Fatness traits are important in pig production since they influence meat quality and fattening efficiency. On the other hand, excessive fat accumulation in humans has become a serious health problem due to worldwide spread of obesity. Since the pig is also considered as an animal model for numerous human diseases, including obesity and metabolic syndrome, comparative genomic studies may bring new insights into genetics of fatness/obesity. Input of genetic factors into phenotypic variability of these traits is rather high and the heritability coefficient (h(2)) of these traits oscillates around 0.5. Genome scanning revealed the presence of more than 500 QTLs for fatness in the pig genome. In addition to QTL studies, many candidate gene polymorphisms have been analyzed in terms of their associations with pig fatness, including genes encoding leptin (LEP) and its receptor (LEPR), insulin-like growth factor 2 (IGF-2), fatty acid-binding proteins (FABP3 and FABP4), melanocortin receptor type 4 (MC4R), and the FTO (fat mass and obesity-associated) gene. Among them, a confirmed effect on pig fatness was found for a well-known polymorphism of the IGF-2 gene. In humans the strongest association with predisposition to obesity was shown for polymorphism of the FTO gene, while in pigs such an association seems to be doubtful. The development of functional genomics has revealed a large number of genes whose expression is associated with fat accumulation and lipid metabolism, so far not studied extensively in terms of the association of their polymorphism with pig fatness. Recently, epigenomic mechanisms, mainly RNA interference, have been considered as a potential source of information on genetic input into the fat accumulation process. The rather limited progress in studies focused on the identification of gene polymorphism related with fatness traits shows that their genetic background is highly complex.

Abstract. Pedigree and molecular data were used to evaluate genetic diversity in the Polish populations of the Polish primitive horse (also known as Polish Konik) and Hucul breeds over the time period of 30 years . Based on genotypes in 12 microsatellite loci (for 3865 Polish primitive horses and 1627 Huculs), as well as on pedigree data derived from over 7000 individuals (both breeds), several indices describing structure of the analysed populations were estimated. For both analysed breeds, we observed an increasing trend of inbreeding since 1980 which seems to be much more stable (oscillating around 10 % in the Polish primitive horse and 5 % in Hucul) since the beginning of 2000s when they were included in conservation programs in Poland. We observed that generally, indices related to genetic diversity are higher in the Hucul breed. Our study indicated that genetic diversity in the Polish primitive horse and Hucul breeds in Poland is still relatively high and conservation programs should be continued to keep it on the "safe" level in the future.

Apart from the well-known role of somatic cell count as a parameter reflecting the inflammatory status of the mammary gland, the composition of cells isolated from milk is considered as a valuable material for gene expression studies in mammals. Due to its unique composition, in recent years an increasing interest in mare's milk consumption has been observed. Thus, investigating the genetic background of horse’s milk variability presents and interesting study model. Relying on 39 milk samples collected from mares representing three breeds (Polish Primitive Horse, Polish Cold-blooded Horse, Polish Warmblood Horse) we aimed to investigate the utility of equine milk somatic cells as a source of mRNA and to screen the best reference genes for RT-qPCR using geNorm and NormFinder algorithms. The results showed that despite relatively low somatic cell counts in mare's milk, the amount and the quality of the extracted RNA are sufficient for gene expression studies. The analysis of the utility of 7 potential reference genes for RT-qPCR experiments for the normalization of equine milk somatic cells revealed some differences between the outcomes of the applied algorithms, although in both cases the KRT8 and TOP2B genes were pointed as the most stable. Analysis by geNorm showed that the combination of 4 reference genes (ACTB, GAPDH, TOP2B and KRT8) is required for apropriate RT-qPCR experiments normalization, whereas NormFinder algorithm pointed the combination of KRT8 and RPS9 genes as the most suitable. The trial study of the relative transcript abundance of the beta-casein gene with the use of various types and numbers of internal control genes confirmed once again that the selection of proper reference gene combinations is crucial for the final results of each real-time PCR experiment.

