Reduced RET expression in gut tissue of individuals carrying risk alleles of Hirschsprung's disease

Receptor tyrosine kinase (RET) single nucleotide polymorphisms (SNPs) are associated with the Hirschsprung's disease (HSCR). We investigated whether the amount of RET expressed in the ganglionic gut of human was dependent on the genotype of three regulatory SNPs (-5G>A rs10900296 and -1A>C rs10900297 in the promoter, and C>T rs2435357 in intron 1). We examined the effects of three regulatory SNPs on the RET gene expression in 67 human ganglionic gut tissues using quantitative real-time PCR. Also, 315 Chinese HSCR patients and 325 ethnically matched controls were genotyped for the three SNPs by polymerase chain reaction (PCR) and direct sequencing. The expression of RET mRNA in human gut tissue did indeed correlate with the genotypes of the individuals. The lowest RET expression was found for those individuals homozygous for the three risk alleles (A-C-T/A-C-T), and the highest for those homozygous for the 'wild-type' counterpart (G-A-C/G-A-C), with expression values ranging from 218.32±125.69 (mean ± SE) in tissues from individuals carrying G-A-C/G-A-C to 31.42±8.42 for individuals carrying A-C-T/A-C-T (P 5 0.018). As expected, alleles -5A, -1C and intron 1 T were associated with HSCR (P 5 5.94 × 10-31, 3.12 3 10-24 and 5.94 × 10-37, respectively) as was the haplotype encompassing the three associated alleles (A-C-T) when compared with the wild-type counterpart G-A-C (χ2 5 155.29, P « 0.0001). To our knowledge, this is the first RET expression genotype-phenotype correlation study conducted on human subjects to indicate common genetic variants in the regulatory region of RET may play a role in mediating susceptibility to HSCR, by conferring a significant reduction of the RET expression. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]

Correction of Hirschsprung-Associated Mutations in Human Induced Pluripotent Stem Cells Via Clustered Regularly Interspaced Short Palindromic Repeats/Cas9, Restores Neural Crest Cell Function

ACKGROUND & AIMS: Hirschsprung disease is caused by failure of enteric neural crest cells (ENCCs) to fully colonize the bowel, leading to bowel obstruction and megacolon. Heterozygous mutations in the coding region of the RET gene cause a severe form of Hirschsprung disease (total colonic aganglionosis). However, 80% of HSCR patients have short-segment Hirschsprung disease (S-HSCR), which has not been associated with genetic factors. We sought to identify mutations associated with S-HSCR, and used the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing system to determine how mutations affect ENCC function. METHODS: We created induced pluripotent stem cell (iPSC) lines from 1 patient with total colonic aganglionosis (with the G731del mutation in RET) and from 2 patients with S-HSCR (without a RET mutation), as well as RET+/- and RET-/- iPSCs. IMR90-iPSC cells were used as the control cell line. Migration and differentiation capacities of iPSC-derived ENCCs were analyzed in differentiation and migration assays. We searched for mutation(s) associated with S-HSCR by combining genetic and transcriptome data from patient blood- and iPSC-derived ENCCs, respectively. Mutations in the iPSCs were corrected using the CRISPR/Cas9 system. RESULTS: ENCCs derived from all iPSC lines, but not control iPSCs, had defects in migration and neuronal lineage differentiation. RET mutations were associated with differentiation and migration defects of ENCCs in vitro. Genetic and transcriptome analyses associated a mutation in the vinculin gene (VCL M209L) with S-HSCR. CRISPR/Cas9 correction of the RET G731del and VCL M209L mutations in iPSCs restored the differentiation and migration capacities of ENCCs. CONCLUSIONS: We identified mutations in VCL associated with S-HSCR. Correction of this mutation in iPSC using CRISPR/Cas9 editing, as well as the RET G731del mutation that causes Hirschsprung disease with total colonic aganglionosis, restored ENCC function. Our study demonstrates how human iPSCs can be used to identify disease-associated mutations and determine how they affect cell functions and contribute to pathogenesis.postprin

Hedgehog/notch-induced premature gliogenesis represents a new disease mechanism for Hirschsprung disease in mice and humans

Hirschsprung (HSCR) disease is a complex genetic disorder attributed to a failure of the enteric neural crest cells (ENCCs) to form ganglia in the hindgut. Hedgehog and Notch are implicated in mediating proliferation and differentiation of ENCCs. Nevertheless, how these signaling molecules may interact to mediate gut colonization by ENCCs and contribute to a primary etiology for HSCR are not known. Here, we report our pathway- based epistasis analysis of data generated by a genome-wide association study on HSCR disease, which indicates that specific genotype constellations of Patched (PTCH1) (which encodes a receptor for Hedgehog) and delta-like 3 (DLL3) (which encodes a receptor for Notch) SNPs confer higher risk to HSCR. Importantly, deletion of Ptch1 in mouse ENCCs induced robust Dll1 expression and activation of the Notch pathway, leading to premature gliogenesis and reduction of ENCC progenitors in mutant bowels. Dll1 integrated Hedgehog and Notch pathways to coordinate neuronal and glial cell differentiation during enteric nervous system development. In addition, Hedgehog-mediated gliogenesis was found to be highly conserved, such that Hedgehog was consistently able to promote gliogenesis of human neural crest-related precursors. Collectively, we defined PTCH1 and DLL3 as HSCR susceptibility genes and suggest that Hedgehog/Notch-induced premature gliogenesis may represent a new disease mechanism for HSCR.published_or_final_versio

Lack of association between nNOS -84G>A polymorphism and risk of infantile hypertrophic pyloric stenosis in a Chinese population

