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As a component of N6-methyladenosine (m6A) “writers,” KIAA1429 was reported to promote breast cancer proliferation and growth in m6A-independent manners. However, the related mechanism of KIAA1429 in breast cancer metastasis has not been reported. In the present study, we found KIAA1429 could significantly promote the migration and invasion of breast cancer cells. Then we demonstrated that knockdown of KIAA1429 could impede breast cancer metastasis in nude mice in vivo. The level of SNAIL expression and epithelial-mesenchymal transition (EMT) progress was positively related with KIAA1429. Furthermore, we confirmed that the suppression of cell migration, invasion, and EMT progress by knockdown of KIAA1429 could be reversed by the upregulation of SNAIL. However, structural maintenance of chromosomes 1A (SMC1A), not KIAA1429, bound with the SNAIL promoter region directly and promoted the transcription of SNAIL. Then we confirmed that KIAA1429 could bind to the motif in the 3′ UTR of SMC1A mRNA directly and enhance SMC1A mRNA stability. In conclusion, our study revealed a novel mechanism of the KIAA1429/SMC1A/SNAIL axis in the regulation of metastasis of breast cancer. Moreover, it first provided detailed investigation of how KIAA1429 regulated the targeted gene expression at posttranscriptional levels as an RNA binding protein unrelated to its m6A modification., Graphical abstract, We provided a novel mechanism of the KIAA1429/SMC1A/SNAIL axis in the regulation of breast cancer invasion and metastasis, which may be a promising therapeutic target for human breast cancer.

Objective: To explore the prognostic value of the expression of genes encoding structural maintenance of chromosomes (SMCs) in human sarcoma. Results: We found that the levels of SMC1A, SMC2, SMC3, SMC4, SMC5 and SMC6 mRNA were all higher in most tumors compared to normal tissues, and especially in sarcoma. According to the Cancer Cell Line Encyclopedia (CCLE), SMC1A, SMC2, SMC3, SMC4, SMC5 and SMC6 are also highly expressed in sarcoma cell lines. Results of Gene Expression Profiling Interactive Analysis (GEPIA) indicated that high expression of SMC1A was significantly related to poor overall survival (OS) (p

Background: The cohesin complex plays an essential role in genome organisation and cell division. A full complement of the cohesin complex and its regulators is important for normal development, since heterozygous mutations in genes encoding these components can be sufficient to produce a disease phenotype. The implication that genes encoding the cohesin subunits or cohesin regulators must be tightly controlled and resistant to variability in expression has not yet been formally tested.Methods: Here, we identify spatial-regulatory connections with potential to regulate expression of cohesin loci (Mitotic: SMC1A, SMC3, STAG1, STAG2, RAD21/RAD21-AS; Meiotic: SMC1B, STAG3, REC8, RAD21L1), cohesin-ring support genes (NIPBL, MAU2, WAPL, PDS5A, PDS5B) and CTCF, including linking their expression to that of other genes. We searched the genome-wide association studies (GWAS) catalogue for SNPs mapped or attributed to cohesin genes by GWAS (GWAS-attributed) and the GTEx catalogue for SNPs mapped to cohesin genes by cis-regulatory variants in one or more of 44 tissues across the human body (expression quantitative trail locus-attributed).Results: Connections that centre on the cohesin ring subunits provide evidence of coordinated regulation that has little tolerance for perturbation. We used the CoDeS3D SNP-gene attribution methodology to identify transcriptional changes across a set of genes coregulated with the cohesin loci that include biological pathways such as extracellular matrix production and proteasome-mediated protein degradation. Remarkably, many of the genes that are coregulated with cohesin loci are themselves intolerant to loss-of-function.Conclusions: The results highlight the importance of robust regulation of cohesin genes and implicate novel pathways that may be important in the human cohesinopathy disorders.

Acute myeloid leukemia (AML) with NPM1 mutation is a disease driving genetic alteration with good prognosis. Although it has been suggested that NPM1 mutation induces chemosensitivity in leukemic cells, the underlying cause for the better survival of NPM1 mutated patients is still not clear. Mutant NPM1 AML has a unique microRNA and their target gene (mRNA) signature compared to wild-type NPM1. Dynamic regulation of miRNA‐mRNA has been reported to influence the prognostic outcome. In the present study, in silico expression data of miRNA and mRNA in AML patients was retrieved from genome data commons, and differentially expressed miRNA and mRNA among NPM1 mutated (n = 21) and NPM1 wild-type (n = 162) cases were identified to establish a dynamic association at the molecular level. In vitro experiments using high-throughput RNA sequencing were performed on human AML cells carrying NPM1 mutated and wild-type allele. The comparison of in vitro transcriptomics data with in silico miRNA‐mRNA expression network data revealed downregulation of SMC1A. On establishing miRNA‐mRNA interactive pairs, it has been observed that hsa-mir-215-5p (logFC: 0.957; p = 0.0189) is involved in the downregulation of SMC1A (logFC: ‐0.481; p = 0.0464) in NPM1 mutated AML. We demonstrated that transient expression of NPM1 mutation upregulates miR-215-5p, which results in downregulation of SMC1A. We have also shown using a rescue experiment that neutralizing miR-215-5p reverses the effect of NPM1 mutation on SMC1A. Using the leukemic blasts from AML patients, we observed higher expression of miR-215-5p and lower expression of SMC1A in NPM1 mutated patients compared to wild-type cases. The overall survival of AML patients was significantly inferior in SMC1A high expressers compared to low expressers (20.3% vs. 58.5%, p = 0.018). The data suggest that dynamic miR-215-SMC1A regulation is potentially modulated by NPM1 mutation, which might serve as an explanation for the better outcome in NPM1 mutated AML.

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 cohesin complex is a large evolutionary conserved functional unit which plays an essential role in DNA repair and replication, chromosome segregation and gene expression. It consists of four core proteins, SMC1A, SMC3, RAD21, and STAG1/2, and by proteins regulating the interaction between the complex and the chromosomes. Mutations in the genes coding for these proteins have been demonstrated to cause multisystem developmental disorders known as “cohesinopathies”. The most frequent and well recognized among these distinctive clinical conditions are the Cornelia de Lange syndrome (CdLS, OMIM 122470) and Roberts syndrome (OMIM 268300). STAG1 belongs to the STAG subunit of the core cohesin complex, along with five other subunits. Pathogenic variants in STAG1 gene have recently been reported to cause an emerging syndromic form of neurodevelopmental disorder that is to date poorly characterized. Here, we describe a 5 year old female patient with neurodevelopmental delay, mild intellectual disability, dysmorphic features and congenital anomalies, in which next generation sequencing analysis allowed us to identify a novel pathogenic variation c.2769_2770del p.(Ile924Serfs*8) in STAG1 gene, which result to be de novo. The variant has never been reported before in medical literature and is absent in public databases. Thus, it is useful to expand the molecular spectrum of clinically relevant alterations of STAG1 and their phenotypic consequences.

