Chromatid Segregation Research Articles

Pan-Cancer analysis and experimental validation identify the oncogenic nature of ESPL1: Potential therapeutic target in colorectal cancer.

Extra spindle pole bodies like 1 (ESPL1) are required to continue the cell cycle, and its primary role is to initiate the final segregation of sister chromatids. Although prior research has revealed a link between ESPL1 and the development of cancer, no systematic pan-cancer analysis has been conducted. Combining multi-omics data with bioinformatics, we have thoroughly described the function of ESPL1 in cancer. In addition, we examined the impact of ESPL1 on the proliferation of numerous cancer cell lines. In addition, the connection between ESPL1 and medication sensitivity was verified using organoids obtained from colorectal cancer patients. All these results confirm the oncogene nature of ESPL1. Herein, we downloaded raw data from numerous publicly available databases and then applied R software and online tools to explore the association of ESPL1 expression with prognosis, survival, tumor microenvironment, tumor heterogeneity, and mutational profiles. To validate the oncogene nature of ESPL1, we have performed a knockdown of the target gene in various cancer cell lines to verify the effect of ESPL1 on proliferation and migration. In addition, patients' derived organoids were used to verify drug sensitivity. The study found that ESPL1 expression was markedly upregulated in tumorous tissues compared to normal tissues, and high expression of ESPL1 was significantly associated with poor prognosis in a range of cancers. Furthermore, the study revealed that tumors with high ESPL1 expression tended to be more heterogeneous based on various tumor heterogeneity indicators. Enrichment analysis showed that ESPL1 is involved in mediating multiple cancer-related pathways. Notably, the study found that interference with ESPL1 expression significantly inhibited the proliferation of tumor cells. Additionally, the higher the expression of ESPL1 in organoids, the greater the sensitivity to PHA-793887, PAC-1, and AZD7762. Taken together, our study provides evidence that ESPL1 may implicate tumorigenesis and disease progression across multiple cancer types, highlighting its potential utility as both a prognostic indicator and therapeutic target.

Centromere proteins are asymmetrically distributed between newly divided germline stem and daughter cells and maintain a balanced niche in Drosophila males.

Stem cells can undergo asymmetric cell division (ACD) giving rise to one new stem cell and one differentiating daughter cell. In Drosophila germline stem cells (GSCs), the centromeric histone CENP-A (CID in flies) is asymmetrically distributed between sister chromatids such that chromosomes that end up in the GSC harbor more CID at centromeres. A model of "mitotic drive" has been proposed in GSCs such that stronger and earlier centromere and kinetochore interactions with microtubules bias sister chromatid segregation. Here we show that in Drosophila males, centromere proteins CID, CAL1, and CENP-C are asymmetrically distributed in newly divided GSCs and daughter cells in S phase. We find that overexpression of CID (either with or without CAL1) or CENP-C depletion disrupts CID asymmetry, with an increased pool of GSCs relative to daughter cells detectable in the niche. This result suggests a shift toward GSC self-renewal rather than differentiation, important for maintaining tissue homeostasis. Overexpression of CAL1 does not disrupt asymmetry, but instead drives germ cell proliferation in the niche. Our results in male GSCs are comparable to female GSCs, indicating that despite differences in signaling, organization, and niche composition, the effects of centromere proteins on GSC maintenance are conserved between the sexes.

Characteristic Analysis of Featured Genes Associated with Cholangiocarcinoma Progression

The noninvasive diagnosis of cholangiocarcinoma (CCA) is insufficiently accurate. Therefore, the discovery of new prognostic markers is vital for the understanding of the CCA mechanism and related treatment. The information on CCA patients in The Cancer Genome Atlas database was used for weighted gene co-expression network analysis. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were applied to analyze the modules of interest. By using receiver operating characteristic (ROC) analysis to analyze the Human Protein Atlas (HPA), the featured genes were subsequently verified. In addition, clinical samples and GSE119336 cohort data were also collected for the validation of these hub genes. Using WGCNA, we identified 61 hub genes that regulated the progression and prognosis of CCA. Eight hub genes (VSNL1, TH, PCP4, IGDCC3, RAD51AP2, MUC2, BUB1, and BUB1B) were identified which exhibited significant interactions with the tumorigenic mechanism and prognosis of CCA. In addition, GO and KEGG clarified that the blue and magenta modules were involved with chromosome segregation, mitotic and oocyte meiosis, the cell cycle, and sister chromatid segregation. Four hub genes (VSNL1, PCP4, BUB1, and BUB1B) were also verified as featured genes of progression and prognosis by the GSE119336 cohort data and five human tissue samples.

