Gap-PCR Screening for Common Large Deletional Mutations of beta-Globin Gene Cluster Revealed a Higher Prevalence of the Turkish Inversion/Deletion (delta beta)(0) Mutation in Antalya

Abstract

Objective: Although the calculated carrier frequency for point mutations of the beta-globin gene is around 10% for Antalya Province, nothing is known about the profile of large deletional mutations involving the beta-globin gene. In this study, we aimed to screen common deletional mutations in the beta-globin gene cluster in patients for whom direct DNA sequencing was not able to demonstrate the mutation(s) responsible for the disease phenotype. Materials and Methods: Thirty-one index cases selected with a series of selection events among 60 cases without detected beta-globin gene mutation from 580 thalassemia-related cases tested by direct sequencing over the last 4 years in our diagnostic center were screened for the most common 8 different large deletional mutations of the beta-globin gene cluster by gap-PCR. Results: We detected 1 homozygous and 9 heterozygous novel unrelated cases for the Turkish inversion/deletion (delta beta)(0) mutation in our series of 31 cases. Our study showed that the Turkish inversion/deletion (delta beta)(0) mutation per se accounts for 16.6% of the unidentified causative alleles and also accounts for 1.5% of all detected mutations over the last 4 years in our laboratory. Conclusion: Since molecular diagnosis of deletional mutations in the beta-globin gene cluster warrants different approaches, it deserves special attention in order to provide prenatal diagnosis and prevention opportunities to the families involved. We conclude that the Turkish inversion/deletion (delta beta)(0), as the most prevalent deletional mutation detected so far, has to be routinely tested for in Antalya, and the gap-PCR approach has valuable diagnostic potential in the patients at risk.