Molecular characterization of G6PD deficiency in Oman

Seven novel glucose-6-phosphate dehydrogenase (G6PD) deficiency variants identified in the Qatari population

Background

Glucose-6-phosphate dehydrogenase deficiency (G6PDD) is the most common red cell enzymopathy in the world. In Qatar, the incidence of G6PDD is estimated at around 5%; however, no study has investigated the genetic basis of G6PDD in the Qatari population yet.

Methods

In this study, we analyzed whole-genome sequencing data generated by the Qatar Genome Programme for 6045 Qatar Biobank participants, to identify G6PDD variants in the Qatari population. In addition, we assessed the impact of the novel variants identified on protein function both in silico and by measuring G6PD enzymatic activity in the subjects carrying them.

Results

We identified 375 variants in/near G6PD gene, of which 20 were high-impact and 16 were moderate-impact variants. Of these, 14 were known G6PDD-causing variants. The most frequent G6PD-causing variants found in the Qatari population were p.Ser188Phe (G6PD Mediterranean), p.Asn126Asp (G6PD A +), p.Val68Met (G6PD Asahi), p.Ala335Thr (G6PD Chatham), and p.Ile48Thr (G6PD Aures) with allele frequencies of 0.0563, 0.0194, 0.00785, 0.0050, and 0.00380, respectively. Furthermore, we have identified seven novel G6PD variants, all of which were confirmed as G6PD-causing variants and classified as class III variants based on the World Health Organization’s classification scheme.

Conclusions

This is the first study investigating the molecular basis of G6PDD in Qatar, and it provides novel insights about G6PDD pathogenesis and highlights the importance of studying such understudied population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40246-021-00358-9.

Role of glucose 6-phosphate dehydrogenase (G6PD) deficiency and its association to Autism Spectrum Disorders

Autism Spectrum Disorder (ASD) is a common group of neurodevelopmental disorders which causes significant alterations in social and communication skills along with repetitive behavior and limited interests. The physiological understanding of ASD is ambiguous. Several reports suggested that environmental, genetic and epigenetic changes, neuroinflammation, mitochondrial dysfunction and metabolic alterations orchestrate the pathological outcomes of ASD. A recent report from Saudi Arabia found a mutation in X-chromosomal housekeeping glucose 6-phosphate dehydrogenase (G6PD) gene in two male ASD patients. Although, the involvement of G6PD-deficiency in the pathogenesis of ASD is poorly understood. Several reports suggested that G6PD deficiency impedes cellular detoxification of reactive oxygen species (ROS), which may result in neuronal damage and neuroinflammation. A deficiency of G6PD in newborn children may play a fundamental role in the pathogenesis of ASD. In this review, we will discuss the implications of G6PD deficiency in pathogenesis, male biasness and theranostics in ASD patients.

Prevalence of glucose-6-phosphate dehydrogenase deficiency and the role of the A- variant in a Saudi population

OBJECTIVES

To estimate the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency among Saudi men, and to establish the frequency of the two mutations/polymorphisms associated with the G6PD A- mutation--G to A at nucleotide 202 (G202A) and A to G at nucleotide 376 (A376G)--in those found to have G6PD deficiency.

METHODS

Blood samples were obtained from healthy male Saudi donors and screened for G6PD deficiency using a fluorescent spot test. Samples from subjects shown to be G6PD deficient and controls were then analysed for the presence of the G202A and A376G mutations on exons 4 and 5, respectively, of the G6PD gene using polymerase chain reaction followed by restriction fragment length polymorphism.

RESULT

A total of 2100 male subjects were screened; of these, 100 (4.76%) were shown to be G6PD deficient. The G6PD A- mutation (presence of both G202A and A376G) was observed in two (2%) of the 100 subjects with G6PD deficiency. There was no significant difference in the frequency of this mutation between those with G6PD deficiency and controls.

CONCLUSION

The G6PD A- mutation (G202A and A376G) does not appear to have a role in G6PD deficiency in a Saudi population.

Methemoglobinemia in an elderly patient with glucose-6-phosphate dehydrogenase deficiency: a case report

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked genetic disorder characterized by low levels of the G6PD enzyme. It is present worldwide but with more prevalence in the Middle East and the Mediterranean areas. We report a case of severe hemolysis due to G6PD deficiency manifesting as methemoglobinemia in a 70 year old Omani male never known to have any previous hemolytic episodes or previously diagnosed of G6PD deficiency.

