Multi‑omics integration identifies regulatory factors underlying bovine subclinical mastitis

Background Mastitis caused by multiple factors remains one of the most common and costly disease of the dairy industry.Multi-omics approaches enable the comprehensive investigation of the complex interactions between mul-tiple layers of information to provide a more holistic view of disease pathogenesis.Therefore,this study investigated the genomic and epigenomic signatures and the possible regulatory mechanisms underlying subclinical mastitis by integrating RNA sequencing data(mRNA and lncRNA),small RNA sequencing data(miRNA)and DNA methylation sequencing data of milk somatic cells from 10 healthy cows and 20 cows with naturally occurring subclinical mastitis caused by Staphylococcus aureus or Staphylococcus chromogenes.Results Functional investigation of the data sets through gene set analysis uncovered 3458 biological process GO terms and 170 KEGG pathways with altered activities during subclinical mastitis,provided further insights into subclin-ical mastitis and revealed the involvement of multi-omics signatures in the altered immune responses and impaired mammary gland productivity during subclinical mastitis.The abundant genomic and epigenomic signatures with sig-nificant alterations related to subclinical mastitis were observed,including 30,846,2552,1276 and 57 differential methylation haplotype blocks(dMHBs),differentially expressed genes(DEGs),lncRNAs(DELs)and miRNAs(DEMs),respectively.Next,5 factors presenting the principal variation of differential multi-omics signatures were identified.The important roles of Factor 1(DEG,DEM and DEL)and Factor 2(dMHB and DEM),in the regulation of immune defense and impaired mammary gland functions during subclinical mastitis were revealed.Each of the omics within Factors 1 and 2 explained about 20%of the source of variation in subclinical mastitis.Also,networks of impor-tant functional gene sets with the involvement of multi-omics signatures were demonstrated,which contributed to a comprehensive view of the possible regulatory mechanisms underlying subclinical mastitis.Furthermore,multi-omics integration enabled the association of the epigenomic regulatory factors(dMHBs,DELs and DEMs)of altered genes in important pathways,such as‘Staphylococcus aureus infection pathway’and‘natural killer cell mediated cyto-toxicity pathway’,etc.,which provides further insights into mastitis regulatory mechanisms.Moreover,few multi-omics signatures(14 dMHBs,25 DEGs,18 DELs and 5 DEMs)were identified as candidate discriminant signatures with capac-ity of distinguishing subclinical mastitis cows from healthy cows.Conclusion The integration of genomic and epigenomic data by multi-omics approaches in this study provided a better understanding of the molecular mechanisms underlying subclinical mastitis and identified multi-omics candidate discriminant signatures for subclinical mastitis,which may ultimately lead to the development of more effective mastitis control and management strategies.

Methylome and transcriptome data integration reveals potential roles of DNA methylation and candidate biomarkers of cow Streptococcus uberis subclinical mastitis

Background:Mastitis caused by different pathogens including Streptococcus uberis(S.uberis)is responsible for huge economic losses to the dairy industry.In order to investigate the potential genetic and epigenetic regulatory mecha‑nisms of subclinical mastitis due to S.uberis,the DNA methylome(whole genome DNA methylation sequencing)and transcriptome(RNA sequencing)of milk somatic cells from cows with naturally occurring S.uberis subclinical mastitis and healthy control cows(n=3/group)were studied.Results:Globally,the DNA methylation levels of CpG sites were low in the promoters and first exons but high in inner exons and introns.The DNA methylation levels at the promoter,first exon and first intron regions were nega‑tively correlated with the expression level of genes at a whole‑genome‑wide scale.In general,DNA methylation level was lower in S.uberis‑positive group(SUG)than in the control group(CTG).A total of 174,342 differentially methylated cytosines(DMCs)(FDR<0.05)were identified between SUG and CTG,including 132,237,7412 and 34,693 DMCs in the context of CpG,CHG and CHH(H=A or T or C),respectively.Besides,101,612 methylation haplotype blocks(MHBs)were identified,including 451 MHBs that were significantly different(dMHB)between the two groups.A total of 2130 differentially expressed(DE)genes(1378 with up‑regulated and 752 with down‑regulated expression)were found in SUG.Integration of methylome and transcriptome data with MethGET program revealed 1623 genes with signifi‑cant changes in their methylation levels and/or gene expression changes(MetGDE genes,MethGET P‑value<0.001).Functional enrichment of genes harboring≥15 DMCs,DE genes and MetGDE genes suggest significant involvement of DNA methylation changes in the regulation of the host immune response to S.uberis infection,especially cytokine activities.Furthermore,discriminant correlation analysis with DIABLO method identified 26 candidate biomarkers,including 6 DE genes,15 CpG‑DMCs and 5 dMHBs that discriminated between SUG and CTG.Conclusion:The integration of methylome and transcriptome of milk somatic cells suggests the possible involve‑ment of DNA methylation changes in the regulation of the host immune response to subclinical mastitis due to S.uberis.The presented genetic and epigenetic biomarkers could contribute to the design of management strategies of subclinical mastitis and breeding for mastitis resistance.

