A new mutation in the beta-globin gene (IVS II-850 G-C) found in a Yugoslavian beta-thalassemia heterozygote.
BACKGROUND
The recent development of laboratory techniques that can rapidly characterize the molecular defects of beta-thalassemia has resulted in the discovery of more than 100 different point mutations in the beta-globin gene. These mutations are population specific. About 20 of them account for over 90% of beta-thal genes in the world. The other mutations are usually found in single families. In this paper we describe a case with a novel mutation at position IVS II-850 (G-C) as a cause of beta-thalassemia.


METHODS
Direct sequencing of PCR amplified DNA was used for the detection of the mutation. ASO probes were synthesized for dot-blot hybridization. Expression of the mutated allele was evaluated through Northern blot and RNA-PCR analyses.


RESULTS
This mutation was found in four members of a family, who exhibited severe microcytosis and hypochromic anemia, with an average alpha/beta ratio of 2.0. The sequencing of PCR amplified DNA showed a G-C mutation at position IVS II-850 of the beta-globin gene. Dot blot analyses confirmed the presence of this substitution in all four carriers. Northern blot and RNA-PCR analyses did not reveal any abnormally spliced mRNA species.


CONCLUSIONS
The G-C substitution at position IVS II-850 is the third mutation in the invariant AG dinucleotide of the acceptor splice site of the second intron of the beta-globin gene. It abolishes normal splicing, which leads to abnormally processed mRNA. It is a relatively rare mutation since it was not detected among the uncharacterized beta-thal chromosomes from Yugoslavia.
Jankovic
L
L
Macedonian Academy of Sciences and Arts, Research Center for New Technologies, Skopje.
Dimovski
A J
AJ
Sukarova
E
E
Juricic
D
D
Efremov
G D
GD
D001483:Base Sequence; D015152:Blotting, Northern; D005914:Globins / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D012326:RNA Splicing; D013789:Thalassemia / Q000097:blood / Q000235:genetics*; D015022:Yugoslavia
D005914:Globins