Molecular Spectrum of α- and β-Thalassemia Mutations in a Large Ethnic Hakka Population in Southern China

Knowledge and attitudes of thalassaemia among high-risk indigenous university students in Bangladesh: A pilot study

BACKGROUND AND OBJECTIVES

Thalassaemia is an inherited life-threatening but preventable haemoglobin disorder. South Asian countries, including Bangladesh, are the hotspots of the world's thalassaemia belt. Indigenous communities are underprivileged and vulnerable to genetic disorders, including thalassaemia. Understanding the perspectives of thalassaemia of future community leaders (indigenous university students) is critical for developing a tailor-made preventive strategy relevant to their communities. In this study, we aimed to assess the level of knowledge and attitudes towards thalassaemia among indigenous university students and determine their thalassaemia carrier status.

METHODS

A cross-sectional survey was conducted among 251 tribal university students using a published questionnaire between May and October 2018. The main survey instrument consisted of 22 anonymous questions. Descriptive and inferential statistical procedures were used for data analysis.

RESULTS

More than half (55%) of the indigenous students had never heard the term 'thalassaemia'. Around half (49%) of the marriages in their communities were consanguineous. The mean knowledge score was abysmal (4.91±2.65 out of a 12-point scale), which was not associated with the consanguinity of their parent but home districts. Multiple linear regression of demographic variables on the total knowledge score revealed that the overall knowledge is significantly associated with their home district (p< 0.05). Participants from science disciplines scored more than 1 point than their counterparts from Arts and Humanities (p = 0.08615).

CONCLUSIONS

For the first time, this study has identified knowledge gaps and misperceptions about thalassaemia among university students from indigenous communities in the southeastern region of Bangladesh. This study serves as a baseline for future interventions (premarital and prenatal screening) targeting future community leaders.

Thalassaemia in China

Because of successful thalassaemia prevention programmes in resource-rich countries and it's huge population China now has the greatest number of new cases of thalassaemia globally as well as more people with thalassaemia than any other country. 30 million Chinese have thalassaemia-associated mutations and about 300,000 have thalassaemia major or intermedia requiring medical intervention. Over the past 2 decades there has been tremendous economic growth in China including per capita spending on health care. There is now nation-wide availability and partial or full insurance for prenatal genetic testing, RBC-transfusions, iron-chelating drugs and haematopoietic cell transplants. Prenatal screening and educational programmes have reduced the incidence of new cases. However, substantial challenges remain. For example, regional differences in access to medical care and unequal economic development require innovations to reduce the medical, financial and psychological burdens of Chinese with thalassaemia and their families. In this review we discuss success in preventing and treating thalassaemia in China highlighting remaining challenges. Our discussion has important implications for resource-poor geospaces challenged with preventing and treating thalassaemia.

Prevalence and molecular characterization of alpha and beta-Thalassemia mutations among Hakka people in southern China

Our aim was to investigate molecular features of thalassemia for proper clinical consultation and prevention in Heyuan. In our research, a total of 25,437 positive screening subjects were further subjected to a genetic analysis of α-thalassemia (α-thal) and β-thalassemia (β-thal). The deletion of α-thal mutation was tested by Gap-PCR, while the non-deletion of α-thal and β-thal mutation were identified by the PCR-reverse dot blot (PCR-RDB) technique. Nested PCR detected Hkαα/-- SEA and Hkαα/αα. Among the 25,437 positive screening subjects, 44.09% (11216/25437) subjects were bearers of thalassemia variations, and 30.85% (7847/25437) subjects showed α-thal changes alone. Among the 23 genotypes with α-thal mutation alone, the three common genotypes were --SEA/αα(68.34%), -α3.7/αα(16.44%), and -α4.2/αα(6.38%). Of the 11.50% (2924/25437) subjects and 29 genotypes with β-thal mutation alone, the three common genotypes were βCD41-42/βN(36.22%), βIVS-II-654/βN(30.88%), and β-28/βN(13.47%). Additionally, of the 1.75% (445/25437) subjects and 55 genotypes showed both α- and β-thal mutations. We also identified 269 cases of Hb H and six patients of Hkαα. Furthermore, the common genotypes of α-thal and β-thal mutations were consistent with allele frequencies of mutations. Our study establishes molecular features of thalassemia among Hakka people in Heyuan. It will be useful for developing strategies to prevent thalassemia.

