Strengthening human genetics research in Africa: report of the 9th meeting of the African Society of Human Genetics in Dakar in May 2016.

The 9th meeting of the African Society of Human Genetics, in partnership with the Senegalese Cancer Research and Study Group and the Human Heredity and Health in Africa (H3Africa) Consortium, was held in Dakar, Senegal. The theme was Strengthening Human Genetics Research in Africa. The 210 delegates came from 21 African countries and from France, Switzerland, UK, UAE, Canada and the USA. The goal was to highlight genetic and genomic science across the African continent with the ultimate goal of improving the health of Africans and those across the globe, and to promote the careers of young African scientists in the field. A session on the sustainability of genomic research in Africa brought to light innovative and practical approaches to supporting research in resource-limited settings and the importance of promoting genetics in academic, research funding, governmental and private sectors. This meeting led to the formation of the Senegalese Society for Human Genetics.

Le 9ème congrès de la Société Africaine de Génétique Humaine, en partenariat avec le Groupe d'Etude et de Recherche sur le Cancer (GERC) et le Consortium H3Africa, s'est tenu à Dakar, au Sénégal. Le thème était «Renforcer la recherche en Génétique Humaine en Afrique¼. Les 210 participants sont venus de 21 pays africains et de six non africains. L'objectif était de valoriser la génétique et la génomique à travers l'Afrique avec comme but ultime d'améliorer la santé des populations, et de promouvoir les carrières des jeunes chercheurs Africains. Une session sur la pérennité de la recherche génomique a révélé des approches innovantes et pratiques supportant la recherche dans des contextes de ressources limitées et l'importance de promouvoir la formation universitaire en génétique, le financement de la recherche par les gouvernements et le privé. Ce congrès conduisit à la création de la Société Sénégalaise de Génétique Humaine.

The need for an integrated approach for chronic disease research and care in Africa.

With the changing distribution of infectious diseases, and an increase in the burden of non-communicable diseases, low- and middle-income countries, including those in Africa, will need to expand their health care capacities to effectively respond to these epidemiological transitions. The interrelated risk factors for chronic infectious and non-communicable diseases and the need for long-term disease management, argue for combined strategies to understand their underlying causes and to design strategies for effective prevention and long-term care. Through multidisciplinary research and implementation partnerships, we advocate an integrated approach for research and healthcare for chronic diseases in Africa.

H3Africa multi-centre study of the prevalence and environmental and genetic determinants of type 2 diabetes in sub-Saharan Africa: study protocol.

The burden and aetiology of type 2 diabetes (T2D) and its microvascular complications may be influenced by varying behavioural and lifestyle environments as well as by genetic susceptibility. These aspects of the epidemiology of T2D have not been reliably clarified in sub-Saharan Africa (SSA), highlighting the need for context-specific epidemiological studies with the statistical resolution to inform potential preventative and therapeutic strategies. Therefore, as part of the Human Heredity and Health in Africa (H3Africa) initiative, we designed a multi-site study comprising case collections and population-based surveys at 11 sites in eight countries across SSA. The goal is to recruit up to 6000 T2D participants and 6000 control participants. We will collect questionnaire data, biophysical measurements and biological samples for chronic disease traits, risk factors and genetic data on all study participants. Through integrating epidemiological and genomic techniques, the study provides a framework for assessing the burden, spectrum and environmental and genetic risk factors for T2D and its complications across SSA. With established mechanisms for fieldwork, data and sample collection and management, data-sharing and consent for re-approaching participants, the study will be a resource for future research studies, including longitudinal studies, prospective case ascertainment of incident disease and interventional studies.

Vitamin D binding protein genotype is associated with plasma 25OHD concentration in West African children.

