Increased RET Activity Coupled with a Reduction in the RET Gene Dosage Causes Intestinal Aganglionosis in Mice

Weighted gene co-expression network analysis and CIBERSORT screening of key genes related to m6A methylation in Hirschsprung's disease

Hirschsprung's disease (HSCR) is a neural crest disease that results from the failure of enteric neural crest cells (ENCCs) to migrate to the corresponding intestinal segment. The RET gene, which regulates enteric neural crest cell proliferation and migration, is considered one of the main risk factors for HSCR and is commonly used to construct HSCR mouse models. The epigenetic mechanism of m6A modification is involved in HSCR. In this study, we analyzed the GEO database (GSE103070) for differentially expressed genes (DEGs) and focused on m6A-related genes. Comparing the RNA-seq data of Wide Type and RET Null, a total of 326 DEGs were identified, of which 245 genes were associated with m6A. According to the CIBERSORT analysis, the proportion of Memory B-cell in RET Null was significantly higher than that of Wide Type. Venn diagram analysis was used to identify key genes in the selected memory B-cell modules and DEGs associated with m6A. Enrichment analysis showed that seven genes were mainly involved in focal adhesion, HIV infection, actin cytoskeleton organization and regulation of binding. These findings could provide a theoretical basis for molecular mechanism studies of HSCR.

A Single RET Mutation in Hirschsprung Disease Induces Intestinal Aganglionosis Via a Dominant-Negative Mechanism

BACKGROUND & AIMS

Hirschsprung disease (HSCR) is a congenital disorder characterized by the absence of the enteric nervous system (ENS). HSCR potentially involves multiple gene aberrations and displays complex patterns of inheritance. Mutations of the RET gene, encoding the RET receptor tyrosine kinase, play a central role in the pathogenesis of HSCR. Although a wide variety of coding RET mutations have been identified, their pathogenetic significance in vivo has remained largely unclear.

METHODS

We introduced a HSCR-associated RET missense mutation, RET(S811F), into the corresponding region (S812) of the mouse Ret gene. Pathogenetic impact of Ret(S812F) was assessed by histologic and functional analyses of the ENS and by biochemical analyses. Interactions of the Ret(S812F) allele with HSCR susceptibility genes, the RET9 allele and the Ednrb gene, were examined by genetic crossing in mice.

RESULTS

Ret^S812F/+ mice displayed intestinal aganglionosis (incidence, 50%) or hypoganglionosis (50%), impaired differentiation of enteric neurons, defecation deficits, and increased lethality. Biochemical analyses revealed that Ret(S811F) protein was not only kinase-deficient but also abrogated function of wild-type RET in trans. Moreover, the Ret(S812F) allele interacted with other HSCR susceptibility genes and caused intestinal aganglionosis with full penetrance.

CONCLUSIONS

This study demonstrates that a single RET missense mutation alone induces intestinal aganglionosis via a dominant-negative mechanism. The Ret^S812F/+ mice model HSCR displays dominant inheritance with incomplete penetrance and serves as a valuable platform for better understanding of the pathogenetic mechanism of HSCR caused by coding RET mutations.

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.