Hirschsprung's disease and variants in genes that regulate enteric neural crest cell proliferation, migration and differentiation

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.

Plasma exosomal miR-199a-3p downregulates cell proliferation and migration in Hirschsprung's disease by targeting mTOR

BACKGROUND

Plasma exosomal microRNAs have been suggested to be potential biomarkers of disease. However, the exosomal microRNAs in Hirschsprung's disease (HSCR) are still unclear. In this study, we analyzed the miRNA profiles of HSCR and elucidated the mechanism of the selected miR-199a-3p in the development of HSCR.

METHODS

Plasma exosomes were isolated, and exosomal miRNA high-throughput sequencing was performed to obtain differentially expressed miRNAs. CCK-8 and Transwell assay were used to determine the function of the most differentially expressed miRNA, which was confirmed in tissue specimen. Thereafter, target genes of the selected miRNAs were predicted by the databases. Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes Genomes (KEGG) analysis, and protein-protein interaction network (PPI) construction of possible target genes were used to perform enrichment analysis and interaction. Finally, the PCR, Western blot and recovery experiment were used to confirm the function of target gene, mammalian target of rapamycin (mTOR), in vitro.

RESULTS

The expression of miR-199a-3p was upregulated in plasma exosomes and diseased colonic tissues of patients with HSCR. In vitro, miR-199a-3p can inhibit cell proliferation and migration. Bioinformatic analysis suggested that mTOR might be a potential target of miR-199a-3p in HSCR. mTOR was discovered to be downregulated by miR-199a-3p in vitro. The negative connection between mTOR and miR-199a-3p was confirmed in tissue samples. mTOR can partially reverse the effect of miR-199a-3p on cell proliferation and migration function in vitro.

CONCLUSIONS

miR-199a-3p suppresses cell growth and motility, partially by targeting mTOR. Plasma exosomal miR-199a-3p, a diagnostic marker, is crucial for the development of HSCR.

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.

Gut innervation and enteric nervous system development: a spatial, temporal and molecular tour de force

During embryonic development, the gut is innervated by intrinsic (enteric) and extrinsic nerves. Focusing on mammalian ENS development, in this Review we highlight how important the different compartments of this innervation are to assure proper gut function. We specifically address the three-dimensional architecture of the innervation, paying special attention to the differences in development along the longitudinal and circumferential axes of the gut. We review recent information about the formation of both intrinsic innervation, which is fairly well-known, as well as the establishment of the extrinsic innervation, which, despite its importance in gut-brain signaling, has received much less attention. We further discuss how external microbial and nutritional cues or neuroimmune interactions may influence development of gut innervation. Finally, we provide summary tables, describing the location and function of several well-known molecules, along with some newer factors that have more recently been implicated in the development of gut innervation.

MiR-195-5p inhibits proliferation and invasion of nerve cells in Hirschsprung disease by targeting GFRA4

Studies have reported that miR-195-5p plays a role in the Hirschsprung disease (HSCR). Our previous work found GDNF family receptor alpha 4 (GFRA4) is also associated with HSCR. In this study, we focused on whether miR-195-5p induces the absence of enteric neurons and enteric neural crest in HSCR by regulating GFRA4. The expression levels of GFRA4 and miR-195-5p in colon tissues were evaluated by real-time PCR (RT-PCR) assay. We overexpressed GFRA4 or miR-195-5p in SH-SY5Y cells, the cell proliferation, cell cycle, apoptosis and invasion were subsequently investigated by CCK-8 assay, EdU staining, Flow cytometry analysis and Transwell assay, respectively. We also established the xenograft model to detect the effect of miR-195-5p on tumor growth and GFRA4 and p-RET expressions. GFRA4 expression was significantly downregulated in the HSCR colon tissues when compared with that in the control tissues. Overexpression of GFRA4 significantly promoted proliferation, invasion and cell cycle arrest, and inhibited apoptosis of SH-SY5Y cells. We also proved that GFRA4 is a direct target of miR-195-5p, and miR-195-5p inhibited proliferation, invasion, cell cycle arrest and differentiation, and accelerated apoptosis in SH-SY5Y cells which can be reversed by GFRA4 overexpression. Furthermore, we demonstrated that miR-195-5p suppressed tumor growth, and observably decreased GFRA4 and p-RET expressions. Our findings suggest that miR-195-5p plays an important role in the pathogenesis of HSCR. MiR-195-5p inhibited proliferation, invasion and cell cycle arrest, and accelerated apoptosis of nerve cells by targeting GFRA4.

