SMC1B is present in mammalian somatic cells and interacts with mitotic cohesin proteins

A Catalogue of Structural Variation across Ancestrally Diverse Asian Genomes

Structural variants (SVs) are significant contributors to inter-individual genetic variation associated with traits and diseases. Current SV studies using whole-genome sequencing (WGS) have a largely Eurocentric composition, with little known about SV diversity in other ancestries, particularly from Asia. Here, we present a WGS catalogue of 73,035 SVs from 8392 Singaporeans of East Asian, Southeast Asian and South Asian ancestries, of which ~65% (47,770 SVs) are novel. We show that Asian populations can be stratified by their global SV patterns and identified 42,239 novel SVs that are specific to Asian populations. 52% of these novel SVs are restricted to one of the three major ancestry groups studied (Indian, Chinese or Malay). We uncovered SVs affecting major clinically actionable loci. Lastly, by identifying SVs in linkage disequilibrium with single-nucleotide variants, we demonstrate the utility of our SV catalogue in the fine-mapping of Asian GWAS variants and identification of potential causative variants. These results augment our knowledge of structural variation across human populations, thereby reducing current ancestry biases in global references of genetic variation afflicting equity, diversity and inclusion in genetic research.

Functional characterization of cooperating MGA mutations in RUNX1::RUNX1T1 acute myeloid leukemia

MGA (Max-gene associated) is a dual-specificity transcription factor that negatively regulates MYC-target genes to inhibit proliferation and promote differentiation. Loss-of-function mutations in MGA have been commonly identified in several hematological neoplasms, including acute myeloid leukemia (AML) with RUNX1::RUNX1T1, however, very little is known about the impact of these MGA alterations on normal hematopoiesis or disease progression. We show that representative MGA mutations identified in patient samples abolish protein-protein interactions and transcriptional activity. Using a series of human and mouse model systems, including a newly developed conditional knock-out mouse strain, we demonstrate that loss of MGA results in upregulation of MYC and E2F targets, cell cycle genes, mTOR signaling, and oxidative phosphorylation in normal hematopoietic cells, leading to enhanced proliferation. The loss of MGA induces an open chromatin state at promoters of genes involved in cell cycle and proliferation. RUNX1::RUNX1T1 expression in Mga-deficient murine hematopoietic cells leads to a more aggressive AML with a significantly shortened latency. These data show that MGA regulates multiple pro-proliferative pathways in hematopoietic cells and cooperates with the RUNX1::RUNX1T1 fusion oncoprotein to enhance leukemogenesis.

Synthetic Lethality between Cohesin and WNT Signaling Pathways in Diverse Cancer Contexts

Cohesin is a highly conserved ring-shaped complex involved in topologically embracing chromatids, gene expression regulation, genome compartmentalization, and genome stability maintenance. Genomic analyses have detected mutations in the cohesin complex in a wide array of human tumors. These findings have led to increased interest in cohesin as a potential target in cancer therapy. Synthetic lethality has been suggested as an approach to exploit genetic differences in cancer cells to influence their selective killing. In this study, we show that mutations in ESCO1, NIPBL, PDS5B, RAD21, SMC1A, SMC3, STAG2, and WAPL genes are synthetically lethal with stimulation of WNT signaling obtained following LY2090314 treatment, a GSK3 inhibitor, in several cancer cell lines. Moreover, treatment led to the stabilization of β-catenin and affected the expression of c-MYC, probably due to the occupancy decrease in cohesin at the c-MYC promoter. Finally, LY2090314 caused gene expression dysregulation mainly involving pathways related to transcription regulation, cell proliferation, and chromatin remodeling. For the first time, our work provides the underlying molecular basis for synthetic lethality due to cohesin mutations and suggests that targeting the WNT may be a promising therapeutic approach for tumors carrying mutated cohesin.

The synergism of SMC1A cohesin gene silencing and bevacizumab against colorectal cancer

BACKGROUND

SMC1A is a subunit of the cohesin complex that participates in many DNA- and chromosome-related biological processes. Previous studies have established that SMC1A is involved in cancer development and in particular, is overexpressed in chromosomally unstable human colorectal cancer (CRC). This study aimed to investigate whether SMC1A could serve as a therapeutic target for CRC.

METHODS

At first, we studied the effects of either SMC1A overexpression or knockdown in vitro. Next, the outcome of SMC1A knocking down (alone or in combination with bevacizumab, a monoclonal antibody against vascular endothelial growth factor) was analyzed in vivo.

