Analysis of single nucleotide polymorphisms in the region of CLDN2-MORC4 in relation to inflammatory bowel disease

MORC4 plays a tumor-promoting role in colorectal cancer via regulating PCGF1/CDKN1A axis in vitro and in vivo

MORC family CW-type zinc finger 4 (MORC4) possessing nuclear matrix binding domains has been observed to be involved in multiple cancer development. By digging three gene expression omnibus (GEO) gene microarrays (GSE110223, GSE110224 and GSE24514), we found that MORC4 was overexpressed in colorectal cancer (CRC) samples (log₂ Fold change >1, p < 0.05). We aimed to investigate the role of MORC4 in CRC malignant behaviors, with an emphasis on polycomb group ring finger 1 (PCGF1)/cyclin-dependent kinase inhibitor 1A (CDKN1A) axis. Firstly, we confirmed MORC4 as an upregulated gene in 60 pairs of frozen CRC and adjacent normal samples. MORC4 overexpression increased proliferation and metastasis, and decreased apoptosis in SW480 and HT29 cells, which was diminished by the knockdown of PCGF1, a transcriptional repressor of CDKN1A (a potent cyclin-dependent kinase inhibitor). MORC4 was further identified as a novel molecule that interacted with PCGF1 via coimmunoprecipitation. MORC4 itself did not substantially suppress CDKN1A transcriptional activity, but it augmented PCGF1's effect on CDKN1A. Additionally, MORC4 acted as the substrate of HECT, C2, and WW domain-containing E3 ubiquitin protein ligase 2 (HECW2) and was degraded through ubiquitin-proteasome system. Collectively, our work suggested that MORC4 accelerated CRC progression via governing PCGF1/CDKN1A signaling.

Inverse and Concordant Mucosal Pathway Gene Expressions in Inflamed and Non-Inflamed Ulcerative Colitis Patients: Potential Relevance to Aetiology and Pathogenesis

Ulcerative colitis (UC) arises from a complex interplay between host and environmental factors, but with a largely unsolved pathophysiology. The pathophysiology was outlined by RNA-sequencing of mucosal biopsies from non-inflamed and inflamed colon of UC patients (14 and 17, respectively), and from 27 patients without intestinal inflammation. Genes differentially expressed (DE), or present in enriched gene sets, were investigated using statistical text analysis of functional protein information. Compared with controls, inflamed and non-inflamed UC mucosa displayed 9360 and 52 DE genes, respectively. Seventy-three non-pseudogenes were DE relative to both gender and inflammation. Mitochondrial processes were downregulated in inflamed and upregulated in non-inflamed UC mucosa, whereas angiogenesis and endoplasmic reticulum (ER) stress were upregulated in both tissue states. Immune responses were upregulated in inflamed mucosa, whereas the non-inflamed UC mucosa presented both up- and downregulated gene sets. DE and enriched genes overlapped with genes present in inflammatory bowel disease genome-wide associated loci (p = 1.43 × 10⁻¹⁸), especially regarding immune responses, respiratory chain, angiogenesis, ER stress, and steroid hormone metabolism. Apart from confirming established pathophysiological mechanisms of immune cells, our study provides evidence for involvement of less described pathways (e.g., respiratory chain, ER stress, fatty-acid oxidation, steroid hormone metabolism and angiogenesis).

Structural and Functional Attributes of Microrchidia Family of Chromatin Remodelers

Chromatin remodelers affect the spatio-temporal dynamics of global gene-expression by structurally modulating and/or reorganizing the chromatin. Microrchidia (MORC) family is a relatively new addition to the four well studied families of chromatin remodeling proteins. In this review, we discuss the current understanding of the structural aspects of human MORCs as well as their epigenetic functions. From a molecular and systems-level perspective, we explore their participation in phase-separated structures, possible influence on various biological processes through protein-protein interactions, and potential extra-nuclear roles. We describe how dysregulation/dysfunction of MORCs can lead to various pathological conditions. We conclude by emphasizing the importance of undertaking integrated efforts to obtain a holistic understanding of the various biological roles of MORCs.

MORC protein family-related signature within human disease and cancer

The microrchidia (MORC) family of proteins is a highly conserved nuclear protein superfamily, whose members contain common domain structures (GHKL-ATPase, CW-type zinc finger and coiled-coil domain) yet exhibit diverse biological functions. Despite the advancing research in previous decades, much of which focuses on their role as epigenetic regulators and in chromatin remodeling, relatively little is known about the role of MORCs in tumorigenesis and pathogenesis. MORCs were first identified as epigenetic regulators and chromatin remodelers in germ cell development. Currently, MORCs are regarded as disease genes that are involved in various human disorders and oncogenes in cancer progression and are expected to be the important biomarkers for diagnosis and treatment. A new paradigm of expanded MORC family function has raised questions regarding the regulation of MORCs and their biological role at the subcellular level. Here, we systematically review the progress of researching MORC members with respect to their domain architectures, diverse biological functions, and distribution characteristics and discuss the emerging roles of the aberrant expression or mutation of MORC family members in human disorders and cancer development. Furthermore, the illustration of related mechanisms of the MORC family has made MORCs promising targets for developing diagnostic tools and therapeutic treatments for human diseases, including cancers.

