Genetic mosaicism of a frameshift mutation in the RET gene in a family with Hirschsprung disease

Revisiting Neuroblastoma: Nrf2, NF-κB and Phox2B as a Promising Network in Neuroblastoma

Neuroblastoma is the most common solid extracranial tumor during childhood; it displays extraordinary heterogeneous clinical courses, from spontaneous regression to poor outcome in high-risk patients due to aggressive growth, metastasizing, and treatment resistance. Therefore, the identification and detailed analysis of promising tumorigenic molecular mechanisms are inevitable. This review highlights the abnormal regulation of NF-κB, Nrf2, and Phox2B as well as their interactions among each other in neuroblastoma. NF-κB and Nrf2 play a key role in antioxidant responses, anti-inflammatory regulation and tumor chemoresistance. Recent studies revealed a regulation of NF-κB by means of the Nrf2/antioxidant response element (ARE) system. On the other hand, Phox2B contributes to the differentiation of immature sympathetic nervous system stem cells: this transcription factor regulates the expression of RET, thereby facilitating cell survival and proliferation. As observed in other tumors, we presume striking interactions between NF-κB, Nrf2, and Phox2B, which might constitute an important crosstalk triangle, whose decompensation may trigger a more aggressive phenotype. Consequently, these transcription factors could be a promising target for novel therapeutic approaches and hence, further investigation on their regulation in neuroblastoma shall be reinforced.

The Emerging Genetic Landscape of Hirschsprung Disease and Its Potential Clinical Applications

Hirschsprung disease (HSCR) is the leading cause of neonatal functional intestinal obstruction. It is a rare congenital disease with an incidence of one in 3,500-5,000 live births. HSCR is characterized by the absence of enteric ganglia in the distal colon, plausibly due to genetic defects perturbing the normal migration, proliferation, differentiation, and/or survival of the enteric neural crest cells as well as impaired interaction with the enteric progenitor cell niche. Early linkage analyses in Mendelian and syndromic forms of HSCR uncovered variants with large effects in major HSCR genes including RET, EDNRB, and their interacting partners in the same biological pathways. With the advances in genome-wide genotyping and next-generation sequencing technologies, there has been a remarkable progress in understanding of the genetic basis of HSCR in the past few years, with common and rare variants with small to moderate effects being uncovered. The discovery of new HSCR genes such as neuregulin and BACE2 as well as the deeper understanding of the roles and mechanisms of known HSCR genes provided solid evidence that many HSCR cases are in the form of complex polygenic/oligogenic disorder where rare variants act in the sensitized background of HSCR-associated common variants. This review summarizes the roadmap of genetic discoveries of HSCR from the earlier family-based linkage analyses to the recent population-based genome-wide analyses coupled with functional genomics, and how these discoveries facilitated our understanding of the genetic architecture of this complex disease and provide the foundation of clinical translation for precision and stratified medicine.

RET somatic mutations are underrecognized in Hirschsprung disease

PURPOSE

We aimed to determine the frequency of RET mosaicism in Hirschsprung disease (HSCR), test whether it has been underestimated, and to assess its contribution to HSCR risk.

METHODS

Targeted exome sequencing (n = 83) and RET single-gene screening (n = 69) were performed. Amplicon-based deep sequencing was applied on multiple tissue samples. TA cloning and sequencing were conducted for validation.

RESULTS

We identified eight de novo mutations in 152 patients (5.2%), of which six were pathogenic mosaic mutations. Two of these patients were somatic mosaics, with mutations detected in blood, colon, and saliva (mutant allele frequency: 35-44%). In addition, germ-line mosaicism was identified in four clinically unaffected subjects, each with an affected child, in multiple tissues (mutant allele frequency: 1-28%).

CONCLUSION

Somatic mutations of the RET gene are underrecognized in HSCR. Molecular investigation of the parents of patients with seemingly sporadic mutations is essential to determine recurrence risk in these families.

Nidogen-1 is a common target of microRNAs MiR-192/215 in the pathogenesis of Hirschsprung's disease

Recent studies have emphasized the important role of microRNA (miRNA) clusters and common target genes in disease progression. Despite the known involvement of the miR-192/215 family in many human diseases, its biological role in Hirschsprung disease (HSCR) remains undefined. In this study, we explored the role of the miR-192/215 family in the pathogenesis of HSCR. Quantitative real-time PCR and western blotting measured relative expression levels of miRNAs, mRNAs, and proteins in 80 HSCR patients and 77 normal colon tissues. Targets were evaluated by dual-luciferase reporter assays, and the functional effects of miR-192/215 on human 293T and SH-SY5Y cells were detected by the Transwell assay, CCK8 assay and flow cytometry. MiR-192/215 was significantly down-regulated in HSCR tissue samples, and their knockdown inhibited cell migration and proliferation in the human 293T and SH-SY5Y cell lines. Nidogen 1 (NID1) was confirmed as a common target gene of miR-192/215 by dual-luciferase reporter gene assay and its expression was inversely correlated with that of miR-192/215 in tissue samples and cell lines. Silencing of NID1 could rescue the extent of the suppressing effects by miR-192/215 inhibitor. The down-regulation of miR-192/215 may contribute to HSCR development by targeting NID1. We proposed the following cascade for the proposed mechanism of miR-192/215 in the pathogenesis of Hirschsprung disease (HSCR) by targeting Nidogen 1 (NID1). Aberrant expression of miR-192/215 inhibits cell migration and cell proliferation via NID1. We think the miR-192/miR-215/NID1 signaling pathway may play an important role in the pathogenesis of HSCR.