SIRT2-mediated deacetylation of SMC1A promotes its phosphorylation and overcomes the oncogenic stress for tumor cell survival., Improper distribution of chromosomes during mitosis can contribute to malignant transformation. Higher eukaryotes have evolved a mitotic catastrophe mechanism for eliminating mitosis-incompetent cells; however, the signaling cascade and its epigenetic regulation are poorly understood. Our analyses of human cancerous tissue revealed that the NAD-dependent deacetylase SIRT2 is up-regulated in early-stage carcinomas of various organs. Mass spectrometry analysis revealed that SIRT2 interacts with and deacetylates the structural maintenance of chromosomes protein 1 (SMC1A), which then promotes SMC1A phosphorylation to properly drive mitosis. We have further demonstrated that inhibition of SIRT2 activity or continuously increasing SMC1A-K579 acetylation causes abnormal chromosome segregation, which, in turn, induces mitotic catastrophe in cancer cells and enhances their vulnerability to chemotherapeutic agents. These findings suggest that regulation of the SIRT2-SMC1A axis through deacetylation-phosphorylation permits escape from mitotic catastrophe, thus allowing early precursor lesions to overcome oncogenic stress.

RAD21 encodes a key component of the cohesin complex, and variants in RAD21 have been associated with Cornelia de Lange Syndrome (CdLS). Limited information on phenotypes attributable to RAD21 variants and genotype–phenotype relationships is currently published. We gathered a series of 49 individuals from 33 families with RAD21 alterations [24 different intragenic sequence variants (2 recurrent), 7 unique microdeletions], including 24 hitherto unpublished cases. We evaluated consequences of 12 intragenic variants by protein modelling and molecular dynamic studies. Full clinical information was available for 29 individuals. Their phenotype is an attenuated CdLS phenotype compared to that caused by variants in NIPBL or SMC1A for facial morphology, limb anomalies, and especially for cognition and behavior. In the 20 individuals with limited clinical information, additional phenotypes include Mungan syndrome (in patients with biallelic variants) and holoprosencephaly, with or without CdLS characteristics. We describe several additional cases with phenotypes including sclerocornea, in which involvement of the RAD21 variant is uncertain. Variants were frequently familial, and genotype–phenotype analyses demonstrated striking interfamilial and intrafamilial variability. Careful phenotyping is essential in interpreting consequences of RAD21 variants, and protein modeling and dynamics can be helpful in determining pathogenicity. The current study should be helpful when counseling families with a RAD21 variation., Spanish Ministry of Science, Innovation and Universities/State Research Agency RTC-2017-6494-1 and RTI2018-094434-B-I00 (MCIU/AEI/FEDER, UE) as well as funds from the European JPIAMR-VRI network “CONNECT” to PG-P

Cornelia de Lange syndrome (CdLS), Rubinstein-Taybi syndrome (RSTS), and KBG syndrome are three distinct developmental human disorders. Variants in seven genes belonging to the cohesin pathway, NIPBL, SMC1A, SMC3, HDAC8, RAD21, ANKRD11, and BRD4, were identified in about 80% of patients with CdLS, suggesting that additional causative genes remain to be discovered. Two genes, CREBBP and EP300, have been associated with RSTS, whereas KBG results from variants in ANKRD11. By exome sequencing, a genetic cause was elucidated in two patients with clinical diagnosis of CdLS but without variants in known CdLS genes. In particular, genetic variants in EP300 and ANKRD11 were identified in the two patients with CdLS. EP300 and ANKRD11 pathogenic variants caused the reduction of the respective proteins suggesting that their low levels contribute to CdLS-like phenotype. These findings highlight the clinical overlap between CdLS, RSTS, and KBG and support the notion that these rare disorders are linked to abnormal chromatin remodeling, which in turn affects the transcriptional machinery.

Cornelia de Lange syndrome (CdLS) is a rare neurodevelopmental syndrome for which mutations in five causative genes that encode (SMC1A, SMC3, RAD21) or regulate (NIPBL, HDAC8) the cohesin complex, account for ~70% of cases. Herein we report on four female Subjects who were found to carry novel intragenic deletions in HDAC8. In one case, the deletion was found in mosaic state and it was determined to be present in ~38% of blood lymphocytes and in nearly all cells of a buccal sample. All deletions, for which parental blood samples were available, were shown to have arisen de novo. X-chromosome inactivation studies demonstrated marked skewing, suggesting strong selection against the mutated HDAC8 allele. Based on an investigation of the deletion breakpoints, we hypothesize that microhomology-mediated replicative mechanisms may be implicated in the formation of some of these rearrangements. This study broadens the mutational spectrum of HDAC8, provides the first description of a causative HDAC8 somatic mutation and increases the knowledge on possible mutational mechanisms underlying copy number variations in HDAC8. Moreover our findings highlight the clinical utility of considering copy number analysis in HDAC8 as well as the analysis on DNA from more than one tissue as an indispensable part of the routine molecular diagnosis of individuals with CdLS or CdLS-overlapping features.

Adult stem and progenitor cells are critical for replenishing lost tissue due to injury or normal turnover. How these cells maintain self-renewal and sustain the tissue they populate are areas of active investigation. Here, we show that the cohesin complex, which has previously been implicated in regulating chromosome segregation and gene expression, is necessary to promote epidermal stem and progenitor cell self-renewal through cell-autonomous mechanisms. Cohesin binds to genomic sites associated with open chromatin, including DNase-I-hypersensitive sites, RNA polymerase II, and histone marks such as H3K27ac and H3K4me3. Reduced cohesin expression results in spontaneous epidermal differentiation due to loss of open chromatin structure and expression of key self-renewal genes. Our results demonstrate a prominent role for cohesin in modulating chromatin structure to allow for enforcement of a stem and progenitor cell gene expression program.

Objective: Glioblastomas multiforme (GBM) is the most malignant brain cancer, which presented vast genomic variation with complicated pathologic mechanism. Method: MicroRNA is a delicate post-transcriptional tuner of gene expression in the organisms by targeting and regulating protein coding genes. MiR-9 was reported as a significant biomarker for GBM patient prognosis and a key factor in regulation of GBM cancer stem cells. To explore the effect of miR-9 on GBM cell growth, we over expressed miR-9 in U87 and U251 cells. The cell viability decreased and apoptosis increased after miR-9 overexpression in these cells. To identify the target of miR-9, we scanned miR-9 binding site in the 3’UTRs region of expression SMC1A (structural maintenance of chromosomes 1A) genes and designed a fluorescent reporter assay to measure miR-9 binding to this region. Our results revealed that miR-9 binds to the 3’sUTR region of SMC1A and down-regulated SMC1A expression. Result: Our results indicated that miR-9 was a potential therapeutic target for GBM through triggering apoptosis of cancer cells.

