Noncoding RET variants explain the strong association with Hirschsprung disease in patients without rare coding sequence variant

Downregulation of miR-144 blocked the proliferation and invasion of nerve cells in Hirschsprung disease by regulating Transcription Factor AP 4 (TFAP4)

BACKGROUND

Hirschsprung's disease (HSCR) is characterized by a dysfunction of enteric neural crest cells (ENCCs) proliferation, migration and premature apoptosis during embryonic development, resulting in aganglionic colon. Our aim is to explore the role of miR-144 with its target gene Transcription Factor AP 4 (TFAP4) in nerve cells in HSCR.

METHODS

The relative expression levels of miR-144 in HSCR colon samples were detected by quantitative real-time PCR (RT-qPCR). Western blot assays were conducted to investigate the TFAP4 protein expressing level. The interaction of miR-144 and TFAP4 was predicted with bioinformatics analysis and examined with luciferase reporter assays. Overexpression or knockdown of miR-144 and TFAP4 in 293T and SH-SY5Y cell lines was applied. Cell proliferation, migration and invasion were detected by CCK-8 assays, Transwell migration and invasion assays. Cell cycle and apoptosis was examined by flow cytometric analysis.

RESULTS

Downregulation of miR-144 and upregulation of TFAP4 were shown in HSCR. Luciferase reporter assay indicated that miR-144 reduced luciferase activity in 293T and SH-SY5Y transfected with TFAP4-WT-3UTR luciferase reporter and confirmed TFAP4 was the downstream target gene of miR-144. Data showed that miR-144 promoted the cell proliferation, migration and invasion of 293T and SH-SY5Y, while TFAP4 blocked the cell proliferation, migration and invasion. TFAP4 overexpression reversed the miR-144-mediated cell proliferation, migration and invasion of 293T and SH-SY5Y.

CONCLUSIONS

Downregulation of miR-144 blocked the cell proliferation and migration of nerve cells via targeting TFAP4 and contributed to the pathogenesis of HSCR. This provides an innovative and candidate target for treatment of HSCR.

Combined GWAS and single cell transcriptomics uncover the underlying genes and cell types in disorders of gut-brain interaction

Disorders of gut-brain interaction (DGBIs), formerly known as functional gastrointestinal disorders, are extremely common and historically difficult to manage. This is largely because their cellular and molecular mechanisms have remained poorly understood and understudied. One approach to unravel the molecular underpinnings of complex disorders such as DGBIs is performing genome wide association studies (GWASs). However, due to the heterogenous and non-specific nature of GI symptoms, it has been difficult to accurately classify cases and controls. Thus, to perform reliable studies, we need to access large patient populations which has been difficult to date. Here, we leveraged the UK Biobank (UKBB) database, containing genetic and medical record data of over half a million individuals, to perform GWAS for five DGBI categories: functional chest pain, functional diarrhea, functional dyspepsia, functional dysphagia, and functional fecal incontinence. By applying strict inclusion and exclusion criteria, we resolved patient populations and identified genes significantly associated with each condition. Leveraging multiple human single-cell RNA-sequencing datasets, we found that the disease associated genes were highly expressed in enteric neurons, which innervate and control GI functions. Further expression and association testing-based analyses revealed specific enteric neuron subtypes consistently linked with each DGBI. Furthermore, protein-protein interaction analysis of each of the disease associated genes revealed protein networks specific to each DGBI, including hedgehog signaling for functional chest pain and neuronal function and neurotransmission for functional diarrhea and functional dyspepsia. Finally, through retrospective medical record analysis we found that drugs that inhibit these networks are associated with an increased disease risk, including serine/threonine kinase 32B drugs for functional chest pain, solute carrier organic anion transporter family member 4C1, mitogen-activated protein kinase 6, and dual serine/threonine and tyrosine protein kinase drugs for functional dyspepsia, and serotonin transporter drugs for functional diarrhea. This study presents a robust strategy for uncovering the tissues, cell types, and genes involved in DGBIs, presenting novel predictions of the mechanisms underlying these historically intractable and poorly understood diseases.

Genetics of Hirschsprung's disease

Hirschsprung's disease (HSCR) is a classical model of enteric neuropathy, occurring in approximately 2-2.8 in 10,000 newborns. It is the commonest form of congenital bowel obstruction and is characterized by the absence of enteric ganglia in distal colon. Recent advances in genome-wide association analysis (GWAS) and next generation sequencing (NGS) studies have led to the discovery of a number of new HSCR candidate genes, thereby providing new insights into the genetic architecture and molecular mechanisms of the disease. Altogether, these findings indicated that genetic heterogeneity, variable penetrance and expressivity, and genetic interaction are the pervasive characteristics of HSCR genetics. In this review, we will provide an update on the genetic landscape of HSCR and discuss how the common and rare variants may act together to modulate the phenotypic manifestation. Translating the genetic findings to genetic risk prediction and to optimize clinical outcomes are undoubtedly the ultimate goals for genetic studies on HSCR. From this perspective, we will further discuss the major obstacles in the clinical translation of these latest genetic findings. Lastly, new measures to address these clinical challenges are suggested to advance precision medicine and to develop novel alternative therapies.