Molecular Spectrum, Ethnic and Geographical Distribution of Thalassemia in the Southern Area of Hainan, China

BACKGROUND

Thalassemia is one of the most common genetic diseases in southern China. Accurate population frequency data regarding the occurrence and distribution of thalassemia are important for designing appropriate prevention strategies for thalassemia. This study aims to reveal the molecular spectrum, ethnic and geographical distribution of thalassemia in the southern area of Hainan Province, China.

METHODS

A total of 9813 suspected carriers of thalassemia were screened for genetic analysis by using the PCR-reverse dot blot hybridization method targeting three known deletions of α-thalassemias (--^SEA, -α^3.7, and -α^4.2), three nondeletional mutations of α-thalassaemias (α^CS, α^QS, and α^WS) and the 17 most common mutations of β-thalassaemias in the Chinese population.

RESULTS

Approximately 6,924 subjects were genetically diagnosed as thalassemia carriers or patients, including 5812 cases of α-thalassemia (83.9%), 369 cases of β-thalassemia (5.3%), and 743 cases of α-composite β-thalassemia (10.7%). A total of 21 distinct genotypes were identified among the 5,812 α-thalassemia carriers, -α^4.2/αα, -α^3.7/αα, and -α^3.7/-α^4.2 were the most common α-thalassemia genotypes. The most frequent β-thalassemia genotype was β^CD41-42/β^N, with a notable proportion of 69.6%, followed by the β^-28M /β^N, β^IVS-II-654/β^N, β^CD71-72/β^N, β^E/β^N, and β^CD17/β^N genotypes. In addition, 37 genotypes were detected among the 743 cases of both α- and β-thalassemia mutations. The α-thalassemia genotypes were most commonly found in the Li people, who accounted for 73.5% of α-thalassemia carriers. The β-thalassemia genotypes were most commonly identified in the Han people, who accounted for 59.4% of β-thalassemia carriers. Among the subjects carrying both α- and β-thalassemia variations, only three ethnic minorities were identified, including the Li, Han, and Miao people, accounting for 82.0, 17.4, and 0.7%, respectively.

CONCLUSIONS

Our study indicates that there is high genetic heterogeneity, geographical and ethnic differences in thalassemia in populations in the southern area of Hainan Province. These findings will be helpful in guiding genetic counseling and prenatal diagnosis of thalassemia in Hainan Province.

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.

Iron Status in Relation to Low-Level Lead Exposure in a Large Population of Children Aged 0-5 Years

There are limited data regarding low lead exposure and iron status in Chinese children. This study aimed to examine the association between low-level lead exposure and iron status in a large population of children aged 0-5 years. We reviewed the records of children aged 0-5 years who had blood lead, iron, ferritin, and hemoglobin measurements during 2014-2017 at the Guangdong Women and Children Hospital. We identified 17,486 children with a blood lead level < 100 μg/L. Multiple linear and logistic regression analyses were performed to estimate the associations between blood lead levels and blood iron, serum ferritin, and hemoglobin. The mean concentrations of blood lead, iron, ferritin, and hemoglobin were 31.50 μg/L, 7.50 mmol/L, 46.98 ng/mL, and 120.41 g/L, respectively. Adjusting for age and sex, blood lead was negatively correlated with iron (r = - 0.073, p < 0.05), ferritin (r = - 0.043, p < 0.05), and hemoglobin (r = - 0.047, p < 0.05). Compared with the 1st quintile of lead exposure, the 5th quintile of lead exposure was associated with a 0.146 mmol/L decrease in blood iron, a 4.678 ng/mL decrease in serum ferritin, and a 1.245 g/L decrease in hemoglobin. Adjusted odds ratios (95% confidence interval) for the 5th quintile of blood lead were 1.39 (1.25-1.55) for iron deficiency and 1.45 (1.26-1.67) for anemia, relative to the 1st quintile. Our study findings confirmed the previously established association of blood lead levels with decreasing iron status and extended previous findings to even low-level lead exposure in Chinese children.