Genomic footprints of wheat evolution in China reflected by a Wheat660K SNP array

Common wheat(Triticum aestiuum L.)is one of the most important crops because it provides about 20%of the total calories for humans.T.aestiuum is an excellent modern species for studying concerted evolution of sub-genomes in polyploid species,because of its large chromosome size and three well-known genome donors.Establishment of common wheat genome reference sequence and development of high-density SNP chips provide an excellent foundation to answer questions of wheat evolution and breeding at the genomic level.By genotyping more than 600 accessions of common wheat and their diploid and tetraploid ancestors using a Wheat660 K SNP array,we found dramatic genome changes due to tetraploidization and hexaploidization,in contrast to weaker influences of domestication and breeding on them.Further,since common wheat was introduced in China in 1500 BCE,Chinese landraces formed two subgroups(T.aestiuum-L1 and T.aestiuum-L2)with considerably diverse geographic distributions and agronomic traits.T.aestiuum-L2,mainly distributed in central and east China is found to have more but smaller oval grains with early maturity characteristics.We found that variation and selection in intergenic regions of the A and B sub-genomes dominated this differentiation,in which chromosomes 7 A and 3 B took the leading roles due to the existence of putative genes related to defense responses and environmental adaption in the highly differentiated regions.Large haplotype blocks were detected on 3 B(232.6-398.3 Mb)and 7 A(211.7-272.9 Mb)in the landraces,forming two distinct haplotypes,respectively.We discovered that artificial crosses in breeding promoted recombination in the whole genome,however,this recombination and differentiation was highly asymmetric among the three sub-genomes in homoeologous regions.In addition,we found that the wide use of European and northern American cultivars in breeding at early era,led dramatic changes in Chinese wheat genome,whereas,the recent breeding functioned to optimize it.This study will provide the insight for reconsideration of wheat evolution and breeding,and a new strategy for parent selection in breeding.

Resequencing of 145 Landmark Cultivars Reveals Asymmetric Sub-genome Selection and Strong Founder Genotype Effects on Wheat Breeding in China

Controlled pedigrees and the multi-decade timescale of national crop plant breeding programs offer a unique experimental context for examining how selection affects plant genomes.More than 3000 wheat cultivars have been registered,released,and documented since 1949 in China.In this study,a set of 145 elite cultivars selected from historical points of wheat breeding in China were re-sequenced.A total of 43.75 Tb of sequence data were generated with an average read depth of 17.94x for each cultivar,and more than 60.92 million SNPs and 2.54 million InDels were captured,based on the Chinese Spring RefSeq genome v1.0.Seventy years of breeder-driven selection led to dramatic changes in grain yield and related phenotypes,with distinct genomic regions and phenotypes tar-geted by different breeders across the decades.There are very clear instances illustrating how introduced Italian and otherforeign germplasm was integrated into Chinese wheat programs and reshaped the genomic landscape of local modern cultivars.Importantly,the resequencing data also highlighted significant asymmetric breeding selec-tion among the three sub-genomes:this was evident in both the collinear blocks for homeologous chromosomes and among sets of three homeologous genes.Accumulation of more newly assembled genes in newer cultivars implied the potential value of these genes in breeding.Conserved and extended sharing of linkage disequilibrium(LD)blocks was highlighted among pedigree-related cultivars,in which fewer haplotype differences were detected.Fixation or replacement of haplotypes from founder genotypes after generations of breeding was related to their breeding value.Based on the haplotype frequency changes in LD blocks of pedigree-related cultivars,we propose a strategy for evaluating the breeding value of any given line on the basis of the accumulation(pyramiding)of bene-ficial haplotypes.Collectively,our study demonstrates the influence of "founder genotypes" on the output of breeding efforts over many decades and also suggests that founder genotype perspectives are in fact more dy-namic when applied in the context of modern genomics-informed breeding.

The 150 most important questions in cancer research and clinical oncology series: questions 94-101

Since the beginning of 2017,Cancer Communications(former title:Chinese Journal of Cancer)has published a series of important questions regarding cancer research and clinical oncology,to provide an enhanced stimulus for can-cer research,and to accelerate collaborations between institutions and investigators.In this edition,the following 8 valuable questions are presented.Question 94.The origin of tumors:time for a new paradigm?Question 95.How can we accelerate the identification of biomarkers for the early detection of pancreatic ductal adenocarcinoma?Question 96.Can we improve the treatment outcomes of metastatic pancreatic ductal adenocarcinoma through precision medicine guided by a combination of the genetic and proteomic information of the tumor?Question 97.What are the parameters that determine a competent immune system that gives a complete response to cancers after immune induction?Question 98.Is high local concentration of metformin essential for its anti-cancer activity?Question 99.How can we monitor the emergence of cancer cells anywhere in the body through plasma testing?Question 100.Can phytochemicals be more specific and efficient at targeting P-glycoproteins to overcome multi-drug resistance in cancer cells?Question 101.Is cell migration a selectable trait in the natural evolution of carcinoma?