Genetic investigation of haemoglobinopathies in a large cohort of asymptomatic individuals reveals a higher carrier rate for β-thalassaemia in Sichuan Province (Southwestern China)

Molecular Characterization of α- and β-Thalassemia Among Children Less Than 18 Years Old in Guizhou, China

BACKGROUND

Thalassemia is an inherited hemolytic disease, the complications and sequelae of which have posed a huge impact on both patients and society. But limited studies have investigated the molecular characterization of α- and β-thalassemia in children from Guizhou, China.

METHODS

Between January 2019 and December 2022, a total of 3301 children, aged 6 months to 18 years, suspected of having thalassemia underwent molecular analysis.

RESULTS

Out of the total sample, 824 (25%) children were found to carry thalassemia mutations. The carrier rates of α-thalassemia, β-thalassemia, and α + β-thalassemia were determined as 8.1%, 15.6%, and 1.3%, respectively. Approximately 96.5% of the α-thalassemia gene mutations were --SEA (51%), ααCS (20.9%), -α3.7 (19.6%), and -α4.2 (5.0%). The most prevalent mutations of β-thalassemia were βCD17(A>T) (41.5%), βCD41-42(-TTCT) (37.7%), and βIVS-II-654(C>T) (11.3%). Additionally, we identified rare cases, including one case with ααHb Nunobiki/αα, two cases with triplicated α-thalassemia (one case with ααα/ααα and βCD41-42/βN and the other with ααα-3.7/αα and βE CD26/βN), and also one case with α Q-Thailandα/-α4.2 and βCD41-42/βN.

CONCLUSIONS

Our study findings provide important insights into the heterogeneity of thalassemia carrier rates and molecular profiles among children in the Guizhou region. The findings support the development of prevention strategies to reduce the incidence of severe thalassemia in the future.

Genotype analysis of 55,281 cases of thalassemia in northern Guangxi

OBJECTIVE

To understand the genotype and distribution of thalassemia in northern Guangxi.

METHODS

The study subjects were 55,281 individuals who came to the Affiliated Hospital of Guilin Medical University for genetic diagnosis of thalassemia from January 2012 to August 2023. All of their household registration was in the precincts of Guibei District and its affiliated counties. Red blood cell parameters and hemoglobin analysis were used for thalassemia screening. Gap-PCR, PCR-reverse dot blot hybridization (PCR-RDB), and multicolor melting curve analysis (MMCA) were used to identify common thalassemia genes. Multiplex ligation-dependent probe amplification (MLPA), Sanger sequencing, and third-generation single-molecule real-time (SMRT) sequencing were employed to identify rare thalassemia genes.

RESULTS

Among the 55,281 samples, 16,442 (29.74%) were diagnosed with thalassemia. The detection rates of α, β, and α combined β-thalassemia were 18.57%, 9.99% and 1.18%, respectively. Among ethnical groups, allele mutation frequency of thalassemia was the highest in Zhuang (44.97%), followed by Yao (40.11%), Dong (31.33%), Han (29.85%), Miao (24.31%), and Hui (20.6%). A total of 11,659 alleles (21.09%) of 8 types of α-thalassemia were identified in 55,281 samples, primarily --SEA (53.9%), followed by -α3.7 (21.3%), including rare alleles: --THAI (0.45%) and HKαα (0.38%). A total of 6367 (11.52%) and 14 types of β-thalassemia alleles were identified, mainly CD41-42 (50.12%), followed by CD17 (22.22%), including rare alleles: βCD37 (0.16%) and Gγ+ (Aγδβ)0/βN (0.05%). A total of 31 genotypes were detected in 10,264 cases of α-thalassemia, and the main types were --SEA/αα (53.23%), -α3.7/αα (19.15%), and -α4.2/αα (7.21%). A total of 34 genotypes were detected in 5525 cases of β-thalassemia, and the main types were βCD41-42/βN (50.53%), βCD17/βN (21.77%), and βIVS-II-654/βN (12.16%). A total of 78 gene types were detected in 653 cases of α- and β-thalassemia, and the main types were --SEA/αα, βCD41-42/βN (18.68%) and -α3.7/αα, βCD41-42/βN (13.02%). There were 580 cases (5.65%) of HbH disease (α0/α+), and 4 cases of Hemoglobin Bart's Hydrops Foetus syndrome (--SEA/--SEA). In addition, there were 92 cases (1.67%) of intermedia or severe types of β-thalassemia (β0/β0, β0/β+, β+/β+), including 23 cases of combined α-thalassemia. Among the samples screened negative for thalassemia, 3.7% of them were found to carry thalassemia genes, and 91.35% of the genotypes were αWSα/αα, -α3.7/αα, and -α4.2/αα. In addition, 40.26% of αWSα/αα, 22.89% of -α3.7/αα, and 18.51% of -α4.2/αα had no hematological phenotype.

CONCLUSION

The population in northern Guangxi exhibited rich ethnic diversity, with high allelic carrying rates among the Zhuang, Yao and Dong ethnic groups. Thalassemia gene mutations are diverse, encompassing a variety of gene types, with α thalassemia predominating, notably the --SEA/αα gene type. The prevalence of intermedia or severe types of thalassemia is not low, but there are still some carriers of thalassemia in people who are initially tested negative.

Molecular analysis of alpha- and beta-thalassemia in Meizhou region and comparison of gene mutation spectrum with different regions of southern China

BACKGROUND

Thalassemia is a group of inherited autosomal recessive hemolytic anemia disease caused by reduced or absent synthesis of globin chain/chains of hemoglobin. Only few studies showed the molecular characterization of α- and β-thalassemia in Meizhou city of China.

METHODS

A total of 22,401 individuals were collected; hematological and hemoglobin electrophoresis analysis and thalassemia genetic testing were performed.

RESULTS

Eleven thousand and thirty (49.24%) cases with microcytosis (mean corpuscular volume (MCV) < 82 fl), 11,074 (49.44%) cases with hypochromia (mean corpuscular Hb (MCH) < 27 pg) in 22,401 subjects, 11,085 cases with abnormal hemoglobin results were identified in subjects aged ≥6 months. 7,322 (32.69%) subjects harbored thalassemia mutations, including 4,841 (21.61%) subjects with α-thalassemia, 2,237 (9.99%) with β-thalassemia, and 244 (1.09%) with α-thalassemia combined β-thalassemia. 18 genotypes of α-thalassemia mutations and 27 genotypes of β-thalassemia mutations were characterized. The most frequent α gene mutation was --SEA (64.69%), followed by -α3.7 (19.93%), -α4.2 (7.73%), αCS α (3.97%), and αWS α (2.83%). The six most common β-thalassemia mutations were IVS-II-654 (C>T) (39.79%), CD41-42 (-TCTT) (33.02%), -28 (A>G) (10.38%), CD17 (A>T) (9.08%), CD27-28 (+C) (2.14%), and CD26 (G>A) (2.02%). In addition, MCV and MCH were sensitive markers for α- and β-thalassemia except for -α3.7 /αα, -α4.2 /αα, αCS α/αα, αWS α/αα, and βCap+40-43 /βN .

CONCLUSIONS

The --SEA , -α3.7 , and -α4.2 deletions were the main mutations of α-thalassemia, while IVS-II-654 (C>T), CD41-42 (-TCTT), -28 (A>G), and CD17 (A>T) mutations of β-thalassemia in Meizhou. There were some differences in thalassemia mutation frequencies in Meizhou city from other populations in China.