Chromosome Dynamics Research Articles

4D live tracing reveals distinct movement trajectories of meiotic chromosomes

Abstract Proper chromosome alignment at the spindle equator is a prerequisite for accurate chromosome segregation during cell division. However, the chromosome movement trajectories prior to alignment remain elusive. Here, we establish a 4D imaging analysis framework to visualize chromosome dynamics and develop a deep-learning model for chromosome movement trajectory classification. Our data reveal that chromosomes follow at least three distinct movement trajectories (retracing, congressing, and quasi-static) to arrive at the equator. We further revealed the distinct roles of multiple kinesin superfamily proteins (KIFs) in coordinating and maintaining the chromosome movement trajectories. In summary, we have presented an efficient and unbiased approach to studying chromosome dynamics during cell division, thereby uncovering a variety of chromosome movement trajectories that precede alignment.

Deciphering Plasmodium Condensin Core Subunits of Structural Maintenance of Chromosomes 2 (SMC2) as a Putative Drug Target for Antimalarial Drug

Background: The structural maintenance of chromosomes (SMC) proteins plays a noteworthy role in chromosome dynamics. Several recent studies reported that the condensin core subunits of structural maintenance of chromosomes 2 (SMC2) play important roles in the atypical mitosis of the Plasmodium life cycle and may perform different functions during different proliferative stages. For eukaryotes, the structural maintenance of chromosomes (SMC) proteins are divided into six subunits and form three heterodimers of structural maintenance of chromosomes (SMC1/3) cohesion complex, structural maintenance of chromosomes (SMC2/4) condensin complex, and structural maintenance of chromosomes (SMC5/6) complex for chromosome cohesion, condensation, and DNA damage repair, respectively. Objective: The objective of this study was to investigate the structural maintenance of chromosomes 2 (SMC2) protein of P. falciparum as a putative drug target of malariacausing Plasmodium falciparum. Methods: In this study, we investigated the structural maintenance of chromosomes 2 (SMC2) protein of P. falciparum as a putative drug target of malaria-causing P. falciparum by using in-silico approaches like Homology modeling, in-silico evaluation of the modeled structure, molecular docking study to investigate the interaction of receptor-ligand, and molecular dynamic simulation study with MM calculation. Results: We reported the structural maintenance of chromosomes 2 (SMC2) protein of P. falciparum as a potent drug target that can pave the way for novel drug discovery to mitigate malaria. Conclusion: In-silico-based studies play a significant role in understanding any protein for potential drug development.

Evolutionary divergent clusters of transcribed extinct truncated retroposons drive low mRNA expression and developmental regulation in the protozoan Leishmania

BackgroundThe Leishmania genome harbors formerly active short interspersed degenerated retroposons (SIDERs) representing the largest family of repetitive elements among trypanosomatids. Their substantial expansion in Leishmania is a strong predictor of important biological functions. In this study, we combined multilevel bioinformatic predictions with high-throughput genomic and transcriptomic analyses to gain novel insights into the diversified roles retroposons of the SIDER2 subfamily play in Leishmania genome evolution and expression.ResultsWe show that SIDER2 retroposons form various evolutionary divergent clusters, each harboring homologous SIDER2 sequences usually located nearby in the linear sequence of chromosomes. This intriguing genomic organization underscores the importance of SIDER2 proximity in shaping chromosome dynamics and co-regulation. Accordingly, we show that transcripts belonging to the same SIDER2 cluster can display similar levels of expression. SIDER2 retroposons are mostly transcribed as part of 3'UTRs and account for 13% of the Leishmania transcriptome. Genome-wide expression profiling studies underscore SIDER2 association generally with low mRNA expression. The remarkable link of SIDER2 retroposons with downregulation of gene expression supports their co-option as major regulators of mRNA abundance. SIDER2 sequences also add to the diversification of the Leishmania gene expression repertoire since ~ 35% of SIDER2-containing transcripts can be differentially regulated throughout the parasite development, with a few encoding key virulence factors. In addition, we provide evidence for a functional bias of SIDER2-containing transcripts with protein kinase and transmembrane transporter activities being most represented.ConclusionsAltogether, these findings provide important conceptual advances into evolutionary innovations of transcribed extinct retroposons acting as major RNA cis-regulators.

