Genes related to heat tolerance in cattle-a review.

Heat stress is described as the cumulative detrimental effect caused by an imbalance between heat production within the body and heat dissipation. When cattle are exposed to heat stress with skin surface temperatures exceeding 35 °C, gene networks within and across cells respond to environmental heat loads with both intra and extracellular signals that coordinate cellular and whole-animal metabolism changes to store heat and rapidly increase evaporative heat loss. In this study, we examined evidence from genes known to be associated with heat tolerance (Hsp70, HSF1, HspB8, SOD1, PRLH, ATP1A1, MTOR, and EIF2AK4). This information could serve as valuable resource material for breeding programs aimed at increasing the thermotolerance of cattle.

TAS2R16 introgression from banteng into indigenous Chinese cattle.

Historical hybridization between southern indigenous Chinese cattle and banteng has been well-documented and has resulted in gene introgression. Bitter taste receptors were reported in indigenous cattle as a result of introgression from banteng. To determine the level of introgression of the taste 2 receptor member 16 (TAS2R16) gene from banteng into Chinese cattle, two missense mutations in the bovine TAS2R16 gene were examined. Here, we explored the prevalence of the two variants in 28 indigenous Chinese cattle and banteng breeds (comprising 750 individuals) to determine the influence of banteng introgressions on Chinese cattle based on PCR and DNA sequencing. In our study, the two mutant alleles had a higher frequency distribution in southern China with strong geographic distribution, especially in the south-central and southeast areas. In conclusion, this study examines the impact of introgression on the frequency distributions of mutations in variable regions and the subsequent adaptation of Chinese indigenous cattle to different environmental conditions.

TRPM4 gene variation associated with climatic conditions in Chinese cattle.

The transient receptor potential (TRP) superfamily has been reported to play an important role in heat tolerance pathways. Based on the Bovine Genome Variation Database and Selective Signatures, a missense mutation (NC_037345.1: c.2237A > G: p. His746Arg) (rs209689836) was identified in the transient receptor potential cation channel subfamily M member 4 (TRPM4) gene, a member of the TRP family, corresponding to heat tolerance. Here, we explored the prevalence of this variant in 19 native Chinese cattle (comprised of 404 individuals) to determine its possible association with heat tolerance in Chinese cattle by using PCR and DNA sequencing. The distribution of alleles of NC_037345.1: c.2237A > G: p. His746Arg displays significant geographical differences across native Chinese cattle breeds, consistent with the distribution of indicine and taurine cattle in China. Additionally, the association analysis indicated that the G allele was significantly associated with mean annual temperature (T), relative humidity (RH) and temperature humidity index (THI) (p < .05), suggesting that cattle carrying allele G were distributed in regions with higher T, RH, and THI. In conclusion, our results suggested that the mutation of the TRPM4 gene in Chinese cattle might be a candidate locus associated with heat tolerance.

Genetic diversity and relationships of Chinese donkeys using microsatellite markers.

Donkeys are one important livestock in China because of their nourishment and medical values. To investigate the genetic diversity and phylogenetic relationships of Chinese donkey breeds, a panel of 25 fluorescently labeled microsatellite markers was applied to genotype 504 animals from 12 Chinese donkey breeds. A total of 226 alleles were detected, and the expected heterozygosity ranged from 0.6315 (Guanzhong) to 0.6999 (Jiami). The mean value of the polymorphism information content, observed number of alleles, and expected number of alleles for all the tested Chinese donkeys were 0.6600, 6.890, and 3.700, respectively, suggesting that Chinese indigenous donkeys have relatively abundant genetic diversity. Although there were abundant genetic variations found, the genetic differentiation between the Chinese donkey breeds was relatively low, which displayed only 5.99 % of the total genetic variance among different breeds. The principal coordinates analysis clearly splits 12 donkey breeds into two major groups. The first group included Xiji, Xinjiang, Liangzhou, Kulun, and Guanzhong donkey breeds. In the other group, Gunsha, Dezhou, Biyang, Taihang, Jiami, Qingyang, and Qinghai donkeys were clustered together. This grouping pattern was further supported by structure analysis and neighbor-joining tree analysis. Furthermore, genetic relationships between different donkey breeds identified in this study were corresponded to their geographic distribution and breeding history. Our results provide comprehensive and precise baseline information for further research on preservation and utilization of Chinese domestic donkeys.

A Missense Mutation of the HSPB7 Gene Associated with Heat Tolerance in Chinese Indicine Cattle.

The small heat shock proteins (HSPB) are expressed in response to heat stress, and the heat shock protein family B (small) member 7 (HSPB7) gene has been reported to play an important role in heat tolerance pathways. Only a missense mutation (NC_037329.1: g.136054902 C > G: p.Ala69Gly) was identified in the HSPB7 gene in indicine cattle, which might be a candidate mutation associated with the heat tolerance. Here, we explore the allele frequency of this mutation in 774 individuals belonging to 32 Chinese indigenous cattle breeds using polymerase chain reaction (PCR) and DNA sequencing methods. The distribution of alleles of NC_037329.1: g.136054902 C > G displays significant geographical difference across native Chinese cattle breeds that the allele C was dominant in northern cattle groups, while allele G was dominant in southern indicine cattle groups. Additionally, the association analysis indicated that the G allele was significantly associated with mean annual temperature (T), relative humidity (RH), and temperature humidity index (THI) (p < 0.01), suggesting that cattle carrying allele G were distributed in regions with higher T, RH, and THI. Our results demonstrate that the mutation of the HSPB7 gene in Chinese indicine cattle might be a candidate gene associated with the heat tolerance.

Analysis of Genetic Diversity and Structure of Guanzhong Horse Using Microsatellite Markers.

To determine the genetic diversity and validate the pedigree record of Chinese Guanzhong horse, 67 individuals were genotyped with eight microsatellite markers. In our study, the mean observed and expected heterozygosities were 0.51 and 0.66, respectively. The mean observed number of alleles for the Guanzhong horse was 3.88. Nonetheless, the total value of FST multiloci clearly indicates that about 0.5% of overall genetic variation is due to line founder differences, while differences among individuals are responsible for the remaining 99.5%. In addition, the polymorphic information content (PIC) result showed that five loci (HTG7, HMS7, HMS2, AHT4, and HMS6) were highly polymorphic (PIC > 0.5) and three loci (HMS3, HTG6, and COR071) were moderate polymorphic (PIC > 0.25). Genetic distances and cluster analysis showed that the genetic relationship among 67 Guanzhong horse was generally consistent with pedigree recorded. Our results not only evaluated the genetic diversity of Chinese Guanzhong horse, but also suggested that the eight microsatellite markers might be used as subservient markers for parentage verification and individual identification in the Guanzhong horse.