Congenital central hypoventilation syndrome (CCHS) is a rare neurocristopathy characterized by absence of adequate autonomic control of respiration with decreased sensitivity to hypoxia and ...hypercapnia. Frameshift mutations and polyalanine triplet expansions in the coding region of PHOX2B have been identified in the vast majority of CCHS patients and a correlation between length of the expanded region and severity of CCHS has been reported. In this work, we have undertaken in vitro analyses aimed at identifying the pathogenetic mechanisms which underlie the effects of PHOX2B mutations in CCHS. According to the known role of this gene, a transcription factor expressed during autonomic nervous system development, we have tested the transcriptional activity of WT and mutant PHOX2B expression constructs on the regulatory regions of two target genes, DβH and PHOX2A. We observed that the two sets of mutations play different roles in the transcriptional regulation of these genes, showing a correlation between the length of polyalanine expansions and the severity of reduced transcriptional activity. In particular, although reduced transactivation due to polyalanine expansions may be caused by retention of the mutated protein in the cytoplasm or in the nuclear aggregates, frameshift mutations did not impair the PHOX2B nuclear income, suggesting a different mechanism through which they would exert the observed effects on target promoters. Moreover, the frameshift due to deletion of a cytosine residue seems to cause sequestration of the corresponding mutant PHOX2B in the nucleolar compartment.
Heterozygous polyalanine repeat expansions of PHOX2B have been associated with Congenital Central Hypoventilation Syndrome, a rare neurocristopathy characterized by absence of adequate control of ...respiration during sleep. Here we report a PHOX2B mutational screening in 63 CCHS patients, 58 of whom presenting with poly-A expansions or frameshift, missense and nonsense mutations. To assess a somatic or germline occurrence of poly-A length variations, the relative amounts of mutant and wild type alleles have been quantified in 20 selected CCHS patients presenting with an expansion, and in their parents. Somatic mosaicism was shown in four parents, while no mosaic was found among CCHS patients. Moreover, while co-segregation analysis of the PHOX2B poly-A expansions with selected marker alleles in the same 20 CCHS trios has not demonstrated any parent-of-origin effect of the mutations, it has provided further clues to clarify the molecular mechanism underlying the expansion occurrence. Finally, the segregation of PHOX2B poly-A anomalous tracts within family members has allowed us to exclude tendency of polymorphic variations towards expansion. This strengthens the notion that expanded polyalanine tracts, identified as frequent disease-causing mutations also in other human diseases, are mitotically and meiotically stable. Published 2007 Wiley-Liss, Inc.
Hirschsprung disease (HSCR) is a rare congenital anomaly characterized by the absence of enteric ganglia in the distal intestinal tract. While classified as a multigenic disorder, the altered ...function of the RET tyrosine kinase receptor is responsible for the majority of the pathogenesis of HSCR. Recent evidence demonstrate a strong association between RET and the homeostasis of immune system. Here, we utilize a unique cohort of fifty HSCR patients to fully characterize the expression of RET receptor on both innate (monocytes and Natural Killer lymphocytes) and adaptive (B and T lymphocytes) human peripheral blood mononuclear cells (PBMCs) and to explore the role of RET signaling in the immune system. We show that the increased expression of RET receptor on immune cell subsets from HSCR individuals correlates with the presence of loss-of-function RET mutations. Moreover, we demonstrate that the engagement of RET on PBMCs induces the modulation of several inflammatory genes. In particular, RET stimulation with glial-cell line derived neurotrophic factor family (GDNF) and glycosyl-phosphatidylinositol membrane anchored co-receptor α1 (GFRα1) trigger the up-modulation of genes encoding either for chemokines (CCL20, CCL2, CCL3, CCL4, CCL7, CXCL1) and cytokines (IL-1β, IL-6 and IL-8) and the down-regulation of chemokine/cytokine receptors (CCR2 and IL8-Rα). Although at different levels, the modulation of these "RET-dependent genes" occurs in both healthy donors and HSCR patients. We also describe another set of genes that, independently from RET stimulation, are differently regulated in healthy donors versus HSCR patients. Among these "RET-independent genes", there are CSF-1R, IL1-R1, IL1-R2 and TGFβ-1, whose levels of transcripts were lower in HSCR patients compared to healthy donors, thus suggesting aberrancies of inflammatory responses at mucosal level. Overall our results demonstrate that immune system actively participates in the physiopathology of HSCR disease by modulating inflammatory programs that are either dependent or independent from RET signaling.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Marta Rusmini: Laboratory of Molecular Genetics, IRCCS, Giannina Gaslini Istitute, Genoa, Italy, Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, ...Italy Ivana Matera: Laboratory of Molecular Genetics, IRCCS, Giannina Gaslini Istitute, Genoa, Italy, Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy Roberto Ravazzolo: Laboratory of Molecular Genetics, IRCCS, Giannina Gaslini Istitute, Genoa, Italy, DINOGMI Department, University of Genova, Genova, Italy Citation: Rusmini M, Griseri P, Lantieri F, Matera I, Hudspeth KL, Roberto A, et al. (2013) Correction: Induction of RET Dependent and Independent Pro-Inflammatory Programs in Human Peripheral Blood Mononuclear Cells from Hirschsprung Patients.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary
Expression profile analysis clusters Gpnmb with known pigment genes, Tyrp1, Dct, and Si. During development, Gpnmb is expressed in a pattern similar to Mitf, Dct and Si with expression vastly ...reduced in Mitf mutant animals. Unlike Dct and Si, Gpnmb remains expressed in a discrete population of caudal melanoblasts in Sox10‐deficient embryos. To understand the transcriptional regulation of Gpnmb we performed a whole genome annotation of 2,460,048 consensus MITF binding sites, and cross‐referenced this with evolutionarily conserved genomic sequences at the GPNMB locus. One conserved element, GPNMB‐MCS3, contained two MITF consensus sites, significantly increased luciferase activity in melanocytes and was sufficient to drive expression in melanoblasts in vivo. Deletion of the 5′‐most MITF consensus site dramatically reduced enhancer activity indicating a significant role for this site in Gpnmb transcriptional regulation. Future analysis of the Gpnmb locus will provide insight into the transcriptional regulation of melanocytes, and Gpnmb expression can be used as a marker for analyzing melanocyte development and disease progression.