Molecular epidemiological and hematological profile of thalassemia in the Dongguan Region of Guangdong Province, Southern China

Background

Thalassemia is a common inherited hematological disease in tropical and subtropical regions. This study aimed to investigate the mutation spectrum of thalassemia in the Dongguan region of southern China and comprehensively analyze hematologic features of thalassemia carriers with various types of globin mutations.

Methods

A hematological screening including hematological indices such as mean corpuscular volume (MCV), mean corpuscular hemoglobin content (MCH), and mean corpuscular hemoglobin concentration (MCHC) was conducted in 19 442 people from Dongguan region, Guangdong province of China. Then, 4891 suspected thalassemia carriers were further investigated by genetic analysis of combined NGS and gap‐PCR.

Results

Totally, 2319 (11.9%) cases were diagnosed as carriers of thalassemia, of which 1483 cases (7.6%) were α‐thalassemia, 741 cases (3.8%) were β‐thalassemia, and 95 cases (0.5%) were co‐inheritance of α‐ and β‐thalassemia. In α‐thalassemia carriers, the phenotypic severity increases with the number of nonfunctional α‐globin genes. The patients with –^SEA/α^WSα genotype have less severe clinical phenotypes than those with other Hb H diseases. As for β‐thalassemia, the MCV and MCH in both β⁰ and β⁺ carriers are markedly reduced.

Conclusions

This is the first comprehensive molecular epidemiological survey and hematological profiling of thalassemia in Dongguan area. This study will be benefit for genetic counseling in the clinic and may help pediatricians to make a correct diagnosis of different types of thalassemia.

Prenatal diagnosis of a rare β-thalassemia gene －90 (C>T) (HBB: c.-140 C>T) mutation associated with deletional Hb H disease (--SEA /-α4.2 )

Background

Hemoglobin H (Hb H) disease can be caused by compound heterozygosity for two different mutations or from homozygotes for mutations, and conventional genetic methods may lead to misdiagnosis when Hb H disease is combined with a rare β‐thalassemia.

Methods

Hematology parameters and hemoglobin electrophoresis analysis, gap‐polymerase chain reaction (gap‐PCR) and reverse dot‐blot hybridization (RDB‐PCR) were employed to identify common α‐thalassemia and Hb H disease. Rare β‐thalassemia mutations were detected by DNA sequencing.

Results

Hematological analysis and hemoglobin electrophoresis revealed a mild anemia α⁰‐thalassemia trait (Hb 90 g/L, MCV 71 fL, and MCH 22.7 pg) compound with β⁺‐thalassemia trait (MCV 71 fL, MCH 22.7 pg, and HbA2 5.51%) for the pregnant woman. DNA sequencing for the β‐globin gene revealed rare a －90 (C>T) (HBB: c.‐140 C>T) mutation for the woman. DNA analysis identified that the fetus inherited the α⁰‐thalassemia mutation [‐‐^SEA (Southeast Asian)] and a rare β⁺‐thalassemia mutation －90 (C>T) (HBB: c.‐140 C>T) from the mother, and the α⁺‐thalassemia mutation [‐α^4.2 (leftward)] from the father.

Conclusion

We reported a rare －90 (C>T) (HBB: c.‐140 C>T) mutation combined with the ‐‐^SEA/‐α^4.2 in a family. This finding enriched the mutation spectrum of thalassemia molecular characteristics in China and emphasized the significance in DNA sequencing in mutation screening for the families with thalassemia.

Development of a genomic DNA reference material panel for thalassemia genetic testing

INTRODUCTION

Thalassemia is one of the most common autosomal recessive inherited diseases worldwide, and it is also highly prevalent and variable in southern China. Various types of genetic testing technologies have been developed for diagnosis and screening of thalassemia. Characterized genomic DNA reference materials (RMs) are necessary for assay development, validation, proficiency testing, and quality assurance. However, there are no publicly available RMs for thalassemia genetic testing as yet.

METHODS

To address the need for the publicly available DNA RMs for thalassemia genetic testing, the National Institutes for Food and Drug Control and the China National GeneBank established 32 new cell lines with three wild-type genotypes and 29 distinct genotypes of thalassemia which account for approximately 90% thalassemia carriers in China. The genomic DNA of 32 cell lines was characterized by four clinical genetic testing laboratories using different genetic testing methods and technology platforms.