Background Cornelia de Lange syndrome (CdLS) is a rare genetic disorder affecting the neurodevelopment, gastrointestinal, musculoskeletal systems. CdLS is caused by mutations within NIPBL, SMC1A, SMC3, RAD21, and HDAC8 genes. These genes codify for the “cohesin complex” playing a role in chromatid adhesion, DNA repair and gene expression regulation. The aim of this study was to investigate retinoic acid (RA) signaling pathway, a master developmental regulator, in CdLS cells. Methods Skin biopsies from CdLS patients and healthy controls were cultured and derived primary fibroblast cells were treated with RA or dimethyl sulfoxide (vehicle). After RA treatment, cells were harvested and RNA was isolated for quantitative real-time polymerase chain reaction experiments. Results We analyzed several components of RA metabolism in a human cell line of kidney fibroblasts (293T), in addition to fibroblasts collected from both NIPBL-mutated patients and healthy donors, with or without RA treatment. In all cases, ADH and RALDH1 gene expression was not affected by RA treatment, while CRABP1 was induced. CRABP2 was dramatically upregulated upon RA treatment in healthy donors but not in CdLS patients cells. Conclusion We investigated if CdLS alterations are associated to perturbation of RA signaling. Cells derived from CdLS patients do not respond to RA signaling as efficiently as healthy controls. RA pathway alterations suggest a possible underlying mechanism for several cellular and developmental abnormalities associated with cohesin function. Birth Defects Research 109:1268–1276, 2017. © 2017 Wiley Periodicals, Inc.

Objective:\ud \ud The phenotype of seizure clustering with febrile illnesses in infancy/early childhood is well recognized. To date the only genetic epilepsy consistently associated with this phenotype is PCDH19, an X-linked disorder restricted to females, and males with mosaicism. The SMC1A gene, which encodes a structural component of the cohesin complex is also located on the X chromosome. Missense variants and small in-frame deletions of SMC1A cause approximately 5% of Cornelia de Lange Syndrome (CdLS). Recently, protein truncating mutations in SMC1A have been reported in five females, all of whom have been affected by a drug-resistant epilepsy, and severe developmental impairment. Our objective was to further delineate the phenotype of SMC1A truncation.\ud Method:\ud \ud Female cases with de novo truncation mutations in SMC1A were identified from the Deciphering Developmental Disorders (DDD) study (n = 8), from postmortem testing of an affected twin (n = 1), and from clinical testing with an epilepsy gene panel (n = 1). Detailed information on the phenotype in each case was obtained.\ud Results:\ud \ud Ten cases with heterozygous de novo mutations in the SMC1A gene are presented. All 10 mutations identified are predicted to result in premature truncation of the SMC1A protein. All cases are female, and none had a clinical diagnosis of CdLS. They presented with onset of epileptic seizures between

Premature ovarian insufficiency (POI) is a severe clinical syndrome defined by ovarian dysfunction in women less than 40 years old who generally manifest with infertility, menstrual disturbance, elevated gonadotrophins, and low estradiol levels. STAG3 is considered a genetic aetiology of POI, which facilitates entry of REC8 into the nucleus of a cell and plays an essential role in gametogenesis. At present, only six truncated variants associated with POI have been reported; there have been no reports of an in-frame variant of STAG3 causing POI. In this study, two novel homozygous in-frame variants (c.877_885del, p.293_295del; c.891_893dupTGA, p.297_298insAsp) in STAG3 were identified in two sisters with POI from a five-generation consanguineous Han Chinese family. To evaluate the effects of these two variants, we performed fluorescence localization and co-immunoprecipitation analyses using in vitro cell model. The two variants were shown to be pathogenic, as neither STAG3 nor REC8 entered nuclei, and interactions between mutant STAG3 and REC8 or SMC1A were absent. To the best of our knowledge, this is the first report on in-frame variants of STAG3 that cause POI. This finding extends the spectrum of variants in STAG3 and sheds new light on the genetic origins of POI.

Cortex development is controlled by temporal patterning of neural progenitor (NP) competence with sequential generation of deep and superficial layer neurons, but underlying mechanisms remain elusive. Here, we report a role of heterogeneous nuclear ribonucleoprotein A3 (HNRNPA3) in regulating the division of early cortical NPs that mainly give rise to deep-layer neurons via direct neurogenesis. HNRNPA3 is highly expressed in NPs of mouse and human cortex at early stages with a unique peri-chromosome pattern. Intriguingly, down-regulation of HNRNPA3 caused chromosome disarrangement, which hindered normal separation of chromosomes during NP division, leading to mitotic delay. Furthermore, HNRNPA3 is associated with the cohesin-core subunit SMC1A and controls its association with chromosomes, implicating a mechanism for the role of HNRNPA3 in regulating chromosome segregation in dividing NPs. Hnrnpa3 deficient mice exhibited reduced cortical thickness, especially of deep layers. Moreover, down-regulation of HNRNPA3 in cultured human cerebral organoids led to marked reduction in NPs and deep-layer neurons. Thus, this study has identified a critical role of HNRNPA3 in NP division and highlighted the relationship between mitosis progression and early neurogenesis.

Introduction The severe epilepsies of infancy and childhood are a heterogeneous group of severe epilepsies characterised by several seizure types, where the epileptic activity in addition to the seizures contributes to cognitive impairment or regression. They account for a significant proportion of the refractory epilepsies and are usually associated with poor outcome.1 The tern developmental epileptic encephalopathies (DEE) is now the preferred term for this group of children. It may be the result of a specific congenital or acquired structural brain lesions, metabolic disorders, chromosomal abnormalities, copy number variants or single-gene defects. Next-generation sequencing (NGS) includes gene panels, whole-exome sequencing (WES) and whole-genome sequencing. The reported rates of diagnosis in DEE using NGS technology ranges from 10–100%. We previously reported a cohort of 50 patients who underwent single research WES for investigations of DEE. The yield at the time of publication was 22% (11 known epilepsy gene, 1 candidate gene).2 38 patients remained undiagnosed. Since then, the number of new genes reported with DEE continues to expand and the technology improved to aid interpretation of variants. Therefore, we reanalysed WES data, with the addition of parental samples for trio analysis, to enable data interpretation and identification of pathogenic disease-causing variants. Methods Re-analysis of WES data, single (proband only) or trio (proband and parents)WES, if parental samples were available. Results We identified a genetic cause in 25 individuals in the cohort; 22 pathogenic variants in DEE genes, 3 candidate genes, increasing the diagnostic yield to 50%. With re-analysis, we identified 10 pathogenic variants (CDKL5, KCNA2, NRXN1, PRODH, RELN, RHOBTB2, SCN1A, SLC1A4, SMC1A), 1 candidate gene (NAPB) and 1 variant of uncertain significance (GRIN2A). A number of genes had not been identified at the time of initial analysis, including RHOBTB2, SLC1A4, SMC1A. Two mosaic variants in CDKL5 and SCN1A were identified with trio WES analysis and reducing read depth filter to 15, previously set at 20. Discussion This study highlights the importance of the re-interrogation of WES data for newly discovered genes. Trio WES had a higher diagnostic yield (50% compared to 22%) in keeping with previous studies. Trio WES is effective for the identification of de novo variants and aids in the interpretation of variants. Reducing read depth filter can aid the identification of mosaic variants, increasing reported to be important in DEE.