RESULTS

We found that SMC1A knockdown affects cell proliferation and reduces the ability to grow in anchorage-independent manner. Next, we demonstrated that the silencing of SMC1A and the combo treatment were effective in increasing overall survival in a xenograft mouse model. Functional analyses indicated that both treatments lead to atypical mitotic figures and gene expression dysregulation. Differentially expressed genes were implicated in several pathways including gene transcription regulation, cellular proliferation, and other transformation-associated processes.

CONCLUSIONS

These results indicate that SMC1A silencing, in combination with bevacizumab, can represent a promising therapeutic strategy for human CRC.

AKT/FOXM1/STMN1 signaling pathway activation by SMC1A promotes tumor growth in breast cancer

BACKGROUND

Upregulation of SMC1A (Structural maintenance of chromosomes 1A) is linked with many types of cancer and its oncogenic function, which has been associated with crucial cellular mechanisms (cell division, cell cycle checkpoints regulation and DNA repair). Recent studies have shown that SMC1A was involved in breast cancer, although the exact mechanisms of SMC1A remain to be determined.

METHODS

Using The Cancer Genome Atlas (TCGA) database, we examined SMC1A expression and its relation to other genes, including FOXM1 and STMN1. Short hairpin RNA was used to subsequently examine the biological roles of SMC1A in MDA-MB-231 and MDA-MB-468 cell lines. Bioinformatics were performed to identify the SMC1A-related gene FOXM1.

RESULTS

Here, we used the TCGA database to show that SMC1A is overexpressed in breast cancer. Later investigations showed SMC1A's role in breast cancer cell survival, apoptosis and invasion. Using bioinformatics and western blot assays, we confirmed that FOXM1 acted as the downstream of SMC1A, and SMC1A knockdown significantly downregulated the FOXM1 expression via the AKT signal pathway. Interestingly, the inhibition effects induced by SMC1A downregulation could be reversed by FOXM1 overexpression. In the clinic, SMC1A expression is favorably linked with FOXM1 expression in breast cancer tumor tissues.

CONCLUSIONS

Collectively, our results not only enhance our knowledge of SMC1A's molecular pathways in breast cancer, but also suggest a potential new therapeutic target.

Functional Characterization of Cooperating MGA Mutations in RUNX1::RUNX1T1 Acute Myeloid Leukemia

MGA (Max-gene associated) is a dual-specificity transcription factor that negatively regulates MYC-target genes to inhibit proliferation and promote differentiation. Loss-of-function mutations in MGA have been commonly identified in several hematological neoplasms, including acute myeloid leukemia (AML) with RUNX1::RUNX1T1, however, very little is known about the impact of these MGA alterations on normal hematopoiesis or disease progression. We show that representative MGA mutations identified in patient samples abolish protein-protein interactions and transcriptional activity. Using a series of human and mouse model systems, including a newly developed conditional knock-out mouse strain, we demonstrate that loss of MGA results in upregulation of MYC and E2F targets, cell cycle genes, mTOR signaling, and oxidative phosphorylation in normal hematopoietic cells, leading to enhanced proliferation. The loss of MGA induces an open chromatin state at promotors of genes involved in cell cycle and proliferation. RUNX1::RUNX1T1 expression in Mga-deficient murine hematopoietic cells leads to a more aggressive AML with a significantly shortened latency. These data show that MGA regulates multiple pro-proliferative pathways in hematopoietic cells and cooperates with the RUNX1::RUNX1 T1 fusion oncoprotein to enhance leukemogenesis.

Identification of microsatellite instability and immune-related prognostic biomarkers in colon adenocarcinoma

Background

Colon adenocarcinoma (COAD) is a prevalent malignancy that causes significant mortality. Microsatellite instability plays a pivotal function in COAD development and immunotherapy resistance. However, the detailed underlying mechanism requires further investigation. Consequently, identifying molecular biomarkers with prognostic significance and revealing the role of MSI in COAD is important for addressing key obstacles in the available treatments.

Methods

CIBERSORT and ESTIMATE analyses were performed to evaluate immune infiltration in COAD samples, followed by correlation analysis for MSI and immune infiltration. Then, differentially expressed genes (DEGs) in MSI and microsatellite stability (MSS) samples were identified and subjected to weighted gene co-expression network analysis (WGCNA). A prognostic model was established with univariate cox regression and LASSO analyses, then evaluated with Kaplan-Meier analysis. The correlation between the prognostic model and immune checkpoint inhibitor (ICI) response was also analyzed.

Results

In total, 701 significant DEGs related to MSI status were identified, and WGCNA revealed two modules associated with the immune score. Then, a seven-gene prognostic model was constructed using LASSO and univariate cox regression analyses to predict survival and ICI response. The high-risk score patients in TCGA and GEO cohorts presented a poor prognosis, as well as a high immune checkpoint expression, so they are more likely to benefit from ICI treatment.