CENP-I directly targets centromeric DNA to support CENP-A deposition and centromere maintenance

The enrichment of histone H3 variant CENP-A is the epigenetic mark of centromere and initiates the assembly of the kinetochore at centromere. The kinetochore is a multi-subunit complex that ensures accurate attachment of microtubule centromere and faithful segregation of sister chromatids during mitosis. As a subunit of kinetochore, CENP-I localization at centromere also depends on CENP-A. However, whether and how CENP-I regulates CENP-A deposition and centromere identity remains unclear. Here, we identified that CENP-I directly interacts with the centromeric DNA and preferentially recognizes AT-rich elements of DNA via a consecutive DNA-binding surface formed by conserved charged residues at the end of N-terminal HEAT repeats. The DNA binding-deficient mutants of CENP-I retained the interaction with CENP-H/K and CENP-M, but significantly diminished the centromeric localization of CENP-I and chromosome alignment in mitosis. Moreover, the DNA binding of CENP-I is required for the centromeric loading of newly synthesized CENP-A. CENP-I stabilizes CENP-A nucleosomes upon binding to nucleosomal DNA instead of histones. These findings unveiled the molecular mechanism of how CENP-I promotes and stabilizes CENP-A deposition and would be insightful for understanding the dynamic interplay of centromere and kinetochore during cell cycle.

Synergistic stabilization of microtubules by BUB-1, HCP-1, and CLS-2 controls microtubule pausing and meiotic spindle assembly.

During cell division, chromosome segregation is orchestrated by a microtubule-based spindle. Interaction between spindle microtubules and kinetochores is central to the bi-orientation of chromosomes. Initially dynamic to allow spindle assembly and kinetochore attachments, which is essential for chromosome alignment, microtubules are eventually stabilized for efficient segregation of sister chromatids and homologous chromosomes during mitosis and meiosis I, respectively. Therefore, the precise control of microtubule dynamics is of utmost importance during mitosis and meiosis. Here, we study the assembly and role of a kinetochore module, comprised of the kinase BUB-1, the two redundant CENP-F orthologs HCP-1/2, and the CLASP family member CLS-2 (hereafter termed the BHC module), in the control of microtubule dynamics in Caenorhabditis elegans oocytes. Using a combination of in vivo structure-function analyses of BHC components and in vitro microtubule-based assays, we show that BHC components stabilize microtubules, which is essential for meiotic spindle formation and accurate chromosome segregation. Overall, our results show that BUB-1 and HCP-1/2 do not only act as targeting components for CLS-2 at kinetochores, but also synergistically control kinetochore-microtubule dynamics by promoting microtubule pause. Together, our results suggest that BUB-1 and HCP-1/2 actively participate in the control of kinetochore-microtubule dynamics in the context of an intact BHC module to promote spindle assembly and accurate chromosome segregation in meiosis.

Potential role for the germ cell-specific Rad21 in early meiosis of oocyte and spermatocyte in the Chinese mitten crab Eriocheir sinensis

Rad21/Rec8 family proteins are vital for sister chromatid segregation in mitosis and homologous recombination in meiosis, but no molecular data are available in crustacean species. In this study, a germ cell-specific Rad21 named EsRad21 was identified in the crab Eriocheir sinensis. EsRad21 mRNA has an open reading frame of 2310 base pairs (bp) encoding a 769 amino acids (aa) protein. RT-PCR showed that EsRad21 mRNA was particularly expressed in testis and ovary. The RT-qPCR results further revealed that the EsRad21 mRNA exhibited similar expression pattern in gonads at various developmental stages. EsRad21 mRNA expression level was the highest in testis at early spermatogenesis stage and ovaries at previtellogenesis stage, thereafter decreased significantly at middle spermatogenesis and vitellogenesis, and finally reach the lowest level at late spermatogenesis and vitellogenesis. In situ hybridization (ISH) analysis showed that EsRad21 mRNA was exclusively expressed in germline cells, but not in gonadal somatic cells. Notably, hybridized signal was detected on chromosomes of metaphase spermatocytes. EsRad21 is thus an underlying helpful indicator of the early phases of germ cell development. RNAi knockdown of EsRad21 downregulated the expression of other meiosis-related genes like Smc5-Smc6 and SPO11 and resulted in high mortality of individuals after 24 h post injection of EsRad21 dsRNA. Taken together, our results showed a potential role for EsRad21 in early meiosis of oocytes and spermatocytes in E. sinensis. This is the first report on the molecular characterization of the Rad21 transcript in a crustacean species.

