Molecular characterisation of red cell glucose-6-phosphate dehydrogenase deficiency in north-west Pakistan

Frequency of G6PD Mediterranean in individuals with and without malaria in Southern Pakistan

Background

Pakistan has an estimated annual burden of 1.5 million malaria cases. The current situation calls for an effective malaria control and eradication programme in this country. Currently, primaquine is an attractive option for eliminating reservoirs of Plasmodium vivax hypnozoites and killing gametocytes of Plasmodium falciparum. However, this drug causes haemolysis in individuals who are glucose-6-phosphate (G6PD) deficient. It is important to map G6PD deficiency and malaria distribution in Pakistan to design an effective malaria eradication regimen. Frequency of G6PD deficiency (G6PDd) in malaria patients has not been reported from Pakistan in any meaningful way. The purpose of this study was to evaluate the frequency of G6PD c.563C>T (G6PD Mediterranean) in male individuals with and without falciparum malaria.

Methods

Two hundred and ten archived DNA samples from males (110 from falciparum malaria patients and 100 from healthy individuals) were utilized in this study. Healthy blood donors were selected based on stringent pre-defined criteria. Patients were confirmed for malaria parasites on microscopy and or immune chromatographic assay detecting P. falciparum histidine-rich protein 2. Parasitaemia was also computed. DNA samples were tested for G6PD c.563C>T mutation through PCR–RFLP according to the previously defined protocol and its allelic frequency was computed.

Results

G6PD c.563C>T was observed in four of 110 patients with falciparum malaria and in two of 100 healthy donors. Mean (± SD) haemoglobin, median (IQR) platelet and median (IQR) parasite count in G6PD-deficient malaria-patients were 8.9 ± 0.9 g/dL, 124 × 109/L (IQR 32, 171) and 57,920/μL of blood (IQR 12,920, 540,000) respectively.

Conclusions

Cumulative allelic frequency for G6PD 563c.C>T was 0.0285 detected in 6 of 210 X-chromosomes in Southern Pakistan. Frequency for this G6PD allele was 0.0364 in malaria-patients and 0.0200 in healthy individuals. Large studies including females are needed to elucidate the true burden of G6PDd in malaria-endemic areas. The information will enable local health policy makers to design effective strategies for eliminating malaria form this region.

A population survey of the glucose-6-phosphate dehydrogenase (G6PD) 563C>T (Mediterranean) mutation in Afghanistan

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common inherited enzyme defect and an important problem in areas with Plasmodium vivax infection because of the risk of haemolysis following administration of primaquine to treat the liver forms of the parasite. We undertook a genotypic survey of 713 male individuals across nine provinces of Afghanistan in which malaria is found, four in the north and five in the east. RFLP typing at nucleotide position 563 detected 40 individuals with the Mediterranean mutation 563C>T, an overall prevalence of 5.6%. This varied according to self-reported ethnicity, with prevalence in the Pashtun/Pashai group of 33/369 (8.9%) compared to 7/344 individuals in the rest of the population (2.0%; p<0.001, Chi-squared test). Multivariate analysis of ethnicity and geographical location indicated an adjusted odds ratio of 3.50 (95% CI 1.36-9.02) for the Pashtun/Pashai group, while location showed only a trend towards higher prevalence in eastern provinces (adjusted odds ratio = 1.73, 0.73-4.13). Testing of known polymorphic markers (1311C>T in exon 11, and C93T in intron XI) in a subset of 82 individuals wild-type at C563 revealed a mixture of 3 haplotypes in the background population and was consistent with data from the 1000 Genomes Project and published studies. By comparison individuals with G6PD deficiency showed a highly skewed haplotype distribution, with 95% showing the CT haplotype, a finding consistent with relatively recent appearance and positive selection of the Mediterranean variant in Afghanistan. Overall, the data confirm that the Mediterranean variant of G6PD is common in many ethnic groups in Afghanistan, indicating that screening for G6PD deficiency is required in all individuals before radical treatment of P. vivax with primaquine.

Neonatal hyperbilirubinemia in infants with G6PD c.563C > T Variant

Background

There is a strong correlation between glucose-6-phosphate dehydrogenase (G6PD) deficiency and neonatal hyperbilirubinemia with a rare but potential threat of devastating acute bilirubin encephalopathy. G6PD deficiency was observed in 4–14% of hospitalized icteric neonates in Pakistan. G6PD c.563C > T is the most frequently reported variant in this population. The present study was aimed at evaluating the time to onset of hyperbilirubinemia and the postnatal bilirubin trajectory in infants having G6PD c.563C > T.

Methods

This was a case–control study conducted at The Aga Khan University, Pakistan during the year 2008. We studied 216 icteric male neonates who were re-admitted for phototherapy during the study period. No selection was exercised. Medical records showed that 32 were G6PD deficient while 184 were G6PD normal. Each infant was studied for birth weight, gestational age, age at the time of presentation, presence of cephalhematoma, sepsis and neurological signs, peak bilirubin level, age at peak bilirubin level, days of hospitalization, whether phototherapy or exchange blood transfusion was initiated, and the outcome. During hospital stay, each baby was tested for complete blood count, reticulocyte count, ABO and Rh blood type, direct antiglobulin test and quantitative G6PD estimation [by kinetic determination of G6PDH]. G6PDgenotype was analyzed in 32 deficient infants through PCR-RFLP analysis and gene sequencing.