Vitamin D is well known for its role in promoting skeletal health. Vitamin D status is determined conventionally by circulating 25-dihydroxyvitamin D (25OHD) concentration. There is evidence indicating that circulating 25OHD concentration is affected by variation in Gc, the gene encoding the vitamin D binding protein (DBP). The composite genotype of two single nucleotide polymorphisms (rs7041 and rs4588) results in different DBP isotypes (Gc1f, Gc1s and Gc2). The protein configurational differences among DBP isotypes affect DBP substrate binding affinity. The aims of this study were to determine 1) Gc variant frequencies in a population from an isolated rural region of The Gambia, West Africa (n=3129) with year-round opportunity for cutaneous vitamin D synthesis and 2) the effects of Gc variants on 25OHD concentration (n=237) in a genetically representative sub-group of children (mean (SD) age: 11.9 (4.8) years). The distribution of Gc variants was Gc1f: 0.86, Gc1s: 0.11 and Gc2: 0.03. The mean (SD) concentration of 25OHD was 59.6 (12.9) nmol/L and was significantly higher in those homozygous for Gc1f compared to other Gc variants (60.7 (13.1) vs. 56.6 (12.1) nmol/L, P=0.03). Plasma 25OHD and 1,25(OH)2D concentration was significantly associated with parathyroid hormone in Gc1f-1f but not in the other Gc variants combined. This study demonstrates that different Gc variants are associated with different 25OHD concentrations in a rural Gambian population. Gc1f-1f, thought to have the highest affinity for 25OHD, had the highest 25OHD concentration compared with lower affinity Gc variants. The considerable difference in Gc1f frequency observed in Gambians compared with other non-West African populations and associated differences in plasma 25OHD concentration, may have implications for the way in which vitamin D status should be interpreted across different ancestral groups.

Actions of hydrogen sulphide on ion transport across rat distal colon.

BACKGROUND AND PURPOSE: The aim of this study was to identify the actions of H(2)S on ion transport across rat distal colon. EXPERIMENTAL APPROACH: Changes in short-circuit current (Isc) induced by the H(2)S-donor, NaHS, were measured in Ussing chambers. Cytosolic Ca(2+) concentration was evaluated using fura-2. KEY RESULTS: NaHS concentration-dependently induced a change in Isc, that was only partially inhibited by the neurotoxin, tetrodotoxin. Lower concentrations (< or =10(-3) mol.L(-1)) of NaHS induced a monophasic increase in Isc, whereas higher concentrations induced an additional, secondary fall of Isc, before a third phase when Isc rose again. Blockers of H(2)S-producing enzymes (expression demonstrated immunohistochemically) decreased basal Isc, suggesting that endogenous production of H(2)S contributes to spontaneous anion secretion. The positive Isc phases induced by NaHS were due to Cl(-) secretion as shown by anion substitution and transport inhibitor experiments, whereas the transient negative Isc induced by higher concentrations of the H(2)S-donor was inhibited by mucosal tetrapentylammonium suggesting a transient K(+) secretion. When applied from the serosal side, glibenclamide, an inhibitor of ATP-sensitive K(+) channels, and tetrapentylammonium, a blocker of Ca(2+)-dependent K(+) channels, suppressed NaHS-induced Cl(-) secretion suggesting different types of K(+) channels are stimulated by the H(2)S-donor. NaHS-induced increase in cytosolic Ca(2+) concentration was confirmed in isolated, fura-2-loaded colonic crypts. This response was not dependent on extracellular Ca(2+), but was inhibited by blockers of intracellular Ca(2+) channels present on Ca(2+) storage organelles. CONCLUSIONS AND IMPLICATIONS: H(2)S induces colonic ion secretion by stimulation of apical as well as basolateral epithelial K(+) channels.

Evolutionary origins of the obesity epidemic: natural selection of thrifty genes or genetic drift following predation release?

This article challenges Speakman's hypothesis that the modern genetic predisposition to obesity has arisen through random genetic drift in the two million years following predation release. We present evidence in support of the hypothesis that a mixture of famines and seasonal food shortages in the post-agricultural era have exerted natural selection in favour of fat storage; an effect most likely mediated through fertility, rather than viability, selection. We conclude that, far from being time to call off the search, recently developed genetic and bioinformatic methods will soon provide a definitive resolution to this long-standing 'thrifty gene' controversy.