Sox10 Is a Specific Biomarker for Neural Crest Stem Cells in Immunohistochemical Staining in Wistar Rats

Objective

Neural crest stem cells (NCSCs) are prototypically migratory cells immigrating from the dorsal neural tube to specific embryonic sites where they generate a variety of cell types. A lot of biomarkers for NCSCs have been identified. However, which biomarkers are the most specific is still unclear.

Methods

The rat embryos harvested in embryonic day 9 (E9), E9.5, E10, E10.5, E11, E12, E13, and E14 were paraffin-embedded and sectioned in transverse. NCSCs were spatiotemporally demonstrated by immunohistochemical staining with RET, p75NTR, Pax7, and Sox10. NCSCs were isolated, cultured, and stained with RET, p75NTR, Pax7, and Sox10.

Results

In the paraffin sections of rat embryos, the immunohistochemical staining of RET, p75NTR, and Sox10 can all be used in demonstrating NCSCs. Sox10 was positive mainly in NCSCs while RET and p75NTR were positive not only in NCSCs but also in other tissue cells. In primary culture cells, Sox10 was mainly in the nucleus of NCSCs, RET was mainly in the membrane, and p75NTR was positive in cytoplasm and membrane.

Conclusions

Sox10 is the specific marker for immunohistochemical staining of NCSCs in paraffin sections. In cultured cells, Sox10, p75NTR, and RET presented a similar staining effect.

Downregulation of miR-140-5p affects the pathogenesis of HSCR by targeting EGR2

BACKGROUND/AIMS

Hirschsprung's disease (HSCR) is the most common digestive disease caused by disorders of neural crest development. Despite the known involvement of miR-140-5p in many human diseases, its biological role in Hirschsprung's disease (HSCR) remains undefined. In this study, we sought to reveal the roles of miR-140-5p in the pathogenesis of HSCR.

METHODS

Quantitative real-time PCR and western blotting were used to measure the relative expression levels of miRNAs, mRNAs, and proteins in stenotic and dilated sections of the colon of 32 HSCR patients. Targets and proteins were evaluated by western blotting, and Transwell, CCK-8, and flow cytometry assays were adopted to detect the functional effects of miR-140-5p on SH-SY5Y cells.

RESULTS

miR-140-5p was significantly downregulated in HSCR tissue samples with increased expression of EGR2, and knockdown of miR-140-5p inhibited cell migration and proliferation and promoted apoptosis in SH-SY5Y cell lines. EGR2 expression was inversely correlated with that of miR-140-5p in cell lines.

CONCLUSIONS

miR-140-5p may influence the pathogenesis of HSCR by targeting EGR2.

Reconstruction of the Global Neural Crest Gene Regulatory Network In Vivo

Precise control of developmental processes is encoded in the genome in the form of gene regulatory networks (GRNs). Such multi-factorial systems are difficult to decode in vertebrates owing to their complex gene hierarchies and dynamic molecular interactions. Here we present a genome-wide in vivo reconstruction of the GRN underlying development of the multipotent neural crest (NC) embryonic cell population. By coupling NC-specific epigenomic and transcriptional profiling at population and single-cell levels with genome/epigenome engineering in vivo, we identify multiple regulatory layers governing NC ontogeny, including NC-specific enhancers and super-enhancers, novel trans-factors, and cis-signatures allowing reverse engineering of the NC-GRN at unprecedented resolution. Furthermore, identification and dissection of divergent upstream combinatorial regulatory codes has afforded new insights into opposing gene circuits that define canonical and neural NC fates early during NC ontogeny. Our integrated approach, allowing dissection of cell-type-specific regulatory circuits in vivo, has broad implications for GRN discovery and investigation.

Increased miR-214 expression suppresses cell migration and proliferation in Hirschsprung disease by interacting with PLAGL2

BACKGROUND

The miR-214 has been reported to be associated with various diseases, but its involvement in the pathophysiology of Hirschsprung disease (HSCR) is almost completely unexplored.