Molecular mechanism of the MORC4 ATPase activation

Human Microrchidia 4 (MORC4) is associated with acute and chronic pancreatitis, inflammatory disorders and cancer but it remains largely uncharacterized. Here, we describe the structure-function relationship of MORC4 and define the molecular mechanism for MORC4 activation. Enzymatic and binding assays reveal that MORC4 has ATPase activity, which is dependent on DNA-binding functions of both the ATPase domain and CW domain of MORC4. The crystal structure of the ATPaseCW cassette of MORC4 and mutagenesis studies show that the DNA-binding site and the histone/ATPase binding site of CW are located on the opposite sides of the domain. The ATPase and CW domains cooperate in binding of MORC4 to the nucleosome core particle (NCP), enhancing the DNA wrapping around the histone core and impeding binding of DNA-associated proteins, such as transcription factors, to the NCP. In cells, MORC4 mediates formation of nuclear bodies in the nucleus and has a role in the progression of S-phase of the cell cycle, and both these functions require CW and catalytic activity of MORC4. Our findings highlight the mechanism for MORC4 activation, which is distinctly different from the mechanisms of action observed in other MORC family members.

MORC4 is a novel breast cancer oncogene regulated by miR-193b-3p

A better understanding of breast cancer pathogenesis would contribute to improved diagnosis and therapy and potentially decreased mortality rates. Here, we found that the MORC family CW-type zinc finger 4 (MORC4) overexpression in breast cancer tissues is associated with poor survival, and the short-interfering RNA knockdown of MORC4 suppresses the growth of breast cancer cells by promoting apoptosis. To investigate the mechanisms associated with MORC4 upregulation, microRNAs potentially targeting MORC4 were analyzed, with miR-193b-3p identified as the regulator and a negative correlation between miR-193b-3p and MORC4 expression determined in both breast cancer cell lines and tissues. Further analysis verified that MORC4 silencing did not affect miR-193b-3p expression, although altered miR-193b-3p expression attenuated MORC4 protein levels. Moreover, dual-luciferase reporter assays verified miR-193b-3p binding to the 3' untranslated region of MORC4. Furthermore, restoration of miR-193b-3p expression in breast cancer cells led to decreased growth and activation of apoptosis, which was consistent with results associated with MORC4 silencing in breast cancer cells. These results identified MORC4 as differentially expressed in breast cancer cells and tissues and its downregulation by miR-193b-3p, as well as its roles in regulating the growth of breast cancer cells via regulation of apoptosis. Our findings offer novel insights into potential mechanisms associated with breast cancer pathogenesis.

Genetic variation and expression levels of tight junction genes identifies association between MAGI3 and inflammatory bowel disease

Background

Inflammatory bowel disease (IBD) is associated with increased intestinal permeability, which involves paracellular passage regulated through tight junctions (TJ). The aim of the study was to investigate single nucleotide polymorphisms (SNP) located in genes encoding interacting TJ proteins and corresponding expressions, in relation to IBD.

Methods

Allelic associations between TJ-related genes (F11R, MAGI1, MAGI2, MAGI3, PARD3, PTEN, and TJP1) and IBD, Crohn’s disease (CD), or ulcerative colitis (UC) were investigated. PTPN22 was included since it’s located in the same genetic region as MAGI3. Gene expression levels were investigated in relation to genotype, inflammatory status, phenotype, and medical treatment.

Results

The two strongest allelic associations were observed between IBD and SNPs in MAGI2 (rs6962966) and MAGI3 (rs1343126). Another MAGI3 SNP marker (rs6689879) contributed to increased ileal MAGI3 expression level in non-IBD controls. Furthermore, association between inflammation and decreased expression levels of MAGI3, PTEN, and TJP1 in colonic IBD as well as UC mucosa, and between inflammation and increased expression of PTPN22 in colonic IBD mucosa, was observed.

Conclusions

Our findings lend support to a genetic basis for modulation of intestinal epithelial barrier in IBD, and we have identified MAGI3 as a new candidate gene for IBD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-017-0620-y) contains supplementary material, which is available to authorized users.

