Association of SNP and STR polymorphisms of insulin-like growth factor 2 receptor (IGF2R) gene with milk traits in Holstein-Friesian cows.

The objective of the study reported in this Research Communication was to investigate the association of polymorphisms in the insulin-like growth factor receptor 2 (IGF2R) gene with milk traits in 283 Polish Holstein-Friesian (PHF) cows from the IGAB PAS farm in Jastrzebiec. IGF2R regulates the availability of biologically active IGF2 which is considered as a genetic marker for milk or meat production in farm animals. Two novel genetic polymorphisms were identified in the bovine IGF2R gene: a polymorphic TG-repeat in intron 23 (g.72389 (TG)15-67), and a g.72479 G > A SNP RFLP-StyI in exon 24. The following milk traits were investigated: milk yield, protein and fat yield, SCC and lactose content. To determine the influence of the IGF2R STR and SNP genotypes on the milk traits, we used the AI-REML (average information restricted maximum likelihood) method with repeatability, multi-trait animal model based on test-day information using DMU package. Statistical analysis revealed that the G/A genotype (P ≤ 0·01) was associated with milk and protein yield, lactose content and somatic cell count (SCC) in Polish HF cows. TGn (29/22, 28/29, 28/22, 28/28) genotypes were associated with high values for milk, (28/22, 28/23) with protein and fat yield, (25/20) with lactose content, and (29/33, 28/28) with low SCC. We suggest that the IGF2R gene polymorphisms could be useful genetic markers for dairy production traits in cattle.

Association of polymorphisms in exons 2 and 10 of the insulin-like growth factor 2 ( IGF2) gene with milk production traits in Polish Holstein-Friesian cattle.

Insulin-like growth factor 2 (IGF2) is considered to be a regulator of post-natal growth and differentiation of the mammary gland. In the present work, associations of two single nucleotide polymorphisms in the bovine IGF2 gene with milk production traits were studied in dairy Holstein-Friesian cows: the already described g.8656C>T transition in exon 2 (RFLP-BsrI) and the newly found g.24507G>T transversion in exon 10 (RFLP-HaeIII), found by sequencing 273-bp exon 10 of the IGF2 gene in six individuals. Associations were analysed individually and in combination with the multi-trait repeatability test-day animal model. The CT/GT haplotype appeared to be associated with most of the milk traits studied (differences were significant at P < or = 0.001). The most frequent CT/GG haplotype seemed inferior to others in fat and protein content and daily yield of fat and protein but superior (together with the TT/GG genotype) when the daily milk yield is considered.

Polymorphism in genes of growth hormone receptor (GHR) and insulin-like growth factor-1 (IGF1) and its association with both the IGF1 expression in liver and its level in blood in Polish Holstein-Friesian cattle.

BACKGROUND: Polymorphisms in the bovine ghr and igf1 genes. Ghr and igf1 genes have been associated with milk and meat production of cattle. However, the molecular and physiological mechanisms underlying such associations are unknown. The objective of this study was to examine the effects of polymorphisms in 5'-regions of the bovine ghr and igf1 genes on the igf1 gene expression in the liver and on the level of IGF1 in blood of Polish Holstein-Friesian cattle. METHODS: Individual and combined effects of single nucleotide polymorphisms (SNPs) in the 5'noncoding regions of the bovine igf1 and ghr genes on the IGF1 level in blood and igf1 gene expression in liver were examined. One SNP in the igf1 gene and four SNPs in the ghr gene were analyzed. IGF1 level in blood was measured by radioimmunoassay (RIA) in 211 heifers and bulls of Polish Holstein-Friesian cattle (of Black-and-White type). The igf1 gene expression was measured in livers of bulls carrying different igf1 and ghr genotypes (from three to nine animals per genotype) using real-time reverse transcription-PCR methods with the gapdh gene as a reference. RESULTS: We showed that C/T transition in the promoter region of the igf1 gene influences the gene expression; relative igf1 expression was higher for animals with the CC genotype than for those with the TT and CT genotypes. TESS analysis showed that C/T transition in the igf1 gene co-localizes with the NF1 transcription factor binding site. Also, the ghr genotype appeared to significantly influence the igf1 gene expression in the liver, and we found the highest expression for the genotypes: RFLP-AluI (AT), RFLP-Fnu4HI(CC), and RFLP-NsiI(GA), and for the combined ghr genotype: AluI(AT)/ Fnu4HI(CC)/NsiI(GA). We discovered a significant association between the igf1 genotype and the IGF1 blood level. The highest IGF1 content in blood serum was found in CC genotype animals (1024 ng/ml) vs 698 ng/m and 859 ng/min in the TT and CT igf1 genotypes, respectively. Moreover, we noticed significant differences between ghr genotypes. The highest blood levels of IGF1 were for the animals carrying the ghr genotypes: RFLP-AluI(AA), RFLP-Fnu4HI(CC), and RFLP-NsiI(AG). Ghr haplotypes also significantly affected the IGF1 blood level. Animals of the combined ghr genotypes AluI(AA)/AccI(CC)/Fnu4HI(CC)/NsiI(AG) and AluI(AA)/AccI(CT)/Fnu4HI (CC)/ NsiI(AG) had a higher IGF1 concentration in blood than other genotype carriers. CONCLUSIONS: The present results indicate that the effects of polymorphism in the igf1 and ghr genes on cattle milk or meat production traits could be at least partially mediated through their effects on the igf1 gene expression in the liver and the IGF1 level in blood.

Gene expression profiling in skeletal muscle of Holstein-Friesian bulls with single-nucleotide polymorphism in the myostatin gene 5'-flanking region.

Myostatin (GDF-8) is a key protein responsible for skeletal muscle growth and development, thus mutations in the mstn gene can have major economic and breeding consequences. The aim of the present study was to investigate myostatin gene expression and transcriptional profile in skeletal muscle of Holstein-Friesian (Black-and-White) bulls carrying a polymorphism in the 5'-flanking region of the mstn gene (G/C transversion at position -7828). Real-time qRT-PCR and cDNA microarray revealed significantly lower mstn expression in muscle of bulls with the CC genotype, as compared to GG and GC genotypes. The direct comparison of skeletal muscle transcriptional profiles between the CC genotype and GG and GC genotypes resulted in identification of genes, of which at least some can be putative targets for myostatin. Using cDNA microarray, we identified 43 common genes (including mstn) with significantly different expression in skeletal muscle of bulls with the CC genotype, as compared to GG and GC genotypes, 15 of which were upregulated and 28 were downregulated in the CC genotype. Classification of molecular function of differentially expressed genes revealed the highest number of genes involved in the expression of cytoskeleton proteins (9), extracellular matrix proteins (4), nucleic acid-binding proteins (4), calcium-binding proteins (4), and transcription factors (4). The biological functions of the largest number of genes involved: protein metabolism and modification (10), signal transduction (10), cell structure (8), and developmental processes (8). The main identified signaling pathways were: Wnt (4), chemokines and cytokines (4), integrin (4), nicotine receptor for acetylocholine (3), TGF-beta (2), and cytoskeleton regulation by Rho GTPase (2). We identified previously unrecognized putatively myostatin-dependent genes, encoding transcription factors (EGR1, Nf1b, ILF1), components of the proteasomal complex (PSMB7, PSMD13) and proteins with some other molecular function in skeletal muscle (ITGB1BP3, Pla2g1b, ISYNA1, TNFAIP6, MST1, TNNT1, CALB3, CACYBP, and CTNNA1).