Common PHOX2B poly-alanine contractions impair RET gene transcription, predisposing to Hirschsprung disease.

Abstract

HSCR is a congenital disorder of the enteric nervous system, characterized by the absence of neurons along a variable length of the gut resulting from loss-of-function RET mutations. Congenital Central Hypoventilation Syndrome (CCHS) is a rare neurocristopathy characterized by impaired response to hypercapnia and hypoxemia caused by heterozygous mutations of the PHOX2B gene, mostly polyalanine (polyA) expansions but also missense, nonsense, and frameshift mutations, while polyA contractions are common in the population and believed neutral. HSCR associated CCHS can present in patients carrying PHOX2B mutations. Indeed, RET expression is orchestrated by different transcriptional factors among which PHOX2B, thus suggesting its possible role in HSCR pathogenesis. Following the observation of HSCR patients carrying in frame trinucleotide deletions within the polyalanine stretch in exon 3 (polyA contractions), we have verified the hypothesis that these PHOX2B variants do reduce its transcriptional activity, likely resulting in a down-regulation of RET expression and, consequently, favouring the development of the HSCR phenotype. Using proper reporter constructs, we show here that the in vitro transactivation of the RET promoter by different HSCR-associated PHOX2B polyA variants has resulted significantly lower compared to the effect of PHOX2B wild type protein. In particular, polyA contractions do induce a reduced transactivation of the RET promoter, milder compared to the severe polyA expansions associated with CCHS+HSCR, and correlated with the length of the deleted trait, with a more pronounced effect when contractions are larger.

• Authors: Eleonora Di Zanni, Annalisa Adamo, Elga Belligni, Margherita Lerone, Giuseppe Martucciello, Girolamo Mattioli, Alessio Pini Prato, Roberto Ravazzolo, Margherita Silengo, Tiziana Bachetti, Isabella Ceccherini
• Journal: Biochimica et biophysica acta. Molecular basis of disease (Biochim Biophys Acta Mol Basis Dis) Vol. 1863 Issue 7 Pg. 1770-1777 (07 2017) ISSN: 0925-4439 [Print] Netherlands
• PMID: 28433712 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2017 Elsevier B.V. All rights reserved.

Chemical References

• Homeodomain Proteins
• NBPhox protein
• Peptides
• Transcription Factors
• polyalanine
• Proto-Oncogene Proteins c-ret
• RET protein, human

Topics

• Base Sequence
• Cell Line, Tumor
• Female
• Gene Expression Regulation
• Genetic Predisposition to Disease
• Hirschsprung Disease (genetics, metabolism, pathology)
• Homeodomain Proteins (genetics, metabolism)
• Humans
• Male
• Peptides (genetics, metabolism)
• Proto-Oncogene Proteins c-ret (biosynthesis, genetics)
• Sequence Deletion
• Transcription Factors (genetics, metabolism)
• Transcription, Genetic