Cornelia de Lange syndrome (CdLS) is a rare multisystem disorder with specific dysmorphic features. Pathogenic genetic variants encoding cohesion complex subunits and interacting proteins (e.g., NIPBL, SMC1A, SMC3, HDAC8, and RAD21) are the major causes of CdLS. However, there are many clinically diagnosed cases of CdLS without pathogenic variants in these genes. To identify further genetic causes of CdLS, we performed whole-exome sequencing in 57 CdLS families, systematically evaluating both single nucleotides variants (SNVs) and copy number variations (CNVs). We identified pathogenic genetic changes in 36 out of 57 (63.2 %) families, including 32 SNVs and four CNVs. Two known CdLS genes, NIPBL and SMC1A, were mutated in 23 and two cases, respectively. Among the remaining 32 individuals, four genes (ANKRD11, EP300, KMT2A, and SETD5) each harbored a pathogenic variant in a single individual. These variants are known to be involved in CdLS-like. Furthermore, pathogenic CNVs were detected in NIPBL, MED13L, and EHMT1, along with pathogenic SNVs in ZMYND11, MED13L, and PHIP. These three latter genes were involved in diseases other than CdLS and CdLS-like. Systematic clinical evaluation of all patients using a recently proposed clinical scoring system showed that ZMYND11, MED13L, and PHIP abnormality may cause CdLS or CdLS-like.

Cornelia de Lange syndrome (CdLS) is a severe genetic disorder characterised by multisystemic malformations. CdLS is due to pathogenetic variants inNIPBL,SMC1A,SMC3,RAD21andHDAC8genes which belong to the cohesin pathway. Cohesin plays a pivotal role in chromatid cohesion, gene expression, and DNA repair. In this review, we will discuss how perturbations in those biological processes contribute to CdLS phenotype and will emphasise the state-of-art of CdLS therapeutic approaches.

Background Cornelia de Lange syndrome (CdLS), a rare, multisystemic disorder, has been linked to genetic alterations in NIPBL, SMC1A, SMC3, HDAC8, and RAD21 genes. Approximately 60% of CdLS patients harbor various NIPBL variants. Genetic changes predicted to affect NIPBL gene splicing represent 15% of all NIPBL genetic abnormalities. Yet, only a few studies have investigated the molecular consequences of such variants. Case presentation This study reports two novel, intronic NIPBL genetic variants in unrelated CdLS patients with the characteristic phenotype. A c.6954 + 3A > C substitution and a c.5862 + 1delG deletion were identified, one of each, in a 6 year-old boy and 39 month-old girl. Further studies confirmed that both variants introduce premature termination codons, resulting in the formation of truncated proteins p.(Ser2255LeufsTer20) and p.(Leu1955Ter), respectively. Conclusion Single nucleotide alterations located within the conserved splice-donor site of intronic regions of the NIPBL gene can give rise to a premature termination of the translation and cause significant changes in the sequence of mRNA transcripts and NIPBL protein structure and function. The latter underline development of Cornelia de Lange syndrome phenotype. Electronic supplementary material The online version of this article (10.1186/s12881-018-0738-y) contains supplementary material, which is available to authorized users.

The nucleophosmin 1 gene (NPM1) is the most frequently mutated gene in acute myeloid leukemia. Notably, NPM1 mutations are always accompanied by additional mutations such as those in cohesin genes RAD21, SMC1A, SMC3, and STAG2 but not in the cohesin regulator, nipped B-like (NIPBL). In this work, we analyzed a cohort of adult patients with acute myeloid leukemia and NPM1 mutation and observed a specific reduction in the expression of NIPBL but not in other cohesin genes. In our zebrafish model, overexpression of the mutated form of NPM1 also induced downregulation of nipblb, the zebrafish ortholog of human NIPBL. To investigate the hematopoietic phenotype and the interaction between mutated NPM1 and nipblb, we generated a zebrafish model with nipblb downregulation which showed an increased number of myeloid progenitors. This phenotype was due to hyper-activation of the canonical Wnt pathway: myeloid cells blocked in an undifferentiated state could be rescued when the Wnt pathway was inhibited by dkk1b mRNA injection or indomethacin administration. Our results reveal, for the first time, a role for NIPBL during zebrafish hematopoiesis and suggest that an interplay between NIPBL/NPM1 may regulate myeloid differentiation in zebrafish and humans through the canonical Wnt pathway and that dysregulation of these interactions may drive leukemic transformation.

Background Cancer cells are characterized by chromosomal instability (CIN) and it is thought that errors in pathways involved in faithful chromosome segregation play a pivotal role in the genesis of CIN. Cohesin forms a large protein ring that binds DNA strands by encircling them. In addition to this central role in chromosome segregation, cohesin is also needed for DNA repair, gene transcription regulation and chromatin architecture. Though mutations in both cohesin and cohesin-regulator genes have been identified in many human cancers, the contribution of cohesin to cancer development is still under debate. Methods Normal mucosa, early adenoma, and carcinoma samples deriving from 16 subjects affected by colorectal cancer (CRC) were analyzed by OncoScan for scoring both chromosome gains and losses (CNVs) and loss of heterozygosity (LOH). Then the expression of SMC1A was analyzed by immunochemistry in 66 subjects affected by CRC. The effects of SMC1A overexpression and mutated SMC1A were analyzed in vivo using immunocompromised mouse models. Finally, we measured global gene expression profiles in induced-tumors by RNA-seq. Results Here we showed that SMC1A cohesin core gene was present as extra-copies, mutated, and overexpressed in human colorectal carcinomas. We then demonstrated that cohesin overexpression led to the development of aggressive cancers in immunocompromised mice through gene expression dysregulation. Conclusion Collectively, these results support a role of defective cohesin in the development of human colorectal cancer. Electronic supplementary material The online version of this article (10.1186/s13046-019-1116-0) contains supplementary material, which is available to authorized users.

Cornelia de Lange syndrome (CdLS) is a heterogeneous developmental disorder where 70% of clinically diagnosed patients harbor a mutation in one of five CdLS associated cohesin proteins. Around 500 mutations have been identified to cause CdLS, however only eight different alterations are identified in RAD21, encoding the RAD21 cohesin protein that constitute the link between SMC1A and SMC3 within the cohesin ring. We report a 15- month-old boy presenting with developmental delay, distinct CdLS facial features, gastrointestinal reflux in early infancy, testis retention fetal pads and diaphragmatic hernia. Exome sequencing revealed a novel RAD21 variant, c.1774_1776del; p.(Gln592del), suggestive of CdLS type 4. Segregation analysis of the two healthy parents confirmed the variant as de novo and bioinformatic analysis predicted the variant as disease-causing. Functional assessment by in silico structural model predicted that the p.Gln592del variant results in a discontinued contact between RAD21-Lys591 and the SMC1A residues Glu1191 and Glu1192, causing changes in the RAD21-SMC1A interface. In conclusion, we report a novel RAD21 p.(Glu592del) variant that expands the clinical description of CdLS type 4 and validate the pathogenicity of the variant by in silico structural modeling that displayed disturbed RAD21-SMC1A interface. pre-print 2,82 MB

We combined de novo mutation (DNM) data from 10,927 individuals with developmental delay and autism to identify 253 candidate neurodevelopmental disease genes with an excess of missense and/or likely gene-disruptive (LGD) mutations. Of these genes, 124 reach exome-wide significance (P

Cornelia de Lange syndrome (CdLS) is an autosomal dominant genetic disorder caused by pathogenic variants in NIPBL, RAD21, SMC3, HDAC8, or SMC1A; all of which code for proteins that are components of, or interact with, the cohesin complex. Despite the identification of multiple genes associated with CdLS, over 25% of individuals strongly suspected to have CdLS have negative genetic testing, indicating that there are additional genes associated with the condition. HDAC2 codes for histone deacetylase 2 (HDAC2) and, like HDAC8, is a Class 1 histone deacetylase. We present a patient with a novel de novo variant in HDAC2 with many clinical features consistent with CdLS including severe developmental delay, limb abnormalities, congenital heart defect, cryptorchidism and hypoplastic genitalia, growth retardation, and characteristic craniofacial features. Although variants in HDAC2 are not currently associated with human disease, the variant identified in this patient is within a highly conserved amino acid residue and has not been observed in healthy populations. This information, along with the patient's clinical presentation and the functional similarity between the HDAC2 and HDAC8 proteins, suggests that HDAC2 should be further investigated as a candidate gene for CdLS or a CdLS-like syndrome.