Loss of RanGAP1 drives chromosome instability and rapid tumorigenesis of osteosarcoma.

Chromothripsis is a catastrophic event of chromosomal instability that involves intensive fragmentation and rearrangements within localized chromosomal regions. However, its cause remains unclear. Here, we show that reduction and inactivation of Ran GTPase-activating protein 1 (RanGAP1) commonly occur in human osteosarcoma, which is associated with a high rate of chromothripsis. In rapidly expanding mouse osteoprogenitors, RanGAP1 deficiency causes chromothripsis in chr1q, instant inactivation of Rb1 and degradation of p53, consequent failure in DNA damage repair, and ultrafast osteosarcoma tumorigenesis. During mitosis, RanGAP1 anchors to the kinetochore, where it recruits PP1-γ to counteract the activity of the spindle-assembly checkpoint (SAC) and prevents TOP2A degradation, thus safeguarding chromatid decatenation. Loss of RanGAP1 causes SAC hyperactivation and chromatid decatenation failure. These findings demonstrate that RanGAP1 maintains mitotic chromosome integrity and that RanGAP1 loss drives tumorigenesis through its direct effects on SAC and decatenation and secondary effects on DNA damage surveillance.

Improved Basic Cytogenetics Challenges Holocentricity of Butterfly Chromosomes

Mitotic chromosomes of butterflies, which look like dots or short filaments in most published data, are generally considered to lack localised centromeres and thus to be holokinetic. This particularity, observed in a number of other invertebrates, is associated with meiotic particularities known as “inverted meiosis,” in which the first division is equational, i.e., centromere splitting-up and segregation of sister chromatids instead of homologous chromosomes. However, the accurate analysis of butterfly chromosomes is difficult because (1) their size is very small, equivalent to 2 bands of a mammalian metaphase chromosome, and (2) they lack satellite DNA/heterochromatin in putative centromere regions and therefore marked primary constrictions. Our improved conditions for basic chromosome preparations, here applied to 6 butterfly species belonging to families Nymphalidae and Pieridae challenges the holocentricity of their chromosomes: in spite of the absence of primary constrictions, sister chromatids are recurrently held together at definite positions during mitotic metaphase, which makes possible to establish karyotypes composed of acrocentric and submetacentric chromosomes. The total number of chromosomes per karyotype is roughly inversely proportional to that of non-acrocentric chromosomes, which suggests the occurrence of frequent robertsonian-like fusions or fissions during evolution. Furthermore, the behaviour and morphological changes of chromosomes along the various phases of meiosis do not seem to differ much from those of canonical meiosis. In particular, at metaphase II chromosomes clearly have 2 sister chromatids, which refutes that anaphase I was equational. Thus, we propose an alternative mechanism to holocentricity for explaining the large variations in chromosome numbers in butterflies: (1) in the ancestral karyotype, composed of about 62 mostly acrocentric chromosomes, the centromeres, devoid of centromeric heterochromatin/satellite DNA, were located at contact with telomeric heterochromatin; (2) the instability of telomeric heterochromatin largely contributed to drive the multiple rearrangements, principally chromosome fusions, which occurred during butterfly evolution.

Non-synonymous, synonymous, and non-coding nucleotide variants contribute to recurrently altered biological processes during retinoblastoma progression.

