PRSS50-mediated inhibition of MKP3/ERK signaling is crucial for meiotic progression and sperm quality

Serine protease 50(PRSS50/TSP50)is highly expressed in spermatocytes.Our study investigated its role in testicular development and spermatogenesis.Initially,PRSS50 knockdown was observed to impair DNA synthesis in spermatocytes.To further explore this,we generated PRSS50 knockout(Prss50^(−/−))mice(Mus musculus),which exhibited abnormal spermatid nuclear compression and reduced male fertility.Furthermore,dysplastic seminiferous tubules and decreased sex hormones were observed in 4-week-old Prss50^(−/−)mice,accompanied by meiotic progression defects and increased apoptosis of spermatogenic cells.Mechanistic analysis indicated that PRSS50 deletion resulted in increased phosphorylation of extracellular signal-regulated protein kinases 1 and 2(ERK1/2)and elevated levels of MAP kinase phosphatase 3(MKP3),a specific ERK antagonist,potentially accounting for testicular dysplasia in adolescent Prss50−/−mice.Taken together,these findings suggest that PRSS50 plays an important role in testicular development and spermatogenesis,with the MKP3/ERK signaling pathway playing a significant role in this process.

Support vector machine for prediction of meiotic recombination hotspots and coldspots in Saccharomyces cerevisiae

A novel method for predicting hotspots and coldspots using support vector machine （SVM） based on statistical learning theory is developed. This method is applied to published 303 hot and 48 cold open reading frames （ORFs） in Saccharomyces cerevisiae. The sequence features of general dinucleotide abundance and dinucleotide abundance based on codon usage are extracted, and then the data sets are classified with different parameters and kernel functions combined with the method of two-fold cross validation. The result indicates that 87.47% accuracy can be reached when classifying hot and cold ORF sequences with the kernel of radial basis function combined with dinucleotide abundance based on codon usage.

Phosphorylation of histone H3 on Ser10 by auto-phosphorylated PAK1 is not essential for chromatin condensation and meiotic progression in porcine oocytes

Background： The p21-activated kinase 1 （PAK1）is essential of microtubule assembly during oocyte meiotic maturation porcine oocytes. for mitosis and plays an important role in the regulatio in mice; however, little is known about its role in Result： Total p21-activated kinase 1 （PAK1） and phosphorylated PAK1 at Thr423 （PAK1^Thr423） were consistently expressed in porcine oocytes from the germinal vesicle （GV） to the second metaphase （MII） stages, but phosphorylation of histone H3 at Serr10 （H3^ser10） was only expressed after the GV stage. Immunofiuorescence analysis revealed that PAK1Thr423 and H3^ser10 colocalized on chromosomes after the GV stage. Blocking of endogenous PAK1^Thr423 by injecting a specific antibody decreased the phosphorylation level of H3^ser10; however, it had no impact on chromatin condensation, meiotic progression, cleavage rate of blastomeres or the rate of blastocyst formation. Conclusion： Phosphorylation of PAK1^Thr423 is a spontaneous activation process and the activated PAK1^Thr423 can promote the phosphorylation of H3^ser10; however, this pathway is not required for meiotic maturation of porcine oocytes or early embryonic development.

Identification of reference genes provides functional insights into meiotic recombination suppressors in Gerbera hybrida

Gerbera Hybrida is one of the important cut flowers across the world.The novel traits are the primarily market requirements and the breeding targets,mainly determined by the degree of genetic variation after hybridization.However,meiotic recombination is highly conserved in most eukaryotes which suppressed the crossover formation and limited the genetic diversity.Recently,several meiotic recombination suppressors have been identified and characterized in plants,whereas it remains elusive in G.hybrida.In order to characterize the expression patterns of these suppressors in G.hybrida,20 candidate reference genes were identified from the transcriptome datasets of G.hybrida,and their expression stabilities during plant development were evaluated by geNorm,NormFinder and BestKeeper.Although the most stable reference genes were variable in different softwares,comprehensive ranking revealed that PGK2 was the most stable reference gene and GAPDH was the most unstable one.The expression patterns of FANCM,FIGL1,RECQ4,RM1,and FLIP further validated that PGK2 was suitable for normalization of gene expression.Our study identified a reliable reference gene for gene expression during meiotic recombination,and provided functional insights into meiotic recombination suppressors in G.hybrida.