RESULTS

The genotyping results are concordant among four laboratories. In addition, the results of stability test demonstrated that the genotypes of these DNA samples are not influenced by preanalytical conditions such as long-term exposure to high-temperature (37°C) environment and repeated freeze-thawing.

CONCLUSION

We developed the first national panel of 32 genomic DNA RMs which are renewable and publicly available for the quality assurance of various genetic testing methods and will facilitate research and development in thalassemia genetic testing.

Alpha and beta-Thalassemia mutations in Hubei area of China

Background

Thalassemia is a group of inherited hemoglobic disorders resulting from defects

in the synthesis of one or more of the hemoglobin chains, which is one of the most prevalent inherited disorders in southern China. Only few studies reported the molecular characterization of α- and β-Thalassemia in Hubei Province in the central of China.

Methods

A total of 4889 clinically suspected cases of thalassemia were analyzed by Gap-PCR, PCR-based reverse dot blot (RDB).

Results

1706 (33.8%) subjects harbored thalassemia mutations, including 539 (11.0%) subjects with α-thalassemia, 1140 (23.3%) subjects with β-thalassemia mutations, and 25 (0.51%) subjects with both α- and β-thalassemia mutations. Seven genotypes of α-thalassemia mutations and 29 genotypes of β-thalassemia mutations were characterized. --^SEA/αα (66.05%), −α^3.7/αα (24.12%), and -α^4.2/αα (3.71%) accounted for 93.88% of the α-thalassemia mutations. βIVS-II-654/βN, βCD41–42/βN, βCD17/βN, βCD27–28/βN, βCD71–72/βN, β − 28/βN, β − 29/βN, βCD43/βN, βE/βN, accounting for 96.40% of all β-thalassemia genotypes. Furthermore, mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) were sensitive markers for both β-thalassemia and α-thalassemia with --^SEA/αα, but not -α^3.7/αα and -α^4.2/αα. Conclusions: Our data indicated great heterogeneity and extensive spectrum of thalassemias in Hubei province of China.

Prevalence and genetic analysis of thalassemia in neonates in Wuhan area: a national megacity in central China

BACKGROUND

Thalassemia is one of the most common genetic diseases in southern China. Accurate population frequency data regarding the occurrence and distribution of thalassemia is important for designing appropriate prevention strategies of thalassemia.

OBJECTIVE

The aim of this study is to reveal the prevalence and the mutation spectrum of thalassemia in neonates in the Wuhan region of central China.

METHODS

About 3796 neonates in Wuhan area of China were analyzed by hematological and genetic analysis.

RESULTS

About 2174 subjects were genetically diagnosed as thalassemia carriers or patients, including 1415 cases of α-thalassemia (65.89%), 731 cases of β-thalassemia (33.62%), and 28 cases of α-composite β-thalassemia (1.29%). A total of 11 genotypes and 6 gene mutations were identified in α-thalassemia anomalies, with -^SEA/deletion (50.72%), -α^3.7/deletion (36.36%), and -α^4.2/deletion (7.38%) being the most common α-thalassemia mutations. β-thalassemia anomalies were associated with 17 genotypes and 12 gene mutations; IVS-2-654 mutation was the most common (41.18%), followed by CD41-42 (23.14%), CD17 (14.64%), CD26 (7.32%), and CD27-28 (4.58%) mutations. In addition, 13 genotypes were identified in α-composite β-thalassemia in thalassemia carrier, with the top six genotypes being IVS-2-654/N/-^SEA/αα (17.86%), CD17/N/-α^3.7/αα (17.86%), IVS-2-654/N/-α^3.7/αα (14.29%), CD41-42/N/-^SEA/αα (10.71%), CD71-72/N/-α^3.7/αα (7.14%), and Cap/N/-^SEA/αα (7.14%).

CONCLUSION

There was high heterogeneity and extensive spectrum of thalassemia in the neonates in Wuhan populations. The findings will be useful for genetic counseling and prenatal diagnosis of thalassemia in the Wuhan region.