Childhood Hearing Impairment in Senegal.

We recently showed that variants in GJB2 explained Hearing Impairment (HI) in 34.1% (n = 15/44) of multiplex families in Senegal. The present study aimed to use community-based nationwide recruitment to determine the etiologies and the clinical profiles of childhood HI in Senegal. Participants with early onset HI were included after clinical examination, including audiological assessment by pure tone audiometry and/or auditory brainstem response. We investigated a total of 406 participants from 295 families, recruited from 13/14 administrative regions of Senegal. Male/female ratio was 1.33 (232/174). Prelingual HI was the most common type of HI and accounted for 80% (n = 325 individuals). The mean age at medical diagnosis for congenital HI was computed at 3.59 ± 2.27 years. Audiological evaluation showed sensorineural HI as the most frequently observed HI (89.16%; n = 362 individuals). Pedigree analysis suggested autosomal recessive inheritance in 61.2% (63/103) of multiplex families and sporadic cases in 27 families (26.2%; 27/103), with a consanguinity rate estimated at 93% (84/90 families). Genetic factors were likely involved in 52.7% (214/406) of the cases, followed by environmental causes (29.57%; 120/406). In 72 cases (17.73%), the etiology was unknown. Clinically, non-syndromic HI was the most common type of HI (90.6%; n = 194/214 individuals). Among families segregating syndromic cases, type 2 Waardenburg syndrome was the most common (36.3%; 4/11 families). This study revealed putative genetic factors, mostly associated with high consanguinity rate, as the leading causes of early-onset HI in Senegal. The high consanguinity could provide a good opportunity to identify variants in known and novel genes involved in childhood HI.

Biomarkers of sickle cell nephropathy in Senegal.

Sickle cell anemia (SCA) is caused by a single point variation in the ß-globin gene (HBB): c.20A> T (p.Glu7Val), in homozygous state. SCA is characterized by sickling of red blood cells in small blood vessels which leads to a range of multiorgan complications, including kidney dysfunction. This case-control study aims at identifying sickle cell nephropathy biomarkers in a group of patients living with SCA from Senegal. A total of 163 patients living with SCA and 177 ethnic matched controls were investigated. Biological phenotyping included evaluation of glycemia, glucosuria, albuminuria, proteinuria, tubular proteinuria, serum creatinine, urine creatinine, urine specific gravity and glomerular filtration rate. Descriptive statistics of biomarkers were performed using the χ2 -test, with the significance level set at p<0.05. Patients living with SCA had a median age of 20 years (range 4 to 57) with a female sex frequency of 53.21%. The median age of the control participants was 29 years (range: 4-77) with a female sex frequency of 66.09%. The following proportions of abnormal biological indices were observed in SCA patients versus (vs.) controls, as follows: hyposthenuria: 35.3%vs.5.2% (p<0.001); glomerular hyperfiltration: 47.66%vs.19.75% (p<0.001), renal insufficiency: 5.47%vs.3.82% (p = 0.182); microalbuminuria: 42.38%vs.5.78% (p<0.001); proteinuria: 39.33%vs.4.62% (p<0.001); tubular proteinuria: 40.97%vs.4.73% (p<0.001) and microglucosuria: 22.5%vs.5.1% (p<0.001). This study shows a relatively high proportion of SCA nephropathy among patients living with SCA in Senegal. Microglucosuria, proteinuria, tubular proteinuria, microalbuminuria, hyposthenuria and glomerular hyperfiltration are the most prevalent biomarkers of nephropathy in this group of Senegalese patients with SCA.

Effects of Senegal haplotype (Xmn1-rs7412844), alpha-thalassemia (3.7kb HBA1/HBA2 deletion), NPRL3-rs11248850 and BCL11A-rs4671393 variants on sickle cell nephropathy.