Circ-ITCH overexpression promoted cell proliferation and migration in Hirschsprung disease through miR-146b-5p/RET axis

BACKGROUND

Hirschsprung disease (HSCR) is a congenital intestinal disease caused by the abnormal proliferation and migration of enteric nerve cells (ENCC). Research suggested critical roles for circular RNA (circRNA) itchy E3 ubiquitin protein ligase (ITCH) in gastrointestinal malignancies progression. However, the function of circ-ITCH in HSCR remains poorly defined.

METHODS

The related genes expression in 30 HSCR patients and 30 controls without HSCR were detected using qRT-PCR. Cell proliferation was assessed by CCK-8 assay and EdU assay. Cell migration was detected with wound-healing assay and transwell assay. The interactions among circ-ITCH, miR-146b-5p, and RET were confirmed by Dual luciferase reporter assay.

RESULTS

Circ-ITCH and RET expressions were downregulated in HSCR patients and cells, while the miR-146b-5p expression was upregulated. Circ-ITCH overexpression facilitated cell proliferation, migration, and activated MAPK pathway, which were reversed by circRNA-ITCH knockdown. Circ-ITCH negatively regulated miR-146b-5p expression. MiR-146b-5p overexpression abolished the promoting effects of circ-ITCH overexpression on cell proliferation and migration. MiR-146b-5p inhibited RET expression. RET overexpression eliminated the inhibitory effects of miR-146b-5p overexpression on cell proliferation and migration.

CONCLUSION

Circ-ITCH overexpression facilitated cell proliferation and migration in HSCR by regulating miR-146b-5p/RET/MAPK axis.

IMPACT

The expressions of Circ-ITCH and RET were markedly reduced in HSCR, while miR-146b-5p expression was increased in HSCR. Circ-ITCH overexpression enhanced the proliferative and migratory abilities of SH-SY5Y and 293T cells. Circ-ITCH negatively regulated miR-146b-5p expression.

Is There Any Mosaicism in REarranged During Transfection Variant in Hirschsprung Disease's Patients?

BACKGROUND

Hirschsprung disease (HSCR) is a heterogeneous genetic disease characterized by the absence of ganglion cells in the intestinal tract. The REarranged during Transfection (RET) is the most responsible gene for its pathogenesis. RET's somatic mosaicisms have been reported for HSCR; however, they are still under-recognized. Therefore, we determined the frequency of somatic mutation of RET rs2435357 in HSCR patients at our institution.

METHODS

We performed RET rs2435357 genotyping from 73 HSCR formalin-fixed and paraffin-embedded (FFPE) rectal and 60 non-HSCR controls using the PCR-RFLP method. Subsequently, we compared those frequencies of genotypes for RET rs2435357 with our previous genotyping data from 93 HSCR blood specimens.

RESULTS

The frequencies of genotypes for RET rs2435357 in HSCR paraffin-embedded rectal were CC 0, CT 11 (15%), and TT 62 (85%), whereas their frequencies in HSCR blood samples were CC 4 (4.3%), CT 22 (23.7%), and TT 67 (72%). Those frequencies differences almost reached a significant level (p = 0.06). Moreover, the frequency of RET rs2435357 risk allele (T) was significantly higher in HSCR patients (135/146, 92.5%) than controls (46/120, 38.3%) (p = 3.4 × 10^-22), with an odds ratio of 19.74 (95% confidence interval = 9.65-40.41).

CONCLUSION

Our study suggests somatic mosaicism in HSCR patients. These findings further imply the complexity of the pathogenesis of HSCR. Moreover, our study confirms the RET rs2435357 as a significant genetic risk factor for HSCR patients.

ERNICA guidelines for the management of rectosigmoid Hirschsprung's disease

BACKGROUND

Hirschsprung's disease (HSCR) is a serious congenital bowel disorder with a prevalence of 1/5000. Currently, there is a lack of systematically developed guidelines to assist clinical decision-making regarding diagnostics and management.

AIMS

This guideline aims to cover the diagnostics and management of rectosigmoid HSCR up to adulthood. It aims to describe the preferred approach of ERNICA, the European Reference Network for rare inherited and congenital digestive disorders.

METHODS

Recommendations within key topics covering the care pathway for rectosigmoid HSCR were developed by an international workgroup of experts from 8 European countries within ERNICA European Reference Network from the disciplines of surgery, medicine, histopathology, microbiology, genetics, and patient organization representatives. Recommendation statements were based on a comprehensive review of the available literature and expert consensus. AGREE II and GRADE approaches were used during development. Evidence levels and levels of agreement are noted.

