Influence of beta-cluster haplotypes, alpha-gene status and UGTA1 polymorphism on clinical and hematological data in sickle-cell disease children from French Guiana

Genetic Variation and Sickle Cell Disease Severity: A Systematic Review and Meta-Analysis

Importance

Sickle cell disease (SCD) is a monogenic disorder, yet clinical outcomes are influenced by additional genetic factors. Despite decades of research, the genetics of SCD remain poorly understood.

Objective

To assess all reported genetic modifiers of SCD, evaluate the design of associated studies, and provide guidelines for future analyses according to modern genetic study recommendations.

Data Sources

PubMed, Web of Science, and Scopus were searched through May 16, 2023, identifying 5290 publications.

Study Selection

At least 2 reviewers identified 571 original, peer-reviewed English-language publications reporting genetic modifiers of human SCD phenotypes, wherein the outcome was not treatment response, and the comparison was not between SCD subtypes or including healthy controls.

Data Extraction and Synthesis

Data relevant to all genetic modifiers of SCD were extracted, evaluated, and presented following STREGA and PRISMA guidelines. Weighted z score meta-analyses and pathway analyses were conducted.

Main Outcomes and Measures

Outcomes were aggregated into 25 categories, grouped as acute complications, chronic conditions, hematologic parameters or biomarkers, and general or mixed measures of SCD severity.

Results

The 571 included studies reported on 29 670 unique individuals (50% ≤ 18 years of age) from 43 countries. Of the 17 757 extracted results (4890 significant) in 1552 genes, 3675 results met the study criteria for meta-analysis: reported phenotype and genotype, association size and direction, variability measure, sample size, and statistical test. Only 173 results for 62 associations could be cross-study combined. The remaining associations could not be aggregated because they were only reported once or methods (eg, study design, reporting practice) and genotype or phenotype definitions were insufficiently harmonized. Gene variants regulating fetal hemoglobin and α-thalassemia (important markers for SCD severity) were frequently identified: 19 single-nucleotide variants in BCL11A, HBS1L-MYB, and HBG2 were significantly associated with fetal hemoglobin (absolute value of Z = 4.00 to 20.66; P = 8.63 × 10-95 to 6.19 × 10-5), and α-thalassemia deletions were significantly associated with increased hemoglobin level and reduced risk of albuminuria, abnormal transcranial Doppler velocity, and stroke (absolute value of Z = 3.43 to 5.16; P = 2.42 × 10-7 to 6.00 × 10-4). However, other associations remain unconfirmed. Pathway analyses of significant genes highlighted the importance of cellular adhesion, inflammation, oxidative and toxic stress, and blood vessel regulation in SCD (23 of the top 25 Gene Ontology pathways involve these processes) and suggested future research areas.

Conclusions and Relevance

The findings of this comprehensive systematic review and meta-analysis of all published genetic modifiers of SCD indicated that implementation of standardized phenotypes, statistical methods, and reporting practices should accelerate discovery and validation of genetic modifiers and development of clinically actionable genetic profiles.

Genetic Background Studies of Eight Common Beta Thalassemia Mutations in Thailand Using β-Globin Gene Haplotype and Phylogenetic Analysis

Single nucleotide polymorphisms are informative for haplotype analysis associated with genetic background and clinical linkage studies of β-thalassemia mutations. Hence, the aim of this study was to investigate five polymorphisms (codon 2 (C/T), IVS II-16 (C/G), IVS II-74 (G/T), IVS II-81 (C/T) and the Hinf I (T/A) polymorphism) on the β-globin gene, related to eight common β-thalassemia mutations in Thailand, including NT-28 (A > G), codon 17 (A > T), codon 19 (A > G), HbE (G > A), IVS I-1 (G > C), IVS I-5 (G > C), codon 41/42 (-TTCT) and IVS II-654 (C > T). The strongest LD (100%) between the β-thalassemia mutation allele and all five SNPs was found in NT-28 (A > G), codon 17 (A > T) and codon 19 (A > G). In the haplotype analysis, we found three haplotypes (H1, H2 and H7) related to Hb E, whereas we only found two haplotypes related to codon 41/42 (-TTCT) (H1, H3) and IVS I-1 (G > C) (H3, H4). Of interest is the finding relating to a single haplotype in the remaining β-thalassemia mutations. Furthermore, phylogenetic tree analysis revealed three clusters of these common β-thalassemia mutations in the Thai population and enabled us to determine the origin of these mutations. Here, we present the results of our study, including four intragenic polymorphisms and the finding that the Hinf I polymorphism could be informative in genetic background analysis, population studies and for predicting the severity of β-thalassemia in Thailand.

About the need to address pediatric health inequalities in French Guiana : a scoping review

INTRODUCTION

French Guiana is a French overseas territory in South America, marked by poverty and inequalities. Access to different services, including healthcare, is unequal depending on where people live. Several studies showed that among adults, the most precarious individuals had greater incidences of chronic and infectious diseases. Although the median age of the population living in this territory is 25, there is no specific focus on the pediatric population although it is documented that socioeconomic inequalities have an impact on child health. The objective of this scoping review is to shed light on health challenges concerning children living in French Guiana.

METHODS

A literature search was performed on PubMed to identify relevant articles, and additional references were added if within the scope of this review.

RESULTS

A total of 106 publications were reviewed. Perinatal health issues were linked to a high rate of teenage pregnancies with poor medical follow-up leading to complications such as preterm deliveries and congenital malformations and abnormalities. Infectious diseases were a significant burden with worrisome vaccination coverage figures for some bacterial infections, partly explaining a high mortality rate attributable to infectious diseases. Herbicide poisoning with paraquat was reported in children, and environment-related concerns such as wild animal attacks as well as lead and mercury exposure were reported. Some children living in remote Amerindian communities had a higher suicide rate than in mainland France, and chronic diseases such as sickle cell disease were reported to have more transfusion-related complications.

CONCLUSION

Children living in French Guiana have worse pediatric health indicators in comparison with children from mainland France.