[Show abstract][Hide abstract] ABSTRACT: Context: At least a third of patients with pheochromocytoma (PCC) or paraganglioma (PGL) harbour an underlying germline mutation in a known PCC/PGL gene. Mutations in genes (SDHB, SDHD, SDHC and SDHA) encoding a component of the tricarboxylic acid (TCA) cycle, succinate dehydrogenase (SDH), are a major cause of inherited PCC and PGL. SDHB mutations are also, albeit less frequently, associated with inherited renal cell carcinoma (RCC). Inactivation of SDH and another TCA cycle component, fumarate hydratase (FH), have both been associated with abnormalities of cellular metabolism, responsible for the activation of hypoxic gene response pathways and epigenetic alterations (e.g. DNA methylation). However, the clinical phenotype of germline mutations in SDHX genes and FH is usually distinct with FH mutations classically associated with hereditary cutaneous and uterine leiomyomatosis and RCC though recently an association with phaeochromocytoma/paraganglioma has been reported. Objective and Design: In order to identify potential novel PCC/PGL predisposition genes we initially undertook exome resequencing studies in a case of childhood PCC and subsequently FH mutation analysis in a further 71 patients with PCC, PGL or head and neck paraganglioma (HNPGL). Results: After identifying a candidate FH missense mutation in the exome study, we then detected a further candidate missense mutation (p.Glu53Lys) by candidate gene sequencing. In vitro analyses demonstrated that both missense mutations (p.Cys434Tyr and p.Glu53Lys) were catalytically inactive. Conclusions: These findings (a) confirm that germline FH mutations may present, albeit rarely, with PCC or PGL and (b) extend the clinical phenotype associated with FH mutations to paediatric PCC.
The Journal of clinical endocrinology and metabolism. 07/2014;
[Show abstract][Hide abstract] ABSTRACT: Acne vulgaris (acne) is a common inflammatory disorder of the cutaneous pilo-sebaceous unit. Here we perform a genome-wide association analysis in the United Kingdom, comparing severe cases of acne (n=1,893) with controls (n=5,132). In a second stage, we genotype putative-associated loci in a further 2,063 acne cases and 1,970 controls. We identify three genome-wide significant associations: 11q13.1 (rs478304, Pcombined=3.23 × 10(-11), odds ratio (OR)=1.20), 5q11.2 (rs38055, Pcombined=4.58 × 10(-9), OR=1.17) and 1q41 (rs1159268, Pcombined=4.08 × 10(-8), OR=1.17). All three loci contain genes linked to the TGFβ cell signalling pathway, namely OVOL1, FST and TGFB2. Transcripts of OVOL1 and TFGB2 have decreased expression in affected compared with normal skin. Collectively, these data support a key role for dysregulation of TGFβ-mediated signalling in susceptibility to acne.
[Show abstract][Hide abstract] ABSTRACT: Adaptor protein complex 1 (AP-1) is an evolutionary conserved heterotetramer that promotes vesicular trafficking between the trans-Golgi network and the endosomes. The knockout of most murine AP-1 complex subunits is embryonically lethal, so the identification of human disease-associated alleles has the unique potential to deliver insights into gene function. Here, we report two founder mutations (c.11T>G [p.Phe4Cys] and c.97C>T [p.Arg33Trp]) in AP1S3, the gene encoding AP-1 complex subunit σ1C, in 15 unrelated individuals with a severe autoinflammatory skin disorder known as pustular psoriasis. Because the variants are predicted to destabilize the 3D structure of the AP-1 complex, we generated AP1S3-knockdown cell lines to investigate the consequences of AP-1 deficiency in skin keratinocytes. We found that AP1S3 silencing disrupted the endosomal translocation of the innate pattern-recognition receptor TLR-3 (Toll-like receptor 3) and resulted in a marked inhibition of downstream signaling. These findings identify pustular psoriasis as an autoinflammatory phenotype caused by defects in vesicular trafficking and demonstrate a requirement of AP-1 for Toll-like receptor homeostasis.