Microbiome and colorectal cancer: Unraveling host-microbiota interactions in colitis-associated colorectal cancer development

Dysbiosis of gut microbiota occurs in many human chronic immune-mediated diseases, such as inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CAC). Reciprocally, uncontrolled immune responses, that may or may not be induced by dysbiosis, are central to the development of IBD and CAC. There has been a surge of interest in investigating the relationship between microbiota, inflammation and CAC. In this review, we discuss recent findings related to gut microbiota and chronic immune-mediated diseases, such as IBD and CAC. Moreover, the molecular mechanisms underlying the roles of chronic inflammation in CAC are examined. Finally, we discuss the development of novel microbiota-based therapeutics for IBD and colorectal cancer.

MORC Proteins: Novel Players in Plant and Animal Health

Microrchidia (MORC) proteins comprise a family of proteins that have been identified in prokaryotes and eukaryotes. They are defined by two hallmark domains: a GHKL-type ATPase and an S5 fold. MORC proteins in plants were first discovered via a genetic screen for Arabidopsis mutants compromised for resistance to a viral pathogen. Subsequent studies expanded their role in plant immunity and revealed their involvement in gene silencing and transposable element repression. Emerging data suggest that MORC proteins also participate in pathogen-induced chromatin remodeling and epigenetic gene regulation. In addition, biochemical analyses recently demonstrated that plant MORCs have topoisomerase II (topo II)-like DNA modifying activities that may be important for their function. Interestingly, animal MORC proteins exhibit many parallels with their plant counterparts, as they have been implicated in disease development and gene silencing. In addition, human MORCs, like plant MORCs, bind salicylic acid and this inhibits some of their topo II-like activities. In this review, we will focus primarily on plant MORCs, although relevant comparisons with animal MORCs will be provided.

The Emerging Role of MORC Family Proteins in Cancer Development and Bone Homeostasis

Microrchidia (MORC or MORC family CW-type zinc finger protein), a highly conserved nuclear protein superfamily, is an interesting new player in signaling-dependent chromatin remodeling and epigenetic regulation. MORC family proteins consist of MORC1, MORC2, MORC3, and MORC4 which display common structural determinants such as CW-type zinc finger and coiled-coil domains. They also exhibit unique structural motifs and tissue-specific expression profiles. MORC1 was first discovered as a key regulator for male meiosis and spermatogenesis. Accumulating biochemical and functional analyses unveil MORC proteins as key regulators for cancer development. More recently, using an ENU mutagenesis mouse model, MORC3 was found to play a role in regulating bone and calcium homeostasis. Here we discuss recent research progress on the emerging role of MORC proteins in cancer development and bone metabolism. Unravelling the cellular and molecular mechanisms by which MORC proteins carry out their functions in a tissue specific manner are important subjects for future investigation. J. Cell. Physiol. 232: 928-934, 2017. © 2016 Wiley Periodicals, Inc.

Association Analysis of PRSS1-PRSS2 and CLDN2-MORC4 Variants in Nonalcoholic Chronic Pancreatitis Using Tropical Calcific Pancreatitis as Model

OBJECTIVE

Association of PRSS1-PRSS2 (rs10273639) and CLDN2-MORC4 (rs12688220 and rs7057398) variants with alcohol-related chronic pancreatitis (CP) is established but with nonalcoholic CP is unclear. We addressed this inconsistency using tropical calcific pancreatitis (TCP) as model.

METHODS

We sequenced 5'-UTR of PRSS1 and genotyped CLDN2-MORC4 variants in 555 patients with TCP and 801 controls and performed association analysis. Gene-gene interaction between PRSS1 and CLDN2-MORC4 variants and with p.Asn34Ser SPINK1 and p.Leu26Val CTSB was also evaluated.

RESULTS

We observed significant association of rs10273639/rs4726576 in PRSS1-PRSS2 (odds ratio [OR] = 0.72; P = 3.50 × 10) and CLDN2-MORC4 variants, rs12688220 (OR = 1.54; P = 1.22 × 10) and rs7057398 (OR = 1.50; P = 1.22 × 10) with TCP. Patients carrying p.Asn34Ser SPINK1 were significantly younger than those with rs4726576 risk genotype (30.0 vs 38.0 years; P = 0.015) and those carrying both were even younger (22.0 years; P = 0.001). Presence of risk allele at rs12688220 in patients carrying p.Asn34Ser SPINK1 delayed the age of onset (32.0 vs 24.0 years; P = 0.013).

CONCLUSIONS

Our study establishes strong association of PRSS1-PRSS2 and CLDN2-MORC4 variants with TCP and thus with nonalcoholic CP. These variants independently interact with p.Asn34Ser SPINK1 and influence the age of onset in TCP. However, latter results need to be replicated in other cohorts.

