Characterisation and confirmation of rare beta-thalassaemia mutations in the Malay, Chinese and Indian ethnic groups in Malaysia

In Malaysia, about 4.5% of the Malay and Chinese populations are heterozygous carriers of β-thalassaemia. The initial identification of rare β-globin gene mutations by genomic sequencing will allow the development of simpler and cost-effective PCR-based techniques to complement the existing amplification refractory mutation system (ARMS) and gap-PCR used for the identification of β-thalassaemia mutations. DNA from 173 β-thalassaemia carriers and five β-thalassaemia major patients from the Malay, Chinese and Indian ethnic groups were first analysed by ARMS and gap-PCR. Ninety-five per cent (174/183) of the 183 β-globin genes studied were characterised using these two techiques. The remaining nine uncharacterised β-globin genes (4.9%) were analysed using genomic sequencing of a 904 bp amplified PCR product consisting of the promoter region, exon 1, intervening sequence (IVS) 1, exon 2 and the 5' IVS2 regions of the β-globin gene. The rare β-globin mutations detected in the Chinese patients were CD27/28 (+C) and CD43 (GAG-TAG), and -88 (C-T) in an Indian patient. Beta-globin mutations at CD16 (-C), IVS1-1 (G-A), IVS2-1 (G-A), -86 (C-G) and Haemoglobin South Florida (CD1, GTG-ATG) were confirmed in the Malay patients. The seven rare β-globin mutations and a rare haemoglobin variant confirmed in this study have been described in other populations but have not been previously described in Malaysian β-thalassemia patients.