Retinoblastomas form in response to biallelic RB1 mutations or MYCN amplification and progress to more aggressive and therapy-resistant phenotypes through accumulation of secondary genomic changes. Progression-related changes include recurrent somatic copy number alterations and typically non-recurrent nucleotide variants, including synonymous and non-coding variants, whose significance has been unclear. To determine if nucleotide variants recurrently affect specific biological processes, we identified altered genes and over-represented variant gene ontologies in 168 exome or whole-genome-sequenced retinoblastomas and 12 tumor-matched cell lines. In addition to RB1 mutations, MYCN amplification, and established retinoblastoma somatic copy number alterations, the analyses revealed enrichment of variant genes related to diverse biological processes including histone monoubiquitination, mRNA processing (P) body assembly, and mitotic sister chromatid segregation and cytokinesis. Importantly, non-coding and synonymous variants increased the enrichment significance of each over-represented biological process term. To assess the effects of such mutations, we examined the consequences of a 3' UTR variant of PCGF3 (a BCOR-binding component of Polycomb repressive complex I), dual 3' UTR variants of CDC14B (a regulator of sister chromatid segregation), and a synonymous variant of DYNC1H1 (a regulator of P-body assembly). One PCGF3 and one of two CDC14B 3' UTR variants impaired gene expression whereas a base-edited DYNC1H1 synonymous variant altered protease sensitivity and stability. Retinoblastoma cell lines retained only ~50% of variants detected in tumors and enriched for new variants affecting p53 signaling. These findings reveal potentially important differences in retinoblastoma cell lines and tumors and implicate synonymous and non-coding variants, along with non-synonymous variants, in retinoblastoma oncogenesis.

Molecular markers as tools in breeding for resistance to Potato Virus Y

Potato virus Y (PVY) is an economically important pathogen of potato as a vegetatively propagated crop. High resistance to all strains of PVY is determined by Ry-genes, which are introgressed into modern potato varieties from a limited number of sources of resistance ‒ Solanum stoloniferum Schlechtd. et Bche., Solanum andigenum Juz. et Buk., Solanum chacoense Bitt. Use of new species Solanum and interspecific hybrids based on them provides for the expansion of existing potato gene pool in breeding for resistance to PVY. Traditional breeding for resistance to viruses has still a great potential, though, it is a long and laborious process. Molecular markers linked to Ry-genes are widely integrated in order to increase the effectiveness of practical breeding. Previous studies have revealed a number of shortcomings in using the molecular markers of Ry-genes. To assess the predictive abilities of molecular markers RYSC3, M45, M6 of the Ryadg gene and YES3-3A of the Rysto gene for resistance to PVY, the F1 generation of two potato populations was studied, in the creation of which inter-specific hybrids were used. The nature of segregation 5:3 obtained by phenotype showed that the original parental forms can be the sources of not only previously identified, but also unidentified Ry-genes and Ny-genes of hypersensitivity. Correlation coefficient between the presence of markers and resistance to PVY was 0.64 for the YES3-3 marker (79 % matching) and 0.54 for RYSC3, М45, М6 markers (76 % matching). There have been revealed the cases of “false positive” results of the study (the presence of a marker in susceptible genotypes), which indicate to the insufficient effectiveness of the markers used. The marker segregation observed in the populations was consistent with chromatid segregation, confirming the simplex nature of Ry-genes inheritance from resistant parents. The ratio of genotypes with the presence/absence of markers was 0.86:1.

Silencing of KNTC1 inhibits hepatocellular carcinoma cells progression via suppressing PI3K/Akt pathway

Kinetochore associated 1 (KNTC1) encodes a kinetochore component in Rod-Zwilch-ZW10 (RZZ) complex which is essential for the segregation of sister chromatids during mitosis and participates in the spindle checkpoint. Recent research demonstrated that kinetochore proteins may be potential biomarkers and may contribute to the development of human malignancies. Our immunohistochemistry experiment showed that KNTC1 was highly expressed in hepatocellular carcinoma (HCC) tissues and correlated with terrible prognosis, indicating that KNTC1 acts a pivotal role in HCC development. Furthermore, lentivirus delivered short hairpin RNA (shRNA) KNTC1 (Lv-shKNTC1) was applied to infect BEL-7404 and SK-HEP-1 to identify roles of KNTC1 on HCC. Lv-shKNTC1 cells showed reduced proliferation ability, increased apoptosis and decreased migration ability. In vivo experiments suggested that xenografts grow significantly slower upon the silencing of KNTC1. Mechanistically, the protein levels of PIK3CA, p-Akt, CCND1, CDK6 are all down-regulated in Lv-KNTC1 cells and the Lv-shKNTC1 tumor tissues of nude mice. Therefore, KNTC1 may affect the biological activity of HCC cells through PI3K/Akt signaling pathway. Further studies revealed that ZW10 is a pivotal protein that participates in KNTC1-induced regulation of PI3K/Akt signaling pathway. In summary, the key finding of this report highlighted the significance of KNTC1 in tumor regression of HCC, demonstrating KNTC1 as an innovative target for adjuvant treatment of HCC.