Results

G6PD variants c.563C > T and c.131 C > G were observed in 21 (65%) and three (9%) of the 32 G6PD deficient infants, respectively. DNA of eight (25%) newborns remained uncharacterized. In contrast to G6PD normal neonates, infants with c.563C > T variant had significantly lower enzyme activity (mean ± 1SD; 0.3 ± 0.2 U/gHb vs. 14.0 ± 4.5 U/gHb, p < 0.001) experienced higher peak levels of total serum bilirubin (mean ± 1SD; 16.8 ± 5.4 mg/dl vs. 13.8 ± 4.6 mg/dl, p = 0.008) which peaked earlier after birth (mean ± 1SD 2.9 ± 1.6 vs. 4.3 ± 2.3 days, p = 0.007). No statistically significant difference was observed in mean weight, age at presentation, hemoglobin, reticulocyte count, TSH level, hospital stay or in the frequency of initiation of phototherapy or blood exchange between the two groups.

Conclusions

We concluded that infants with G6PD c.563C > T variant developed jaundice earlier than infants with normal G6PD enzyme levels. Compared to G6PD normal infants, G6PD c.563C > T carrying infants had significantly low G6PD activity.

Molecular characterization of glucose-6-phosphate dehydrogenase deficiency in Pakistani population

INTRODUCTION

Glucose-6-phosphate dehydrogenase (G6PD; E.C. 1.1.1.49) deficiency is the commonest inborn error of metabolism with more than 140 genetic variants. The incidence of G6PD deficiency is 2-9% in Pakistan, but G6PD variants were never studied comprehensively. We therefore designed this study to describe the frequency of G6PD variants and their associated enzyme activities in Pakistan.

METHODS

Patients diagnosed with G6PD deficiency were enrolled. RFLP-PCR was utilized to identify common mutations previously reported from Asian countries. Where mutational analysis failed, amplification of 9-12 exons with subsequent gene sequencing was performed. G6PD enzyme activity was assessed through the quantitative enzyme assay.

RESULTS

Two hundred and seventy-six G6PD-deficient subjects (237 male and 39 women) were investigated. G6PD Mediterranean (563C-T) was the most common genetic variant (n=216 or 78%). G6PD Chatham (1003A-G) and G6PD Orissa (131C-G) were observed in 14 (5%) and two (0.7%) subjects respectively. A novel mutation 973 G-A with a predicated amino acid change of asp325asn was identified in exon 9. This was named G6PD Karachi after the place of origin of proband. Polymorphism in position 1311C/T was uniformly observed with all variants. Forty-three or 17% of DNA samples remained uncharacterized. Very low levels of G6PD enzyme activity was observed with 563C-T mutation.

CONCLUSION

We concluded that 563C-T was the commonest G6PD variant, while 1003A-G and 131C-G were less-frequent genetic variants of G6PD in Pakistani population. A novel genetic variant 973G-A was also identified. Very low levels of G6PD enzyme activity was seen with G6PD 563C-T. Mutational analysis failed in a significant proportion of samples warranting further work.

Population study of 1311 C/T polymorphism of Glucose 6 Phosphate Dehydrogenase gene in Pakistan - an analysis of 715 X-chromosomes

Background

Nucleotide 1311 polymorphism at exon 11 of G6PD gene is widely prevalent in various populations of the world. The aim of the study was to evaluate 1311 polymorphism in subjects carrying G6PD Mediterranean gene and in general population living in Pakistan.

Results

Patients already known to be G6PD deficient were tested for 563C-T (G6PD Mediterranean) and 1311 C-T mutation through RFLP based PCR and gene sequencing. A control group not known to be G6PD deficient was tested for 1311C/T only.

C-T transition at nt 1311 was detected in 60/234 X-chromosomes with 563 C-T mutation (gene frequency of 0.26) while in 130 of normal 402 X-chromosomes (gene frequency of 0.32).

Conclusion

We conclude that 1311 T is a frequent polymorphism both in general populations and in subjects with G6PD Mediterranean gene in Pakistan. The prevalence is higher compared to most of the populations of the world. The present study will help in understanding genetic basis of G6PD deficiency in Pakistani population and in developing ancestral links of its various ethnic groups.