The American Journal of Human Genetics 05/2014; 94(5):790-7. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies (GWASs) perform per-SNP association tests to identify variants involved in disease or trait susceptibility. However, such an approach is not powerful enough to unravel genes that are not individually contributing to the disease/trait, but that may have a role in interaction with other genes as a group. Pathway analysis is an alternative way to highlight such group of genes. Using SNP association P-values from eight multiple sclerosis (MS) GWAS data sets, we performed a candidate pathway analysis for MS susceptibility by considering genes interacting in the cell adhesion molecule (CAMs) biological pathway using Cytoscape software. This network is a strong candidate, as it is involved in the crossing of the blood-brain barrier by the T cells, an early event in MS pathophysiology, and is used as an efficient therapeutic target. We drew up a list of 76 genes belonging to the CAM network. We highlighted 64 networks enriched with CAM genes with low P-values. Filtering by a percentage of CAM genes up to 50% and rejecting enriched signals mainly driven by transcription factors, we highlighted five networks associated with MS susceptibility. One of them, constituted of ITGAL, ICAM1 and ICAM3 genes, could be of interest to develop novel therapeutic targets.Genes and Immunity advance online publication, 16 January 2014; doi:10.1038/gene.2013.70.
[Show abstract][Hide abstract] ABSTRACT: Dissecting how genetic and environmental influences impact on learning is helpful for maximizing numeracy and literacy. Here we show, using twin and genome-wide analysis, that there is a substantial genetic component to children's ability in reading and mathematics, and estimate that around one half of the observed correlation in these traits is due to shared genetic effects (so-called Generalist Genes). Thus, our results highlight the potential role of the learning environment in contributing to differences in a child's cognitive abilities at age twelve.
[Show abstract][Hide abstract] ABSTRACT: Background:Invasive lobular breast cancer (ILC) and lobular carcinoma in situ (LCIS) are characterised by loss of E-cadherin expression. However germline CDH1 mutations are rare in cases of ILC with no family history of hereditary diffuse gastric cancer (HDGC) and have not been described in women with LCIS.Methods:We screened the CDH1 gene in 50 cases of bilateral LCIS/ILC using Sanger sequencing and MLPA.Results:Sanger sequencing revealed four pathogenic germline mutations, including a novel splicing mutation (c.48+1G>A). The remaining three (c.1465insC, c.1942G>T, c.2398delC) have been previously described. All four cases had bilateral LCIS +/- ILC and no family history of gastric cancer.Conclusion:CDH1 germline mutations have not been previously described in women with LCIS. We have shown that germline CDH1 mutations are associated with early onset of bilateral LCIS with or without ILC in women without a family history of gastric cancer. CDH1 mutation screening should be considered in women with early onset of bilateral LCIS/ILC with no family history of HDGC.British Journal of Cancer advance online publication 24 December 2013; doi:10.1038/bjc.2013.792 www.bjcancer.com.
British Journal of Cancer 12/2013; · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Schizophrenia is an idiopathic mental disorder with a heritable component and a substantial public health impact. We conducted a multi-stage genome-wide association study (GWAS) for schizophrenia beginning with a Swedish national sample (5,001 cases and 6,243 controls) followed by meta-analysis with previous schizophrenia GWAS (8,832 cases and 12,067 controls) and finally by replication of SNPs in 168 genomic regions in independent samples (7,413 cases, 19,762 controls and 581 parent-offspring trios). We identified 22 loci associated at genome-wide significance; 13 of these are new, and 1 was previously implicated in bipolar disorder. Examination of candidate genes at these loci suggests the involvement of neuronal calcium signaling. We estimate that 8,300 independent, mostly common SNPs (95% credible interval of 6,300-10,200 SNPs) contribute to risk for schizophrenia and that these collectively account for at least 32% of the variance in liability. Common genetic variation has an important role in the etiology of schizophrenia, and larger studies will allow more detailed understanding of this disorder.
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies (GWAS) have identified common variants of modest-effect size at hundreds of loci for common autoimmune diseases; however, a substantial fraction of heritability remains unexplained, to which rare variants may contribute. To discover rare variants and test them for association with a phenotype, most studies re-sequence a small initial sample size and then genotype the discovered variants in a larger sample set. This approach fails to analyse a large fraction of the rare variants present in the entire sample set. Here we perform simultaneous amplicon-sequencing-based variant discovery and genotyping for coding exons of 25 GWAS risk genes in 41,911 UK residents of white European origin, comprising 24,892 subjects with six autoimmune disease phenotypes and 17,019 controls, and show that rare coding-region variants at known loci have a negligible role in common autoimmune disease susceptibility. These results do not support the rare-variant synthetic genome-wide-association hypothesis (in which unobserved rare causal variants lead to association detected at common tag variants). Many known autoimmune disease risk loci contain multiple, independently associated, common and low-frequency variants, and so genes at these loci are a priori stronger candidates for harbouring rare coding-region variants than other genes. Our data indicate that the missing heritability for common autoimmune diseases may not be attributable to the rare coding-region variant portion of the allelic spectrum, but perhaps, as others have proposed, may be a result of many common-variant loci of weak effect.