The two major histological types of gastric cancer, intestinal and diffuse subtypes, have distinct epidemiological and pathophysiological features and were also suggested to be of diverse clinical outcomes. Although the gene expression spectrum of gastric cancer subtypes has been reported by previous studies, its linkage with gastric cancer clinical features and outcomes remains elusive. We investigated large-sample online gastric cancer datasets for seeking genes correlated with the clinical diversities between gastric cancer intestinal and diffuse subtypes. Genes differently expressed between the two subtypes were assessed by multiple statistical analysis and were testified on cellular level by quantitative RT-PCR. Related genes were combined to generate a risk signature, and their mutual linkages were also explored. Among genes overexpressed in intestinal subtype, ATPIF1, PRDX2, PRKAR2A, and SMC1A were correlated with positive prognosis. Among genes overexpressed in diffuse subtype, DTNA, GPR161, IDS, RHOQ, and TSHZ2 were correlated with negative prognosis. These nine genes were all novel independent prognostic factors. When used in combination as signatures, these two gene sets displayed strong efficacy for prediction of the prognosis and clinical variables in gastric and colorectal cancer. Hence, these two genes sets were respectively defined as the favorable intestinal-like and adverse diffuse-like gene sets. We identified nine novel genes correlated with the clinical diversity between the intestinal and diffuse subtypes of gastric cancer. The malignant changes from the intestinal to diffuse subtype might be due to the reduction of the four intestinal-like genes, as well as the elevation of the five diffuse-like genes.

Cornelia de Lange Syndrome (CdLS) encompasses a broad spectrum of phenotypes characterized by distinctive craniofacial abnormalities, limb malformations, growth retardation, and intellectual disability. CdLS spectrum disorders are referred to as cohesinopathies, with ∼70% of patients having a mutation in a gene encoding a core cohesin protein (SMC1A, SMC3, or RAD21) or a cohesin regulatory protein (NIPBL or HDAC8). Notably, the regulatory function of HDAC8 in cohesin biology has only recently been discovered. This Zn2+ -dependent hydrolase catalyzes the deacetylation of SMC3, a necessary step for cohesin recycling during the cell cycle. To date, 23 different missense mutants in the gene encoding HDAC8 have been identified in children with developmental features that overlap those of CdLS. Enzymological, biophysical, and structural studies of CdLS HDAC8 protein mutants have yielded critical insight on compromised catalysis in vitro. Most CdLS HDAC8 mutations trigger structural changes that directly or indirectly impact substrate binding and catalysis. Additionally, several mutations significantly compromise protein thermostability. Intriguingly, catalytic activity in many HDAC8 mutants can be partially or fully restored by an N-acylthiourea activator, suggesting a plausible strategy for the chemical rescue of compromised HDAC8 catalysis in vivo.

Cohesin is a highly-conserved protein complex that plays important roles in sister chromatid cohesion, chromatin structure, gene expression, and DNA repair. In humans, cohesin is a ubiquitously expressed, multi-subunit protein complex composed of core subunits SMC1A, SMC3, RAD21, STAG1/2 and regulatory subunits WAPL, PDS5A/B, CDCA5, NIPBL, and MAU2. Recent studies have demonstrated that genes encoding cohesin subunits are somatically mutated in a wide range of human cancers. STAG2 is the most commonly mutated subunit, and in a recent analysis was identified as one of only 12 genes that are significantly mutated in four or more cancer types. In this review we summarize the findings reported to date and comment on potential functional implications of cohesin mutation in the pathogenesis of human cancer.

The reduction of DNA damage repair capacity in terminally differentiated cells may be involved in sensitivity to cancer chemotherapy drugs; however, the underlying molecular mechanism is still not fully understood. Herein, we evaluated the role of miR-638 in the regulation of DNA damage repair in terminally differentiated cells. Our results show that miR-638 expression was up-regulated during cellular terminal differentiation and involved in mediating DNA damage repair processes. Results from a luciferase reporting experiment show that structural maintenance of chromosomes (SMC)1A was a potential target of miR-638; this was verified by western blot assays during cell differentiation and DNA damage induction. Overexpression of miR-638 enhanced the sensitivity of cancer cells to cisplatin, thus reducing cell viability in response to chemotherapy drug treatment. Furthermore, miR-638 overexpression affected DNA damage repair processes by interfering with the recruitment of the DNA damage repair-related protein, γH2AX, to DNA break sites. These findings indicate that miR-638 might act as a sensitizer in cancer chemotherapy and accompany chemotherapy drugs to enhance chemotherapeutic efficacy and to improve the chance of recovery from cancer.

Cornelia de Lange Syndrome (CdLS) is an autosomal dominant (NIPBL, SMC3, and RAD21) or X-linked (SMC1A and HDAC8) disorder, characterized by distinctive craniofacial appearance, growth retardation, intellectual disability, and limb anomalies. In 2005, the Spanish CdLS Reference Center was started and now we have more than 270 cases in our database. In this special issue, we describe some of the unique or atypical patients studied by our group, whose clinical features have contributed to the expansion of the CdLS classical phenotype, helping clinicians to diagnose it. We include the case of a male with unilateral tibial hypoplasia and peroneal agenesis who had a mutation in NIPBL; we also describe one patient with a mutation in NIPBL and somatic mosaicism identified by new generation sequencing techniques; we also include one patient with CdLS and Turner syndrome; and last, an interesting patient with a duplication of the SMC1A gene. Finally, we make a short review of the splicing mutations we have found in NIPBL regarding the new knowledge on the physiological variants of the gene. © 2016 Wiley Periodicals, Inc.

