Temperature regulates negative supercoils to modulate meiotic crossovers and chromosome organization

Crossover recombination is a hallmark of meiosis that holds the paternal and maternal chromosomes(homologs)together for their faithful segregation,while promoting genetic diversity of the progeny.The pattern of crossover is mainly controlled by the architecture of the meiotic chromosomes.Environmental factors,especially temperature,also play an important role in modulating crossovers.However,it is unclear how temperature affects crossovers.Here,we examined the distribution of budding yeast axis components(Red1,Hop1,and Rec8)and the crossover-associated Zip3 foci in detail at different temperatures,and found that both increased and decreased temperatures result in shorter meiotic chromosome axes and more crossovers.Further investigations showed that temperature changes coordinately enhanced the hyperabundant accumulation of Hop1 and Red1 on chromosomes and the number of Zip3 foci.Most importantly,temperature-induced changes in the distribution of axis proteins and Zip3 foci depend on changes in DNA negative supercoils.These results suggest that yeast meiosis senses temperature changes by increasing the level of negative supercoils to increase crossovers and modulate chromosome organization.These findings provide a new perspective on understanding the effect and mechanism of temperature on meiotic recombination and chromosome organization,with important implications for evolution and breeding.

Polysaccharide-rich extract of Potentilla anserina ameliorates nonalcoholic fatty liver disease in free fatty acid-induced HepG2 cells and high-fat/sugar diet-fed mice

Potentilla anserina L.(PA)belongs to the Rosaceae family,is a common edible plant in the Qinghai-Tibet Plateau areas of China.This study elucidates the mechanism upon which crude polysaccharide of PA(PAP)on fat accumulation in HepG2 cells stimulated by oleic acid(OA)and high fat high sugar induced mice.The result revealed that PAP inhibited lipid accumulation in obese mice and ameliorated the degree of damage in OA-induced HepG2 cells.Specifically,compared to the control group,the TG and TC levels were decreased in cells and mice serum,the aspartate transaminase and alamine aminotransferase contents were declined in liver of obese mice by PAP treatment.The expressions of adipogenic genes of SREBP-1c,C/EBPα,PPARγ,and FAS were inhibited after PAP treatment.Moreover,PAP increased the mRNA levels of CPT-1 and PPARα,which were involved in fatty acid oxidation.The present results indicated the PAP could alleviate the damage of liver associated with obesity and PAP treatment might provide a dietary therapeutic option for the treatment of hyperlipidemia.

Crossover patterns under meiotic chromosome program

Repairing DNA double-strand breaks(DSBs)with homologous chromosomes as templates is the hallmark of meiosis.The critical outcome of meiotic homologous recombination is crossovers,which ensure faithful chromosome segregation and promote genetic diversity of progenies.Crossover patterns are tightly controlled and exhibit three characteristics:obligatory crossover,crossover interference,and crossover homeostasis.Aberrant crossover patterns are the leading cause of infertility,miscarriage,and congenital disease.Crossover recombination occurs in the context of meiotic chromosomes,and it is tightly integrated with and regulated by meiotic chromosome structure both locally and globally.Meiotic chromosomes are organized in a loop-axis architecture.Diverse evidence shows that chromosome axis length determines crossover frequency.Interestingly,short chromosomes show different crossover patterns compared to long chromosomes.A high frequency of human embryos are aneuploid,primarily derived from female meiosis errors.Dramatically increased aneuploidy in older women is the well-known“maternal age effect.”However,a high frequency of aneuploidy also occurs in young women,derived from crossover maturation inefficiency in human females.In addition,frequency of human aneuploidy also shows other age-dependent alterations.Here,current advances in the understanding of these issues are reviewed,regulation of crossover patterns by meiotic chromosomes are discussed,and issues that remain to be investigated are suggested.

Protect chromosomes from end-to-end fusion during meiotic bouquet

Meiosis generates gametes with half the parental chromosome complements,and thus is crucial for successful sexual reproduction.During meiotic prophase I,a series of specialized events occur to ensure correct paternal and maternal homologous chromosomes（homologs）segregation during anaphase I.They include recognition,alignment,pairing and synapsis of the homologs and meiotic recombination which provides a link between homologs.