Revisiting a Complex Rearrangement Involving a 619 Base Pairs Deletion, 6 Nucleotide Insertion Followed by a A > G Substitution Causing ß°-Thalassemia.

One of the prevalent inherited blood disorders is thalassemia syndrome that characterized by reduction (ß+) or absence (ß0) of ß globin chain synthesis. The ß globin (HBB) gene map in the short arm of chromosome 11 and most of the mutations in this gene are single nucleotide substitutions, insertions or deletions of nucleotides. Nucleotide sequence analysis of a partially deleted ß-globin gene from an Iranian carrier of ß-thalassemia displayed a complex rearrangement involving a 619 base pairs (bp) deletion. This rearrangement had originally been named as the 619 bp deletion and later on as the 619 bp deletion with a 7 bp insertion. In our study, using by single chain sequencing, we have shown that the actual rearrangement involves a 619 bp deletion, a 6 bp insertion followed by a G > A substitution deleting the exon 3 of the ß-globin gene. This clarification has to be inserted into the relevant databases as some of them still site the original 619 bp deletion with wrong breakpoints.