METHODS

In our study, we conducted a series of experiments to unravel the biological role of miR-214 in the pathophysiology of HSCR. qRT-PCR and western blotting were utilized to investigate the relative expression levels of miR-214, mRNAs, and proteins of related genes in colon tissues from 20 controls without HSCR and 24 patients with HSCR. The potential biological role of miR-214 in two cell lines (SKN-SH and SH-SY5Y) was assessed using the CCK8 assay, EdU staining, transwell assay, and flow cytometry. The dual-luciferase reporter assay was used to confirm PLAGL2 as a common target gene of miR-214.

RESULTS

All results suggested that miR-214 is upregulated in HSCR tissue samples compared with controls. Additionally, we found that miR-214 could inhibit cell proliferation and migration by directly downregulating the expression of PLAGL2, and the extent of the miR-214-mediated inhibitory effects could be rescued by a PLAGL2 overexpression plasmid.

CONCLUSION

Our results revealed that miR-214 is indeed involved in the pathophysiology of HSCR and suppresses cell proliferation and migration by directly downregulating PLAGL2 in cell models.

Altered Expression of Phox2 Transcription Factors in the Locus Coeruleus in Major Depressive Disorder Mimicked by Chronic Stress and Corticosterone Treatment In Vivo and In Vitro

Phox2a and Phox2b are two homeodomain transcription factors playing a pivotal role in the development of noradrenergic neurons during the embryonic period. However, their expression and function in adulthood remain to be elucidated. Using human postmortem brain tissues, rat stress models and cultured cells, this study aimed to examine the alteration of Phox2a and Phox2b expression. The results show that Phox2a and Phox2b are normally expressed in the human locus coeruleus (LC) in adulthood. Furthermore, the levels of Phox2a protein and mRNA and protein levels of Phox2b were significantly elevated in the LC of brain donors that suffered from the major depressive disorder, as compared to age-matched and psychiatrically normal control donors. Fischer 344 rats subjected to chronic social defeat showed higher mRNA and protein levels of Phox2a and Phox2b in the LC, as compared to non-stressed control rats. In rats chronically administered oral corticosterone, mRNA and protein levels of Phox2b, but not Phox2a, in the LC were significantly increased. In addition, the corticosterone-induced increase in Phox2b protein was reversed by simultaneous treatment with either mifepristone or spironolactone. Exposing SH-SY5Y cells to corticosterone significantly increased expression of Phox2a and Phox2b, which was blocked by corticosteroid receptor antagonists. Taken together, these experiments reveal that Phox2 genes are expressed throughout the lifetime in the LC of humans and Fischer 344 rats. Alterations in their expression may play a role in major depressive disorder and possibly other stress-related disorders through their modulatory effects on the noradrenergic phenotype.

Modifying impact of RET gene haplotypes on medullary thyroid carcinoma clinical course

The clinical course of medullary thyroid carcinoma (MTC) associated with the MEN2A syndrome as well as of sporadic MTC shows considerable heterogeneity. The disease picture varies not only between the same RET proto-oncogene mutation carriers but also among sporadic MTC patients with no RET germinal mutations, which suggests the involvement of additional modulators of the disease. However, genetic factors responsible for this heterogeneity of the MTC clinical course still remain unknown. The aim of this study was to determine if polymorphic variants or specific haplotypes of the RET gene may modify the MTC clinical course. We genotyped the following loci: c.73+9277T>C, c.135G>A, c.1296A>G, c.2071G>A, c.2307T>C, c.2508C>T and c.2712C>G in 142 MTC patients and controls. We demonstrated considerable differences in the genotypes distribution within c.73+9277T>C, c.135G>A and c.2307T>C loci Our results show that the c.73+9277T variant associated with a decreased activity of the MCS+9.7 RET enhancer is rare in hereditary MTC patients with primary hyperparathyroidism, and thus, may influence the MTC clinical picture. The decreased activity of the RET promoter enhancer reduces RET expression level and may counterbalance the activating mutation in this gene. Frequent co-occurrence of the c.73+9277T allele with p.E768D, p.Y791F, p.V804M or p.R844Q RET mutations may be associated with their attenuation and milder clinical picture of the disease. Haplotypes analysis showed that C-G-A-G-T-(C)-C (c.73+9277T>C - c.135G>A - c.1296A>G - c.2071G>A - c.2307T>G - (c.2508C>T) - c.2712C>G) alleles combination predisposes to pheochromocytomas and primary hyperparathyroidism. We consider that RET haplotypes defining may become an auxiliary diagnostic tool in MTC patients.