Machine learning unravels inherent structural patterns in Escherichia coli Hi-C matrices and predicts chromosome dynamics.

High dimensional nature of the chromosomal conformation contact map ('Hi-C Map'), even for microscopically small bacterial cell, poses challenges for extracting meaningful information related to its complex organization. Here we first demonstrate that an artificial deep neural network-based machine-learnt (ML) low-dimensional representation of a recently reported Hi-C interaction map of archetypal bacteria Escherichia coli can decode crucial underlying structural pattern. The ML-derived representation of Hi-C map can automatically detect a set of spatially distinct domains across E. coli genome, sharing reminiscences of six putative macro-domains previously posited via recombination assay. Subsequently, a ML-generated model assimilates the intricate relationship between large array of Hi-C-derived chromosomal contact probabilities and respective diffusive dynamics of each individual chromosomal gene and identifies an optimal number of functionally important chromosomal contact-pairs that are majorly responsible for heterogenous, coordinate-dependent sub-diffusive motions of chromosomal loci. Finally, the ML models, trained on wild-type E. coli show-cased its predictive capabilities on mutant bacterial strains, shedding light on the structural and dynamic nuances of ΔMatP30MM and ΔMukBEF22MM chromosomes. Overall our results illuminate the power of ML techniques in unraveling the complex relationship between structure and dynamics of bacterial chromosomal loci, promising meaningful connections between ML-derived insights and biological phenomena.

Improved low-invasive mRNA electroporation method into immature mouse oocytes visualizes protein dynamics during development†.

One of the major causes of oocyte quality deterioration, chromosome segregation abnormalities manifest mainly during meiosis I, which occurs before and during ovulation. However, currently, there is a technical limitation in the introduction of mRNA into premature oocytes without impairing embryonic developmental ability. In this study, we established a low-invasive electroporation (EP) method to introduce mRNA into pre-ovulatory, germinal vesicle (GV) mouse oocytes in an easier manner than the traditional microinjection method. The EP method with an optimized impedance value resulted in the efficient introduction of mRNAs encoding enhanced green fluorescent protein (EGFP) into the GV oocytes surrounded by cumulus cells at a survival rate of 95.0%. Furthermore, the introduction of histone H2B-EGFP mRNA into the GV oocytes labeled most of the oocytes without affecting the blastocyst development rate, indicating the feasibility of the visualization of oocyte chromosomal dynamics that enable us to assay chromosomal integrity in oocyte maturation and cell count in embryonic development. The establishment of this EP method offers extensive assays to select pre-implantation embryos and enables the surveying of essential factors for mammalian oocyte quality determination.

Deciphering the Relationship between Cell Growth and Cell Cycle in Individual Escherichia coli Cells by Flow Cytometry.

Accurate coordination of chromosome replication and cell division is essential for cellular processes, yet the regulatory mechanisms governing the bacterial cell cycle remain contentious. The lack of quantitative data connecting key cell cycle players at the single-cell level across large samples hinders consensus. Employing high-throughput flow cytometry, we quantitatively correlated the expression levels of key cell cycle proteins (FtsZ, MreB, and DnaA) with DNA content in individual bacteria. Our findings reveal distinct correlations depending on the chromosome number (CN), specifically whether CN ≤2 or ≥4, unveiling a mixed regulatory scenario in populations where CN of 2 or 4 coexist. We observed function-dependent regulations for these key proteins across nonoverlapping division cycles and various nutrient conditions. Notably, a logarithmic relationship between total protein content and replication origin number across nutrient conditions suggests a unified mechanism governing cell cycle progression, confirming the applicability of Schaechter's growth law to cells with CN ≥4. For the first time, we established a proportional relationship between the synthesis rates of key cell cycle proteins and chromosome dynamics in cells with CN ≥4. Drug experiments highlighted CN 2 and 4 as pivotal turning points influencing cellular resource allocation. This high-throughput, single-cell analysis provides interconnected quantitative insights into key molecular events, facilitating a predictive understanding of the relationship between cell growth and cell cycle.

