenced in 30 animals, resulting in the detection of 6 novel variants as well as one previously reported SNP. Three linked mutations in the promoter region (-780T/G, g.-768T/G, and g.-222A/G) and only two genotypes were identified in two Polish breeds (TTA/TTA and TTA/GGG). Three SNPs in the coding region [g.1599G/A (421aa), g.1626G/A (429aa), and g.1641G/A (434aa)] appeared to be silent substitutions and segregated as two intragene haplotypes: GGG and AAA. Expression analysis showed that the mutations in the promoter region are highly associated with the MEF2A mRNA level in the longissimus dorsi muscle of bulls carrying two different genotypes. The higher MEF2A mRNA level was estimated in the muscle of bulls carrying the TTA/TTA (p<0.01) genotype as compared with those with TTA/GGG. The results obtained suggest that the nucleotide sequence mutation in MEF2A might be useful marker for body growth traits in cattle.

A novel polymorphisms in intron 12 of the bovine calpastatin gene.

Calpastatin (CAST) is a specific inhibitor of the ubiquitous calcium-dependent proteases-mu-calpain and m-calpain, found in mammalian tissues. This proteolytic system plays a key role in the tenderization process that occurs during post-mortem storage of meat under refrigerated conditioning. Fragments of the bovine CAST gene including intron 12 were amplified and subjected to SSCP analysis. Four new SNPs were found within intron 12 of the CAST gene: a transition T/C at position 3893+155* A/G at position 3893+163, a transversion T/A at position 3893+223 and a substitution A/G at position 3893+428 (consensus sequence--GenBank AY834771). The genetic variants in the bovine CAST gene can be analyzed with RFLP method and was studied in 375 bulls of six breeds, including Hereford, Aberdeen-angus, Simmental, Charolaise, Limousine and Polish Black-and-White (BW; Fresian) breeds.

Bovine mu-calpain (CAPN1) gene: new SNP within intron 14.

The calpain system originally comprised molecules: two Ca2+-dependent proteases, mu-calpain and m-calpain, and a third polypeptide, calpastatin, whose only known function is to inhibit the two calpains. This proteolytic system plays a key role in the tenderisation process that occurs during post-mortem storage of meat under refrigerated conditioning. Their polymorphism is examined from the point of view of their effect on corresponding production traits. The calpain genes are investigated as potential candidate genes for a quantitative trait locus (QTL) affecting meat tenderness. In this study a new single nucleotide polymorphism (SNP) was found within intron 14 of the bovine CAPN1 gene, being transition C --> T at position 4685 nt (consensus sequence - GenBank No. AF 248054), as this mutation creates a new FokI restriction site detected with PCR-RFLP analysis. This sequence fragment of the SNP position has already been deposited in the GenBank database under accession No. AY639597. The RFLP-FokI polymorphism was studied in 141 bulls of seven breeds, including the native Polish Red (PR, preserved), and Polish Black-and White (BW) breed. The frequency of alleles T and C varied between the breeds considered, the mean reaching 0.38 and 0.62, respectively. Associations between CAPN1/FokI gene polymorphism and meat production traits were studied in BW (n = 84) young bulls. In the animals of the TT genotype the lean share in valuable cuts (%) was found more favourable than in CC animals.

Relationship between microsatellite marker alleles on chromosomes 1-5 originating from the Rhode Island Red and Green-legged Partrigenous breeds and egg production and quality traits in F(2) mapping population.

The objective of this study was to determine the relationship between the origin of marker alleles from the Rhode Island Red (RIR) and Green-legged Partrigenous (GlP) breeds and chosen egg production and quality traits in F(2) generation consisting of 10 full-sib families. Polymorphism analysis of 23 microsatellite markers within the mapping population (519 F(2)) was made. In parental generation 17 alleles were identified as specific for the GlP and 23 for the RIR. The least squares method was used to evaluate the significance of effects of genotype (GlP/GlP, RIR/RIR, GlP/RIR) on the analysed quantitative traits. Thirty traits of egg production and quality were measured during the laying period. It was shown that the effects of the genotype (GlP/GlP, RIR/RIR, GlP/RIR) at the loci on analysed traits of F(2) animals were diversified. Significant effects were found for 16 traits. These results confirm that the analysed microsatellite loci may be linked to the genes affecting egg production and quality traits. The loci examined and the experimental population constitutes a valuable material for QTL mapping (linkage analysis).