Demethylation of GFRA4 Promotes Cell Proliferation and Invasion in Hirschsprung Disease

Hirschsprung disease (HSCR) is congenital intestinal aganglionosis attributed to a failure to migrate and survive of neural crest-derived cells. Glial cell-derived neurotrophic factor alpha 4 (GFRA4) is expressed in the derivatives of the neural crest in the enteric nervous system, but whether it is related with HSCR still remains unclear. This study was designed to investigate its role and epigenetic mechanisms in HSCR in vitro. The expression of GFRA4 mRNA in HSCR tissues was determined using quantitative real-time PCR analysis. In this study, we found that GFRA4 expression was significantly reduced in HSCR tissues and cells through GFRA4 methylation by quantitative real-time PCR analysis, methylation-specific PCR, and bisulfite sequencing PCR. DNA methyltransferase inhibitor, 5-AzaC, concomitantly upregulated the protein levels of GFRA4, as well as DNA methyltransferase1 (DNMT1) and DNMT2 in SH-5YSY cells. Moreover, we found upregulated GFRA4 significantly promoted cell proliferation, cell cycle progression and invasion, but inhibited apoptosis in SH-5YSY cells, whereas GFRA4 knockdown caused the opposite effects in SH-5YSY cells by CCK-8, 5-ethynyl-2'-deoxyuridine (EdU), flow cytometry, and Transwell assays. In conclusion, our results support that aberrant CpG hypermethylation at least partly accounts for GFRA4 silencing in HSCR, which impairs its protective role in enteric nervous system.

Preliminary identification of key miRNAs, signaling pathways, and genes associated with Hirschsprung's disease by analysis of tissue microRNA expression profiles

BACKGROUND

Hirschsprung's disease (HSCR) is a congenital gut motility disorder of infants, and if left untreated, it is fatal to the affected infants. This study aimed to identify key microRNAs (miRNAs), signaling pathways and genes involved in the pathogenesis of HSCR.

METHODS

The miRNA microarray dataset GSE77296 was downloaded. Nine colon tissue samples were available: six from HSCR patients and three matched control samples. Differentially expressed miRNAs (DEMs) were identified after data preprocessing. Target genes of the selected upregulated and downregulated DEMs were predicted. In addition, functional enrichment analyses for the selected DEMs and target genes were conducted. Finally, interaction networks between the DEMs and target genes were constructed.

RESULTS

A total of 162 DEMs (73 upregulated and 89 downregulated) were obtained. A total of 2511 DEM-target gene pairs for the 40 selected DEMs were identified, including 1645 pairs for the upregulated DEMs and 866 pairs for the downregulated DEMs. The upregulated DEM miR-141-3p and down-regulated DEM miR-30a-3p were identified as key miRNAs by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and network analyses. Besides, KEGG pathway enrichment analysis revealed that pathways in cancer and the mitogen-activated protein kinase (MAPK) signaling pathway were key pathways. The key genes frizzled class receptor 3 (FZD3) and docking protein 6 (DOK6) were obtained through the DEM-target gene interaction networks.

CONCLUSION

Two key miRNAs (miR-141-3p and miR-30a-3p), the MAPK signaling pathway and two key genes (FZD3 and DOK6) were implicated in the pathogenesis of HSCR.