RESULTS

Thirty-three statements within 9 key areas were generated. Most recommendations were based on expert opinion.

CONCLUSION

In rare or low-prevalence diseases such as HSCR, there remains limited availability of high-quality clinical evidence. Consensus-based guidelines for care are presented.

Genetic variants in RET, ARHGEF3 and CTNNAL1, and relevant interaction networks, contribute to the risk of Hirschsprung disease

Hirschsprung disease (HSCR), the most common enteric neuropathy, stands as a model for complex genetic disorders. It has recently been demonstrated that both ARHGEF3 and CTNNAL1 map to the RET-dependent HSCR susceptibility loci. We therefore sought to explore whether genetic variants within RET, ARHGEF3 and CTNNAL1, and their genetic interaction networks are associated with HSCR. Taking advantage of a strategy that combined the MassArray system and gene-gene interaction analysis with case-control study, we interrogated 38 polymorphisms within RET, ARHGEF3 and CTNNAL1 in 1015 subjects (502 HSCR cases and 513 controls) of Han Chinese origin. There were statistically significant associations between 20 genetic variants in these three genes and HSCR. Haplotype analysis also revealed some significant global P values, i.e. RET_ rs2435357-rs752978-rs74400468-rs2435353-rs2075913-rs17028-rs2435355 (P = 3.79×10^-58). Using the MDR and GeneMANIA platforms, we found strong genetic interactions among RET, ARHGEF3, and CTNNAL1 and our previously studied GAL, GAP43, NRSN1, PTCH1, GABRG2 and RELN genes. These results offer the first indication that genetic markers of RET, ARHGEF3 and CTNNAL1 and relevant genetic interaction networks confer the altered risk to HSCR in the Han Chinese population.

Copy number variations in candidate genomic regions confirm genetic heterogeneity and parental bias in Hirschsprung disease

Background

Hirschsprung Disease (HSCR) is a congenital defect of the intestinal innervations characterized by complex inheritance. Many susceptibility genes including RET, the major HSCR gene, and several linked regions and associated loci have been shown to contribute to disease pathogenesis. Nonetheless, a proportion of patients still remains unexplained. Copy Number Variations (CNVs) have already been involved in HSCR, and for this reason we performed Comparative Genomic Hybridization (CGH), using a custom array with high density probes.

Results

A total of 20 HSCR candidate regions/genes was tested in 55 sporadic patients and four patients with already known chromosomal aberrations. Among 83 calls, 12 variants were experimentally validated, three of which involving the HSCR crucial genes SEMA3A/3D, NRG1, and PHOX2B. Conversely RET involvement in HSCR does not seem to rely on the presence of CNVs while, interestingly, several gains and losses did co-occur with another RET defect, thus confirming that more than one predisposing event is necessary for HSCR to develop. New loci were also shown to be involved, such as ALDH1A2, already found to play a major role in the enteric nervous system. Finally, all the inherited CNVs were of maternal origin.

Conclusions

Our results confirm a wide genetic heterogeneity in HSCR occurrence and support a role of candidate genes in expression regulation and cell signaling, thus contributing to depict further the molecular complexity of the genomic regions involved in the Enteric Nervous System development. The observed maternal transmission bias for HSCR associated CNVs supports the hypothesis that in females these variants might be more tolerated, requiring additional alterations to develop HSCR disease.

Outcomes in patients with Hirschsprung disease following definitive surgery

Objective

Several pull-through procedures have been described for Hirschsprung disease (HSCR) with varying outcomes. We aimed to describe the outcomes in HSCR patients < 18 year of age who underwent surgical procedures at Dr. Sardjito Hospital, Yogyakarta, Indonesia from January 2013 to December 2014.

Results

We utilized 67 HSCR patients, of whom 49 (73%) were males and 18 (27%) females. Neonatal presentation was seen in 57 cases (85%) and most patients (98.5%) had short-segment HSCR. The clinical manifestations were mainly abdominal distension (94%) and delayed passage of meconium (45%). The most common definitive treatment performed was transanal endorectal pull-through (TEPT) (54%), followed by Soave (18%) and Duhamel (13%) procedures. Enterocolitis occurred in 13% of the HSCR patients after endorectal pull-through, but did not reach a significant level (p-value = 0.65), while the constipation rate was significantly higher in HSCR patients who underwent posterior neurectomy compared with those other procedures (OR = 15.5, 95% CI = 1.8–132.5; p-value = 0.019). In conclusions, most HSCR patients in Indonesia were diagnosed in the neonatal period and underwent the TEPT procedure. Furthermore, the risk of constipation is increased in HSCR patients following posterior neurectomy compared with other definitive surgical techniques.