Common Variants in CLDN2 and MORC4 Genes Confer Disease Susceptibility in Patients with Chronic Pancreatitis

A recent genome-wide association study (GWAS) identified association with variants in X-linked CLDN2 and MORC4, and PRSS1-PRSS2 loci with chronic pancreatitis (CP) in North American patients of European ancestry. We selected 9 variants from the reported GWAS and replicated the association with CP in Indian patients by genotyping 1807 unrelated Indians of Indo-European ethnicity, including 519 patients with CP and 1288 controls. The etiology of CP was idiopathic in 83.62% and alcoholic in 16.38% of 519 patients. Our study confirmed a significant association of 2 variants in CLDN2 gene (rs4409525-OR 1.71, P = 1.38 x 10-09; rs12008279-OR 1.56, P = 1.53 x 10-04) and 2 variants in MORC4 gene (rs12688220-OR 1.72, P = 9.20 x 10-09; rs6622126-OR 1.75, P = 4.04x10-05) in Indian patients with CP. We also found significant association at PRSS1-PRSS2 locus (OR 0.60; P = 9.92 x 10-06) and SAMD12-TNFRSF11B (OR 0.49, 95% CI [0.31-0.78], P = 0.0027). A variant in the gene MORC4 (rs12688220) showed significant interaction with alcohol (OR for homozygous and heterozygous risk allele -14.62 and 1.51 respectively, P = 0.0068) suggesting gene-environment interaction. A combined analysis of the genes CLDN2 and MORC4 based on an effective risk allele score revealed a higher percentage of individuals homozygous for the risk allele in CP cases with 5.09 fold enhanced risk in individuals with 7 or more effective risk alleles compared with individuals with 3 or less risk alleles (P = 1.88 x 10-14). Genetic variants in CLDN2 and MORC4 genes were associated with CP in Indian patients.

Single-Nucleotide Polymorphisms of Tight Junction Component Claudin-1 Associated with Leukoaraiosis

BACKGROUND

The blood-brain barrier (BBB) plays a major role in the development of leukoaraiosis (LA). The junctional complex of BBB consists of tight junction (TJ) and adherens junction (AJ). Claudin-1 is the integral component of TJ. The aim of this study was to evaluate whether genetic variations in claudin-1 gene are associated with the development of LA.

METHODS

LA has to be diagnosed based on images. A total of 228 LA cases and 203 controls were enrolled from the individuals who underwent brain magnetic resonance imaging with obtainable vascular risk factors. Genotyping of claudin-1 single-nucleotide polymorphisms (SNPs) (rs17501010, rs893051, and rs9290927) was performed by real-time polymerase chain reaction with LightSNiP reagents (coupled primer and probe) and FastStart DNAMaster HybProbe (Roche Diagnostic, GmBH, Mannheim, Germany) in LightCycler 2.0.

RESULTS

Among the 3 SNPs of claudin-1, a significant genetic difference was found only between control and LA (both LA-periventricular white matter [PVWM] and LA-subcortical deep white matter) with SNP rs9290927. However, their haplotypes G-G-T and G-C-A were significantly different between LA-PVWM and control, which increase the development of LA-PVWM with odds ratios of 1.45 and .57, respectively.

CONCLUSIONS

This study demonstrated first evidence of genetic polymorphism of TJ component claudin-1 and their haplotypes associated with LA.

Claudin-4 is required for AMPK-modulated paracellular permeability in submandibular gland cells

Tight junction plays an important role in mediating paracellular permeability in epithelia. We previously found that activation of AMP-activated protein kinase (AMPK) increased saliva secretion by modulating paracellular permeability in submandibular glands. However, the molecular mechanisms underlying AMPK-modulated paracellular permeability are unknown. In this study, we found that AICAR, an AMPK agonist, increased saliva secretion in the isolated rat submandibular glands, decreased transepithelial electrical resistance (TER), and increased 4 kDa FITC-dextran flux in cultured SMG-C6 cells. AICAR also induced redistribution of tight junction protein claudin-4, but not claudin-1, claudin-3, occludin, or ZO-1, from the cytoplasm to the membrane. Moreover, knockdown of claudin-4 by shRNA suppressed while claudin-4 re-expression restored the TER and 4 kDa FITC-dextran flux responses to AICAR. Additionally, AICAR increased ERK1/2 phosphorylation, and inhibition of ERK1/2 by U0126, an ERK1/2 kinase inhibitor, or by siRNA decreased AICAR-induced TER responses. AICAR induced the serine S199 phosphorylation of claudin-4 and enhanced the interaction of claudin-4 and occludin. Furthermore, pretreatment with U0126 significantly suppressed AMPK-modulated phosphorylation, redistribution, and interaction with occludin of claudin-4. Taken together, these results indicated that claudin-4 played a crucial role in AMPK-modulated paracellular permeability and ERK1/2 was required in AMPK-modulated tight junction barrier function in submandibular gland.