Conclusion

The seven-gene prognostic model constructed could predict the survival of COAD and ICI response and serve as a reference for immunotherapy decisions.

Studying the nature of ascending-descending-floating-sinking of Chinese medicines based on gonadotropin-releasing hormone

OBJECTIVE

to explore the nature of ascending-descending-floating-sinking of Traditional Chinese Medicine on normal rats using gonadotropin-releasing hormone (GnRh).

METHODS

Normal male Sprague-Dawley rats were orally administered six floating Chinese medicines and seven sinking Chinese medicines for 14 d. then, GnRh and relevant indicators were detected. Initially, the different effects of floating and sinking drugs on the body were explored. To verify the effects of floating and sinking drugs on the body, normal rats were orally administered Mahuang (Herba Ephedra Sinica) and Tinglizi (Semen Lepidii Apetali) for 14 d. Then, GnRh antagonists were administered. We observed the changes of relevant indicators and clarified the correlation between GnRh and the laws of floating and sinking.

RESULTS

Floating Chinese medicines significantly increased the testicular coefficients; GnRh level in the serum; the protein level of GnRh receptor (GnRhR) in the testis; and the mRNA levels of androgen receptor (AR), small C-terminal domain phosphatase (SCP) 3, SCP2, SYCE1, SMC1B, SMC3, and Rec8 (P < 0.01 or < 0.05). Sinking Chinese medicines did not react similarly, while GnRh antagonists blocked the regulatory effect of Mahuang (Herba Ephedra Sinica) but did not affect Tinglizi (Semen Lepidii Apetali).

CONCLUSIONS

GnRh may be closely related to the nature of ascending-descending-floating-sinking of Chinese medicine. Floating Chinese medicines may promote their medicinal properties by regulating GnRH level; however, sinking Chinese medicines did not affect GnRh level.

Single-Cell RNA Sequencing Revealed the Heterogeneity of Gonadal Primordial Germ Cells in Zebra Finch (Taeniopygia guttata)

Primordial germ cells (PGCs) are undifferentiated gametes with heterogeneity, an evolutionarily conserved characteristic across various organisms. Although dynamic selection at the level of early germ cell populations is an important biological feature linked to fertility, the heterogeneity of PGCs in avian species has not been characterized. In this study, we sought to evaluate PGC heterogeneity in zebra finch using a single-cell RNA sequencing (scRNA-seq) approach. Using scRNA-seq of embryonic gonadal cells from male and female zebra finches at Hamburger and Hamilton (HH) stage 28, we annotated nine cell types from 20 cell clusters. We found that PGCs previously considered a single population can be separated into three subtypes showing differences in apoptosis, proliferation, and other biological processes. The three PGC subtypes were specifically enriched for genes showing expression patterns related to germness or pluripotency, suggesting functional differences in PGCs according to the three subtypes. Additionally, we discovered a novel biomarker, SMC1B, for gonadal PGCs in zebra finch. The results provide the first evidence of substantial heterogeneity in PGCs previously considered a single population in birds. This discovery expands our understanding of PGCs to avian species, and provides a basis for further research.

Clinical Significance and Integrative Analysis of the SMC Family in Hepatocellular Carcinoma

Worldwide, hepatocellular carcinoma (HCC) is one of the most malignant cancers with poor prognosis. The structural maintenance of chromosomes (SMC) gene family has been shown to play important roles in human cancers. Nevertheless, the role of SMC members in HCC is not well-understood. In this study, we comprehensively explored the role of the SMC family in HCC using a series of bioinformatic analysis tools. Studies have demonstrated that the mRNA expression levels of SMC1A, SMC1B, SMC2, SMC4, and SMC6 are significantly overexpressed in HCC, and the protein levels of SMC1A, SMC2, SMC3, SMC4, SMC5, and SMC6 are similarly elevated. Moreover, HCC patients with high SMC2 and SMC4 expression levels exhibit poor survival. Using KEGG and GO analyses, we analyzed the enrichment of gene expression in the biological functions and pathways of the SMC family in HCC. Immune infiltration analysis revealed that the expression of the SMC family is closely associated with B cells, CD4+ T cells, CD8+ T cells, macrophages, neutrophils, and DCs. In conclusion, our findings will enhance a more thorough understanding of the SMC family in HCC progression and provide new directions for the diagnosis and treatment of HCC in the future.

