Whole-Exome Sequencing Identified Novel CLMP Mutations in a Family With Congenital Short Bowel Syndrome Presenting Differently in Two Probands

CXADR-Like Membrane Protein Regulates Colonic Epithelial Cell Proliferation and Prevents Tumor Growth

BACKGROUND & AIMS

CXADR-like membrane protein (CLMP) is structurally related to coxsackie and adenovirus receptor. Pathogenic variants in CLMP gene have been associated with congenital short bowel syndrome, implying a role for CLMP in intestinal development. However, the contribution of CLMP to regulating gut development and homeostasis is unknown.

METHODS

In this study, we investigated CLMP function in the colonic epithelium using complementary in vivo and in vitro approaches, including mice with inducible intestinal epithelial cell (IEC)-specific deletion of CLMP (ClmpΔIEC), intestinal organoids, IECs with overexpression, or loss of CLMP and RNA sequencing data from individuals with colorectal cancer.

RESULTS

Loss of CLMP enhanced IEC proliferation and, conversely, CLMP overexpression reduced proliferation. Xenograft experiments revealed increased tumor growth in mice implanted with CLMP-deficient colonic tumor cells, and poor engraftment was observed with CLMP-overexpressing cells. ClmpΔIEC mice showed exacerbated tumor burden in an azoxymethane and dextran sulfate sodium-induced colonic tumorigenesis model, and CLMP expression was reduced in human colorectal cancer samples. Mechanistic studies revealed that CLMP-dependent regulation of IEC proliferation is linked to signaling through mTOR-Akt-β-catenin pathways.

CONCLUSIONS

These results reveal novel insights into CLMP function in the colonic epithelium, highlighting an important role in regulating IEC proliferation, suggesting tumor suppressive function in colon cancer.

The IgSF Cell Adhesion Protein CLMP and Congenital Short Bowel Syndrome (CSBS)

The immunoglobulin-like cell adhesion molecule CLMP is a member of the CAR family of cell adhesion proteins and is implicated in human congenital short-bowel syndrome (CSBS). CSBS is a rare but very severe disease for which no cure is currently available. In this review, we compare data from human CSBS patients and a mouse knockout model. These data indicate that CSBS is characterized by a defect in intestinal elongation during embryonic development and impaired peristalsis. The latter is driven by uncoordinated calcium signaling via gap junctions, which is linked to a reduction in connexin43 and 45 levels in the circumferential smooth muscle layer of the intestine. Furthermore, we discuss how mutations in the CLMP gene affect other organs and tissues, including the ureter. Here, the absence of CLMP produces a severe bilateral hydronephrosis—also caused by a reduced level of connexin43 and associated uncoordinated calcium signaling via gap junctions.

Transcriptome Analysis Identifies Doublesex and Mab-3 Related Transcription Factor (DMRT3) in Nasal Polyp Epithelial Cells of Patients Suffering from Non-Steroidal Anti-Inflammatory Drug-Exacerbated Respiratory Disease (AERD)

Background: Aspirin-exacerbated respiratory disease (AERD) is a syndrome characterised by chronic rhinosinusitis, nasal polyps, asthma and aspirin intolerance. An imbalance of eicosanoid metabolism with anover-production of cysteinyl leukotrienes (CysLTs) has been associated with AERD. However, the precise mechanisms underlying AERD are unknown. Objective: To establish the transcriptome of the nasal polyp airway epithelial cells derived from AERD patients to discover gene expression patterns in this disease. Methods: Nasal airway epithelial cells were isolated from 12 AERD polyps and 8 AERD non-polyp nasal mucosa samples as controls from the same subjects. Utilising the Illumina HiSeq 2500 platform, RNA samples were sequenced. Potential gene candidate DMRT3 was selected from the differentially-expressed genes for validation. Results: Comparative transcriptome profiling of nasal epithelial cells was accomplished in AERD. A total of 20 genes had twofold mean regulation expression differences or greater. In addition, 8 genes were upregulated, including doublesex and mab-3 related transcription factor 3 (DMRT3), and 12 genes were downregulated. Differentially regulated genes comprised roles in inflammation, defence and immunity. Metabolic process and embryonic development pathways were significantly enriched. Enzyme-linked immune sorbent assay (ELISA) results of DMRT3 in AERD patients were significantly upregulated compared to controls (p = 0.03). Immunohistochemistry (IHC) of AERD nasal polyps localised DMRT3 and was predominantly released in the airway epithelia. Conclusion: Findings suggest that DMRT3 could be potentially involved in nasal polyp development in AERD patients. Furthermore, several genes are downregulated, hinting at the dedifferentiation phenomenon in AERD polyps. However, further studies are imperative to confirm the exact mechanism of polyp formation in AERD patients.

Congenital Short-Bowel Syndrome Is Associated With a Novel Deletion Mutation in the CLMP Gene: Mutations in CLMP Caused CSBS

Objective: To describe the clinical presentation and novel mutation in the coxsackie and adenovirus receptor-like membrane protein (CLMP) gene in a Chinese family with congenital short bowel syndrome (CSBS). Methods: We collected clinical data from a Chinese family with inherited CSBS, and performed whole exon sequencing of the children and their parents. The pathogenic sites of candidate genes were targeted, and the detected exon deletions were verified by quantitative PCR. Results: Two siblings in this family presented with bilious vomiting, and were diagnosed with CSBS on laparotomy. Two siblings and their parents underwent complete exome sequencing of the peripheral blood. Both children had CLMP gene exons 3-5 homozygous deletion mutation, while the parents had a heterozygous mutation. Conclusion: This study identified a novel mutation of the CLMP gene in a Chinese family with CSBS. Identification of this mutation can help with genetic counseling and prenatal diagnosis of CSBS.