Rapid meiotic prophase chromosome movements in Arabidopsis thaliana are linked to essential reorganization at the nuclear envelope

Meiotic rapid prophase chromosome movements (RPMs) require connections between the chromosomes and the cytoskeleton, involving SUN (Sad1/UNC-84)-domain-containing proteins at the inner nuclear envelope (NE). RPMs remain significantly understudied in plants, with respect to their importance in the regulation of meiosis. Here, we demonstrate that Arabidopsis thaliana meiotic centromeres undergo rapid (up to 500 nm/s) and uncoordinated movements during the zygotene and pachytene stages. These centromere movements are not affected by altered chromosome organization and recombination but are abolished in the double mutant sun1 sun2. We also document the changes in chromosome dynamics and nucleus organization during the transition from leptotene to zygotene, including telomere attachment to SUN-enriched NE domains, bouquet formation, and nucleolus displacement, all of which were defective in sun1 sun2. These results establish A. thaliana as a model species for studying the functional implications of meiotic RPMs and demonstrate the mechanistic conservation of telomere-led RPMs in plants.

O-070 Cas9-based chromosome labelling reveals large-scale age-dependent centromere reorganisation in human oocytes

Abstract Study question Can centromeres be labelled in live human oocytes using Cas9 system and is the labelling efficiency affected by advancing female age? Summary answer Centromeres in human oocytes can be labelled using Cas9 system. Signal intensity decreases in oocytes from older patients, suggesting centromeric DNA unravelling as oocytes age. What is known already Aneuploidy in human oocytes is associated with infertility, pregnancy loss or genetic diseases in offspring. It arises due to abnormal chromosome segregation during meiosis, with the risk increasing with advancing female age. This is attributed to age-dependent loss of pericentromere-localised cohesion which holds sister chromatids together. Our work revealed that shugoshin-2 (Sgo2), a protein involved in protection of sister chromatid cohesion is also lost with age. This can exacerbate the effects of maternal age by rendering residual cohesin at pericentromeres vulnerable to loss in anaphase I. This hints at more extensive alterations to centromere organisation with advanced maternal age. Study design, size, duration This study uses human oocytes deselected from fertility treatment donated for research purposes with informed consent (HFEA RO155). The oocytes were collected fresh at germinal vesicle (GV), metaphase I (MI) or metaphase II (MII) stage, injected with Cas9 labelling system and live imaged or fixed. Participants/materials, setting, methods Centromeres were labelled in human oocytes using a dead (nuclease-deficient) (d)Cas9-EGFP protein and alpha satellite-specific small guide RNAs (sgRNA). Human oocytes were injected with dCas9-EGFP:sgAlphaSat and live-imaged using dual colour confocal microscopy with SPY555-DNA dye to also visualise chromosomes. High resolution imaging results were analysed with in-house automated kinetochore tracking software. Additional oocytes were fixed and processed for immunofluorescence to determine the high resolution localisation of dCas9-EGFP:sgAlphaSat and Sgo2 molecules. Main results and the role of chance We found that centromeres in human oocytes are efficiently labelled when using Cas9 system. During both meiosis I and II the dCas9-EGFP:sgAlphaSat probe co-localised with pericentromeric bridge and subcentromeric pools of Sgo2. We observed that the dCas9-EGFP:sgAlphaSat signal fades with advancing female age. Quantification reveals that in meiosis II the loss is abrupt at around 35 years of age, resembling Sgo2 behaviour. Initial live imaging indicates that already compromised signal in older oocytes is completely lost about 4hrs after germinal vesicle breakdown, suggesting that advancing age renders centromeres more vulnerable as meiosis I progresses. We have successfully tracked the centromeres in high resolution imaging using the automated software, which allows for detailed investigation of human meiosis chromosome dynamics. This method has been previously validated and successfully used for other cell systems. Limitations, reasons for caution Availability of human oocytes for research purposes is low, limiting our sample size. Moreover, most oocytes used for this study were deselected from treatment of patients diagnosed with infertility, potentially affecting their quality. Wider implications of the findings Our results reveal a large-scale change in centromeric DNA structure in human oocytes with increasing age. Live centromere labelling is a first successful attempt to bivalent tracking in human meiosis with potential to provide insight into age-related loss of fertility in women. Trial registration number n/a

Chromosome segregation during spermatogenesis occurs through a unique center-kinetic mechanism in holocentric moth species.