The Zebrafish Meiotic Cohesin Complex Protein Smc1b Is Required for Key Events in Meiotic Prophase I

The eukaryotic structural maintenance of chromosomes (SMC) proteins are involved in key processes of chromosome structure and dynamics. SMC1β was identified as a component of the meiotic cohesin complex in vertebrates, which aids in keeping sister chromatids together prior to segregation in meiosis II and is involved in association of homologous chromosomes in meiosis I. The role of SMC1β in meiosis has primarily been studied in mice, where mutant male and female mice are infertile due to germ cell arrest at pachytene and metaphase II stages, respectively. Here, we investigate the function of zebrafish Smc1b to understand the role of this protein more broadly in vertebrates. We found that zebrafish smc1b is necessary for fertility and has important roles in meiosis, yet has no other apparent roles in development. Therefore, smc1b functions primarily in meiosis in both fish and mammals. In zebrafish, we showed that smc1b mutant spermatocytes initiated telomere clustering in leptotene, but failed to complete this process and progress into zygotene. Furthermore, mutant spermatocytes displayed a complete failure of synapsis between homologous chromosomes and homolog pairing only occurred at chromosome ends. Interestingly, meiotic DNA double strand breaks occurred in the absence of Smc1b despite failed pairing and synapsis. Overall, our findings point to an essential role of Smc1b in the leptotene to zygotene transition during zebrafish spermatogenesis. In addition, ovarian follicles failed to form in smc1b mutants, suggesting an essential role in female meiosis as well. Our results indicate that there are some key differences in Smc1b requirement in meiosis among vertebrates: while Smc1b is not required for homolog pairing and synapsis in mice, it is essential for these processes in zebrafish.

Identification and Validation of a Novel DNA Damage and DNA Repair Related Genes Based Signature for Colon Cancer Prognosis

Backgrounds: Colorectal cancer (CRC) with high incidence, has the third highest mortality of tumors. DNA damage and repair influence a variety of tumors. However, the role of these genes in colon cancer prognosis has been less systematically investigated. Here, we aim to establish a corresponding prognostic signature providing new therapeutic opportunities for CRC. Method: After related genes were collected from GSEA, univariate Cox regression was performed to evaluate each gene's prognostic relevance through the TCGA-COAD dataset. Stepwise COX regression was used to establish a risk prediction model through the training sets randomly separated from the TCGA cohort and validated in the remaining testing sets and two GEO datasets (GSE17538 and GSE38832). A 12-DNA-damage-and-repair-related gene-based signature able to classify COAD patients into high and low-risk groups was developed. The predictive ability of the risk model or nomogram were evaluated by different bioinformatics- methods. Gene functional enrichment analysis was performed to analyze the co-expressed genes of the risk-based genes. Result: A 12-gene based prognostic signature established within 160 significant survival-related genes from DNA damage and repair related gene sets performed well with an AUC of ROC 0.80 for 5 years in the TCGA-CODA dataset. The signature includes CCNB3, ISY1, CDC25C, SMC1B, MC1R, LSP1P4, RIN2, TPM1, ELL3, POLG, CD36, and NEK4. Kaplan-Meier survival curves showed that the prognosis of the risk status owns more significant differences than T, M, N, and stage prognostic parameters. A nomogram was constructed by LASSO regression analysis with T, M, N, age, and risk as prognostic parameters. ROC curve, C-index, Calibration analysis, and Decision Curve Analysis showed the risk module and nomogram performed best in years 1, 3, and 5. KEGG, GO, and GSEA enrichment analyses suggest the risk involved in a variety of important biological processes and well-known cancer-related pathways. These differences may be the key factors affecting the final prognosis. Conclusion: The established gene signature for CRC prognosis provides a new molecular tool for clinical evaluation of prognosis, individualized diagnosis, and treatment. Therapies based on targeted DNA damage and repair mechanisms may formulate more sensitive and potential chemotherapy regimens, thereby expanding treatment options and potentially improving the clinical outcome of CRC patients.

Fertility Relevance Probability Analysis Shortlists Genetic Markers for Male Fertility Impairment

Impairment of male fertility is one of the major public health issues worldwide. Nevertheless, genetic causes of male sub- and infertility can often only be suspected due to the lack of reliable and easy-to-use routine tests. Yet, the development of a marker panel is complicated by the large quantity of potentially predictive markers. Actually, hundreds or even thousands of genes could have fertility relevance. Thus, a systematic method enabling a selection of the most predictive markers out of the many candidates is required. As a criterion for marker selection, we derived a gene-specific score, which we refer to as fertility relevance probability (FRP). For this purpose, we first categorized 2,753 testis-expressed genes as either candidate markers or non-candidates, according to phenotypes in male knockout mice. In a parallel approach, 2,502 genes were classified as candidate markers or non-candidates based on phenotypes in men. Subsequently, we conducted logistic regression analyses with evolutionary rates of genes (dN/dS), transcription levels in testis relative to other organs, and connectivity of the encoded proteins in a protein-protein interaction network as covariates. In confirmation of the procedure, FRP values showed the expected pattern, thus being overall higher in genes with known relevance for fertility than in their counterparts without corresponding evidence. In addition, higher FRP values corresponded with an increased dysregulation of protein abundance in spermatozoa of 37 men with normal and 38 men with impaired fertility. Present analyses resulted in a ranking of genes according to their probable predictive power as candidate markers for male fertility impairment. Thus, AKAP4, TNP1, DAZL, BRDT, DMRT1, SPO11, ZPBP, HORMAD1, and SMC1B are prime candidates toward a marker panel for male fertility impairment. Additional candidate markers are DDX4, SHCBP1L, CCDC155, ODF1, DMRTB1, ASZ1, BOLL, FKBP6, SLC25A31, PRSS21, and RNF17. FRP inference additionally provides clues for potential new markers, thereunder TEX37 and POU4F2. The results of our logistic regression analyses are freely available at the PreFer Genes website (https://prefer-genes.uni-mainz.de/).