Sites of action of hydrogen peroxide on ion transport across rat distal colon.

BACKGROUND AND PURPOSE: The aim of this study was the identification of the mechanism of oxidant-induced intestinal secretion. EXPERIMENTAL APPROACH: The action of H2O2 on ion transport across rat distal colon was evaluated in Ussing chambers. Changes in cytosolic Ca2+ concentration were measured using fura-2. KEY RESULTS: H2O2 concentration-dependently induced an increase in short-circuit current (Isc), which was due to a stimulation of Cl(-) secretion. The effect of H2O2 was dependent on the presence of serosal Ca2+. It was inhibited after emptying of intracellular Ca2+ stores by cyclopiazonic acid or blockade of ryanodine receptors by ruthenium red, whereas a blocker of inositol 1,4,5-trisphosphate receptors was less effective. Fura 2-experiments confirmed an increase in the cytosolic Ca2+ concentration in the presence of H2O2. Measurements of Cl- currents across the apical membrane at basolaterally depolarized epithelia revealed the activation of a glibenclamide-sensitive, SITS-resistant Cl- conductance by the oxidant. The activation of this conductance was inhibited after blockade of protein kinases with staurosporine. When the apical membrane was permeabilized with nystatin, two sites of action of H2O2 were identified at the basolateral membrane. The oxidant stimulated a basolateral tetrapentylammonium-sensitive K+ conductance and increased the current generated by the Na+-K+ pump. Pretreatment of the tissues with H2O2 reduced the action of subsequently administered Ca2+-, cAMP- and cGMP-dependent secretagogues demonstrating a long-term downregulation after the initial secretory response evoked by the oxidant. CONCLUSIONS AND IMPLICATIONS: H2O2 affects colonic anion secretion by action sites at both the apical, as well as the basolateral membrane.

PTPRC (CD45) variation and disease association studied using single nucleotide polymorphism tagging.

CD45 is a haemopoietic tyrosine phosphatase, crucial for lymphocyte signalling. Two polymorphisms (C77G and A138G), which alter CD45 isoform expression, are associated with autoimmune and infectious diseases. Using HapMap data, we show that there is substantial linkage disequilibrium across the CD45 gene (PTPRC), with similar patterns in different populations. Employing a set of single nucleotide polymorphisms, correlated with a substantial proportion of variation across this gene, we tested for association with type 1 diabetes, Graves' disease in a Japanese population, hepatitis C in UK population and tuberculin response in a Chinese population. A limited number of common haplotypes was found. Most 138G alleles are present on only one haplotype, which is associated with Graves' disease, supporting previous data that A138G is a functionally important CD45 polymorphism.

Ca2+-induced Cl- efflux at rat distal colonic epithelium.

With the aid of the halide-sensitive dye 6-methoxy-N-ethylquinolinium iodide (MEQ), changes in intracellular Cl(-) concentration were measured to characterize the role of Ca(2+)-dependent Cl(-) channels at the rat distal colon. In order to avoid indirect effects of secretagogues mediated by changes in the driving force for Cl(-) exit (i.e., mediated by opening of Ca(2+)-dependent K(+) channels), all experiments were performed under depolarized conditions, i.e., in the presence of high extracellular K(+) concentrations. The Ca(2+)-dependent secretagogue carbachol induced a stilbene-sensitive Cl(-) efflux, which was mimicked by the Ca(2+) ionophore ionomycin. Surprisingly, the activation of Ca(2+)-dependent Cl(-) efflux was resistant against blockers of classical Ca(2+) signaling pathways such as phospholipase C, protein kinase C and calmodulin. Hence, alternative pathways must be involved in the signaling cascade. One possible signaling molecule seems to be nitric oxide (NO) as the NO donor sodium nitroprusside could induce Cl(- )efflux. Vice versa, the NO synthase inhibitor N-omega-monomethyl-arginine (L: -NMMA) reduced the carbachol-induced Cl(- )efflux. This indicates that NO may be involved in part of the signaling cascade. In order to test the ability of the epithelium to produce NO, the expression of different isoforms of NO synthase was verified by immunohistochemistry. In addition, the cytoskeleton seems to play a role in the activation of Ca(2+)-dependent Cl(-) channels. Inhibitors of microtubule association such as nocodazole and colchicine as well as jasplakinolide, a drug that enhances actin polymerization, inhibited the carbachol-induced Cl(-) efflux. Consequently, the activation of apical Cl(-) channels by muscarinic receptor stimulation differs in signal transduction from the classical phospholipase C/protein kinase C way.