Precise regulation of chromosome dynamics in the germline is essential for reproductive success across species. Yet, the mechanisms underlying meiotic chromosomal events such as homolog pairing and chromosome segregation are not fully understood in many species. Here, we employ Oligopaint DNA FISH to investigate mechanisms of meiotic homolog pairing and chromosome segregation in the holocentric pantry moth, Plodia interpunctella, and compare our findings to new and previous studies in the silkworm moth, Bombyx mori, which diverged from P. interpunctella over 100 million years ago. We find that pairing in both Bombyx and Plodia spermatogenesis is initiated at gene-rich chromosome ends. Additionally, both species form rod shaped cruciform-like bivalents at metaphase I. However, unlike the telomere-oriented chromosome segregation mechanism observed in Bombyx, Plodia can orient bivalents in multiple different ways at metaphase I. Surprisingly, in both species we find that kinetochores consistently assemble at non-telomeric loci toward the center of chromosomes regardless of where chromosome centers are located in the bivalent. Additionally, sister kinetochores do not seem to be paired in these species. Instead, four distinct kinetochores are easily observed at metaphase I. Despite this, we find clear end-on microtubule attachments and not lateral microtubule attachments co-orienting these separated kinetochores. These findings challenge the classical view of segregation where paired, poleward-facing kinetochores are required for accurate homolog separation in meiosis I. Our studies here highlight the importance of exploring fundamental processes in non-model systems, as employing novel organisms can lead to the discovery of novel biology.

First FASEB conference in Africa-The 2023 FASEB conference on Imaging Cellular and Chromosome Dynamics held on August 27-30, 2023 in Accra, Ghana.

Access to scientific meetings and conferences is limited in low- and middle-income countries (LMIC). Efforts are being implemented to rectify this issue through short workshops, seminars, and conferences. Sena Institute of Technology (SIT), a nonprofit research institute based in Ghana, is one such organization championing this initiative. Through a partnership with the Federation of American Societies for Experimental Biology (FASEB), SIT hosted the first FASEB conference in Africa from August 27-30, 2023 in Ghana. The 3-day conference brought together scientists specialized in imaging, genetics, and cell biology from across the globe to discuss the theme "Imaging Cellular and Chromosome Dynamics." The Ghanaian Ministry of Environment, Science, Technology and Innovation (MESTI) and the Ghana Tourism Authority (GTA) provided local support to the meeting. At the end of the conference, participants recommended continuing engagement and the organization of more such meetings on the African continent.

Mendelian segregation and high recombination rates facilitate genetic analyses in Cryptosporidium parvum.

Very little is known about the process of meiosis in the apicomplexan parasite Cryptosporidium despite the essentiality of sex in its life cycle. Most cell lines only support asexual growth of Cryptosporidium parvum (C. parvum), but stem cell derived intestinal epithelial cells grown under air-liquid interface (ALI) conditions support the sexual cycle. To examine chromosomal dynamics during meiosis in C. parvum, we generated two transgenic lines of parasites that were fluorescently tagged with mCherry or GFP on chromosomes 1 or 5, respectively. Infection of ALI cultures or Ifngr1-/- mice with mCherry and GFP parasites resulted in cross-fertilization and the formation of "yellow" oocysts, which contain 4 haploid sporozoites that are the product of meiosis. Recombinant oocysts from the F1 generation were purified and used to infect HCT-8 cultures, and phenotypes of the progeny were observed by microscopy. All possible phenotypes predicted by independent segregation were represented equally (~25%) in the population, indicating that C. parvum chromosomes exhibit a Mendelian inheritance pattern. The most common pattern observed from the outgrowth of single oocysts included all possible parental and recombinant phenotypes derived from a single meiotic event, suggesting a high rate of crossover. To estimate the frequency of crossover, additional loci on chromosomes 1 and 5 were tagged and used to monitor intrachromosomal crosses in Ifngr1-/- mice. Both chromosomes showed a high frequency of crossover compared to other apicomplexans with map distances (i.e., 1% recombination) of 3-12 kb. Overall, a high recombination rate may explain many unique characteristics observed in Cryptosporidium spp. such as high rates of speciation, wide variation in host range, and rapid evolution of host-specific virulence factors.