Atg7-Mediated Autophagy Is Involved in the Neural Crest Cell Generation in Chick Embryo

Autophagy plays a very important role in numerous physiological and pathological events. However, it still remains unclear whether Atg7-induced autophagy is involved in the regulation of neural crest cell production. In this study, we found the co-location of Atg7 and Pax7⁺ neural crest cells in early chick embryo development. Upregulation of Atg7 with unilateral transfection of full-length Atg7 increased Pax7⁺ and HNK-1⁺ cephalic and trunk neural crest cell numbers compared to either Control-GFP transfection or opposite neural tubes, suggesting that Atg7 over-expression in neural tubes could enhance the production of neural crest cells. BMP4 in situ hybridization and p-Smad1/5/8 immunofluorescent staining demonstrated that upregulation of Atg7 in neural tubes suppressed the BMP4/Smad signaling, which is considered to promote the delamination of neural crest cells. Interestingly, upregulation of Atg7 in neural tubes could significantly accelerate cell progression into the S phase, implying that Atg7 modulates cell cycle progression. However, β-catenin expression was not significantly altered. Finally, we demonstrated that upregulation of the Atg7 gene could activate autophagy as did Atg8. We have also observed that similar phenotypes, such as more HNK-1⁺ neural crest cells in the unilateral Atg8 transfection side of neural tubes, and the transfection with full-length Atg8-GFP certainly promote the numbers of BrdU⁺ neural crest cells in comparison to the GFP control. Taken together, we reveal that Atg7-induced autophagy is involved in regulating the production of neural crest cells in early chick embryos through the modification of the cell cycle.

Hirschsprung's disease: clinical dysmorphology, genes, micro-RNAs, and future perspectives

On the occasion of the 100th anniversary of Dr. Harald Hirschsprung's death, there is a worldwide significant research effort toward identifying and understanding the role of genes and biochemical pathways involved in the pathogenesis as well as the use of new therapies for the disease harboring his name (Hirschsprung disease, HSCR). HSCR (aganglionic megacolon) is a frequent diagnostic and clinical challenge in perinatology and pediatric surgery, and a major cause of neonatal intestinal obstruction. HSCR is characterized by the absence of ganglia of the enteric nervous system, mostly in the distal gastrointestinal tract. This review focuses on current understanding of genes and pathways associated with HSCR and summarizes recent knowledge related to micro RNAs (miRNAs) and HSCR pathogenesis. While commonly sporadic, Mendelian patterns of inheritance have been described in syndromic cases with HSCR. Although only half of the patients with HSCR have mutations in specific genes related to early embryonic development, recent pathway-based analysis suggests that gene modules with common functions may be associated with HSCR in different populations. This comprehensive profile of functional gene modules may serve as a useful resource for future developmental, biochemical, and genetic studies providing insights into the complex nature of HSCR.

Exome-Wide Association Study Identified New Risk Loci for Hirschsprung's Disease

Hirschsprung disease (HSCR) is a rare congenital disease caused by impaired proliferation and migration of neural crest cells. In this study, we aimed to investigate the genetic loci involved in the pathogenesis of HSCR. The exome-wide scan was performed to screen the genetic variants with minor allele frequency (MAF) < 0.05 in exonic regions. Candidate mutation type and the wild type were overexpressed to investigate the affection on cell proliferation and migration. We found that ten variants were associated with HSCR at P < 10^-4 in the single-variant analysis while ten genes were also associated with HSCR at P < 10^-4 in the optimized sequence kernel association test (SKAT-O) test analysis. Among these SNPs, the missense variants catechol-O-methyltransferase (COMT) (rs6267) and armadillo repeat gene deleted in velocardiofacial syndrome (ARVCF) (rs80068543) indicated an ectopic expression in colon tissues of HSCR patients. The Ala72Ser variant in COMT induced proliferation suppression through NOTCH signal pathway, while the ARVCF affected cell migration via the downregulating of RHOA and ROC. In conclusion, this exome array study identified the COMT and ARVCF missense coding variants as candidate loci for HSCR. The finding implies the abnormal variant of COMT and ARVCF may account for the pathogenesis of HSCR.