Contributions of HOX genes to cancer hallmarks: Enrichment pathway analysis and review

Homeobox genes function as master regulatory transcription factors during development, and their expression is often altered in cancer. The HOX gene family was initially studied intensively to understand how the expression of each gene was involved in forming axial patterns and shaping the body plan during embryogenesis. More recent investigations have discovered that HOX genes can also play an important role in cancer. The literature has shown that the expression of HOX genes may be increased or decreased in different tumors and that these alterations may differ depending on the specific HOX gene involved and the type of cancer being investigated. New studies are also emerging, showing the critical role of some members of the HOX gene family in tumor progression and variation in clinical response. However, there has been limited systematic evaluation of the various contributions of each member of the HOX gene family in the pathways that drive the common phenotypic changes (or "hallmarks") and that underlie the transformation of normal cells to cancer cells. In this review, we investigate the context of the engagement of HOX gene targets and their downstream pathways in the acquisition of competence of tumor cells to undergo malignant transformation and tumor progression. We also summarize published findings on the involvement of HOX genes in carcinogenesis and use bioinformatics methods to examine how their downstream targets and pathways are involved in each hallmark of the cancer phenotype.

The multiple facets of the SMC1A gene

Structural Maintenance of Chromosomes (SMCs) are part of a large family of ring complexes that participates in a number of DNA transactions. Among SMCs, SMC1A gene is unique. It encodes a subunit of the cohesin-core complex that tethers sister chromatids together to ensure correct chromosome segregation in both mitosis and meiosis. As a member of the cohesin ring, SMC1A takes part in gene transcription regulation and genome organization; and it participates in the DNA Damage Repair (DDR) pathway, being phosphorylated by Ataxia Telangiectasia Mutated (ATM) and Ataxia Telangiectasia and Rad3 Related (ATR) threonine/serine kinases. It is also a component of the Recombination protein complex (RC-1) involved in DNA repair by recombination. SMC1A pathogenic variants have been described in Cornelia de Lange syndrome (CdLS), a human rare disease, and recently SMC1A variants have been associated with epilepsy or resembling Rett syndrome phenotype. Finally, SMC1A variants have been identified in several human cancers. In this review, our current knowledge of the SMC1A gene has been summarized.

Chromosome Missegregation in Single Human Oocytes Is Related to the Age and Gene Expression Profile

The growing trend for women to postpone childbearing has resulted in a dramatic increase in the incidence of aneuploid pregnancies. Despite the importance to human reproductive health, the events precipitating female age-related meiotic errors are poorly understood. To gain new insight into the molecular basis of age-related chromosome missegregation in human oocytes, we combined the transcriptome profiles of twenty single oocytes (derived from females divided into two groups according to age <35 and ≥35 years) with their chromosome status obtained by array comparative genomic hybridization (aCGH). Furthermore, we compared the transcription profile of the single oocyte with the surrounding cumulus cells (CCs). RNA-seq data showed differences in gene expression between young and old oocytes. Dysregulated genes play a role in important biological processes such as gene transcription regulation, cytoskeleton organization, pathways related to RNA maturation and translation. The comparison of the transcription profile of the oocyte and the corresponding CCs highlighted the differential expression of genes belonging to the G protein-coupled receptor superfamily. Finally, we detected the loss of a X chromosome in two oocytes derived from women belonging to the ≥35 years age group. These aneuploidies may be caused by the detriment of REEP4, an endoplasmic reticulum protein, in women aged ≥35 years. Here we gained new insight into the complex regulatory circuit between the oocyte and the surrounding CCs and uncovered a new putative molecular basis of age-related chromosome missegregation in human oocytes.