Altered CD45 expression in C77G carriers influences immune function and outcome of hepatitis C infection.

BACKGROUND: A polymorphism in exon 4 (C77G) of CD45 that alters CD45 splicing has been associated with autoimmune and infectious diseases in humans. OBJECTIVE: To investigate the effect of C77G in hepatitis C virus (HCV) infected individuals and study the phenotype and function of peripheral blood mononuclear cells (PBMC) from healthy and hepatitis C infected C77G carriers. RESULTS: C77G individuals showed an increased proportion of primed CD45RA and effector memory CD8 T cells and more rapid activation of the lymphocyte specific protein tyrosine kinase (Lck) following CD3 stimulation. Transgenic mice with CD45 expression mimicking that in human C77G variants had more activated/memory T cells, more rapid proliferative responses, and activation of Lck. CONCLUSIONS: Changes in CD45 isoform expression can alter immune function in human C77G variants and CD45 transgenic mice. The C77G allele may influence the outcome of HCV infection.

Percutaneous transluminal angioplasty for renovascular hypertension in a neonate.

AIM: To report on the first case of successful percutaneous transluminal renal artery angioplasty in a neonate. CASE REPORT: a 5-d-old neonate was admitted with cardiorespiratory failure. Monitoring of blood pressure revealed severe arterial hypertension. Doppler sonography detected stenotic flow in the right renal artery. A (99m)Tc-MAG3 scan revealed highly diminished elimination by the right kidney. Selective renin levels were 23,968 ng/l in the right and 3770 ng/l in the left renal vein and the aorta. Percutaneous transluminal angioplasty using a 2 x 10 mm balloon catheter was performed on the 8th day of life. RESULTS: The patient was discharged from hospital normotensive without anti-hypertensive medication. During 8 mo follow-up the blood pressure remained normal, Doppler sonography revealed no recurrent artery stenosis, and renal function improved. CONCLUSION: Neonatal percutaneous transluminal angioplasty for renal artery stenosis may be feasible in selected patients.

Stent implantation for recurrent interatrial obstruction in an infant with hypoplastic left heart syndrome.

We report the case of a 19-month-old girl with hypoplastic left heart syndrome who, after Norwood stage 1 and 2 procedures, developed recurrent interatrial obstruction and was treated effectively with stent implantation. The stent was explanted electively 14 months after implantation and showed almost no endothelium formation. Therefore, there was no need for redo atrioseptectomy and the surgical intervention could be staged electively.

Linkage analysis of susceptibility to leprosy type using an IBD regression method.

Leprosy is a chronic disease caused by infection with Mycobacterium leprae, which is manifested across a wide clinical spectrum. There is evidence that susceptibility both to leprosy per se and to the clinical type of leprosy is influenced by host genetic factors. This paper describes the application of an identity by descent regression search for genetic determinants of leprosy type among families from Karonga District, Northern Malawi. Suggestive evidence was found for linkage to leprosy type on chr 21q22 (P<0.001). The methodological implications of the approach and the findings are discussed.

Inducible nitric oxide synthase gene (NOS2A) haplotypes and the outcome of hepatitis C virus infection.