[Show abstract][Hide abstract] ABSTRACT: Infantile cholestatic diseases can be caused by mutations in a number of genes involved in different hepatocyte molecular pathways. Whilst some of the essential pathways have a well understood function, such as bile biosynthesis and transport, the role of the others is not known. Here we report the findings of a clinical, biochemical and molecular study of a family with three patients affected with a severe infantile cholestatic disease. A novel homozygous frameshift germline mutation (c.587delG) in the AKR1D1 gene; which encodes the enzyme Delta 4-3-oxosteroid 5beta--reductase that is required for synthesis of primary bile acids and is crucial for establishment of normal bile flow, was found in all 3 patients. Although the initial bile acid analysis was inconclusive, subsequent testing confirmed the diagnosis of a bile acid biogenesis disorder. An additional novel homozygous frameshift mutation (c.3391delC) was detected in SKIV2L in one of the patients. SKIV2L encodes a homologue of a yeast ski2 protein proposed to be involved in RNA processing and mutations in SKIV2L were recently described in patients with Tricohepatoenteric syndrome (THES). A combination of autozygosity mapping and whole-exome-sequencing allowed the identification of causal mutations in this family with a complex liver phenotype. Although the initial 2 affected cousins died in the first year of life, accurate diagnosis and management of the youngest patient led to successful treatment of the liver disease and disease-free survival.
[Show abstract][Hide abstract] ABSTRACT: Adenosine diphosphate (ADP)-ribosylation is a post-translational protein modification implicated in the regulation of a range of cellular processes. A family of proteins that catalyse ADP-ribosylation reactions are the poly(ADP-ribose) (PAR) polymerases (PARPs). PARPs covalently attach an ADP-ribose nucleotide to target proteins and some PARP family members can subsequently add additional ADP-ribose units to generate a PAR chain. The hydrolysis of PAR chains is catalysed by PAR glycohydrolase (PARG). PARG is unable to cleave the mono(ADP-ribose) unit directly linked to the protein and although the enzymatic activity that catalyses this reaction has been detected in mammalian cell extracts, the protein(s) responsible remain unknown. Here, we report the homozygous mutation of the c6orf130 gene in patients with severe neurodegeneration, and identify C6orf130 as a PARP-interacting protein that removes mono(ADP-ribosyl)ation on glutamate amino acid residues in PARP-modified proteins. X-ray structures and biochemical analysis of C6orf130 suggest a mechanism of catalytic reversal involving a transient C6orf130 lysyl-(ADP-ribose) intermediate. Furthermore, depletion of C6orf130 protein in cells leads to proliferation and DNA repair defects. Collectively, our data suggest that C6orf130 enzymatic activity has a role in the turnover and recycling of protein ADP-ribosylation, and we have implicated the importance of this protein in supporting normal cellular function in humans.
[Show abstract][Hide abstract] ABSTRACT: Heterozygous loss of function mutations in the type II bone morphogenetic protein receptor (BMPR-II), a member of the transforming growth factor (TGF-β) receptor family, underlie the majority of familial cases of pulmonary arterial hypertension (PAH). The TGF-β1 pathway is activated in PAH and inhibitors of TGF-β1 signaling prevent the development and progression of PAH in experimental models. However, the effect of currently utilized therapies on the TGF-β pathway is not known. Prostacyclin analogues remain the first line of treatment for clinical PAH. We hypothesized that these agents effectively decrease the activity of the TGF-β1 pathway. Beraprost sodium (BPS), a prostacyclin analogue selectively inhibits proliferation in a dose-dependent manner in mouse primary pulmonary arterial smooth muscle cells (PASMCs) harbouring a pathogenic BMPR2 nonsense mutation in both the presence and absence of TGF-β1 stimulation. This study demonstrates that this agent inhibits TGF-β1-induced SMAD-dependent and -independent signaling via a PKA dependent pathway by reducing the phosphorylation of SMADs 2 and 3 and p38MAPK proteins. Finally, in a monocrotaline (MCT)-induced rat model of PAH, which is associated with increased TGF-β signaling, this study confirms that treprostinil (TPS), a stable prostacyclin analogue, inhibits the TGF-β pathway by reducing SMAD3 phosphorylation. Taken together, these data suggest that prostacyclin analogues inhibit dysregulated TGF-β signaling in vitro and in vivo and reduce BMPR-II-mediated proliferation defects in mutant mice PASMCs.