Cornelia de Lange syndrome (CdLS) is a rare, genetically heterogeneous multisystem developmental disorder with a high degree of variability in its clinical presentation. Approximately 65% of probands harbor mutations in genes that encode core components (SMC1A, SMC3, and RAD21) or regulators (NIPBL, HDAC8) of the cohesin complex, of which mutations in NIPBL are the most common. Cohesin plays a canonical role in sister chromatid cohesion during cell division and non-canonical roles in DNA repair, stem cell maintenance and differentiation, and regulation of gene expression. Disruption of the latter role seems to be the major contributor to the underlying molecular pathogenesis of CdLS. NIPBL is required for loading and unloading the cohesin complex onto chromosomes. The expression levels of NIPBL itself appear to be tightly regulated and highly evolutionarily conserved. Droplet digital PCR was used to quantify NIPBL mRNA expression levels with high precision from a cohort of 37 samples (NIPBL, SMC1A, SMC3, and HDAC8 mutation positive probands and negative control). Probands with severe forms of CdLS or severe mutation types were found to have lower levels of NIPBL in comparison to phenotypically milder patients and controls. Levels of NIPBL also correlated with the presence of mutations in different CdLS-causing genes. The data suggests that NIPBL levels are closely correlated with the severity of CdLS and with specific causative genes and types of mutations. ddPCR may provide a tool to assist in diagnostic approaches to CdLS, for genetic counseling and prognosis, and for monitoring potential therapeutic modalities in the future. © 2016 Wiley Periodicals, Inc.

De novo missense mutations and in-frame coding deletions in the X-linked gene SMC1A (structural maintenance of chromosomes 1A), encoding part of the cohesin complex, are known to cause Cornelia de Lange syndrome in both males and females. For a long time, loss-of-function (LoF) mutations in SMC1A were considered incompatible with life, as such mutations had not been reported in neither male nor female patients. However, recently, the authors and others reported LoF mutations in females with intellectual disability (ID) and epilepsy. Here we present the detailed phenotype of two females with de novo LoF mutations in SMC1A, including a de novo mutation of single base deletion [c.2364del, p.(Asn788Lysfs*10)], predicted to result in a frameshift, and a de novo deletion of exon 16, resulting in an out-of-frame mRNA splice product [p.(Leu808Argfs*6)]. By combining our patients with the other recently reported females carrying SMC1A LoF mutations, we ascertained a phenotypic spectrum of (severe) ID, therapy-resistant epilepsy, absence/delay of speech, hypotonia and small hands and feet. Our data show the existence of a novel phenotypic entity - distinct from CdLS - and caused by de novo SMC1A LoF mutations.

Cornelia de Lange syndrome (CdLS) is a clinically heterogeneous disorder characterized by typical facial dysmorphism, cognitive impairment and multiple congenital anomalies. Approximately 75% of patients carry a variant in one of the five cohesin-related genes NIPBL, SMC1A, SMC3, RAD21 and HDAC8. Herein we report on the clinical and molecular characterization of 11 patients carrying 10 distinct variants in HDAC8. Given the high number of variants identified so far, we advise sequencing of HDAC8 as an indispensable part of the routine molecular diagnostic for patients with CdLS or CdLS-overlapping features. The phenotype of our patients is very broad, whereas males tend to be more severely affected than females, who instead often present with less canonical CdLS features. The extensive clinical variability observed in the heterozygous females might be at least partially associated with a completely skewed X-inactivation, observed in seven out of eight female patients. Our cohort also includes two affected siblings whose unaffected mother was found to be mosaic for the causative mutation inherited to both affected children. This further supports the urgent need for an integration of highly sensitive sequencing technology to allow an appropriate molecular diagnostic, genetic counseling and risk prediction.

Objective The structural maintenance of chromosomes (SMC) 1A protein is a component of the cohesin multiprotein complex that is essential for sister chromatid cohesion. SMC1A gene mutations have been reported in colorectal cancer. This study aimed to investigate the role of SMC1A gene expression in colorectal cancer in vitro. Methods SMC1A gene expression was silenced by lentivirus-mediated infection with small interfering RNA (siRNA) in the human colorectal cancer cell line HT-29. Cell proliferation rates, SMC1A mRNA and protein levels, apoptosis and chemosensitivity to oxaliplatin were evaluated using routine in vitro assays, real-time polymerase chain reaction, Western blotting and flow cytometry. Results Knockdown of SMC1A protein and mRNA levels resulted in the inhibition of cell proliferation, an increased rate of apoptosis and enhanced chemosensitivity to oxaliplatin in HT-29 cells. Conclusions The findings of this study suggest that SMC1A plays an oncogenic role in colorectal cancer and that it might be a promising target for colorectal cancer therapy.

RAD21 (also known as KIAA0078, NXP1, HR21, Mcd1, Scc1, and hereafter called RAD21), an essential gene, encodes a DNA double-strand break (DSB) repair protein that is evolutionarily conserved in all eukaryotes from budding yeast to humans. RAD21 protein is a structural component of the highly conserved cohesin complex consisting of RAD21, SMC1a, SMC3, and SCC3 [STAG1 (SA1) and STAG2 (SA2) in metazoans] proteins, involved in sister chromatid cohesion. This function is essential for proper chromosome segregation, post-replicative DNA repair, and prevention of inappropriate recombination between repetitive regions. In interphase, cohesin also functions in the control of gene expression by binding to numerous sites within the genome. In addition to playing roles in the normal cell cycle and DNA DSB repair, RAD21 is also linked to the apoptotic pathways. Germline heterozygous or homozygous missense mutations in RAD21 have been associated with human genetic disorders, including developmental diseases such as Cornelia de Lange syndrome (CdLS) and chronic intestinal pseudo-obstruction (CIPO) called Mungan syndrome, respectively, and collectively termed as cohesinopathies. Somatic mutations and amplification of the RAD21 have also been widely reported in both human solid and hematopoietic tumors. Considering the role of RAD21 in a broad range of cellular processes that are hot spots in neoplasm, it is not surprising that the deregulation of RAD21 has been increasingly evident in human cancers. Herein, we review the biology of RAD21 and the cellular processes that this important protein regulates and discuss the significance of RAD21 deregulation in cancer and cohesinopathies.

Cornelia de Lange syndrome (CdLS) is a rare disease characterized by cognitive impairment, multisystemic alterations and premature aging. Furthermore, CdLS cells display gene expression dysregulation and genomic instability. Here, we demonstrated that treatment with antioxidant drugs, such as ascorbic acid and riboceine, reduced the level of genomic instability and extended the in vitro lifespan of CdLS cell lines. We also found that antioxidant treatment partially rescued the phenotype of a zebrafish model of CdLS. Gene expression profiling showed that antioxidant drugs caused dysregulation of gene transcription; notably, a number of genes coding for the zinc finger (ZNF)-containing Krueppel-associated box (KRAB) protein domain (KRAB-ZNF) were found to be downregulated. Taken together, these data suggest that antioxidant drugs have the potential to ameliorate the developmental phenotype of CdLS.

Cullin-RING-type E3 ligases (CRLs) control a broad range of biological processes by ubiquitylating numerous cellular substrates. However, the role of CRL E3 ligases in chromatid cohesion is unknown. In this study, we identified a new CRL-type E3 ligase (designated as CRL7SMU1 complex) that has an essential role in the maintenance of chromatid cohesion. We demonstrate that SMU1, DDB1, CUL7 and RNF40 are integral components of this complex. SMU1, by acting as a substrate recognition module, binds to H2B and mediates monoubiquitylation at the lysine (K) residue K120 through CRL7SMU1 E3 ligase complex. Depletion of CRL7SMU1 leads to loss of H2B ubiquitylation at the SMC1a locus and, thus, subsequently compromised SMC1a expression in cells. Knockdown of CRL7SMU1 components or loss of H2B ubiquitylation leads to defective sister chromatid cohesion, which is rescued by restoration of SMC1a expression. Together, our results unveil an important role of CRL7SMU1 E3 ligase in promoting H2B ubiquitylation for maintenance of sister chromatid cohesion during mitosis.This article has an associated First Person interview with the first author of the paper.