Pins homolog LGN regulates meiotic spindle organization in mouse oocytes

Mouse oocytes undergo polarization during meiotic maturation, and this polarization is essential for asymmetric cell divisions that maximize retention of maternal components required for early development. Without conventional centrosomes, the meiotic spindle has less focused poles and is barrel-shaped. The migration of meiotic spindles to the cortex is accompanied by a local reorganization and polarization of the cortex. LGN is a conserved protein involved in cell polarity and regulation of spindle organization. In the present study, we characterized the localization dynamics of LGN during mouse oocyte maturation and analyzed the effects of LGN upregulation and downregulation on meiotic spindle organization. At the germinal vesicle stage, LGN is distributed both cytoplasmically and at the cortex. During maturation, LGN localizes to the meiotic spindle apparatus and cortical LGN becomes less concentrated at the actin cap region. Excessive LGN induces meiotic spindle organization defects by elongating the spindle and enhancing pole focusing, whereas depletion of LGN by RNA interference results in meiotic spindle deformation and chromosome misalignment. Furthermore, the N-terminus of LGN has the ability of full-length LGN to regulate spindle organization, whereas the C-terminus of LGN controls cortical localization and polarization. Our results reveal that LGN is cortically polarized in mouse oocytes and is critical for meiotic spindle organization.

Casein kinase 2 modulates the spindle assembly checkpoint to orchestrate porcine oocyte meiotic progression

Background:CK2(casein kinase 2)is a serine/threonine-selective protein kinase that has been involved in a variety of cellular processes such as DNA repair,cell cycle control and circadian rhythm regulation.However,its functional roles in oocyte meiosis have not been fully determined.Results:We report that CK2 is essential for porcine oocyte meiotic maturation by regulating spindle assembly checkpoint(SAC).Immunostaining and immunoblotting analysis showed that CK2 was constantly expressed and located on the chromosomes during the entire oocyte meiotic maturation.Inhibition of CK2 activity by its selective inhibitor CX-4945 impaired the first polar body extrusion and arrested oocytes at M I stage,accompanied by the presence of BubR1 at kinetochores,indicative of activated SAC.In addition,we found that spindle/chromosome structure was disrupted in CK2-inhibited oocytes due to the weakened microtubule stability,which is a major cause resulting in the activation of SAC.Last,we found that the level DNA damage as assessed byγH2A.X staining was considerably elevated when CK2 was inhibited,suggesting that DNA damage might be another critical factor leading to the SAC activation and meiotic failure of oocytes.Conclusions:Our findings demonstrate that CK2 promotes the porcine oocyte maturation by ensuring normal spindle assembly and DNA damage repair.

NEW OBSERVATIONS ON THE MEIOTIC PROCESS IN THE MARINE DINOFLAGELLATE NOCTILUCA SCINTILLANS (NOCTILUCALES, DINOPHYCEAE)

The meiotic process in Noctiluca scintillans were observed under light microscope. Some abnormal cell divisions, incompletely separated "zoospores" and the changes of the zoospores are described in this paper. Together with the findings of field samplings and the previous results by other researchers, the process of meiosis in N. scintillans was supposed to be a pathway to reduce the extra high density of NH 3-N within the cell in order to ensure normal population growth.

Investigation on Evolutionary Relationships of the Subgenomes in Interspecific Triploid Cotton via Meiotic FISH

We report in this paper primary studies on interspecific species of cotton vis GISH(genomic in situ hybridization).We use interspecific triploid hybrids(F1 from hybridization of allotetraploid cultivated species with diploid A,D,or C genome species) and two cultivated tetraploids to study

The genome-wide meiotic recombination landscape in ciliates and its implications for crossover regulation and genome evolution

Meiotic recombination is essential for sexual reproduction and its regulation has been extensively studied in many taxa.However,genome-wide recombination landscape has not been reported in ciliates and it remains unknown how it is affected by the unique features of ciliates:the synaptonemal complex(SC)-independent meiosis and the nuclear dimorphism.Here,we show the recombination landscape in the model ciliate Tetrahymena thermophila by analyzing single-nucleotide polymorphism datasets from 38 hybrid progeny.We detect 1021 crossover(CO)events(35.8 per meiosis),corresponding to an overall CO rate of 9.9 cM/Mb.However,gene conversion by non-crossover is rare(1.03 per meiosis)and not biased towards G or C alleles.Consistent with the reported roles of SC in CO interference,we find no obvious sign of CO interference.CO tends to occur within germ-soma common genomic regions and many of the 44 identified CO hotspots localize at the centromeric or subtelomeric regions.Gene ontology analyses show that CO hotspots are strongly associated with genes responding to environmental changes.We discuss these results with respect to how nuclear dimorphism has potentially driven the formation of the observed recombination landscape to facilitate environmental adaptation and the sharing of machinery among meiotic and somatic recombination.

