The organization,regulation,and biological functions of the synaptonemal complex

The synaptonemal complex(SC)is a meiosis-specific proteinaceous macromolecular structure that assembles between paired homologous chromosomes during meiosis in various eukaryotes.The SC has a highly conserved ultrastructure and plays critical roles in controlling multiple steps in meiotic recombination and crossover formation,ensuring accurate meiotic chromosome segregation.Recent studies in different organisms,facilitated by advances in super-resolution microscopy,have provided insights into the macromolecular structure of the SC,including the internal organization of the meiotic chromosome axis and SC central region,the regulatory pathways that control SC assembly and dynamics,and the biological functions exerted by the SC and its substructures.This review summarizes recent discoveries about how the SC is organized and regulated that help to explain the biological functions associated with this meiosis-specific structure.

Reproductive aging:biological pathways and potential interventive strategies

Reproductive aging is a natural process conserved across species and is well-known in females.It shows age-related follicle depletion and reduction of oocyte quality,eventually causing reproductive senescence and menopause.Although reproductive aging in males is not well noticed as in females,it also causes infertility and has deleterious consequences on the offspring.Various factors have been suggested to contribute to reproductive aging,including oxidative stress,mitochondrial defects,telomere shortening,meiotic chromosome segregation errors and genetic alterations.With the increasing trend of pregnancy age,it is particularly crucial to find interventions to preserve or extend human fertility.Studies in humans and model organisms have provided insights into the biological pathways associated with reproductive aging,and a series of potential interventive strategies have been tested.Here,we review factors affecting reproductive aging in females and males and summarize interventive strategies that may help delay or rescue the aging phenotypes of reproduction.

Altered Local Field Potential Relationship Between the Parafascicular Thalamic Nucleus and Dorsal Striatum in Hemiparkinsonian Rats

The thalamostriatal pathway is implicated in Parkinson's disease(PD); however, PD-related changes in the relationship between oscillatory activity in the centromedian-parafascicular complex(CM/Pf, or the Pf in rodents) and the dorsal striatum(DS) remain unclear.Therefore, we simultaneously recorded local field potentials(LFPs) in both the Pf and DS of hemiparkinsonian and control rats during epochs of rest or treadmill walking. The dopamine-lesioned rats showed increased LFP power in the beta band(12 Hz–35 Hz) in the Pf and DS during both epochs, but decreased LFP power in the delta(0.5 Hz–3 Hz) band in the Pf during rest epochs and in the DS during both epochs, compared to control rats. In addition,exaggerated low gamma(35 Hz–70 Hz) oscillations after dopamine loss were restricted to the Pf regardless of the behavioral state. Furthermore, enhanced synchronization of LFP oscillations was found between the Pf and DS after the dopamine lesion. Significant increases occurred in the mean coherence in both theta(3 Hz–7 Hz) and beta bands,and a significant increase was also noted in the phase coherence in the beta band between the Pf and DS during rest epochs. During the treadmill walking epochs, significant increases were found in both the alpha(7 Hz–12 Hz)and beta bands for two coherence measures. Collectively,dramatic changes in the relative LFP power and coherence in the thalamostriatal pathway may underlie the dysfunction of the basal ganglia-thalamocortical network circuits in PD, contributing to some of the motor and non-motor symptoms of the disease.

SYP-5 regulates meiotic thermotolerance in Caenorhabditis elegans

Meiosis produces the haploid gametes required by all sexually reproducing organisms,occurring in specific temperature ranges in different organisms.However,how meiotic thermotolerance is regulated remains largely unknown.Using the model organism Caenorhabditis elegans,here,we identified the synaptonemal complex(SC)protein SYP-5 as a critical regulator of meiotic thermotolerance.syp-5-null mutants maintained a high percentage of viable progeny at 20℃ but produced significantly fewer viable progeny at 25℃,a permissive temperature in wild-type worms.Cytological analysis of meiotic events in the mutants revealed that while SC assembly and disassembly,as well as DNA double-strand break repair kinetics,were not affected by the elevated temperature,crossover designation,and bivalent formation were significantly affected.More severe homolog segregation errors were also observed at elevated temperature.A temperature switching assay revealed that late meiotic prophase events were not temperature-sensitive and that meiotic defects during pachytene stage were responsible for the reduced viability of syp-5 mutants at the elevated temperature.Moreover,SC polycomplex formation and hexanediol sensitivity analysis suggested that SYP-5 was required for the normal properties of the SC,and charge-interacting elements in SC components were involved in regulating meiotic thermotolerance.Together,these findings provide a novel molecular mechanism for meiotic thermotolerance regulation.