Deletions within 11q12.3-11q13.1 are very rare and to date only two cases have been described in the literature. In this study we describe a 23-year-old male patient with intellectual disability, behavioral problems, dysmorphic features, dysphagia, gastroesophageal reflux and skeletal abnormalities. Cornelia de Lange syndrome (CdLS, OMIM #122470; #300590; #610759; #300882; #614701) was suggested as a differential diagnosis in childhood although he lacked some of the features typical for this disorder. He does not have a mutation in any of the five known CdLS genes (NIPBL, SMC1A, SMC3, HDAC8, RAD21), but a 1.6Mb deletion at chromosome region 11q12.3-11q13.1 was detected by chromosome microarray. The deletion contains several genes including PPP2R5B, which has been associated with intellectual disability and overgrowth; NRXN2, which has been associated with intellectual disability and autism spectrum disorder; and CDCA5, which is part of the cohesin pathway, as are all the five known CdLS genes. It is therefore possible that deletion of CDCA5 may account for some of the CdLS like features of the present case.

Cornelia de Lange syndrome (CdLS) and KBG syndrome are two distinct developmental pathologies sharing common features such as intellectual disability, psychomotor delay, and some craniofacial and limb abnormalities. Mutations in one of the five genes NIPBL, SMC1A, SMC3, HDAC8 or RAD21, were identified in at least 70% of the patients with CdLS. Consequently, additional causative genes, either unknown or responsible of partially merging entities, possibly account for the remaining 30% of the patients. In contrast, KBG has only been associated with mutations in ANKRD11. By exome sequencing we could identify heterozygous loss-of-function mutations in ANKRD11 in two patients with the clinical diagnosis of CdLS. Both patients show features reminiscent of CdLS such as characteristic facies as well as a small head circumference which is not described for KBG syndrome. Patient A, who carries the mutation in a mosaic state, is a 4-year-old girl with features reminiscent of CdLS. Patient B, a 15-year-old boy, shows a complex phenotype which resembled CdLS during infancy, but has developed to a more KBG overlapping phenotype during childhood. These findings point out the importance of screening ANKRD11 in young CdLS patients who were found to be negative for mutations in the five known CdLS genes.

Cornelia de Lange syndrome (CdLS) is a dominantly inherited developmental disorder characterized by distinctive facial features, mental retardation, and upper limb defects, with the involvement of multiple organs and systems. To date, mutations have been identified in five genes responsible for CdLS: NIPBL, SMC1A, SMC3, RAD21, and HDAC8. Here, we present a clinical and molecular characterization of five unrelated Chinese patients whose clinical presentation is consistent with that of CdLS. There were no chromosomal abnormalities in the five children. In three patients, DNA sequencing revealed a previously reported frameshift mutation c.2479delA (p.Arg827GlyfsX20), and two novel mutations including a heterozygous mutation c.6272 G>T (p.Cys2091Phe) and a frameshift mutation c.1672delA (p.Thr558LeufsX7) in NIPBL. For the remaining patients, large deletions and/or duplications within the NIPBL gene were excluded as playing a role in the pathogenesis, by Multiplex Ligation-dependent Probe Amplification (MLPA) analysis. These findings broaden the mutation spectrum of NIPBL and further our understanding of the diverse and variable effects of NIPBL mutations on CdLS.

Item does not contain fulltext SMC1A encodes one of the proteins of the cohesin complex. SMC1A variants are known to cause a phenotype resembling Cornelia de Lange syndrome (CdLS). Exome sequencing has allowed recognizing SMC1A variants in individuals with encephalopathy with epilepsy who do not resemble CdLS. We performed an international, interdisciplinary study on 51 individuals with SMC1A variants for physical and behavioral characteristics, and compare results to those in 67 individuals with NIPBL variants. For the Netherlands all known individuals with SMC1A variants were studied, both with and without CdLS phenotype. Individuals with SMC1A variants can resemble CdLS, but manifestations are less marked compared to individuals with NIPBL variants: growth is less disturbed, facial signs are less marked (except for periocular signs and thin upper vermillion), there are no major limb anomalies, and they have a higher level of cognitive and adaptive functioning. Self-injurious behavior is more frequent and more severe in the NIPBL group. In the Dutch group 5 of 13 individuals (all females) had a phenotype that shows a remarkable resemblance to Rett syndrome: epileptic encephalopathy, severe or profound intellectual disability, stereotypic movements, and (in some) regression. Their missense, nonsense, and frameshift mutations are evenly spread over the gene. We conclude that SMC1A variants can result in a phenotype resembling CdLS and a phenotype resembling Rett syndrome. Resemblances between the SMC1A group and the NIPBL group suggest that a disturbed cohesin function contributes to the phenotype, but differences between these groups may also be explained by other underlying mechanisms such as moonlighting of the cohesin genes.

Cornelia de Lange syndrome (CdLS) is a complex multisystem developmental disorder caused by mutations in cohesin subunits and regulators. While its precise molecular mechanisms are not well defined, they point toward a global deregulation of the transcriptional gene expression program. Cohesin is associated with the boundaries of chromosome domains and with enhancer and promoter regions connecting the three-dimensional genome organization with transcriptional regulation. Here, we show that connected gene communities, structures emerging from the interactions of noncoding regulatory elements and genes in the three-dimensional chromosomal space, provide a molecular explanation for the pathoetiology of CdLS associated with mutations in the cohesin-loading factor NIPBL and the cohesin subunit SMC1A. NIPBL and cohesin are important constituents of connected gene communities that are centrally positioned at noncoding regulatory elements. Accordingly, genes deregulated in CdLS are positioned within reach of NIPBL- and cohesin-occupied regions through promoter–promoter interactions. Our findings suggest a dynamic model where NIPBL loads cohesin to connect genes in communities, offering an explanation for the gene expression deregulation in the CdLS.

Children with severe, undiagnosed developmental disorders (DDs) are enriched for damaging de novo mutations (DNMs) in developmentally important genes. We exome sequenced 4,294 families with children with DDs, and meta-analysed these data with published data on 3,287 children with similar disorders. We show that the most significant factors influencing the diagnostic yield of de novo mutations are the sex of the child, the relatedness of their parents and the age of both father and mother. We identified 95 genes enriched for damaging de novo mutation at genome-wide significance (P < 5 x 10-7), including fourteen genes for which compelling data for causation was previously lacking. The large number of genome-wide significant findings allow us to demonstrate that, at current cost differentials, exome sequencing has much greater power than genome sequencing for novel gene discovery in genetically heterogeneous disorders. We estimate that 42.5% of our cohort likely carry pathogenic de novo single nucleotide variants (SNVs) and indels in coding sequences, with approximately half operating by a loss-of-function mechanism, and the remainder being gain-of-function. We established that most haploinsufficient developmental disorders have already been identified, but that many gain-of-function disorders remain to be discovered. Extrapolating from the DDD cohort to the general population, we estimate that de novo dominant developmental disorders have an average birth prevalence of 1 in 168 to 1 in 377, depending on parental age.