Dynamic chromosome association with nuclear organelles in living cells.

The development of progressively sophisticated tools complemented by the integration of live cell imaging enhances our understanding of the four-dimensional (4D) nucleome, revealing elaborate molecular interactions and chromatin states. Yet, the dynamics of chromosomes in relation to nuclear organelles or to each other across cell cycle in living cells are underexplored. We have developed photoconvertible GFP H3-Dendra2 stably expressing in PC3M cells. The nuclear lamina and perinucleolar associated heterochromatin or diffuse chromosome regions were photoconverted through a single-point activation using a confocal microscope. The results demonstrated a dynamic nature for both types of chromosomes in the same cell cycle and across mitosis. While some chromosome domains were heritably associated with either nuclear lamina or nucleoli, others changed alliance to different nuclear organelles postmitotically. In addition, co-photoconverted chromosome domains often do not stay together within the same cell cycle and across mitosis, suggesting a transient nature of chromosome neighborhoods. Long-range spreading and movement of chromosomes were also observed. Interestingly, when cells were treated with a low concentration of actinomycin D that inhibits Pol I transcription through intercalating GC-rich DNA, chromosome movement was significantly blocked. Treatment with another Pol I inhibitor, metarrestin, which does not impact DNA, had little effect on the movement, suggesting that the DNA structure itself plays a role in chromosome dynamics. Furthermore, inhibition of Pol II transcription with α-amanitin also reduced the chromosome movement, demonstrating that Pol II, but not Pol I transcription, is important for chromosome dynamics in the nucleus.

Temporal dynamics of faster neo-Z evolution in butterflies.

The faster-Z/X hypothesis predicts that sex-linked genes should diverge faster than autosomal genes. However, studies across different lineages have shown mixed support for this effect. So far, most analyses have focused on old and well-differentiated sex chromosomes, but less is known about the divergence of more recently acquired neo-sex chromosomes. In Lepidoptera (moths and butterflies), Z-autosome fusions are frequent, but the evolutionary dynamics of neo-Z chromosomes have not been explored in detail. Here, we analyzed the faster-Z effect in Leptidea sinapis, a butterfly with three Z chromosomes. We show that the neo-Z chromosomes have been acquired stepwise, resulting in strata of differentiation and masculinization. While all Z chromosomes showed evidence of the faster-Z effect, selection for genes on the youngest neo-Z chromosome (Z3) appears to have been hampered by a largely intact, homologous neo-W chromosome. However, the intermediately aged neo-Z chromosome (Z2), which lacks W gametologs, showed fewer evolutionary constraints, resulting in particularly fast evolution. Our results therefore support that neo-sex chromosomes can constitute temporary hot-spots of adaptation and divergence. The underlying dynamics are likely causally linked to shifts in selective constraints, evolution of gene expression, and degeneration of W-linked gametologs which gradually expose Z-linked genes to selection.

Complete telomere-to-telomere genomes uncover virulence evolution conferred by chromosome fusion in oomycete plant pathogens