OBJECTIVE: Sickle cell anemia (SCA) can cause substantial kidney dysfunction resulting in sickle cell nephropathy, which may be affected by the presence of modifier genes. This study evaluates the effects of some modifier genes on sickle cell nephropathy. METHODS: Patients living with SCA were recruited. Alpha-thalassemia (3.7kb HBA1/HBA2 deletion) was genotyped using gap PCR multiplex. Senegal haplotype (Xmn1-rs7412844), BCL11A-rs4671393 and NPRL3-rs11248850 were genotyped using Mass Array. The effects of variants on kidney dysfunction were then evaluated using multivariate analysis. RESULTS: The number of patients living with SCA included in this study was 162 with a median age of 20 years [minimum-maximum: 4-57] and a female frequency of 53.21%. Senegal haplotype, BCL11A-rs4671393 variant were protective factors against albuminuria stage A2 with an odds ratio (OR) of 0.22 (95% CI 0.05-0.90) and 0.27 (95% CI 0.08-0.96) respectively. The combination NPRL3-rs11248850 variant - 3.7kb HBA1/HBA2 deletion was a protective factor against albuminuria stage A2 (OR = 0.087, 95% Cl 0.01-0.78) but it was a risk factor for glomerular hyperfiltration (OR = 17.69, 95% CI 1.85-169.31). CONCLUSIONS: All four variants displayed a protective effect against albuminuria stage A2. The combination alpha-thalassemia - NPRL3-rs11248850 variant is a risk factor for glomerular hyperfiltration.

Influence of Oxidative Stress Biomarkers and Genetic Polymorphisms on the Clinical Severity of Hydroxyurea-Free Senegalese Children with Sickle Cell Anemia.

Oxidative stress would play a role in the pathophysiology of sickle cell anemia (SCA). We tested the impact of common SCA genetic modifiers (alpha-thalassemia, G6PD deficiency, HbF quantitative trait loci; QTL) and pro/antioxidant genes polymorphisms (SOD2 rs4880, XO rs207454, MPO rs233322) on oxidative stress biomarkers (AOPP, MDA, MPO, XO, MnSOD, CAT, GPx) and clinical severity in 301 Senegalese SCA hydroxyurea-free children at steady-state (median age 9.1 years, sex ratio H/F = 1.3). Plasma oxidative stress biomarkers were compared with those of a control group (AA). CAT activity, AOPP, and MDA levels were higher in SCA than in AA individuals while XO, GPX, and MnSOD activities were lower. The presence of alpha-thalassemia decreased MDA level and MPO activity but no effect of the HbF QTL or G6PD deficiency was observed. SCA children who experienced their first hospitalized complication before 3 years old had higher MnSOD and CAT activities than the other children while those with no hospitalized VOC in the previous 2 years presented higher GPX activity. Age of the first hospitalized complication and AOPP levels were affected by the MPO rs2333227 SNP. Our results suggest that alpha-thalassemia modulates oxidative stress in SCA, presumably because of a reduction in the MPO activity.

Gene expression profiling in blood from cerebral malaria patients and mild malaria patients living in Senegal.

BACKGROUND: Plasmodium falciparum malaria remains a major health problem in Africa. The mechanisms of pathogenesis are not fully understood. Transcriptomic studies may provide new insights into molecular pathways involved in the severe form of the disease. METHODS: Blood transcriptional levels were assessed in patients with cerebral malaria, non-cerebral malaria, or mild malaria by using microarray technology to look for gene expression profiles associated with clinical status. Multi-way ANOVA was used to extract differentially expressed genes. Network and pathways analyses were used to detect enrichment for biological pathways. RESULTS: We identified a set of 443 genes that were differentially expressed in the three patient groups after applying a false discovery rate of 10%. Since the cerebral patients displayed a particular transcriptional pattern, we focused our analysis on the differences between cerebral malaria patients and mild malaria patients. We further found 842 differentially expressed genes after applying a false discovery rate of 10%. Unsupervised hierarchical clustering of cerebral malaria-informative genes led to clustering of the cerebral malaria patients. The support vector machine method allowed us to correctly classify five out of six cerebral malaria patients and six of six mild malaria patients. Furthermore, the products of the differentially expressed genes were mapped onto a human protein-protein network. This led to the identification of the proteins with the highest number of interactions, including GSK3B, RELA, and APP. The enrichment analysis of the gene functional annotation indicates that genes involved in immune signalling pathways play a role in the occurrence of cerebral malaria. These include BCR-, TCR-, TLR-, cytokine-, FcεRI-, and FCGR- signalling pathways and natural killer cell cytotoxicity pathways, which are involved in the activation of immune cells. In addition, our results revealed an enrichment of genes involved in Alzheimer's disease. CONCLUSIONS: In the present study, we examine a set of genes whose expression differed in cerebral malaria patients and mild malaria patients. Moreover, our results provide new insights into the potential effect of the dysregulation of gene expression in immune pathways. Host genetic variation may partly explain such alteration of gene expression. Further studies are required to investigate this in African populations.