Long none coding RNA HOTTIP/HOXA13 act as synergistic role by decreasing cell migration and proliferation in Hirschsprung disease

Long noncoding RNAs (lncRNAs) have been confirmed to be associated with various human diseases. However, whether they are associated with Hirschsprung disease (HSCR) progression remains unclear. In this study, we designed the experiment to explore the relationship between lncRNA HOTTIP and HOXA13, and their pathogenicity to HSCR. Quantitative real-time PCR and Western blot were performed to detect the levels of lncRNA, mRNAs, and proteins in colon tissues from 79 patients with HSCR and 79 controls. Small RNA interference transfection was used to study the function experiments in human 293T and SK-N-BE cell lines. The cell viability and activities were detected by the transwell assays, CCK8 assay, and flow cytometry, respectively. LncRNA HOTTIP and HOXA13 were significantly down-regulated in HSCR compared to the controls. Meanwhile, the declined extent of their expression levels makes sense between two main phenotype of HSCR. SiRNA-mediated knock-down of HOTTIP or HOXA13 correlated with decreased levels of each other and both reduced the cell migration and proliferation without affecting cell apoptosis or cell cycle. Our study demonstrates that aberrant reduction of HOTTIP and HOXA13, which have a bidirectional regulatory loop, may play an important role in the pathogenesis of HSCR.

Laboratory procedures update on Hirschsprung disease

OBJECTIVES

The detection of ganglion cells in rectal biopsies of infants or toddlers with severe constipation is routinely performed by pediatric pathologists in many institutions. Hirschsprung disease (HD) is defined by the lack of ganglion cells (aganglionosis). The early recognition and the prompt implementation of surgical procedures obviously protect infants affected with HD from potential life-threatening conditions, including enterocolitis and debilitating constipation. Image-based and non-image-based clinical techniques and some laboratory tests have been reevaluated along the years, but often fragmentarily. Immunohistochemical markers have been increasingly used in pathology laboratories to detect ganglion cells and nerve fibers. Recently, calretinin, a vitamin D-dependent calcium-binding protein with expression in ganglion cells and nerves, has been described as an adjunctive or primary diagnostic test in HD. The aim of the present study was to systematically summarize and update laboratory procedures targeting ganglion cells in rectal biopsies.

METHODS

Procedures and tests have been reviewed and values of specificity and sensitivity have been calculated according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Contrast enema has the lowest sensitivity and specificity of all of the 3-index investigations under the lens: contrast enema, anorectal manometry, and biopsy with histology. The latter procedure seems to have the highest sensitivity and specificity. Acetylcholinesterase staining on fresh-frozen material has been found to have slightly higher rates of sensitivity and specificity when compared with hematoxylin and eosin only. Calretinin staining may be supportive for the diagnosis, although some cases with false-positivity may be of some concern.

CONCLUSIONS

Hematoxylin and eosin with or without acetylcholinesterase remains the criterion standard according to our PRISMA-based data. In our opinion, the number of false-positive results with potential overtreatment may limit the increasing advocacy for calretinin staining. Both the "primum non nocere" dictum and the "loss aversion heuristic" need to be satisfied harmoniously by preventing harm from unnecessary surgery.

Generalized functional linear models for gene-based case-control association studies

By using functional data analysis techniques, we developed generalized functional linear models for testing association between a dichotomous trait and multiple genetic variants in a genetic region while adjusting for covariates. Both fixed and mixed effect models are developed and compared. Extensive simulations show that Rao's efficient score tests of the fixed effect models are very conservative since they generate lower type I errors than nominal levels, and global tests of the mixed effect models generate accurate type I errors. Furthermore, we found that the Rao's efficient score test statistics of the fixed effect models have higher power than the sequence kernel association test (SKAT) and its optimal unified version (SKAT-O) in most cases when the causal variants are both rare and common. When the causal variants are all rare (i.e., minor allele frequencies less than 0.03), the Rao's efficient score test statistics and the global tests have similar or slightly lower power than SKAT and SKAT-O. In practice, it is not known whether rare variants or common variants in a gene region are disease related. All we can assume is that a combination of rare and common variants influences disease susceptibility. Thus, the improved performance of our models when the causal variants are both rare and common shows that the proposed models can be very useful in dissecting complex traits. We compare the performance of our methods with SKAT and SKAT-O on real neural tube defects and Hirschsprung's disease datasets. The Rao's efficient score test statistics and the global tests are more sensitive than SKAT and SKAT-O in the real data analysis. Our methods can be used in either gene-disease genome-wide/exome-wide association studies or candidate gene analyses.