Molecular characterization of erythrocyte glucose-6-phosphate dehydrogenase deficiency in Tunisia

Screening of G6PD deficiency was carried out on 79 unrelated subjects (32 females and 47 males), all coming from out consultation. DNA from deficient subject (11 females and 30 males) was analyzed for the presence of G6PD mutation. Known mutations were studied by the appropriate restriction enzyme digestion of fragment amplified by PCR. Where the mutation could not be identified in this way, the samples were subjected to SSCP analysis and abnormal fragments were sequenced. Through these methods, seven different mutations have been identified. Among deficient females, eight had the African variant A-(tow of them were homozygous) and three had the Mediterranean variant, one of them was homozygous and have had a haemolytic crisis after ingestion of fava beans showing at birth manifestation of neonatal jaundice. Among deficient males, four were hospitalized and transfused after a haemolytic crisis due to ingestion of fava beans. All of them have had manifestation of neonatal jaundice. Of them, one carried the Mediterranean variant and three others had the African variant A-. Among the remaining deficient males, 15 had A-variant, two had the Aurès mutation. SSCP analysis of nine mild deficient males, revealed the presence of the association of 1311 CT/93 TC in two subjects, a newly described silent mutation in the exon 12 associated with the polymorphism in the intron 11 93 TC in one subject and tow single intronic base deletion. The first is IVS V 17 (-C) found in two subjects and the second is IVS VIII 43 (-G) encountered in four subjects.

Molecular basis of G6PD deficiency in India

G6PD deficiency has been reported from India more than 30 years ago and about 13 variants have been characterized biochemically. Here, we report the results of an epidemiological study investigating G6PD deficiency and the mutations among 14 heterogenous populations of India. Of the 3166 males tested, 332 (10.5%) were found to be G6PD-deficient and the prevalence rate varied from 5.7% to 27.9% in the different population groups. Molecular characterization revealed that G6PD Mediterranean (563 C-->T) was the commonest (60.4%) deficient variant followed by G6PD Kerala-Kalyan (949 G-->A; 24.5%) and G6PD Orissa (131 C-->G; 13.3%). G6PD Mediterranean had a more widespread distribution as compared to G6PD Kerala-Kalyan and G6PD Orissa and was associated with both 1311 C and 1311 T polymorhism. G6PD Mediterranean was found to have significantly lower red cell enzyme activity and more severe clinical manifestations than the other two. G6PD Chatham (1003 G-->A) with undetected red cell enzyme activity and G6PD Insuli (989 G-->A) with normal G6PD activity were very rare in the Indian population. The absence of a large number of mutations causing G6PD deficiency points to the fact that the genetic diversity of these populations is considerably lowered than expected.

Glucose-6-phosphate dehydrogenase mutations and haplotypes in Mexican Mestizos

In a screening for glucose-6-phosphate dehydrogenase (G-6-PD) deficiency in 1985 unrelated male subjects from the general population (Groups A and B) belonging to four states of the Pacific coast, 21 G-6-PD-deficient subjects were detected. Screening for mutations at the G-6-PD gene by PCR-restriction enzyme in these 21 G-6-PD-deficient subjects as well as in 14 G-6-PD-deficient patients with hemolytic anemia belonging to several states of Mexico showed two common G-6-PD variants: G-6-PD A-(202A/376G) (19 cases) and G-6-PD A-(376G/968C) (9 cases). In 7 individuals the mutations responsible for the enzyme deficiency remain to be determined. Furthermore, four silent polymorphic sites at the G-6-PD gene (PvuII, PstI, 1311, and NlaIII) were investigated in the 28 individuals with G-6-PD A- variants and in 137 G-6-PD normal subjects. As expected, only 10 different haplotypes were observed. To date, in our project aiming to determine the molecular basis of G-6-PD deficiency in Mexico, 60 unrelated G-6-PD-deficient Mexican males-25 in previous studies and 35 in the present work-have been studied. More than 75% of these individuals are from states of the Pacific coast (Sinaloa, Nayarit, Jalisco, Michoacán, Guerrero, Oaxaca, and Chiapas). The results show that although G-6-PD deficiency is heterogeneous at the DNA level in Mexico, only three polymorphic variants have been observed: G-6-PD A-(202A/376G) (36 cases), G-6-PD A-(376G/968C) (13 cases), and G-6-PD Seattle(844C) (2 cases). G-6-PD A- variants are relatively distributed homogeneously and both variants explain 82% of the overall prevalence of G-6-PD deficiency. The variant G-6-PD A-(202A/376G) represents 73% of the G-6-PD A- alleles. Our data also show that the variant G-6-PD A-(376G/968C)-which has been observed in Mexico in the context of two different haplotypes-is more common than previously supposed. The three polymorphic variants that we observed in Mexico are on the same haplotypes as found in subjects from Africa, the Canary Islands, and Spain.

Molecular characterisation of red cell glucose-6-phosphate dehydrogenase deficiency in Singapore Chinese

Sixty-two G6PD deficient Chinese males have been investigated for the presence of seven mutations of the coding region of the G6PD gene by natural and artificially created amplified restriction sites. The results show that the G to T substitution at nucleotide (nt) 1376 and G to A substitution at nt 1388 represent 24% and 21% of G6PD deficiency, respectively, in the Singapore Chinese; 37% of the sample could not be characterised. The remaining samples were identified as follows: 10% C-->T at nt 563, 5% A-->G at nt 95, and 3% C-->T at nt 1024. The G to A substitution (nt 487) and the substitution A-->G (nt 493) were not present in this sample. None of the subjects with the Mediterranean mutation (563 C-->T) had the silent mutation at 1311 (C-->T). This study confirms the extreme molecular heterogeneity of the G6PD gene in the Chinese.