Genetic Background of the Sickle Cell Disease Pediatric Population of Dakar, Senegal, and Characterization of a Novel Frameshift ß-Thalassemia Mutation [HBB: c.265_266del; p.Leu89Glufs*2].

Sickle cell disease is a genetic disorder with a large variability in the pattern and severity of clinical manifestations. Different genetic modulators have been identified but very few epidemiologic data are available on these modifier genes in Senegal. This study aimed to determine their prevalence in a Senegalese sickle cell disease pediatric population. The following genetic parameters were genotyped in 295 sickle cell disease children of the Dakar pediatric hospital: sickle cell disease genotype [ßS/ßS (HBB: c.20A>T), ßS/ßC (HBB: c.19G>A), ßS/ß0-thalassemia (ß0-thal)], XmnI polymorphism, the five most common α-thalassemia (α-thal) deletions and the A(-) and Betica glucose-6-phosphate-dehydrogenase (G6PD) deficient variants. Despite very few ßS/ßC and ßS/ß0-thal children (1.0% each), a novel frameshift ß0-thal mutation was characterized: HBB: c.265_266del; p.Leu89Glufs*2. The -α3.7 (rightward) deletion was the only α-thal deletion identified in this cohort (12.0% allelic frequency). Most of ßS/ßS patients (61.9%) were homozygous for the XmnI polymorphism and assumed to carry a Senegal/Senegal ßS haplotype. The remaining haplotypes were predominantly of the Benin type. While the Betica G6PD variant was quite frequent (13.0%), a low frequency of the A(-) variant was detected (1.0-2.0%). The systematic genotyping of the -α3.7 deletion and of the G6PD Betica variant in sickle cell disease patients from Senegal could be useful to identify patients at risk for several complications, such as cerebral vasculopathy, where it has been demonstrated that a normal α-globin genotype and G6PD deficiency are predisposing factors. These patients should be eligible for a transcranial Doppler examination that is not routinely offered in Senegal.

Relationship between Antibody Levels, IgG Binding to Plasmodium falciparum-Infected Erythrocytes, and Disease Outcome in Hospitalized Urban Malaria Patients from Dakar, Sénégal.

Background. Management of clinical malaria requires the development of reliable diagnostic methods and efficient biomarkers for follow-up of patients. Protection is partly based on IgG responses to parasite antigens exposed at the surface of infected erythrocytes (iRBCs). These IgG responses appeared low during clinical infection, particularly in severe disease. Methods. We analyzed the IgG binding capacity to the surface of live erythrocytes infected by knob positive FCR3 strain. Sera from 69 cerebral malaria (CM) and 72 mild malaria (MM) cases were analyzed by ELISA for IgG responses to five antigens from iRBC and by flow cytometry for IgG binding as expressed in labeling index ratio (LIR). The relationship between IgG levels, LIR, parasitemia, age, and the clinical outcomes was evaluated. Results. We found a significant decrease of LIR in adult CM fatal cases compared to surviving patients (p = 0.019). In MM, LIRs were correlated to IgG anti-iRBC and anti-PfEMP3/5 levels. In CM, no correlation was found between LIR, IgG levels, and parasitemia. Conclusion. The IgG binding assay was able to discriminate outcome of cerebral malaria cases and it deserves further development as a potential functional-associated assay for symptomatic malaria analysis.