Inducible nitric oxide synthase (iNOS) is an important molecule involved in the host defense against infectious agents. iNOS is encoded by the NOS2A gene and well-defined haplotypes exist with respect to this gene. We examined whether these haplotypes were associated with the outcome of hepatitis C virus (HCV) infection in 619 Caucasian patients from seven European liver centres. We observed five major haplotypes: (-277A)+(-1026G)+(-1659C): haplotype 1; (-277G)+(-1026T)+(-1659C): haplotype 2; (-277G)+(-1026G)+(-1659C): haplotype 3; (-277G)+(-1026T)+(-1659T): haplotype 4; and (-277A)+(-1026T)+(-1659C): haplotype 5. Distributions of these haplotypes are comparable with those of previous studies. Homozygotes for haplotype 2 or those with haplotypes 2/4 were more likely than those with the 1/1 (wild type) combination to have self-limiting infections (odds ratios (OR)=3.43; 95% confidence intervals (95% CI): 1.10-8.0; P=0.0206 and OR=5.15; 95% CI: 1.32-14.32; P=0.0018, respectively). Conversely, carriage of haplotype 1 was associated with the lack of self-limiting disease (OR=0.48; 95% CI: 0.27-0.83; P=0.009). The effect was mainly among males (OR=0.41; 95% CI: 0.182-0.942; P=0.031 for males, and OR=0.55; 95% CI: 0.24-1.37; P=0.136 for women). Carriage of haplotype 1 was not associated with initial response (P=0.268) or sustained response (P>0.171). Combinations of haplotypes 1/4 were more likely to respond to interferon monotherapy in comparison of initial responders to nonresponders (OR=2.25; 95% CI: 1.05-5.68; P=0.0275).

Polymorphisms in interferon-induced genes and the outcome of hepatitis C virus infection: roles of MxA, OAS-1 and PKR.

Interferon stimulates the expression of a number of genes encoding enzymes with antiviral activities, including myxovirus resistance-1 (MxA), 2-5-oligoadenylate synthetase 1 (OAS-1) and double-stranded RNA-dependent protein kinase (PKR). We examined whether polymorphisms in these genes influenced the outcome of hepatitis C virus (HCV) infection. We observed a lower frequency of the GG genotype at position -88 in the MxA gene promoter in self-limiting HCV infection (OR=0.56; 95% CI: 0.35-0.8; P=0.010) and in nonresponders to therapy (OR=0.49; 95% CI: 0.25-0.95; P=0.020). This genotype predominantly influenced the outcome of treatment in patients with viral genotype 1 (OR=0.22 95% CI: 0.07-0.67; P=0.002). A polymorphism in the 3'-untranslated region of the OAS-1 gene was associated with outcome of infection (GG genotype less frequent in self-limiting infection: OR=0.43; 95% CI: 0.21-0.86; P=0.010). A polymorphism at position -168 in the promoter region of the PKR gene was associated with self-limiting infection (CT genotype: OR=2.75; 95% CI: 1.45-5.24; P=0.002). Further associations were found with a CGG trinucleotide repeat in the 5'UTR region of the PKR gene. Polymorphisms in the interferon-induced genes, MxA, OAS-1 and PKR appear thus associated with HCV outcome.

Factor V Leiden polymorphism and the rate of fibrosis development in chronic hepatitis C virus infection.

BACKGROUND: The rate of progression to cirrhosis varies among individuals chronically infected with the hepatitis C virus (HCV). Coagulation pathway activation in models of hepatic fibrosis suggests variation in coagulation pathway components may influence the rate of fibrosis. We hypothesised that polymorphisms of the coagulation factors II and V affect the rate of progression to cirrhosis in HCV infected subjects. METHODS: We studied the relationship between rate of fibrosis (calculated by dividing the fibrosis stage by duration of infection) and genotypes of specific coagulation pathway genes in 352 White European patients infected with HCV. Genotyping was performed using reverse line blot hybridisation. RESULTS: The rate of fibrosis was significantly higher in patients with the factor V Leiden genotype (Arg560Gln) (ANOVA, p=0.004). In disease association studies, a significant association was seen (Fisher's exact test, p=0.029; odds ratio 3.28 for fast progression to cirrhosis (expected to reach cirrhosis in less than 30 years) if heterozygous for factor V Leiden). No associations were seen between factor II genotype and fibrosis rate. CONCLUSIONS: Possession of the factor V Leiden polymorphism significantly increases the risk of rapid disease progression in HCV, suggesting a role for the coagulation system in the pathogenesis of fibrotic liver disease.