Abbreviations used: AF -abdominal fat weight; BF -backfat thickness; FC -feed conversion ratio; FOXO1 -forkhead box O1; FXR -farnesoid X receptor; GRglucocorticoid receptor; HNF4α -hepatic nuclear factor 4α; IMF -intramuscular fat content; LD -longissimus dorsi; LXRα -liver X receptor-α; MEF2 -myocyte enhancer factor 2; NRF-1 -nuclear respiratory factor 1; NRF-2 -nuclear respiratory factor 2; PCRpolymerase chain reaction; PL -Polish Landrace; PLW -Polish Large White; PPARα -peroxisome proliferative activated receptor-α; PPARβ/δ -peroxisome proliferative activated receptor-β/δ; PPARGC1A -peroxisome proliferative activated receptor-γ, coactivator-1α; QTL -quantitative trait loci; RFLP -restriction fragment length polymorphism; RYR1 -ryanodine receptor 1; SNP -single nucleotide polymorphism; SSC8 -Sus scrofa chromosome 8; SSCP -single strand conformation polymorphism substantially between breeds. The association of the SNPs with production traits was tested for G/A (Thr359Thr), C/A (Arg369Arg) and T/A (Cys430Ser) substitutions in Polish Large White, Polish Landrace and line 990. The analysis revealed only breed-specific associations. The T/A (Cys430Ser) SNP was related to the feed conversion ratio in the Polish Large White (P=0.02), and the silent G/A and C/A substitutions were respectively associated with abdominal fat in line 990 and backfat thickness in Polish Landrace (P=0.04). The combined effects of the substitutions were estimated as haplotype effects. Three significant contrasts between haplotypes were calculated, but the observed associations were again only breed-specific.

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Genes encoding adipokines are important functional candidates for development of obesity. In this study we screened for polymorphism 5'-flanking regions of the adiponectin (ADIPOQ), leptin (LEP) and resistin (RETN) genes in a cohort of Polish obese children and adolescents (n = 243) and a control group of non-obese adults (n = 100). Altogether 13 SNPs (single nucleotide polymorphisms) and 1 InDel (insertion/deletion polymorphism) were found. Among them five polymorphisms, localized in the LEP gene, turned out to be novel, but their distribution was insufficient for association studies. We found no consistent evidence for association between obesity and the SNPs demonstrating minor allele frequency (MAF) above 0.2 (ADIPOQ: -11377C>G, LEP: -2548C>T, 19A>G, RETN: -1300G>A, -1258C>T, -420C>G). Comparison of polymorphisms distribution in patients and control group suggested association with ADIPOQ -11377C>G (Pearson test P = 2.76 × 10(-11)), however, we did not observe any effect of this polymorphism on BMI or relative BMI (RBMI) within obese patients (P = 0.41). We conclude that the tested SNPs are not useful markers of childhood and adolescence obesity in Polish population.

There are five genes encoding melanocortin receptors. Among canids, the genes have mainly been studied in the dog (MC1R, MC2R and MC4R). The MC4R gene has also been analysed in the red fox. In this report, we present a study of chromosome localization, comparative sequence analysis and polymorphism of the MC3R gene in the dog, red fox, arctic fox and Chinese raccoon dog. The gene was localized by FISH to the following chromosome: 24q24-25 in the dog, 14p16 in the red fox, 18q13 in the arctic fox and NPP4p15 in the Chinese raccoon dog. A high identity level of the MC3R gene sequences was observed among the species, ranging from 96.0% (red fox--Chinese raccoon dog) to 99.5% (red fox--arctic fox). Altogether, eight polymorphic sites were found in the red fox, six in the Chinese raccoon dog and two in the dog, while the arctic fox appeared to be monomorphic. In addition, association of several polymorphisms with body weight was analysed in red foxes (the number of genotyped animals ranged from 319 to 379). Two polymorphisms in the red fox, i.e. a silent substitution c.957A>C and c.*185C>T in the 3'-flanking sequence, showed a significant association (P < 0.01) with body weight.

The 3-dimensional arrangement of chromosomes and genes within a nuclear space is considered to represent the level of transcriptional regulation. Understanding how the nuclear architecture of adipocyte cells contributes to gene expression has become the subject of greatinterest in the context of obesity research. In this study we investigated nuclear positioning of 3 gene loci involved in lipid metabolism in the pig (Sus scrofa, SSC) which is considered as an important animal model for obesity in humans. We found that the position of the SCD gene in the 3-dimensional space of the cell nucleus is not correlated with transcriptional activity. The gene locus as well as chromosome territory SSC14 occupied the same peripheral location in adipocyte and fibroblast cells, in spite of the fact that their transcription level differs significantly between both cell types. For the 2 other investigated genes, i.e. ACACA and SREBF1 and their chromosome territory (SSC12), slightly different nuclear locations were found. They occupied intermediate nuclear positions in fibroblast nuclei, while in adipocytes they were positioned in the nuclear interior. The more internal location of these genes corresponds to increased transcription levels in fat cells. Our results confirm the non-random position of genes and chromosome territories in nuclei of adult porcine cells and indicate that relationship between transcription activity and gene positioning exists only for some but not all genes.