Gene expression profiling informs HPV cervical histopathology but not recurrence/relapse after LEEP in ART-suppressed HIV+HPV+ women

Identification of factors associated with human papillomavirus (HPV) cervical histopathology or recurrence/relapse following loop electrosurgical excision procedure (LEEP) would allow for better management of the disease. We investigated whether gene signatures could (i) associate with HPV cervical histopathology and (ii) identify women with post-LEEP disease recurrence/relapse. Gene array analysis was performed on paraffin-embedded cervical tissue-isolated RNA from two cross-sectional cohorts of antiretroviral therapy (ART)-suppressed HIV+HPV+ coinfected women: (i) 55 women in South Africa recruited into three groups: high risk (HR) (-) (n = 16) and HR (+) (n = 15) HPV without cervical histopathology and HR (+) HPV with cervical intraepithelial neoplasia (CIN) grade 1/2/3 (n = 24), (ii) 28 women in Botswana with CIN2/3 treated with LEEP 12-month prior to recruitment and presenting with (n = 13) and without (n = 15) lesion recurrence/relapse (tissue was analyzed at first LEEP). Three distinct gene expression signatures identified were able to segregate: (i) HR+ HPV and CIN1/2/3, (ii) HR HPV-free and cervical histopathology-free and (iii) HR+ HPV and cervical histopathology-free. Immune activation and neoplasia-associated genes (n = 272 genes; e.g. IL-1A, IL-8, TCAM1, POU4F1, MCM2, SMC1B, CXCL6, MMP12) were a feature of cancer precursor dysplasia within HR HPV infection. No difference in LEEP tissue gene expression was detected between women with or without recurrence/relapse. In conclusion, distinctive gene signatures were associated with presence of cervical histopathology in tissues from ART-suppressed HIV+/HPV+ coinfected women. Lack of detection of LEEP tissue gene signature able to segregate subsequent post-LEEP disease recurrence/relapse indicates additional factors independent of local gene expression as determinants of recurrence/relapse.

Quantitative proteomics analysis of sporadic parathyroid adenoma tissue samples

OBJECTIVE

Molecular pathogenesis of parathyroid tumors is incompletely understood. Identification of novel molecules and understanding their role in parathyroid tumorigenesis by proteomics approach would be informative with potential clinical implications.

METHOD

Adenomatous (n = 5) and normal (n = 2) parathyroid tissue lysates were analyzed for protein profile by LC-MS/MS method and the proteins were classified using bioinformatics tools such as PANTHER and toppfun functional enrichment tool. Identified proteins were further validated by western blotting and qRT-PCR (n = 20).

RESULT

Comparative proteomics analysis revealed that a total of 206 proteins (74 upregulated and 132 downregulated) were differentially expressed (≥ twofold change) in adenomas. Bioinformatics analysis revealed that 48 proteins were associated with plasma membrane, 49 with macromolecular complex, 39 were cytoplasm, 38 were organelle related, 21 were cell junction and 10 were extracellular proteins. These proteins belonged to a diverse protein family such as enzymes, transcription factors, cell signalling, cell adhesion, cytoskeleton proteins, receptors, and calcium-binding proteins. The major biological processes predicted for the proteins were a cellular, metabolic and developmental process, cellular localization, and biological regulation. The differentially expressed proteins were found to be associated with MAPK, phospholipase C (PLC) and phosphatidylinositol (PI) signalling pathways, and with chromatin organization. Western blot and qRT-PCR analysis of three proteins (DNAJC2, ACO2, and PRDX2) validated the LC-MS/MS findings.

CONCLUSION

This exploratory study demonstrates the feasibility of proteomics approach in finding the dysregulated proteins in benign parathyroid adenomas, and our preliminary results suggest that MAPK, PLC and PI signalling pathways and chromatin organization are involved in parathyroid tumorigenesis.

Prdm9 and Meiotic Cohesin Proteins Cooperatively Promote DNA Double-Strand Break Formation in Mammalian Spermatocytes

Meiotic recombination is required for correct segregation of chromosomes to gametes and to generate genetic diversity. In mice and humans, DNA double-strand breaks (DSBs) are initiated by SPO11 at recombination hotspots activated by PRDM9-catalyzed histone modifications on open chromatin. However, the DSB-initiating and repair proteins are associated with a linear proteinaceous scaffold called the chromosome axis, the core of which is composed of cohesin proteins. STAG3 is a stromalin subunit common to all meiosis-specific cohesin complexes. Mutations of meiotic cohesin proteins, especially STAG3, perturb both axis formation and recombination in the mouse, prompting determination of how the processes are mechanistically related. Protein interaction and genetic analyses revealed that PRDM9 interacts with STAG3 and REC8 in cooperative relationships that promote normal levels of meiotic DSBs at recombination hotspots in spermatocytes. The efficacy of the Prdm9-Stag3 genetic interaction in promoting DSB formation depends on PRDM9-mediated histone methyltransferase activity. Moreover, STAG3 deficiency has a major effect on DSB number even in the absence of PRDM9, showing that its role is not restricted to canonical PRDM9-activated hotspots. STAG3 and REC8 promote axis localization of the DSB-promoting proteins HORMAD1, IHO1, and MEI4, as well as SPO11 activity. These results establish that PRDM9 and axis-associated cohesin complexes together coordinate and facilitate meiotic recombination by recruiting key proteins for initiation of DSBs, thereby associating activated hotspots with DSB-initiating complexes on the axis.

