Molecular epidemiological study of alpha- and beta-thalassemia in Sihui city.
OBJECTIVE
To investigate alpha- and beta-thalassemia (alpha- and beta-thal) gene frequencies and gene mutation spectrum in the population of Sihui City.


METHODS
The umbilical cord blood samples from 1 007 neonates and peripheral blood samples from 1 524 apparently healthy adults for pre-marriage health check in Sihui city were collected for molecular epidemiologic study of alpha- and beta-thal respectively. The diagnostic standard for alpha-thal was the presence of Hb Bart's, and that for beta-thal was both the decrease of mean corpuscular volume (MCV<80 fl) and the increase of Hb A(2) level (> or = 3.5%). The samples of identified subjects with positive thal genotypes were further examined with PCR-based DNA analysis for determining the alpha- or beta-globin gene genotype, while those from subjects with positive genotypes but without mutations known to Chinese subjects were subjected to DNA sequence analysis of beta-globin gene. In addition, the alpha-thal alleles, -alpha(3.7) and -alpha(4.2) were examined in all umbilical cord blood samples.


CONCLUSIONS
Of all the 1 007 umbilical cord blood samples, 110 were identified as from alpha-thal gene carriers, 3 from patients Hb H disease and 1 from patients with hydrops fetalis, which meant an alpha-thal gene frequency of 11.72% (118/1 007). Three types of alpha-gene deletion were identified in this cohort, with the frequency of 53.4% (--SEA)), 34.7% (-alpha(3.7)) and 11.9% (-alpha(4.2)) respectively. By examining the peripheral venous blood samples from the 1,524 healthy adult subjects, 59 subjects were found to be beta-thal gene carriers with a rate of 3.87% (59/1,524), whose genotypes were determined and from whom 7 beta-thal mutations were identified. Of these 59 beta-thal gene carriers, 11 were diagnosed as having heterozygotes compound for beta- and alpha-thal genes with the deletion of the --(SEA) in 7 cases and -alpha(3.7) in 4 cases respectively, showing an incidence of 0.72% (11/1,524). The three commonest point mutations, beta CD41-42 (-CTTT) frameshift mutation, beta IVS2-654(C-->T) aberrant splicing mutation and beta-28 (A-->G) transcription mutation occurred with a total frequency of 84.75% among subjects with beta-thal allele mutations. In addition, a novel mutation, beta-globin gene promoter -90 (C-->T) allele was detected for the first time in Chinese subjects.
Tan
Jin-rong
JR
Women and Children's Hospital of Sihui, Sihui 526200, China.
Li
Wen-jun
WJ
Ma
Jian-ying
JY
Mo
Qiu-hua
QH
Li
Li-yun
LY
Jia
Shi-qi
SQ
Lao
Xiong-wu
XW
Li
Li-yan
LY
He
Ru-qiao
RQ
Xu
Xiang-min
XM
D000328:Adult; D002681:China / Q000453:epidemiology; D005260:Female; D005787:Gene Frequency; D006579:Heterozygote; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009154:Mutation; D017085:alpha-Thalassemia / Q000453:epidemiology* / Q000235:genetics; D017086:beta-Thalassemia / Q000453:epidemiology* / Q000235:genetics