Background: Infantile hypertrophic pyloric stenosis (IHPS) is one of the most common gastrointestinal obstructions in the infancy requiring surgery. Reduced expression of neuronal nitric oxide synthase (nNOS), which plays an important role in the regulation of the human pyloric muscle, is thought to underlie IHPS. The role of nNOS in IHPS has been supported by the genetic association of a functional regulatory nNOS polymorphism (-84G>A) with IHPS in whites. We reasoned that the corroboration of this association in a population of different ethnic origin would prompt follow-up studies and further investigation of the IHPS pathology at molecular level. Thus, we attempted to reproduce the original findings in a Chinese population of comparable size in what would be the first genetic study on IHPS conducted in Chinese. Methods: nNOS -84G>A genotypes were analyzed in 56 patients and 86 controls by polymerase chain reaction and DNA sequencing. Logistic regression was used to compute odds ratios. Results: Our study could not corroborate the association previously reported. Although the frequency of the IHPS-associated allele (-84A) in controls (0.205) was similar to that reported for white controls, there was a dramatic difference in -84A frequencies between white and Chinese patients (0.198). Similarly, there was no difference in the nNOS -84G>A genotype distribution between patients and controls, even when the GA and AA genotypes were combined to compare GG genotype (odds ratio, 1.01; 95% confidence interval, 0.47-2.19). Conclusions: Failure to replicate the initial finding does not detract from its validity, because genetic effects may differ across populations. Differences across populations in linkage disequilibrium and/or allele frequencies may contribute to this lack of replication. The role nNOS in IHPS awaits further investigation. © 2010 Elsevier Inc. All rights reserved.postprin

Genome-wide copy number variation study in anorectal malformations

Anorectal malformations (ARMs, congenital obstruction of the anal opening) are among the most common birth defects requiring surgical treatment (2-5/10 000 live-births) and carry significant chronic morbidity. ARMs present either as isolated or as part of the phenotypic spectrum of some chromosomal abnormalities or monogenic syndromes. The etiology is unknown. To assess the genetic contribution to ARMs, we investigated single-nucleotide polymorphisms and copy number variations (CNVs) at genome-wide scale. A total of 363 Han Chinese sporadic ARM patients and 4006 Han Chinese controls were included. Overall, we detected a 1.3-fold significant excess of rare CNVs in patients. Stratification of patients by presence/absence of other congenital anomalies showed that while syndromic ARM patients carried significantly longer rare duplications than controls (P = 0.049), non-syndromic patients were enriched with both rare deletions and duplications when compared with controls (P = 0.00031). Twelve chromosomal aberrations and 114 rare CNVs were observed in patients but not in 868 controls nor 11 943 healthy individuals from the Database of Genomic Variants. Importantly, these aberrations were observed in isolated ARM patients. Gene-based analysis revealed 79 genes interfered by CNVs in patients only. In particular, we identified a de novo DKK4 duplication. DKK4 is a member of the WNT signaling pathway which is involved in the development of the anorectal region. In mice, Wnt disruption results in ARMs. Our data suggest a role for rare CNVs not only in syndromic but also in isolated ARM patients and provide a list of plausible candidate genes for the disorder.postprin

Differential effects of alpha-adrenoceptor agonists on relaxation in the mesenteric artery and aorta of the rat

Poster session 7: Adrenoceptors / Adrenergic Nerve : poster no. P7-

L-arginine and arginase products increase contractions to dexmedetomidine in the rat aorta with endothelium

Oral Presentation: Session 1 - Healthy Aging: no. 1.23The 15th Research Postgraduate Symposium (PRS 2010), the University of Hong Kong, Hong Kong, China, 1-2 December 2010

Effects of dexmedetomidine in the mesenteric artery and the aorta of endotoxin induced rat

pp. 51-77 of this journal issue contain abstracts of the 12th ICSM Annual Scientific Meeting 2008INTRODUCTION: Dexmedetomidine is an anesthetic agent, with known α2 adrenergic effects, used both in humans and in animals. The present experiments were designed to compare the vascular effects of dexmedetomidine in rat arteries during normal and septic conditions. METHODS: Ten weeks old male normal Sprague Dawley rats were used. The mesenteric arteries and thoracic aortae were dissected and suspended into 5 ml organ chambers for isometric tension recording. In some experiments, endotoxin from E-coli lipopolysaccharide (O55:B5) was injected 10 mg/kg intraperitoneally 2 or 24 hours before the start of experiments. RESULTS: In the mesenteric arteries, dexmedetomidine caused concentration-dependent relaxations (with a maximal response averaging 50%). It induced smaller relaxations in the rat aorta (maximal response averaging 10%). At concentrations above 100 nM, the relaxation was reverted to a concentration-dependent contraction in the mesenteric arteries. In the presence of L-NAME (a nitric oxide synthase inhibitor) and after the removal of the endothelium, the drug-induced relaxation was abolished in mesenteric arteries. The secondary contraction was reduced when prazosin (α1 adrenergic antagonist) was added to the bath solution. After endotoxin administration, the relaxations in mesenteric arteries were reduced to around 20% in both 2 and 24 hours treatment durations. Endotoxin did not affect the magnitude of the secondary contraction, which were still abolished in the presence of prazosin. CONCLUSIONS: The vascular effects of dexmedetomidine depend on the vascular bed studied. The vasodilatation caused by dexmedetomidine is nitric oxide and endothelium-dependent in the rat mesenteric artery. This relaxation can be reduced during sepsis, while α1 adrenoceptors are responsible for the secondary contraction at higher concentrations of dexmedetomidine.link_to_OA_fulltex

Effects of Dexmedetomidine in the Mesenteric Artery and the Aorta of the Rat

Poster presentations: Theme 3 - Public Health: no. 3.1