Variations in chromosome number are occasionally observed among oomycetes, a group that includes many plant pathogens, but the emergence of such variations and their effects on genome and virulence evolution remain ambiguous. We generated complete telomere-to-telomere genome assemblies for Phytophthora sojae, Globisporangium ultimum, Pythium oligandrum, and G. spinosum. Reconstructing the karyotype of the most recent common ancestor in Peronosporales revealed that frequent chromosome fusion and fission drove changes in chromosome number. Centromeres enriched with Copia-like transposons may contribute to chromosome fusion and fission events. Chromosome fusion facilitated the emergence of pathogenicity genes and their adaptive evolution. Effectors tended to duplicate in the sub-telomere regions of fused chromosomes, which exhibited evolutionary features distinct to the non-fused chromosomes. By integrating ancestral genomic dynamics and structural predictions, we have identified secreted Ankyrin repeat-containing proteins (ANKs) as a novel class of effectors in P. sojae. Phylogenetic analysis and experiments further revealed that ANK is a specifically expanded effector family in oomycetes. These results revealed chromosome dynamics in oomycete plant pathogens, and provided novel insights into karyotype and effector evolution.

Pan-cancer analysis of telomere maintenance mechanisms

Telomeres, protective caps at chromosome ends, maintain genomic stability and control cell lifespan. Dysregulated telomere maintenance mechanisms (TMMs) are cancer hallmarks, enabling unchecked cell proliferation. We conducted a pan-cancer evaluation of TMM using RNA sequencing data from The Cancer Genome Atlas for 33 different cancer types and analyzed the activities of telomerase-dependent (TEL) and alternative lengthening of telomeres (ALT) TMM pathways in detail. To further characterize the TMM profiles, we categorized the tumors based on their ALT and TEL TMM pathway activities into five major phenotypes: ALThigh TELlow, ALTlow TELlow, ALTmiddle TELmiddle, ALThigh TELhigh, and ALTlow TELhigh. These phenotypes refer to variations in telomere maintenance strategies, shedding light on the heterogeneous nature of telomere regulation in cancer. Moreover, we investigated the clinical implications of TMM phenotypes by examining their associations with clinical characteristics and patient outcomes. Specific TMM profiles were linked to specific survival patterns, emphasizing the potential of TMM profiling as a prognostic indicator and aiding in personalized cancer treatment strategies. Gene ontology analysis of the TMM phenotypes unveiled enriched biological processes associated with cell cycle regulation (both TEL and ALT), DNA replication (TEL), and chromosome dynamics (ALT) showing that telomere maintenance is tightly intertwined with cellular processes governing proliferation and genomic stability. Overall, our study provides an overview of the complexity of transcriptional regulation of telomere maintenance mechanisms in cancer.

Gametocidal genes: from a discovery to the application in wheat breeding.

Some species of the genus Aegilops, a wild relative of wheat, carry chromosomes that after introducing to wheat exhibit preferential transmission to progeny. Their selective retention is a result of the abortion of gametes lacking them due to induced chromosomal aberrations. These chromosomes are termed Gametocidal (Gc) and, based on their effects, they are categorized into three types: mild, intense or severe, and very strong. Gc elements within the same homoeologous chromosome groups of Aegilops (II, III, or IV) demonstrate similar Gc action. This review explores the intriguing dynamics of Gc chromosomes and encompasses comprehensive insights into their source species, behavioral aspects, mode of action, interactions, suppressions, and practical applications of the Gc system in wheat breeding. By delving into these areas, this work aims to contribute to the development of novel plant genetic resources for wheat breeding. The insights provided herein shed light on the utilization of Gc chromosomes to produce chromosomal rearrangements in wheat and its wild relatives, thereby facilitating the generation of chromosome deletions, translocations, and telosomic lines. The Gc approach has significantly advanced various aspects of wheat genetics, including the introgression of novel genes and alleles, molecular markers and gene mapping, and the exploration of homoeologous relationships within Triticeae species. The mystery lies in why gametes possessing Gc genes maintain their normality while those lacking Gc genes suffer abnormalities, highlighting an unresolved research gap necessitating deeper investigation.

Remarkable chromosomes and karyotypes: A top 10 list.

Chromosomes and karyotypes are particularly rich in oddities and extremes. Described below are 10 remarkable chromosomes and karyotypes sprinkled throughout the tree of life. These include variants in chromosome number, structure, and dynamics both natural and engineered. This versatility highlights the robustness and tolerance of the mitotic and meiotic machinery to dramatic changes in chromosome and karyotype architecture. These examples also illustrate that the robustness comes at a cost, enabling the evolution of chromosomes that subvert mitosis and meiosis.