Cornelia de Lange syndrome (CdLS; MIM #122470, 300590, 610759, 614701, 300882) is a rare and clinically variable disorder that affects multiple organs. It is characterized by intellectual disability (mild to severe), distinctive facial features, prenatal and postnatal growth retardation, and hirsutism. Congenital anomalies include malformations of the upper limbs, gastrointestinal malformation/rotation, pyloric stenosis, diaphragmatic hernia, heart defects and genitourinary malformations. Gastroesophageal reflux disease is present in almost all patients. In addition to classic forms, milder phenotypes have been reported. To date five genes [NIPBL (Nipped-B-like protein), SMC1A (structural maintenance of chromosomes 1A), SMC3 (structural maintenance of chromosomes 3), RAD21 (human homolog of Schizosaccharomyces pombe radiation sensitive mutant 21) and HDAC8 (histone deacetylase 8)] have been associated with CdLS and mutations of these genes comprise the underlying defect in 70% of the patients. Here, we will provide a brief review of the clinical features of CdLS, summarize the known underlying genetic defects, prenatal and postnatal diagnosis possibilities, and genetic counseling.

Cornelia de Lange Syndrome (CdLS) is a multiple congenital anomaly disorder resulting from mutations in genes that encode the core components of the cohesin complex, SMC1A, SMC3, and RAD21, or two of its regulatory proteins, NIPBL and HDAC8. HDAC8 is the human SMC3 lysine deacetylase required for cohesin recycling in the cell cycle. To date, 16 different missense mutations in HDAC8 have recently been identified in children diagnosed with CdLS. To understand the molecular effects of these mutations in causing CdLS and overlapping phenotypes, we have fully characterized the structure and function of five HDAC8 mutants: C153F, A188T, I243N, T311M, and H334R. X-ray crystal structures reveal that each mutation causes local structural changes that compromise catalysis and/or thermostability. For example, the C153F mutation triggers conformational changes that block acetate product release channels, resulting in only 2% residual catalytic activity. In contrast, the H334R mutation causes structural changes in a polypeptide loop distant from the active site and results in 91% residual activity, but the thermostability of this mutant is significantly compromised. Strikingly, the catalytic activity of these mutants can be partially or fully rescued in vitro by the HDAC8 activator N-(phenylcarbamothioyl)benzamide. These results suggest that HDAC8 activators might be useful leads in the search for new therapeutic strategies in managing CdLS.

Chromosome missegregation leads to chromosomal instability (CIN), thought to play a role in cancer development. As cohesin functions in guaranteeing correct chromosome segregation, increasing data suggest its involvement in tumorigenesis. In a screen of a large series of early colorectal adenomas, a precocious step during colorectal tumorigenesis, we identified 11 mutations in SMC1A core cohesin subunit. In addition, we sequenced the SMC1A gene in colorectal carcinomas and we found only one mutation. Finally, the transfection of the SMC1A mutations identified in early adenomas and wild-type SMC1A gene silencing in normal human fibroblasts led to CIN. Our findings that SMC1A mutations decrease from early adenomas to colorectal cancers and that mutations lead to CIN suggest that mutant cohesin could play a pivotal role during colorectal cancer development.

Cohesin is a multi-protein complex composed of four core subunits (SMC1A, SMC3, RAD21, and either STAG1 or STAG2) that is responsible for the cohesion of sister chromatids following DNA replication until its cleavage during mitosis thereby enabling faithful segregation of sister chromatids into two daughter cells. Recent cancer genomics analyses have discovered a high frequency of somatic mutations in the genes encoding the core cohesin subunits as well as cohesin regulatory factors (e.g. NIPBL, PDS5B, ESPL1) in a select subset of human tumors including glioblastoma, Ewing sarcoma, urothelial carcinoma, acute myeloid leukemia, and acute megakaryoblastic leukemia. Herein we review these studies including discussion of the functional significance of cohesin inactivation in tumorigenesis and potential therapeutic mechanisms to selectively target cancers harboring cohesin mutations. [BMB Reports 2014; 47(6): 299-310]

Mutations causing loss of PRC2 activity - including -7/-7q deletions – frequently occur in adult AML, MDS, and pediatric ML-DS and JMML. Yet, leukemogenesis is orchestrated by the cooperation of multiple mutations and we therefore aimed to decipher the mutational and molecular context in PRC2 loss guided transformation. Using an in vivo multiplexed CRISPR-Cas9 cooperation screening we identified two highly potent genetic configurations of 5 gRNAs (Nf1, Bcor, Tet2, Stag2, Smc1a and Runx1, Bcor, Tet2, Stag2, Sh2b3), resulting in high penetrance (100%) and short latency (5 to 12 weeks) leukemia when combined with the Ezh2 gRNA. NGS based mutation analysis in leukemic samples from both combinations indicated a cooperating effect between loss of function mutations in Bcor, Tet2, Runx1 and Ezh2. Reduced complexity screenings using only these gRNAs could validate the cooperation. Importantly, removal of the Ezh2 gRNA from the pools significantly delayed the leukemia onset. In vitro transformation assays underlined both the transforming potential of the mutational combinations and the dependency on the Ezh2 loss as fitness of the transformed cells lacking Ezh2 increased compared to wildtype counterparts. Interestingly, comparing global gene expression profiles of Ezh2 negative and positive samples revealed distinct upregulation of fetal gene expression signatures including known onco-fetal genes, suggesting that the Ezh2 loss may induce transformation by reactivating a fetal gene expression profile. Especially upregulation of the genes Plag1, Cdc42bpa, Gkap1 and Yes1 could be validated by qPCR experiments. CRISPR-Cas9 cooperation screenings were powerful to unravel cooperating effects of the loss of Ezh2 with mutations in Bcor, Runx1 and Tet2. Uncovered oncogenic dependencies on onco-fetal genes may be exploited for therapeutic approaches in the future.

Francisco Real and colleagues report exome sequencing in urothelial bladder tumors. They show that STAG2, a subunit of the cohesin complex, is recurrently mutated and provide evidence that STAG2 loss does not lead to increases in aneuploidy. Urothelial bladder cancer (UBC) is heterogeneous at the clinical, pathological and genetic levels. Tumor invasiveness (T) and grade (G) are the main factors associated with outcome and determine patient management1. A discovery exome sequencing screen (n = 17), followed by a prevalence screen (n = 60), identified new genes mutated in this tumor coding for proteins involved in chromatin modification (MLL2, ASXL2 and BPTF), cell division (STAG2, SMC1A and SMC1B) and DNA repair (ATM, ERCC2 and FANCA). STAG2, a subunit of cohesin, was significantly and commonly mutated or lost in UBC, mainly in tumors of low stage or grade, and its loss was associated with improved outcome. Loss of expression was often observed in chromosomally stable tumors, and STAG2 knockdown in bladder cancer cells did not increase aneuploidy. STAG2 reintroduction in non-expressing cells led to reduced colony formation. Our findings indicate that STAG2 is a new UBC tumor suppressor acting through mechanisms that are different from its role in preventing aneuploidy.