Introns control stochastic allele expression bias

Maternal histone methyltransferases antagonistically regulate monoallelic expression in C. elegans

Undefined epigenetic programs act to probabilistically silence individual autosomal alleles, generating unique individuals, even from genetic clones. This sort of random monoallelic expression can explain variation in traits and diseases that differences in genes and environments cannot. Here, we developed the nematode Caenorhabditis elegans to study monoallelic expression in whole tissues, and defined a developmental genetic regulation pathway. We found maternal H3K9 histone methyltransferase (HMT) SET-25/SUV39/G9a works with HPL-2/HP1 and LIN-61/L3MBTL2 to randomly silence alleles in the intestinal progenitor E-cell of 8-cell embryos to cause monoallelic expression. SET-25 was antagonized by another maternal H3K9 HMT, MET-2/SETDB1, which works with LIN-65/ATF7ZIP and ARLE-14/ARL14EP to prevent monoallelic expression. The HMT-catalytic SET domains of both MET-2 and SET-25 were required for regulating monoallelic expression. Our data support a model wherein SET-25 and MET-2 regulate histones during development to generate patterns of somatic monoallelic expression that are persistent but not heritable.

Genomic Imprinting and Random Monoallelic Expression

The review discusses the mechanisms of monoallelic expression, such as genomic imprinting, in which gene transcription depends on the parental origin of the allele, and random monoallelic transcription. Data on the regulation of gene activity in the imprinted regions are summarized with a particular focus on the areas controlling imprinting and factors influencing the variability of the imprintome. The prospects of studies of the monoallelic expression are discussed.

Detection of key gene InDels in JAK/STAT pathway and their associations with growth traits in four Chinese sheep breeds

OBJECTIVE

The Janus kinase/signal transducer and transporter activator (JAK/STAT) signaling pathway plays crucial roles in lipid metabolism, glucose metabolism and cell senescence, suggesting that they are potential candidate genes affecting growth traits in animals. The present study aimed to evaluate the association between InDels in the JAK/STAT pathway and growth traits of four Chinese sheep breeds, including Tong sheep, Hu sheep, Small-tailed Han sheep and Lanzhou fat-tailed sheep.

RESULTS

Seventy-six indel loci of 11 genes in JAK/STAT were detected, and three genotypes were selected at four loci by PCR amplification, electrophoresis and sequencing, including one locus in STAT3, one locus in STAT5A, and two loci in JAK1. The Correlation analysis indicated that there was no significant correlation between STAT3 and growth traits in four sheep breeds (P > 0.05); STAT5A was significantly associated with body height, rump width and tube circumference in Hu sheep and body length in Tong sheep (P < 0.05); JAK1 was significantly correlated with body height, body oblique length, cross height and tube circumference in Hu sheep (P < 0.05) and body oblique length, cross height and tube circumference in small-tailed Han sheep (P < 0.05).

CONCLUSION

Overall, our results indicated a potential association between the growth traits of sheep and the InDels of JAK1 and STAT5A.

Transgressive and parental dominant gene expression and cytosine methylation during seed development in Brassica napus hybrids

KEY MESSAGE

Transcriptomic and epigenomic profiling of gene expression and small RNAs during seed and seedling development reveals expression and methylation dominance levels with implications on early stage heterosis in oilseed rape. The enhanced performance of hybrids through heterosis remains a key aspect in plant breeding; however, the underlying mechanisms are still not fully elucidated. To investigate the potential role of transcriptomic and epigenomic patterns in early expression of hybrid vigor, we investigated gene expression, small RNA abundance and genome-wide methylation in hybrids from two distant Brassica napus ecotypes during seed and seedling developmental stages using next-generation sequencing. A total of 31117, 344, 36229 and 7399 differentially expressed genes, microRNAs, small interfering RNAs and differentially methylated regions were identified, respectively. Approximately 70% of the differentially expressed or methylated features displayed parental dominance levels where the hybrid followed the same patterns as the parents. Via gene ontology enrichment and microRNA-target association analyses during seed development, we found copies of reproductive, developmental and meiotic genes with transgressive and paternal dominance patterns. Interestingly, maternal dominance was more prominent in hypermethylated and downregulated features during seed formation, contrasting to the general maternal gamete demethylation reported during gametogenesis in angiosperms. Associations between methylation and gene expression allowed identification of putative epialleles with diverse pivotal biological functions during seed formation. Furthermore, most differentially methylated regions, differentially expressed siRNAs and transposable elements were in regions that flanked genes without differential expression. This suggests that differential expression and methylation of epigenomic features may help maintain expression of pivotal genes in a hybrid context. Differential expression and methylation patterns during seed formation in an F₁ hybrid provide novel insights into genes and mechanisms with potential roles in early heterosis.

Random allelic expression in the adult human body

Genes are typically assumed to express both parental alleles similarly, yet cell lines show random allelic expression (RAE) for many autosomal genes that could shape genetic effects. Thus, understanding RAE in human tissues could improve our understanding of phenotypic variation. Here, we develop a methodology to perform genome-wide profiling of RAE and biallelic expression in GTEx datasets for 832 people and 54 tissues. We report 2,762 autosomal genes with some RAE properties similar to randomly inactivated X-linked genes. We found that RAE is associated with rapidly evolving regions in the human genome, adaptive signaling processes, and genes linked to age-related diseases such as neurodegeneration and cancer. We define putative mechanistic subtypes of RAE distinguished by gene overlaps on sense and antisense DNA strands, aggregation in clusters near telomeres, and increased regulatory complexity and inputs compared with biallelic genes. We provide foundations to study RAE in human phenotypes, evolution, and disease.