Genetic services and testing in the Sultanate of Oman. Sultanate of Oman steps into modern genetics

The Sultanate of Oman is a rapidly developing Muslim country with well-organised government-funded health care services, including primary, secondary and tertiary, and rapidly expanding medical genetic facilities. At the present time, the Omani population is characterised by a rapid rate of growth, large family size, consanguineous marriages, and the presence of genetic isolates. The preservation of a tribal structure in the community coupled with traditional isolation has produced unique and favourable circumstances for building genealogical records and the study of genetic disease. Genetic services developed in the Sultanate of Oman in the past decade have become an important component of health care. The recently constructed Genetic Centre in Muscat expects to meet the needs of the Omani population in provision of genetic services and research, in a manner deferential to the cultural and religious traditions of the country.

Prevalence and molecular identification of the mediterranean variant among G6PD-deficient Sistani and Balouch males in Southeastern Iran

To determine the prevalence of G6PD deficiency and a Mediterranean mutation among males in southeastern Iran, we studied 1,097 Sistani and Balouch schoolboys. A questionnaire was used to collect demographic data and a history of malaria infection; blood samples were evaluated for G6PD deficiency and the G6PD Mediterranean mutation. Of the 1,097 boys screened, 175 were G6PD deficient (5.8 % of the Sistani boys and 19.3 % of the Balouch boys). The malaria survey indicated that among Balouch subjects, malaria infection was about 14 times that of Sistani subjects. Molecular characterization of G6PD-deficient samples revealed a general frequency of 85.1 % for the Mediterranean variant among all subjects (75 % among Sistani and 86.2 % among Balouch cases). The high prevalence of G6PD deficiency among Balouch populations confirms the hypothesis that the distribution of G6PD deficiency is concordant with the geographic distribution of malaria.

Molecular characterization of glucose-6-phosphate dehydrogenase deficiency in Jeddah, Kingdom of Saudi Arabia

Background

The development of polymerase chain reaction (PCR)-based methods for the detection of known mutations has facilitated detecting specific red blood cell (RBC) enzyme deficiencies. We carried out a study on glucose-6-phosphate dehydrogenase (G6PD) deficient subjects in Jeddah to evaluate the molecular characteristics of this enzyme deficiency and the frequency of nucleotide1311 and IVS-XI-93 polymorphisms in the glucose-6-phosphate dehydrogenase gene.

Results

A total of 1584 unrelated Saudis (984 neonates and 600 adults) were screened for glucose-6-phosphate dehydrogenase deficiency. The prevalence of glucose-6-phosphate dehydrogenase deficiency was 6.9% (n = 110). G6PD Mediterranean mutation was observed in 98 (89.1%) cases, G6PD Aures in 11 (10.0%) cases, and G6PD Chatham in 1 (0.9%) case. None of the samples showed G6PD A‾ mutation. Samples from 29 deficient subjects (25 males and 4 females) were examined for polymorphism. The association of two polymorphisms of exon/intron 11 (c.1311T/IVS-XI-93C) was observed in 14 (42.4%) of 33 chromosomes studied. This association was found in 9 (31.0%) carriers of G6PD Mediterranean and in 4 (13.8%) carriers of G6PD Aures.

Conclusions

The majority of mutations were G6PD Mediterranean, followed by G6PD Aures and < 1% G6PD Chatham. We conclude that 1311T is a frequent polymorphism in subjects with G6PD Mediterranean and Aures variants in Jeddah.

Molecular characterization of glucose-6-phosphate dehydrogenase gene defect in the Kuwaiti population

CONTEXT

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the most common human enzyme deficiencies. More than 130 different molecular abnormalities have been described worldwide, with considerable variation in the enzyme among various racial groups. Data from Kuwaiti populations are scarce, and the studies available are the result of screening male blood donors who may not be truly representative of the Kuwaiti population.

OBJECTIVE

The objective of this study was to investigate the mutation spectrum of the G6PD gene among Kuwaiti Arabs.

DESIGN

DNA was extracted from 82 G6PD-deficient Kuwaiti subjects (75 men and 7 women) and screened for gene mutations using polymerase chain reaction/restriction fragment length polymorphism and polymerase chain reaction/single-strand conformation polymorphism followed by direct sequencing. A total of 1209 randomly selected Kuwaiti adult subjects of both sexes were then screened for any characterized mutation.