A TOP6BL mutation abolishes meiotic DNA double-strand break formation and causes human infertility

Meiosis is pivotal for sexual reproduction and fertility. Meiotic programmed DNA double-strand breaks(DSBs) initiate homologous recombination, ensuring faithful chromosome segregation and generation of gametes. However, few studies have focused on meiotic DSB formation in human reproduction.Here, we report four infertile siblings born to a consanguineous marriage, with three brothers suffering from non-obstructive azoospermia and one sister suffering from unexplained infertility with normal menstrual cycles and normal ovary sizes with follicular activity. An autosomal recessive mutation in TOP6BL was found co-segregating with infertility in this family. Investigation of one male patient revealed failure in programmed meiotic DSB formation and meiotic arrest prior to pachytene stage of prophase I.Mouse models carrying similar mutations to that in patients recapitulated the spermatogenic abnormalities of the patient. Pathogenicity of the mutation in the female patient was supported by observations in mice that meiotic programmed DSBs failed to form in mutant oocytes and oocyte maturation failure due to absence of meiotic recombination. Our study thus illustrates the phenotypical characteristics and the genotype-phenotype correlations of meiotic DSB formation failure in humans.

Centromere pairing precedes meiotic chromosome pairing in plants

Meiosis is a specialized eukaryotic cell division, in which diploid cells undergo a single round of DNA replication and two rounds of nuclear division to produce haploid gametes. In most eukaryotes, the core events of meiotic prophase I are chromosomal pairing,synapsis and recombination. To ensure accurate chromosomal segregation, homologs have to identify and align along each other at the onset of meiosis. Although much progress has been made in elucidating meiotic processes, information on the mechanisms underlying chromosome pairing is limited in contrast to the meiotic recombination and synapsis events. Recent research in many organisms indicated that centromere interactions during early meiotic prophase facilitate homologous chromosome pairing, and functional centromere is a prerequisite for centromere pairing such as in maize. Here, we summarize the recent achievements of chromosome pairing research on plants and other organisms, and outline centromere interactions, nuclear chromosome orientation,and meiotic cohesin, as main determinants of chromosome pairing in early meiotic prophase.

A new TEX11 mutation causes azoospermia and testicular meiotic arrest

There are many unknown genetic factors that lead to infertility in nonobstructive azoospermia men.Here,we performed whole-exome sequencing in blood samples obtained from 40 azoospermia patients with meiotic arrest and found a novel c.151_154del(p.D51fs)frame-shift mutation in exon 3 of the testis expressed 11(TEX11)gene in one patient.Sanger sequencing analysis of the patient and 288 fertile men was performed to validate the mutation.Immunohistochemical analysis showed TEX11 expression in late-pachytene spermatocytes and in round spermatids in fertile human testes.In contrast,testes of the patient with TEX11 mutation underwent meiotic arrest and lacked TEX11 expression.Western blotting of human embryonic kidney(HEK293)cells transfected with a vector for the p.D51fs TEX11 variant detected no TEX11 expression.In conclusion,we identified a novel frame-shift mutation in the TEX11 gene in an azoospermia patient,emphasizing that this gene should be included in genetic screening panels for the clinical evaluation of azoospermia patients.

Rescue of male infertility through correcting a genetic mutation causing meiotic arrest in spermatogonial stem cells

Azoospermia patients who carry a monogenetic mutation that causes meiotic arrest may have their biological child through genetic correction in spermatogonial stem cells(SSCs).However,such therapy for infertility has not been experimentally investigated yet.In this study,a mouse model with an X-linked testis-expressed 11(TEX11)mutation(Tex11PM/Y)identified in azoospermia patients exhibited meiotic arrest due to aberrant chromosome segregation.Tex11PM/Y SSCs could be isolated and expanded in vitro normally,and the mutation was corrected by clustered regularly interspaced short palindromic repeats(CRISPR)–CRISPR-associated endonuclease 9(Cas9),leading to the generation of repaired SSC lines.Whole-genome sequencing demonstrated that the mutation rate in repaired SSCs is comparable with that of autonomous mutation in untreated Tex11PM/Y SSCs,and no predicted off-target sites are modified.Repaired SSCs could restore spermatogenesis in infertile males and give rise to fertile offspring at a high efficiency.In summary,our study establishes a paradigm for the treatment of male azoospermia by combining in vitro expansion of SSCs and gene therapy.

