RESUMEN
Cattle and water buffalo belong to the same subfamily Bovinae and share chromosome banding and gene order homology. In this study, we used genome-wide Illumina BovineSNP50 BeadChip to analyze 91 DNA samples from three breeds of water buffalo (Nili-Ravi, Murrah and their crossbred with local GuangXi buffalos in China), to demonstrate the genetic divergence between cattle and water buffalo through a large single nucleotide polymorphism (SNP) transferability study at the whole genome level, and performed association analysis of functional traits in water buffalo as well. A total of 40,766 (75.5 %) bovine SNPs were found in the water buffalo genome, but 49,936 (92.5 %) were with only one allele, and finally 935 were identified to be polymorphic and useful for association analysis in water buffalo. Therefore, the genome sequences of water buffalo and cattle shared a high level of homology but the polymorphic status of the bovine SNPs varied between these two species. The different patterns of mutations between species may associate with their phenotypic divergence due to genome evolution. Among 935 bovine SNPs, we identified a total of 9 and 7 SNPs significantly associated to fertility and milk production traits in water buffalo, respectively. However, more works in larger sample size are needed in future to verify these candidate SNPs for water buffalo.
Asunto(s)
Búfalos/genética , Bovinos/genética , Estudio de Asociación del Genoma Completo , Polimorfismo de Nucleótido Simple , Animales , Cromosomas de los Mamíferos/genética , Evolución Molecular , Femenino , Fertilidad/genética , Frecuencia de los Genes , Técnicas de Genotipaje , Heterocigoto , Lactancia/genética , Leche/metabolismo , Modelos Genéticos , Análisis de Secuencia por Matrices de Oligonucleótidos , Análisis de Componente Principal , Análisis de Secuencia de ADN , Homología de Secuencia de Ácido NucleicoRESUMEN
Dairy cows mobilise body tissues to support milk production and, because glucose supplies are limited, lipids are used preferentially for energy production. Lipogenic activity is switched off and lipolytic mechanisms in adipose tissue increase through changes in the expression of several key enzymes. This results in a loss of body condition, together with high circulating concentrations of non-esterified fatty acids. Changes in the synthesis, secretion and signalling pathways of somatotrophic hormones (insulin, growth hormone, insulin-like growth factor 1) and adipokines (e.g. leptin) are central to the regulation of these processes. A high reliance on fatty acids as an energy source in the peripartum period causes oxidative damage to mitochondria in metabolically active tissues, including the liver and reproductive tract. The expression of genes involved in insulin resistance (PDK4, AHSG) is increased, together with expression of TIEG1, a transcription factor that can induce apoptosis via the mitochondrial pathway. Polymorphisms in TFAM and UCP2, two autosomal mitochondrial genes, have been associated with longevity in dairy cows. Polymorphisms in many other genes that affect lipid metabolism also show some associations with fertility traits. These include DGAT1, SCD1, DECR1, CRH, CBFA2T1, GH, LEP and NPY. Excess lipid accumulation in oocytes and the regenerating endometrium reduces fertility via reductions in embryo survival and increased inflammatory changes, respectively.