Neuroblastoma (NB) is a childhood malignancy originating from neural crest cells, which seldom occurs in association with other neurocristopathies. Owing to the rarity of familial NB cases, only a ...few linkage data are available and no mutations in candidate genes have been demonstrated up till now. Germline mutations in a small proportion of NB patients have been recently reported in the paired-like homeobox 2B (PHOX2B) gene, suggesting its role in NB predisposition. On the basis of this indication, we screened three Italian families with recurrence of NB and one family with occurrence of ganglioneuroblastoma and isolated Hirschsprung disease for PHOX2B defects. Our analysis did not show any mutation, excluding PHOX2B as the NB susceptibility gene in the families we analysed. Our findings combined with those derived from other PHOX2B mutation screenings and from genome-wide linkage analysis support a remarkable genetic heterogeneity of NB and suggest an oligogenic model of disease transmission. Furthermore, as PHOX2B mutations were mainly observed in some NB families with multifocal and syndromic NB, features that are missing in the families we have studied, we suggest they represent second-site modifications responsible for a specific phenotype rather than causal mutations of a major locus.
Variants in the ACTG2 gene, encoding a protein crucial for correct enteric muscle contraction, have been found in patients affected with chronic intestinal pseudo‐obstruction, either congenital or ...late‐onset visceral myopathy, and megacystis‐microcolon‐intestinal hypoperistalsis syndrome. Here we report about ten pediatric and one adult patients, from nine families, carrying ACTG2 variants: four show novel still unpublished missense variants, including one that is apparently transmitted according to a recessive mode of inheritance. Four of the remaining five probands carry variants affecting arginine residues, that have already been associated with a severe phenotype. A de novo occurrence of the variants could be confirmed in six of these families. Since a genotype–phenotype correlation is affected by extrinsic factors, such as, diagnosis delay, quality of clinical management, and intra‐familial variability, we have undertaken 3D molecular modeling to get further insights into the effects of the variants here described. The present findings and further ACTG2 testing of patients presenting with intestinal pseudo‐obstruction, will improve our understanding of visceral myopathies, including implications in the prognosis and genetic counseling of this set of severe disorders.
Chronic Intestinal Pseudo‐Obstruction (CIPO):
wide phenotypic spectrum of severity
Different ACTG2 variants
AD or AR inheritance
Transmitted or de novo
Abnormal gut motility is a feature of several mitochondrial encephalomyopathies, and mutations in genes such as TYMP and POLG, have been linked to these rare diseases. The human genome encodes three ...DNA ligases, of which only one, ligase III (LIG3), has a mitochondrial splice variant and is crucial for mitochondrial health. We investigated the effect of reduced LIG3 activity and resulting mitochondrial dysfunction in seven patients from three independent families, who showed the common occurrence of gut dysmotility and neurological manifestations reminiscent of mitochondrial neurogastrointestinal encephalomyopathy. DNA from these patients was subjected to whole exome sequencing. In all patients, compound heterozygous variants in a new disease gene, LIG3, were identified. All variants were predicted to have a damaging effect on the protein. The LIG3 gene encodes the only mitochondrial DNA (mtDNA) ligase and therefore plays a pivotal role in mtDNA repair and replication. In vitro assays in patient-derived cells showed a decrease in LIG3 protein levels and ligase activity. We demonstrated that the LIG3 gene defects affect mtDNA maintenance, leading to mtDNA depletion without the accumulation of multiple deletions as observed in other mitochondrial disorders. This mitochondrial dysfunction is likely to cause the phenotypes observed in these patients. The most prominent and consistent clinical signs were severe gut dysmotility and neurological abnormalities, including leukoencephalopathy, epilepsy, migraine, stroke-like episodes, and neurogenic bladder. A decrease in the number of myenteric neurons, and increased fibrosis and elastin levels were the most prominent changes in the gut. Cytochrome c oxidase (COX) deficient fibres in skeletal muscle were also observed. Disruption of lig3 in zebrafish reproduced the brain alterations and impaired gut transit in vivo. In conclusion, we identified variants in the LIG3 gene that result in a mitochondrial disease characterized by predominant gut dysmotility, encephalopathy, and neuromuscular abnormalities. Bonora et al. identify a new mitochondrial recessive disorder caused by biallelic variants in the LIG3 gene encoding DNA ligase III, which is responsible for mitochondrial DNA repair. Clinical signs include gut dysmotility and neurological features such as leucoencephalopathy, epilepsy and stroke-like episodes.
Genetics of enteric neuropathies Brosens, Erwin; Burns, Alan J.; Brooks, Alice S. ...
Developmental biology,
09/2016, Letnik:
417, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abnormal development or disturbed functioning of the enteric nervous system (ENS), the intrinsic innervation of the gastrointestinal tract, is associated with the development of neuropathic ...gastrointestinal motility disorders. Here, we review the underlying molecular basis of these disorders and hypothesize that many of them have a common defective biological mechanism. Genetic burden and environmental components affecting this common mechanism are ultimately responsible for disease severity and symptom heterogeneity. We believe that they act together as the fulcrum in a seesaw balanced with harmful and protective factors, and are responsible for a continuum of symptoms ranging from neuronal hyperplasia to absence of neurons.
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