Behavior of Meiotic Chromosomes in Pinus wallichiana,P.strobus and Their Hybrid and nrDNA Localization in Pollen Mother Cells of the Hybrid by Using FISH

The complete process of meiosis was investigated in Pinus wallichiana, P. strobus and their artificial hybrid （F1） using microsporocytes. It is revealed that there were slightly lower chiasma frequency, lower ring bivalent frequency, lower meiotic index and distinctly higher frequency of aberrance （chromosomal bridges, fragments or micronuclei） in pollen mother cells （PMCs） of the hybrid （F1） than those of the parental species, which showed a certain degree of differentiation between homologous chromosomes of the two parents. However, relatively higher frequency of ring bivalents and higher meiotic index in all the three entities indicate the great stability of genomes of parental species, and the differentiation of genomes between the two parents must have been slight. Total nineteen signal loci of 18S rDNA were observed in nine bivalents of the hybrid （F1）, among which one bivalent bears two loci, while the others have only one. It is suggested that distinct differentiation at genetic level existed in homologous chromosomes of the two parental species, whereas only slight differentiation at karyotypic and genomic levels take place between the parent species.

Meiotic nuclear divisions 1(MND1)fuels cell cycle progression by activating a KLF6/E2F1 positive feedback loop in lung adenocarcinoma

Background:Considering the increase in the proportion of lung adenocarcinoma(LUAD)cases among all lung cancers and its considerable contribution to cancer-related deaths worldwide,we sought to identify novel oncogenes to provide potential targets and facilitate a better understanding of the malignant progression of LUAD.Methods:The results from the screening of transcriptome and survival analyses according to the integrated Gene Expression Omnibus(GEO)datasets and The Cancer Genome Atlas(TCGA)data were combined,and a promising risk biomarker called meiotic nuclear divisions 1(MND1)was selectively acquired.Cell viability assays and subcutaneous xenograftmodelswere used to validate the oncogenic role ofMND1 in LUADcell proliferation and tumor growth.Aseries of assays,including mass spectrometry,co-immunoprecipitation(Co-IP),and chromatin immunoprecipitation(ChIP),were performed to explore the underlying mechanism.Results:MND1 up-regulation was identified to be an independent risk factor for overall survival in LUAD patients evaluated by both tissue microarray staining and third party data analysis.In vivo and in vitro assays showed that MND1 promoted LUAD cell proliferation by regulating cell cycle.The results of the Co-IP,ChIP and dual-luciferase reporter assays validated that MND1 competitively bound to tumor suppressor Kruppel-like factor 6(KLF6),and thereby protecting E2F transcription factor 1(E2F1)from KLF6-induced transcriptional repression.Luciferase reporter and ChIP assays found that E2F1 activated MND1 transcription by binding to its promoter in a feedback manner.Conclusions:MND1,KLF6,and E2F1 form a positive feedback loop to regulate cell cycle and confer DDP resistance in LUAD.MND1 is crucial for malignant progression and may be a potential therapeutic target in LUAD patients.

New insights into the role of DNA synthesis in meiotic recombination

Meiosis comprises two rounds of nuclear division following a single phase of DNA replication, leading to the production of haploid gametes and is essential for sexual reproduction in eukaryotes. Unlike mitosis, meiosis involves homologous chromosome pairing, synapsis, and recombination during prophase I. Meiotic recombination not only ensures the accurate segregation of homologs, but also redistributes alleles among offspring. DNA synthesis is a critical process during meiotic recombination, but our understanding of the proteins that execute and regulate it is limited. This review summarizes the recent advances in defining the role of DNA synthesis in meiotic recombina- tion through analyses of DNA synthesis genes, with specific emphasis on DNA polymerases （e.g., Pole and PolS）, replication processivity factor RFC1 and translesion polymerases （e.g., Pol~）. We also present a new double strand break repair model for meiotic recombination, which includes lagging strand DNA synthesis and leading strand elongation. Finally, we propose that DNA synthesis is one of critical factors for discriminating meiotic recombination pathways and that this differentiation may be conserved among eukaryotes.

inGAP-family:Accurate Detection of Meiotic Recombination Loci and Causal Mutations by Filtering Out Artificial Variants due to Genome Complexities

Accurately identifying DNA polymorphisms can bridge the gap between phenotypes and genotypes and is essential for molecular marker assisted genetic studies.Genome complexities,including large-scale structural variations,bring great challenges to bioinformatic analysis for obtaining high-confidence genomic variants,as sequence differences between non-allelic loci of two or more genomes can be misinterpreted as polymorphisms.It is important to correctly filter out artificial variants to avoid false genotyping or estimation of allele frequencies.Here,we present an efficient and effective framework,inGAP-family,to discover,filter,and visualize DNA polymorphisms and structural variants(SVs)from alignment of short reads.Applying this method to polymorphism detection on real datasets shows that elimination of artificial variants greatly facilitates the precise identification of meiotic recombination points as well as causal mutations in mutant genomes or quantitative trait loci.In addition,inGAP-family provides a user-friendly graphical interface for detecting polymorphisms and SVs,further evaluating predicted variants and identifying mutations related to genotypes.It is accessible at https://sourceforge.net/projects/ingap-family/.

