Project description:Meiotic recombination differs between males and females, however, when and how these differences are established is unknown. We identify extensive sex differences at recombination initiation by mapping hotspots of meiotic DNA double strand breaks in male and female mice. Contrary to past findings in humans, few hotspots are used uniquely in either sex. Instead, grossly different recombination landscapes result from up to 15-fold differences in hotspot use between males and females. Indeed, most recombination occurs at sex-biased hotspots. Sex biased hotspots appear to be partly determined by chromosome structure, and DNA methylation, absent in females at the onset of meiosis, plays a substantial role. Sex differences are also evident later in meiosis as the repair frequency of distal meiotic breaks as crossovers diverges in males and females. Suppression of distal crossovers may help to minimize age-related aneuploidy that arises due to cohesion loss during dictyate arrest in females.
Project description:Sex condition has been demonstrated to alter meat quality and sex is a major factor that affects the fatty acid composition of lipids of carcass dissectible or intramuscular depot fats. But the possible genetic molecular mechanism of gender causing meat quality differences is not well defined. Qinchuan cattle, Qinghai yak and Guangxi buffalo are three typical indigenous species of cattle in China. Obivious differences of meat quality exist among the three species of cattle. Few studies have been conducted to elucidate the muscle tissue expression of genes involved in pathways and mechanisms leading to meat quality differences beyond the phenotype properties of beef. Bovine Genome Arrays were used to construct muscle expression profiles of the longuissimus dorsi from Qinchuan cattle at 36 months and screen differentially expressed genes in the longuissimus dorsi muscle tissues among different genders of Qinchuan cattle, between Qinchuan cattle and Qinghai yak, and between Qinchuan cattle and Guangxi buffalo.
Project description:Background: Transcriptomic variation among cattle breeds and their crossbreds may help to better understanding of consequences of crossbreeding and heterosis. In this study the differences in biological functions and pathways of three crossbreds including 50 and 75 percent Holstein were compared with their purebred parents, Holstein and Taleshi (an indigenous breed) cattle. Results: Five populations and their ten comparisons were studied by bioinformatics tools for transcriptome analysis. We pooled blood RNA of at least 8 animals of each population prior to RNA sequencing. The obtained results showed that total expressed transcripts in all populations were 72,812 with 22,627 annotated genes. Functional analysis of differentially expressed genes (DEGs) showed that the genetics information processing and metabolism were the most highly-impacted pathways. Among all significantly enriched pathways, eukaryotic translation initiation factor-2 signaling had the highest activation z-score (5.3) in crossbred compared to purebred cattle. The majority of upstream regulators of genes including transcription regulators and cytokines were differentially expressed among populations in which their activation z-score in purebred was more than crossbred cattle. Conclusions: Crossing of Holstein with Taleshi breed resulted in higher activity of pathways related to genetic information processing and lower activity of pathways related to immunity and inflammatory responses. To the best of our knowledge, this is the first study where the differences in pathways and functions were studied using high throughput sequencing of blood in a cattle crossbreeding program. The analysis revealed that the most important differences between studied genotypes, especially between purebred and crossbred cattle, were related to immune functions and metabolism.
Project description:Background: African animal trypanosomiasis (AAT) caused by tsetse fly-transmitted protozoa of the genus Trypanosoma is a major constraint on livestock and agricultural production in Africa and is among the top ten global cattle diseases impacting on the poor. Here we show that a functional genomics approach can be used to identify temporal changes in host peripheral blood mononuclear cell (PBMC) gene expression due to disease progression. We also show that major gene expression differences exist between cattle from trypanotolerant and trypanosusceptible breeds. Using bovine long oligonucleotide microarrays and real time quantitative reverse transcription PCR (qRT-PCR) validation we analysed PBMC gene expression in naïve trypanotolerant and trypanosusceptible cattle experimentally challenged with Trypanosoma congolense across a 34-day infection time course. Results: Trypanotolerant N’Dama cattle displayed a rapid and distinct transcriptional response to infection, with a ten-fold higher number of genes differentially expressed at day 14 post infection compared to trypanosusceptible Boran cattle. These analyses identified coordinated temporal gene expression changes for both breeds in responses to trypanosome infection. In addition, a panel of genes were identified that showed pronounced differences in gene expression between the two breeds, which may underlie the phenomena of trypanotolerance and trypanosusceptibility. Gene ontology (GO) analysis demonstrate that the products of these genes may contribute to increased mitochondrial mRNA translational efficiency, a more pronounced B cell response, an elevated activation status and a heightened response to stress in trypanotolerant cattle. Conclusions: This study has revealed an extensive and diverse range of cellular processes that are altered temporally in response to trypanosome infection in African cattle. Results indicate that the trypanotolerant N’Dama cattle respond more rapidly and with a greater magnitude to infection compared to the trypanosusceptible Boran cattle. Specifically, a subset of the genes analyzed by qRT-PCR, which display significant breed differences, could collectively contribute to the trypanotolerance trait in N’Dama.
Project description:The purpose of the present study was to provide a comprehensive transcriptome profiling of mammary gland and to find the key differences in the milk production and related traits between Jersey and Kashmiri cattle. Casein and whey protein genes were found to be highly expressed throughout the lactation cycle. Largest differences in DEGs was reported between D15 and D90 with 1805 genes in Kashmiri cattle and between D15 and D250 with 3392 genes in Jersey cattle.
Project description:Using whole-genome bisulfite sequencing (WGBS), we profiled the DNA methylome of cattle sperms through comparison with three bovine somatic tissues (mammary grand, brain and blood). Large differences between cattle sperms and somatic tissues were observed in the methylation patterns.
Project description:Genetic recombination generates novel trait combinations, and understanding how recombination is distributed across the genome is key to modern genetics. The PRDM9 protein defines recombination hotspots; however, megabase-scale recombination patterning is independent of PRDM9. The single round of DNA replication, which precedes recombination in meiosis, may establish these patterns; therefore, we devised an approach to study meiotic replication that includes robust and sensitive mapping of replication origins. We find that meiotic DNA replication is distinct; reduced origin firing slows replication in meiosis, and a distinctive replication pattern in human males underlies the subtelomeric increase in recombination. We detected a robust correlation between replication and both contemporary and historical recombination and found that replication origin density coupled with chromosome size determines the recombination potential of individual chromosomes. Our findings and methods have implications for understanding the mechanisms underlying DNA replication, genetic recombination, and the landscape of mammalian germline variation.