Studying meiotic cohesin in somatic cells reveals that Rec8-containing cohesin requires Stag3 to function and is regulated by Wapl and sororin

The DNA-embracing, ring-shaped multiprotein complex cohesin mediates sister chromatid cohesion and is stepwise displaced in mitosis by Wapl and separase (also known as ESPL1) to facilitate anaphase. Proper regulation of chromosome cohesion throughout meiosis is critical for preventing formation of aneuploid gametes, which are associated with trisomies and infertility in humans. Studying cohesion in meiocytes is complicated by their difficult experimental amenability and the absence of cohesin turnover. Here, we use cultured somatic cells to unravel fundamental aspects of meiotic cohesin. When expressed in Hek293 cells, the kleisin Rec8 displays no affinity for the peripheral cohesin subunits Stag1 or Stag2 and remains cytoplasmic. However, co-expression of Stag3 is sufficient for Rec8 to enter the nucleus, load onto chromatin, and functionally replace its mitotic counterpart Scc1 (also known as RAD21) during sister chromatid cohesion and dissolution. Rec8-Stag3 cohesin physically interacts with Pds5, Wapl and sororin (also known as CDCA5). Importantly, Rec8-Stag3 cohesin is shown to be susceptible to Wapl-dependent ring opening and sororin-mediated protection. These findings exemplify that our model system is suitable to rapidly generate testable predictions for important unresolved issues of meiotic cohesion regulation.

Increased separase activity and occurrence of centrosome aberrations concur with transformation of MDS

ESPL1/separase, a cysteine endopeptidase, is a key player in centrosome duplication and mitotic sister chromatid separation. Aberrant expression and/or altered separase proteolytic activity are associated with centrosome amplification, aneuploidy, tumorigenesis and disease progression. Since centrosome alterations are a common and early detectable feature in patients with myelodysplastic syndrome (MDS) and cytogenetic aberrations play an important role in disease risk stratification, we examined separase activity on single cell level in 67 bone marrow samples obtained from patients with MDS, secondary acute myeloid leukemia (sAML), de novo acute myeloid leukemia (AML) and healthy controls by a flow cytometric separase activity assay. The separase activity distribution (SAD) value, a calculated measure for the occurrence of cells with prominent separase activity within the analyzed sample, was tested for correlation with the centrosome, karyotype and gene mutation status. We found higher SAD values in bone marrow cells of sAML patients than in corresponding cells of MDS patients. This concurred with an increased incidence of aberrant centrosome phenotypes in sAML vs. MDS samples. No correlation was found between SAD values and the karyotype/gene mutation status. During follow-up of four MDS patients we observed increasing SAD values after transformation to sAML, in two patients SAD values decreased during azacitidine therapy. Cell culture experiments employing MDS-L cells as an in vitro model of MDS revealed that treatment with rigosertib, a PLK1 inhibitor and therapeutic drug known to induce G2/M arrest, results in decreased SAD values. In conclusion, the appearance of cells with unusual high separase activity levels, as indicated by increased SAD values, concurs with the transformation of MDS to sAML and may reflect separase dysregulation potentially contributing to clonal evolution during MDS progression. Separase activity measurement may therefore be useful as a novel additional molecular marker for disease monitoring.

Separase prevents genomic instability by controlling replication fork speed

Proper chromosome segregation is crucial for preserving genomic integrity, and errors in this process cause chromosome mis-segregation, which may contribute to cancer development. Sister chromatid separation is triggered by Separase, an evolutionary conserved protease that cleaves the cohesin complex, allowing the dissolution of sister chromatid cohesion. Here we provide evidence that Separase participates in genomic stability maintenance by controlling replication fork speed. We found that Separase interacted with the replication licensing factors MCM2-7, and genome-wide data showed that Separase co-localized with MCM complex and cohesin. Unexpectedly, the depletion of Separase increased the fork velocity about 1.5-fold and caused a strong acetylation of cohesin's SMC3 subunit and altered checkpoint response. Notably, Separase silencing triggered genomic instability in both HeLa and human primary fibroblast cells. Our results show a novel mechanism for fork progression mediated by Separase and thus the basis for genomic instability associated with tumorigenesis.