Vitrification of In vitro-matured Oocytes:Effects of Meiotic Spindle Morphology on Clinical Outcome

Objective:The meiotic spindle controls chromosome movement and mediates various functions essential for fertilization and early postfertilization events.This study aimed to examine whether vitrification causes meiotic damage in vitro-matured metaphase II(MII)human oocytes,and whether the meiotic spindle morphology influences the subsequent developmental outcomes.Methods:The spindle characteristics of MII human oocytes in vitro matured were studied before and after vitrification using PolScope imaging and immunofluorescence staining.The developmental competence of oocytes was also examined.Results:A total of 419 human MII oocytes were obtained from 593 intracytoplasmic sperm injection cycles at our hospital.Of these oocytes,54 were used for immunofluorescence staining,whereas the other oocytes were examined by PolScope imaging and classified into three groups according to the meiotic spindle morphology:(A)normal morphology,(B)weak refraction and short meiotic spindle,and(C)no detectable meiotic spindle.The three groups demonstrated statistically significant differences in terms of survival after vitrification.However,differences were not found in terms of oocyte chromosome structure and meiotic spindle morphology on immunofluorescence staining performed before and after vitrification.Oocyte survival,fertilization,and early embryonic development rates were significantly higher in Group A than in Groups B and C with or without vitrification.While vitrification had no effect on these metrics in Group A,Groups B and C demonstrated significantly lower fertilization and cleavage rates after vitrification/warming.Conclusions:Screening for normal meiotic spindle morphology and chromosome configuration before vitrification may increase the yield of healthy viable oocytes for various assisted reproductive technologies.

DIRECT PREPARATION AND MEIOTIC ANALYSIS OF HUMAN SEMEN

A meiotic study of human semen specimens was carried out in 60 cases. Among them, 20 were normal controls, 20 suffered from infertility, and 20 had a history of recurrent spontaneous abortions. Of the cases of infertility and abortion, 50% were found to hare numerical and / or structural chromosomal aberrations in spite of the normal blood karyotype. It is suggested that chromosomal aberrations may be the cause of sterility and abortion. The success rate of semen chromosome G-banding in the infertility, abortion and control groups was 70%, 55% and 25% respectively. The semen samples of three cases of heterozygous carriers with reciprocal chromosomal translocation were also studied. The ring quadrivalents were identified in all cases. The results may explain the recurrent abortions in these patients.

Development of Triticum aestivum-Leymus racemosus ditelosomic substitution line 7Lr#1S(7A) with resistance to wheat scab and its meiotic behavior analysis

Leymus racemosus is highly resistant to wheat scab (Fusarum head bright). The transfer of scab resistant gene from L. racemosus to Triticum aestivum is of great significance for broadening the base of wheat resistance. In the present study, the pollen of T. aestivum-L. racemosus monosomic addition line with scab resistance was treated by irradiation with 1200 R 60Co-γ-rays prior to pollinating to emasculated wheat cv. Mianyang 85-45. Nine plants with a telocentric chromosome 7Lr#1S were observed in M1, and one ditelosomic substitution line 7Lr#1S was selected from selfcrossing progenies and confirmed by chromosome C-banding and GISH. Furthermore, a co-dominant EST-SSR marker CINAU 31 was employed to identify this substitution line. A pair of chromosome 7A of common wheat were found to be replaced by a pair of telocentric chromosome 7Lr#1S, and further investigation showed that chromosome configuration of the substitution line at MI of PMCs after GISH was 17.50○II W + 2.19 IIW + 0.42II7Lr#1S + 1.08 I7Lr#1S + 0.69 IW. Two telocentric chromosomes paired as a bivalent in 59.7% of PMCs. Abnormal chromosome behaviors of telocentric chromosomes were observed in part of PMCs at anaphase I and telophase I, including the moving of two telocentric chromosomes to the same pole, lagging and earlier separation of their sister chromatid. All these abnormal behaviors can be grouped into three distinct types of tetrads according to different numbers of 7Lr#1S in their daughter cells and various micronucleus in some tetrads. However, due to the high transmission frequency of the female and male gametes with a 7Lr#1S, 84% of the selfcrossing progeny plants had ditelosomic substitution. The substitution line showed high resistance to wheat scab in a successive two-year test both in the greenhouse and field; hence, the line will be particularly valuable for alien gene mapping, small fragment translocation induction and telosomic cytological behavior analysis.