Depletion or cleavage of cohesin during anaphase differentially affects chromatin structure and segregation.

Chromosome segregation requires both the separation of sister chromatids and the sustained condensation of chromatids during anaphase. In yeast cells, cohesin is not only required for sister chromatid cohesion but also plays a major role determining the structure of individual chromatids in metaphase. Separase cleavage is thought to remove all cohesin complexes from chromosomes to initiate anaphase. It is thus not clear how the length and organisation of segregating chromatids is maintained during anaphase in the absence of cohesin. Here, we show that degradation of cohesin at the anaphase onset causes aberrant chromatid segregation. Hi-C analysis on segregating chromatids demonstrates that cohesin depletion causes loss of intrachromatid organisation. Surprisingly, tobacco etch virus (TEV)-mediated cleavage of cohesin does not dramatically disrupt chromatid organisation in anaphase, explaining why bulk segregation is achieved. In addition, we identified a small pool of cohesin complexes bound to telophase chromosomes in wild-type cells and show that they play a role in the organisation of centromeric regions. Our data demonstrates that in yeast cells cohesin function is not over in metaphase, but extends to the anaphase period when chromatids are segregating.

SMC complexes can traverse physical roadblocks bigger than their ring size.

Ring-shaped structural maintenance of chromosomes (SMC) complexes like condensin and cohesin extrude loops of DNA. It remains, however, unclear how they can extrude DNA loops in chromatin that is bound with proteins. Here, we use invitro single-molecule visualization to show that nucleosomes, RNA polymerase, and dCas9 pose virtually no barrier to loop extrusion by yeast condensin. We find that even DNA-bound nanoparticles as large as 200nm, much bigger than the SMC ring size, also translocate into DNA loops during extrusion by condensin and cohesin. This even occurs for a single-chain version of cohesin in which the ring-forming subunits are covalently linked and cannot open to entrap DNA. The data show that SMC-driven loop extrusion has surprisingly little difficulty in accommodating large roadblocks into the loop. The findings also show that the extruded DNA does not pass through the SMC ring (pseudo)topologically, hence pointing to a nontopological mechanism for DNA loop extrusion.

Asymmetric chromatin retention and nuclear envelopes separate chromosomes in fused cells in vivo

Hybrid cells derived through fertilization or somatic cell fusion recognize and separate chromosomes of different origins. The underlying mechanisms are unknown but could prevent aneuploidy and tumor formation. Here, we acutely induce fusion between Drosophila neural stem cells (neuroblasts; NBs) and differentiating ganglion mother cells (GMCs) in vivo to define how epigenetically distinct chromatin is recognized and segregated. We find that NB-GMC hybrid cells align both endogenous (neuroblast-origin) and ectopic (GMC-origin) chromosomes at the metaphase plate through centrosome derived dual-spindles. Physical separation of endogenous and ectopic chromatin is achieved through asymmetric, microtubule-dependent chromatin retention in interphase and physical boundaries imposed by nuclear envelopes. The chromatin separation mechanisms described here could apply to the first zygotic division in insects, arthropods, and vertebrates or potentially inform biased chromatid segregation in stem cells.

Identification of Signal Pathways and Hub Genes of Pulmonary Arterial Hypertension by Bioinformatic Analysis.

