Transfusion-dependent thalassemia in Northern Sarawak: a molecular study to identify different genotypes in the multi-ethnic groups and the importance of genomic sequencing in unstudied populations

First Report of Filipino β0-Thalassemia/β-Thalassemia in a Chinese Family

A pregnant woman living in Fujian Province, southeastern China, presented due to a risk of having a baby with β-thalassemia major, during her second pregnancy, since she and her husband were suspected as β-thalassemia carriers and their affected daughter was a transfusion-dependent patient. Using the common α-thalassemia and β-thalassemia genotypes test, the pregnant woman was diagnosed as a β-thalassemia carrier with βIVS-2 - 654 (C→T)/βN genotype and her daughter had a homozygosity for IVS - 2 - 654 (C→T) mutation, however, no abnormalities were detected in her husband. SMRT identified a Filipino β0-deletion in her husband, and MLPA also revealed an unknown deletion in the HBB gene. Electrophoresis showed approximately 350 bp of the PCR product, and the β-Filipino genotype presented novel fracture fragments ranging from 5,112,884 to 5,231,358 bp, and lacked a 118,475 bp fragment relative to the wild-type sequence. The daughter was therefore diagnosed with the βIVS-2 - 654 (C→T)/βFilipino genotype. Prenatal diagnosis with umbilical cord blood at 27th week of gestation showed heteroztgosity for IVS - 2 - 654 (C→T) mutation in the fetus and continued pregnancy was recommended. In conclusion, we identified the Filipino β0-deletion in a Chinese family, from Fujian area, for the first time, during prenatal screening.

Evidence of new intragenic HBB haplotypes model for the prediction of beta-thalassemia in the Malaysian population

This study sought to determine the potential role of HBB haplotypes to predict beta-thalassemia in the Malaysian population. A total of 543 archived samples were selected for this study. Five tagging SNPs in the beta-globin gene (HBB; NG_000007.3) were analyzed for SNP-based and haplotype association using SHEsis online software. Single-SNP-based association analysis showed three SNPs have a statistically significant association with beta-thalassemia. When Bonferroni correction was applied, four SNPs were found statistically significant with beta-thalassemia; IVS2-74T>G (padj = 0.047), IVS2-16G>C (padj = 0.017), IVS2-666C>T (padj = 0.017) and 3'UTR + 314G>A (padj = 0.002). However, 3'UTR + 233G>C did not yield a significant association with padj value = 0.076. Further investigation using combined five SNPs for haplotype association analysis revealed three susceptible haplotypes with significant p values of which, haplotypes 1-2-2-1-1 (p = 6.49 × 10-7, OR = 10.371 [3.345-32.148]), 1-2-1-1-1 (p = 0.009, OR = 1.423 [1.095-1.850] and 1-1-1-1-1 (p = 1.39 × 10-4, OR = 10.221 [2.345-44.555]). Three haplotypes showed protective effect with significant p value of which, 2-2-1-1-1 (p = 0.006, OR = 0.668 [0.500-0.893]), 1-1-2-2-1 (p = 0.013, OR = 0.357 [0.153-0.830]) and 1-1-2-1-1 (p = 0.033, OR = 0.745 [0.567-0.977]). This study has identified the potential use of intragenic polymorphic markers in the HBB gene, which were significantly associated with beta-thalassemia. Combining these five SNPs defined a new haplotype model for beta-thalassemia and further evaluation for predicting severity in beta-thalassemia.

Next-generation sequencing improves molecular epidemiological characterization of thalassemia in Chenzhou Region, P.R. China

Objectives

Thalassemia is a highly prevalent monogenic inherited disease in southern China. It is important to collect epidemiological data comprehensively for proper prevention and treatment.

Methods

In this study, blood samples collected from 15 807 residents of Chenzhou were primarily screened by hematological tests. A total of 3973 samples of suspected thalassemia carriers were further characterized by combined next‐generation sequencing (NGS) and Gap‐PCR.

Results

In total, 1704 subjects were diagnosed as thalassemia carriers with a total prevalence rate of 10.78%, including 943 α‐thalassemia carriers, 708 β‐thalassemia carriers, and 53 composite α and β‐thalassemia carriers. The prevalence rates of α‐thalassemia, β‐thalassemia, and composite α and β‐thalassemia were 5.97%, 4.48%, and 0.34%, respectively. Meanwhile, we characterized 19 α‐thalassemia variations and 21 β‐thalassemia variations in thalassemia carriers. Approximately 2.88% of thalassemia carriers would be missed by traditional genetic analysis. In addition, four novel thalassemia mutations and one novel abnormal hemoglobin mutation were identified.

Conclusions

Our data suggest a high prevalence of thalassemia and a diverse spectrum of thalassemia‐associated variations in Chenzhou. Also, combined NGS and Gap‐PCR is an effective thalassemia screening method. Our findings might be helpful for prevention and treatment of thalassemia in this region.

A novel gap-PCR with high resolution melting analysis for the detection of α-thalassaemia Southeast Asian and Filipino β°-thalassaemia deletion

Homozygosity for the α-thalassaemia Southeast Asian (α-SEA) and Filipino β⁰-thalassaemia (β-FIL) deletions can cause serious complications leading to foetal death or life-long blood transfusions. A rapid and accurate molecular detection assay is essential in populations where the deletions are common. In this study, gap-polymerase chain reaction (PCR) with high resolution melting (HRM) analysis was developed to detect both the large deletions. Melting curves at 86.9 ± 0.1 °C were generated by normal individuals without the α-SEA deletion, 84.7 ± 0.1 °C by homozygous α-SEA deletion individuals and two melting curves at 84.7 ± 0.1 °C and 86.9 ± 0.1 °C by α-SEA deletion carriers. Normal individuals without the β-FIL deletion produce amplicons with a melting temperature (Tm) at 74.6 ± 0.1 °C, homozygous β-FIL individuals produce amplicons with Tm at 73.6 ± 0.1 °C and heterozygous β-FIL individuals generate two amplicons with Tm at 73.6 ± 0.1 °C and 74.6 ± 0.1 °C. Evaluation using blinded tests on 220 DNA samples showed 100% sensitivity and specificity. The developed assays are sensitive and specific for rapid molecular and prenatal diagnosis for the α-SEA and β-FIL deletions.