RESULTS

G6PD Mediterranean(563C-->T), and A-(202G-->A,376A-->G) genotypes were characterized as the most common variants among the G6PD-deficient population, representing 0.742 and 0.124 allele frequencies, respectively. The 2 previously described mutations, G6PD Chatham(1003G-->A) and Aures(143T-->C), were found at lower frequencies (0.101 and 0.034, respectively). The allele frequencies for these 4 G6PD variants among the randomly selected Kuwaitis were 0.035, 0.0074, 0.0046, and 0.0023 for Mediterranean, A-, Chatham, and Aures, respectively.

CONCLUSION

This study has characterized the molecular heterogeneity of G6PD variants among ethnic Kuwaitis. The findings suggest that gene flow from the Indian subcontinent, sub-Saharan African, and other parts of the Mediterranean may have contributed to the observed G6PD mutations seen in the Kuwaiti population.

Distribution of apolipoprotein E alleles in the Omani population

OBJECTIVE

To estimate the apolipoprotein E (apo E) allele distribution in the Omani population and to compare them with those of other populations.

SUBJECTS AND METHODS

One hundred and sixty-two healthy Omanis of Arab Bedouin origin were genotyped by polymerase chain reaction followed by restriction fragment length polymorphism.

RESULTS

The apo E allele frequencies were: epsilon2, 0.052; epsilon3, 0.886; epsilon4, 0.062. This pattern of distribution, characterized by the lowest epsilon4 and among the highest epsilon3 allele frequencies in the world, was very similar to that of Arabs, Southern Europeans of the Mediterranean basin, Indians, and Japanese populations.

CONCLUSION

The results indicate that the allelic distribution of apo E in healthy Omanis is characterized by low Apo epsilon4 and high epsilon3 allele frequencies similar to those of other Arab, Southern European, Japanese and Indian populations. The homogeneous distribution of apo E alleles in this group of populations might have been influenced by diet and/or genetic admixture.

Molecular characterization of glucose-6-phosphate dehydrogenase deficiency in the Eastern Province of Saudi Arabia

The level of activity of the enzyme glucose-6-phosphate dehydrogenase (G6PD) was determined in 154 unrelated Saudi males and females with G6PD deficiency who were residing in the Eastern Province of Saudi Arabia. DNA was extracted from blood samples and analyzed for known G6PD mutations by polymerase chain reaction (PCR) and restriction fragment length polymorphism techniques. Two different polymorphic mutations were identified which accounted for 90% of the samples analyzed. Of 114 G6PD-deficient males, 96 had G6PD Mediterranean, nine had African deficient variant G6PD A- and in nine the mutation has not been identified. Of the 40 G6PD-deficient females, 34 were homozygous for the G6PD Mediterranean mutation and six were genetic compound, G6PD Mediterranean/G6PD A-. The data indicate that the G6PD Mediterranean mutation is the most common (84%) in the Eastern Province, followed by G6PD A- (5.8%). Seventy one subjects who suffered from favism were found to carry the Mediterranean mutation.

Diversity in expression of glucose-6-phosphate dehydrogenase deficiency in females

The aims of this study were to determine the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in the United Arab Emirates (UAE), to describe the different mutations in the population, to determine its prevalence, and to study inheritance patterns in families of G6PD-deficient individuals. All infants born at Tawam Hospital, Al-Ain, UAE from January 1994 to September 1996 were screened at birth for their G6PD status. In addition, those attending well-baby clinics during the period were also screened for the disorder. Families of 40 known G6PD-deficient individuals, selected randomly from the records of three hospitals in the country, were assessed for G6PD deficiency. Where appropriate, this was followed by definition of G6PD mutations. Of 8198 infants, 746 (9.1%), comprising 15% of males and 5% of females tested, were found to be G6PD deficient. A total of 27 families were further assessed: of these, all but one family had the nt563 Mediterranean mutation. In one family, two individuals had the nt202 African mutation. The high manifestation of G6PD deficiency in women may be due to the preferential expression of the G6PD-deficient gene and X-inactivation of the normal gene, and/or to the presence of an 'enhancer' gene that makes the expression of the G6PD deficiency more likely. The high level of consanguinity which, theoretically, should result in a high proportion of homozygotes and consequently a higher proportion of females with the deficiency, was not found to be a significant factor.