DCas9 Tells Tales: Probing Gene Function and Transcription Regulation in Cancer.

Clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing is evolving into an essential tool in the field of biological and medical research. Notably, the development of catalytically deactivated Cas9 (dCas9) enzyme has substantially broadened its traditional boundaries in gene editing or perturbation. The conjugation of dCas9 with various molecular effectors allows precise control over transcriptional processes, epigenetic modifications, visualization of chromosomal dynamics, and several other applications. This expanded repertoire of CRISPR-Cas9 applications has emerged as an invaluable molecular tool kit that empowers researchers to comprehensively interrogate and gain insights into health and diseases. This review delves into the advancements in Cas9 protein engineering, specifically on the generation of various dCas9 tools that have significantly enhanced the CRISPR-based technology capability and versatility. We subsequently discuss the multifaceted applications of dCas9, especially in interrogating the regulation and function of genes that involve in supporting cancer pathogenesis. In addition, we also delineate the designing and utilization of dCas9-based tools as well as highlighting its current constraints and transformative potentials in cancer research.

Effects of rpl1001 Gene Deletion on Cell Division of Fission Yeast and Its Molecular Mechanism.

The rpl1001 gene encodes 60S ribosomal protein L10, which is involved in intracellular protein synthesis and cell growth. However, it is not yet known whether it is involved in the regulation of cell mitosis dynamics. This study focuses on the growth, spore production, cell morphology, the dynamics of microtubules, chromosomes, actin, myosin, and mitochondria of fission yeast (Schizosaccharomyces pombe) to investigate the impact of rpl1001 deletion on cell mitosis. RNA-Seq and bioinformatics analyses were also used to reveal key genes, such as hsp16, mfm1 and isp3, and proteasome pathways. The results showed that rpl1001 deletion resulted in slow cell growth, abnormal spore production, altered cell morphology, and abnormal microtubule number and length during interphase. The cell dynamics of the rpl1001Δ strain showed that the formation of a monopolar spindle leads to abnormal chromosome segregation with increased rate of spindle elongation in anaphase of mitosis, decreased total time of division, prolonged formation time of actin and myosin loops, and increased expression of mitochondrial proteins. Analysis of the RNA-Seq sequencing results showed that the proteasome pathway, up-regulation of isp3, and down-regulation of mfm1 and mfm2 in the rpl1001Δ strain were the main factors underpinning the increased number of spore production. Also, in the rpl1001Δ strain, down-regulation of dis1 caused the abnormal microtubule and chromosome dynamics, and down-regulation of hsp16 and pgk1 were the key genes affecting the delay of actin ring and myosin ring formation. This study reveals the effect and molecular mechanism of rpl1001 gene deletion on cell division, which provides the scientific basis for further clarifying the function of the Rpl1001 protein in cell division.

Regulation of meiotic telomere dynamics through membrane fluidity promoted by AdipoR2-ELOVL2

The cellular membrane in male meiotic germ cells contains a unique class of phospholipids and sphingolipids that is required for male reproduction. Here, we show that a conserved membrane fluidity sensor, AdipoR2, regulates the meiosis-specific lipidome in mouse testes by promoting the synthesis of sphingolipids containing very-long-chain polyunsaturated fatty acids (VLC-PUFAs). AdipoR2 upregulates the expression of a fatty acid elongase, ELOVL2, both transcriptionally and post-transcriptionally, to synthesize VLC-PUFA. The depletion of VLC-PUFAs and subsequent accumulation of palmitic acid in AdipoR2 knockout testes stiffens the cellular membrane and causes the invagination of the nuclear envelope. This condition impairs the nuclear peripheral distribution of meiotic telomeres, leading to errors in homologous synapsis and recombination. Further, the stiffened membrane impairs the formation of intercellular bridges and the germ cell syncytium, which disrupts the orderly arrangement of cell types within the seminiferous tubules. According to our findings we propose a framework in which the highly-fluid membrane microenvironment shaped by AdipoR2-ELOVL2 underpins meiosis-specific chromosome dynamics in testes.