Interferon-alpha receptor-1 (IFNAR1) variants are associated with protection against cerebral malaria in the Gambia.

The chromosome 21q22.11 cytokine receptor cluster contains four genes that encode subunits of the receptors for the cytokines interleukin-10 and interferon-alpha, -beta and -gamma that may have a role in malaria pathogenesis. A total of 15 polymorphic markers located within these genes were initially genotyped in 190 controls and 190 severe malaria cases from The Gambia. Two interferon-alpha receptor-1 (IFNAR1) gene SNPs (17470 and L168 V) showed evidence for an association with severe malaria phenotypes and were typed in a larger series of samples comprising 538 severe malaria cases, 338 mild malaria cases and 562 controls. Both the 17470-G/G and L168V-G/G genotypes were associated with protection against severe malaria, in general, and cerebral malaria, in particular (P=0.004 and 0.003, respectively). IFNAR1 diplotypes were then constructed for these two markers using the PHASE software package. The (17470-G L168V-G/17470-G L168V-G) diplotype was found to be associated with a reduced risk of cerebral malaria and the (17470-C L168V-C/17470-G L168V-G) diplotype with an increased risk of cerebral malaria (overall 3 x 2 chi(2)=12.8, d.f.=2, P=0.002 and 3 x 2 chi(2)=15.2, d.f.=2, P=0.0005, respectively). These data suggest a role for the type I interferon pathway in resistance to cerebral malaria.

[Idiopathic left ventricular tachycardia in childhood: typical clinical findings and different therapeutic options]. / Idiopathische linksventrikuläre Tachykardie im Kindesalter: typische Befunde und verschiedene Therapieoptionen.

We report 3 adolescents with structurally normal heart who were referred to hospital due to long-lasting palpitations. Initial 12-lead-ECG showed sustained, monomorphic ventricular tachycardia, right bundle branch block QRS morphology and axis deviation. After failure of different anti-arrhythmic drugs finally the intravenous medication with verapamil led to termination of ventricular tachycardia in all three patients. All clinical findings and the responsiveness to verapamil are consistent with the diagnosis of idiopathic left ventricular tachycardia. In one patient an electrophysiological study was done and increased left ventricular vulnerability was shown. After inducing a tachycardia originating from the left ventricle radiofrequency catheter ablation of the left-posterior fascicle was successfully performed. The tachycardia was not inducible after this ablation. Since that investigation the patient has been asymptomatic without anti-arrhythmic treatment. Two of three patients have been on oral verapamil prophylactically and have been free of symptoms.

Association of low-density lipoprotein receptor polymorphisms and outcome of hepatitis C infection.

The low-density lipoprotein receptor (LDLR) has been proposed to promote hepatitis C virus endocytosis and the cell membrane protein CD81 may also promote HCV host cell entry. The CD81 gene was sequenced to screen for novel polymorphisms, but no SNPs were identified. Polymorphisms within the LDLR gene are associated with the pathogenesis of familial hypercholesterolemia, atherosclerosis and obesity. We therefore studied genetic variation within the LDLR gene and clinical features of hepatitis C infection. An amino acid change in exon 8 was associated with severity of fibrosis; a SNP in exon 10 correlated with viral clearance and overall inflammation, and a SNP in the 3'UTR appeared to influence treatment response. There were no other significant associations between any of the SNPs studied and the clinical measures of hepatitis C infection. We furthermore report on linkage disequilibrium within the gene and haplotype frequencies in our population. Our findings support a possible role for the LDLR in the modulation of disease progression by affecting immune responses, rather than functioning as receptor for HCV.