Pulmonary arterial hypertension (PAH) is a progressive and complex pulmonary vascular disease with poor prognosis. The aim of this study was to provide a new understanding of the pathogenesis of disease and potential treatment targets for patients with PAH based on multiple-microarray analysis.Two microarray datasets (GSE53408 and GSE113439) downloaded from the Gene Expression Omnibus (GEO) database were analysed. All the raw data were processed by R, and differentially expressed genes (DEGs) were screened out by the “limma” package. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed and visualized by R and Cytoscape software. Protein-protein interactions (PPI) of DEGs were analysed based on the NetworkAnalyst online tool. A total of 442 upregulated DEGs and 84 downregulated DEGs were identified. GO enrichment analysis showed that these DEGs were mainly enriched in mitotic nuclear division, organelle fission, chromosome segregation, nuclear division, and sister chromatid segregation. Significant KEGG pathway enrichment included ribosome biogenesis in eukaryotes, RNA transport, proteoglycans in cancer, dilated cardiomyopathy, rheumatoid arthritis, vascular smooth muscle contraction, focal adhesion, regulation of the actin cytoskeleton, and hypertrophic cardiomyopathy. The PPI network identified 10 hub genes including HSP90AA1, CDC5L, MDM2, LRRK2, CFTR, IQGAP1, CAND1, TOP2A, DDX21, and HIF1A. We elucidated potential biomarkers and therapeutic targets for PAH by bioinformatic analysis, which provides a theoretical basis for future study.

ShRNA‑mediated knockdown of KNTC1 inhibits non-small-cell lung cancer through regulating PSMB8

In view of the important roles played by Kinetochore proteins in mitosis, we believed that they may contribute to the development and progression of human cancers, which has been reported recently elsewhere. Kinetochore-associated 1 (KNTC1) participates in the segregation of sister chromatids during mitosis, the effects of which on non-small-cell lung cancer (NSCLC) remain unclear. Here, we sought to identify the biological significance of KNTC1 in NSCLC. KNTC1 protein expression in NSCLC tissues was investigated by immunohistochemistry. Lentivirus delivered short hairpin RNA (shRNA) was utilized to establish KNTC1 silence NSCLC cell lines. The effects of KNTC1 depletion on NSCLC cell proliferation, migration, apoptosis, and tumor formation were analyzed by MTT assay, wound-healing assay, transwell assay, flow cytometry assay, and in nude mouse models in vivo. After KNTC1 reduction, NSCLC cell viability, proliferation, migration, and invasion were restrained. A xenograft tumor model was also provided to demonstrate the inhibited tumorigenesis in NSCLC. In addition, the downstream mechanism analysis indicated that KNTC1 depletion was positively associated with PSMB8. The findings of the present study suggested that KNTC1 may have a pivotal role in mediating NSCLC progression and may act as a novel therapeutic target for NSCLC.

Identification of molecular subtypes in lung adenocarcinoma based on DNA methylation and gene expression profiling-a bioinformatic analysis.

BackgroundMolecular typing based on deoxyribonucleic acid (DNA) methylation and gene expression can extend understandings of the molecular mechanisms involved in lung adenocarcinoma (LUAD) and enhance current diagnostic, treatment, and prognosis prediction approaches.MethodsGene expression and DNA methylation data sets of LUAD were obtained from The Cancer Genome Atlas (TCGA), and the differential gene and methylation expression levels were analyzed.ResultsWe successfully divided the LUAD samples into 2 clinically relevant subtypes with significantly different survival times and tumor stages according to the transcriptome and methylation data. We found significant differences in the survival status, age, gender, tumor stage, node stage, and clinical stage between the 2 subtypes. The hub genes identified in the subnetworks, including NCAPG, CCNB1, DLGAP5, HLA-DQA1, HLA-DPA1, HLA-DPB1, SFTP, SCGBA1A, and SFTPD, were correlated with the cell cycle and immune system. The Gene Ontology annotation of the hub genes showed that the biological processes included organelle fission mitotic nuclear division, and sister chromatid segregation. The cellular components included chromosomal region, spindle, and kinetochore. The molecular functions included tubulin-binding, microtubule-binding, and DNA replication origin binding. The Kyoto Encyclopedia of Genes and Genomes signaling pathways related to the hub genes mainly included the cell cycle, human T-cell leukemia virus (type 1) infection, inflammatory bowel disease, and the intestinal immune network for immunoglobulin A production. The clinical stage difference was also confirmed in the validation group using the GSE32863 data set.ConclusionsOur findings extend understandings of the pathogenesis of LUAD and can be used to improve current diagnosis, treatment, and prognosis prediction strategies.