Enteric nervous system development: migration, differentiation, and disease

The enteric nervous system (ENS) provides the intrinsic innervation of the bowel and is the most neurochemically diverse branch of the peripheral nervous system, consisting of two layers of ganglia and fibers encircling the gastrointestinal tract. The ENS is vital for life and is capable of autonomous regulation of motility and secretion. Developmental studies in model organisms and genetic studies of the most common congenital disease of the ENS, Hirschsprung disease, have provided a detailed understanding of ENS development. The ENS originates in the neural crest, mostly from the vagal levels of the neuraxis, which invades, proliferates, and migrates within the intestinal wall until the entire bowel is colonized with enteric neural crest-derived cells (ENCDCs). After initial migration, the ENS develops further by responding to guidance factors and morphogens that pattern the bowel concentrically, differentiating into glia and neuronal subtypes and wiring together to form a functional nervous system. Molecules controlling this process, including glial cell line-derived neurotrophic factor and its receptor RET, endothelin (ET)-3 and its receptor endothelin receptor type B, and transcription factors such as SOX10 and PHOX2B, are required for ENS development in humans. Important areas of active investigation include mechanisms that guide ENCDC migration, the role and signals downstream of endothelin receptor type B, and control of differentiation, neurochemical coding, and axonal targeting. Recent work also focuses on disease treatment by exploring the natural role of ENS stem cells and investigating potential therapeutic uses. Disease prevention may also be possible by modifying the fetal microenvironment to reduce the penetrance of Hirschsprung disease-causing mutations.

Development and developmental disorders of the enteric nervous system

The enteric nervous system (ENS) arises from neural crest-derived cells that migrate into and along the gut, leading to the formation of a complex network of neurons and glial cells that regulates motility, secretion and blood flow. This Review summarizes the progress made in the past 5 years in our understanding of ENS development, including the migratory pathways of neural crest-derived cells as they colonize the gut. The importance of interactions between neural crest-derived cells, between signalling pathways and between developmental processes (such as proliferation and migration) in ensuring the correct development of the ENS is also presented. The signalling pathways involved in ENS development that were determined using animal models are also described, as is the evidence for the involvement of the genes encoding these molecules in Hirschsprung disease-the best characterized paediatric enteric neuropathy. Finally, the aetiology and treatment of Hirschsprung disease in the clinic and the potential involvement of defects in ENS development in other paediatric motility disorders are outlined.

Chromosomal and related Mendelian syndromes associated with Hirschsprung's disease

Hirschsprung's disease (HSCR) is a fairly frequent cause of intestinal obstruction in children. It is characterized as a sex-linked heterogonous disorder with variable severity and incomplete penetrance giving rise to a variable pattern of inheritance. Although Hirschsprung's disease occurs as an isolated phenotype in at least 70% of cases, it is not infrequently associated with a number of congenital abnormalities and associated syndromes, demonstrating a spectrum of congenital anomalies. Certain of these syndromic phenotypes have been linked to distinct genetic sites, indicating underlying genetic associations of the disease and probable gene-gene interaction, in its pathogenesis. These associations with HSCR include Down's syndrome and other chromosomal anomalies, Waardenburg syndrome and other Dominant sensorineural deafness, the Congenital Central Hypoventilation and Mowat-Wilson and other brain-related syndromes, as well as the MEN2 and other tumour associations. A number of other autosomal recessive syndromes include the Shah-Waardenburg, the Bardet-Biedl and Cartilage-hair hypoplasia, Goldberg-Shprintzen syndromes and other syndromes related to cholesterol and fat metabolism among others. The genetics of Hirschsprung's disease are highly complex with the majority of known genetic sites relating to the main susceptibility pathways (RET an EDNRB). Non-syndromic non-familial, short-segment HSCR appears to represent a non-Mendelian condition with variable expression and sex-dependent penetrance. Syndromic and familial forms, on the other hand, have complex patterns of inheritance and being reported as autosomal dominant, recessive and polygenic patterns of inheritance. The phenotypic variability and incomplete penetrance observed in Hirschsprung's disease could also be explained by the involvement of modifier genes, especially in its syndromic forms. In this review, we look at the chromosomal and Mendelian associations and their underlying signalling pathways, to obtain a better understanding of the pathogenetic mechanisms involved in developing aganglionosis of the distal bowel.