American Journal of Respiratory Cell and Molecular Biology 02/2013; · 4.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently pathogenic variants in the MLL2 gene were identified as the most common cause of Kabuki (Niikawa-Kuroki) syndrome (MIM#147920). To further elucidate the genotype-phenotype correlation we studied a large cohort of 86 clinically defined patients with Kabuki syndrome for mutations in MLL2. All patients were assessed using a standardized phenotype list and all were scored using a newly developed clinical score list for KS (MLL2-Kabuki score 0 to 10). Sequencing of the full coding region and intron-exon boundaries of MLL2 identified a total of 45 likely pathogenic mutations (52%): 31 nonsense, 10 missense and 4 splice-site mutations, 34 of which were novel. In 5 additional patients, novel, i.e. non-dbSNP132 variants of clinically unknown relevance, were identified. Patients with likely pathogenic nonsense or missense MLL2 mutations were usually more severely affected (median 'MLL2-Kabuki score' of 6) as compared to the patients without MLL2 mutations (median " MLL2-Kabuki score' of 5), a significant difference (p-value <0.0014). Several typical facial features such as large dysplastic ears, arched eyebrows with sparse lateral third, blue sclerae, a flat nasal tip with a broad nasal root, and a thin upper and a full lower lip were observed more often in mutation positive patients.
[Show abstract][Hide abstract] ABSTRACT: To identify susceptibility loci for visceral leishmaniasis, we undertook genome-wide association studies in two populations: 989 cases and 1,089 controls from India and 357 cases in 308 Brazilian families (1,970 individuals). The HLA-DRB1-HLA-DQA1 locus was the only region to show strong evidence of association in both populations. Replication at this region was undertaken in a second Indian population comprising 941 cases and 990 controls, and combined analysis across the three cohorts for rs9271858 at this locus showed P(combined) = 2.76 × 10(-17) and odds ratio (OR) = 1.41, 95% confidence interval (CI) = 1.30-1.52. A conditional analysis provided evidence for multiple associations within the HLA-DRB1-HLA-DQA1 region, and a model in which risk differed between three groups of haplotypes better explained the signal and was significant in the Indian discovery and replication cohorts. In conclusion, the HLA-DRB1-HLA-DQA1 HLA class II region contributes to visceral leishmaniasis susceptibility in India and Brazil, suggesting shared genetic risk factors for visceral leishmaniasis that cross the epidemiological divides of geography and parasite species.
[Show abstract][Hide abstract] ABSTRACT: Psoriasis is an immune-mediated skin disorder that is inherited as a complex genetic trait. Although genome-wide association scans (GWAS) have identified 36 disease susceptibility regions, more than 50% of the genetic variance can be attributed to a single Major Histocompatibility Complex (MHC) locus, known as PSORS1. Genetic studies indicate that HLA-C is the strongest PSORS1 candidate gene, since markers tagging HLA-Cw*0602 consistently generate the most significant association signals in GWAS. However, it is unclear whether HLA-Cw*0602 is itself the causal PSORS1 allele, especially as the role of SNPs that may affect its expression has not been investigated. Here, we have undertaken an in-depth molecular characterization of the PSORS1 interval, with a view to identifying regulatory variants that may contribute to disease susceptibility. By analysing high-density SNP data, we refined PSORS1 to a 179 kb region encompassing HLA-C and the neighbouring HCG27 pseudogene. We compared multiple MHC sequences spanning this refined locus and identified 144 candidate susceptibility variants, which are unique to chromosomes bearing HLA-Cw*0602. In parallel, we investigated the epigenetic profile of the critical PSORS1 interval and uncovered three enhancer elements likely to be active in T lymphocytes. Finally we showed that nine candidate susceptibility SNPs map within a HLA-C enhancer and that three of these variants co-localise with binding sites for immune-related transcription factors. These data indicate that SNPs affecting HLA-Cw*0602 expression are likely to contribute to psoriasis susceptibility and highlight the importance of integrating multiple experimental approaches in the investigation of complex genomic regions such as the MHC.
PLoS ONE 01/2013; 8(8):e71690. · 3.53 Impact Factor