Nonrandom sister chromatid segregation mediates rDNA copy number maintenance in Drosophila.

Although considered to be exact copies of each other, sister chromatids can segregate nonrandomly in some cases. For example, sister chromatids of the X and Y chromosomes segregate nonrandomly during asymmetric division of male germline stem cells (GSCs) in Drosophila melanogaster. Here, we demonstrate that the ribosomal DNA (rDNA) loci, which are located on the X and Y chromosomes, and an rDNA binding protein Indra are required for nonrandom sister chromatid segregation (NRSS). We provide the evidence that NRSS, following unequal sister chromatid exchange, is a mechanism by which GSCs recover rDNA copy number, counteracting the spontaneous copy number loss that occurs during aging. Our study reveals an unexpected role for NRSS in maintaining germline immortality through maintenance of a vulnerable genomic element, rDNA.

Non-random chromosome segregation and chromosome eliminations in the fly Bradysia (Sciara).

Mendelian inheritance is based upon random segregation of homologous chromosomes during meiosis and perfect duplication and division of chromosomes in mitosis so that the entire genomic content is passed down to the daughter cells. The unusual chromosome mechanics of the fly Bradysia (previously called Sciara) presents many exceptions to the canonical processes. In male meiosis I, there is a monopolar spindle and non-random segregation such that all the paternal homologs move away from the single pole and are eliminated. In male meiosis II, there is a bipolar spindle and segregation of the sister chromatids except for the X dyad that undergoes non-disjunction. The daughter cell that is nullo-X degenerates, whereas the sperm has two copies of the X. Fertilization restores the diploid state, but there are three copies of the X chromosome, of which one or two of the paternally derived X chromosomes will be eliminated in an early cleavage division. Bradysia (Sciara) coprophila also has germ line limited L chromosomes that are eliminated from the soma. Current information and the molecular mechanisms for chromosome imprinting and eliminations, which are just beginning to be studied, will be reviewed here.

Identification of Different miRNAs and Their Relevant miRNA Targeted Genes Involved in Sister Chromatid Cohesion and Segregation (SCCS)/chromatin Remodeling Pathway on T1G3 Urothelial Carcinoma (UC) Response to BCG Immunotherapy.

Till now, no definite clinical or laboratory marker can predict the recurrence or progression of T1 G3 urothelial carcinoma (UC). Genetic aberrations of the chromatin remodeling genes and sister chromatid cohesion and segregation (SCCS) were identified in UC. Here we investigated the impact of novel miRNAs and their targeted expressed SCCS and chromatin remodeling genes on T1G3 UC response to Bacillus Calmette-Guérin (BCG) therapy. One hundred tissue samples were obtained from NMIBC patients. Gene expression and immunohistochemical assay of STAG2, ARID1A, NCOR1and UTX were assessed. MiRNA analysis for their targeting miRNAs (miR-21, miR-31, Let7a and miR-199a) was carried out. Assessed genes were compared between responders and no responders to BCG. Univariate and multivariate analysis of predictors of disease recurrence and progression were performed using cox regression analysis. Thirty-two and 22 patients developed recurrence and progression to MIBC (BCG non-responders). BCG non-responders showed statistically significant higher expression of miR-21 and their targeted STAG2, miR-199a and NCOR1 gene (P < .001), and lower expression of miR-31, Let7a, ARID1A and UTX genes (P < .001). Higher miR-199a (P=.006) and lower miR-31 (P=.01), ARID1A (P=.008) and UTX (P=.03) were independent predictor of higher tumor recurrence. Recurrent disease (P=.003), higher expression of STAG2 (P=.01), NCOR1 (P=.01) and miR-21 (P=.03) genes and lower expression of miR-31 (P=.02), Let7a (P=.04) and ARID1A (P=.04) genes were the independent predictor of disease progression. Upregulation of STAG2 and NCOR1 and down regulation of ARID1A and UTX genes and their targeting miRNAs were associated with UC non-response to BCG.