Structural Maintenance of Chromosomes protein 1: Role in Genome Stability and Tumorigenesis

SMC1 (Structural Maintenance of Chromosomes protein 1), well known as one of the SMC superfamily members, has been explored to function in many activities including chromosome dynamics, cell cycle checkpoint, DNA damage repair and genome stability. Upon being properly assembled as part of cohesin, SMC1 can be phosphorylated by ATM and mediate downstream DNA damage repair after ionizing irradiation. Abnormal gene expression or mutation of SMC1 can cause defect in the DNA damage repair pathway, which has been strongly associated with tumorigenesis. Here we focus to discuss SMC1's role in genome stability maintenance and tumorigenesis. Deciphering the underlying molecular mechanism can provide insight into novel strategies for cancer treatment.

De novo loss-of-function variants in STAG2 are associated with developmental delay, microcephaly, and congenital anomalies

The cohesin complex is an evolutionarily conserved multi-subunit protein complex which regulates sister chromatid cohesion during mitosis and meiosis. Additionally, the cohesin complex regulates DNA replication, DNA repair, and transcription. The core of the complex consists of four subunits: SMC1A, SMC3, RAD21, and STAG1/2. Loss-of-function mutations in many of these proteins have been implicated in human developmental disorders collectively termed "cohesinopathies." Through clinical exome sequencing (CES) of an 8-year-old girl with a clinical history of global developmental delay, microcephaly, microtia with hearing loss, language delay, ADHD, and dysmorphic features, we describe a heterozygous de novo variant (c.205C>T; p.(Arg69*)) in the integral cohesin structural protein, STAG2. This variant is associated with decreased STAG2 protein expression. The analyses of metaphase spreads did not exhibit premature sister chromatid separation; however, delayed sister chromatid cohesion was observed. To further support the pathogenicity of STAG2 variants, we identified two additional female cases from the DECIPHER research database with mutations in STAG2 and phenotypes similar to our patient. Interestingly, the clinical features of these three cases are remarkably similar to those observed in other well-established cohesinopathies. Herein, we suggest that STAG2 is a dosage-sensitive gene and that heterozygous loss-of-function variants lead to a cohesinopathy.

Cohesin Mutations in Myeloid Malignancies

Acute Myeloid Leukemia (AML) is a hematologic malignancy with a poor prognosis. Recent genome-wide sequencing studies have identified frequent mutations in genes encoding members of the cohesin complex. Mutations in cohesin contribute to myeloid malignancies by conferring enhanced self-renewal of hematopoietic stem and progenitor cells but the mechanisms behind this phenotype have not been fully elucidated. Of note, cohesin mutations are highly prevalent in acute megakaryocytic leukemia associated with Down syndrome (DS-AMKL), where they occur in over half of patients. Evidence suggests that cohesin mutations alter gene expression through changes in chromatin accessibility and/or aberrant targeting of epigenetic complexes. In this review we discuss the pathogenic mechanisms by which cohesin mutations contribute to myeloid malignancies.

Cohesin Mutations in Cancer

Cohesin is a large ring-shaped protein complex, conserved from yeast to human, which participates in most DNA transactions that take place in the nucleus. It mediates sister chromatid cohesion, which is essential for chromosome segregation and homologous recombination (HR)-mediated DNA repair. Together with architectural proteins and transcriptional regulators, such as CTCF and Mediator, respectively, it contributes to genome organization at different scales and thereby affects transcription, DNA replication, and locus rearrangement. Although cohesin is essential for cell viability, partial loss of function can affect these processes differently in distinct cell types. Mutations in genes encoding cohesin subunits and regulators of the complex have been identified in several cancers. Understanding the functional significance of these alterations may have relevant implications for patient classification, risk prediction, and choice of treatment. Moreover, identification of vulnerabilities in cancer cells harboring cohesin mutations may provide new therapeutic opportunities and guide the design of personalized treatments.

Genome stability: What we have learned from cohesinopathies

Cohesin is a multiprotein complex involved in many DNA-related processes such as proper chromosome segregation, replication, transcription, and repair. Mutations in cohesin gene pathways are responsible for human diseases, collectively referred to as cohesinopathies. In addition, both cohesin gene expression dysregulation and mutations have been identified in cancer. Cohesinopathy cells are characterized by genome instability (GIN) visualized by a constellation of markers such as chromosome aneuploidies, chromosome aberrations, precocious sister chromatid separation, premature centromere separation, micronuclei formation, and sensitivity to genotoxic drugs. The emerging picture suggests that GIN observed in cohesinopathies may result from the synergistic effects of the multiple cohesin dysfunctions. © 2016 Wiley Periodicals, Inc.