(Alpha)alpha 5.3: a novel alpha(+)-thalassemia deletion with the breakpoints in the alpha 2-globin gene and in close proximity to an Alu family repeat between the psi alpha 2- and psi alpha 1-globin genes

Abstract

A novel 5.3-kb deletion of the alpha-globin gene cluster was observed in a family from Naples, Southern Italy. It removes the 5′ end of the alpha 2-globin gene, causing an alpha (+)-thalassemia defect. Because of the presence of the residual 3′ end of the alpha 2-globin gene, we indicated this new haplotype with the symbol (alpha)alpha 5.3. The 5′ breakpoint, the first to be reported in the intergene region of the psi alpha 2- and psi alpha 1-globin genes, is located 822 bp upstream of the cap site of the psi alpha 1-gene and about 150 bp upstream of a 300- nt Alu family member. The 3′ breakpoint is located in the IVS-1 nt 58 of the alpha 2-globin gene. The 5.3-kb deleted fragment shows particular characteristics: it contains four Alu sequences having long regions 80% complementary and the 5′-GGCC-3′ short repeat at both ends. The sequences spanning across the breakpoints on the same strand and containing this repeat on their 3′ and 5′ ends, respectively, are 17 of 25 base complementary. These particular features led us to assume the formation of a multistem-loop due to the intrastrand interaction between the complementary regions as intermediate to the deletion. The unusual localization of the 5′ breakpoint suggests that even the intergene region of the psi alpha 2- and psi alpha 1-globin genes may function as a deletion target.

Sequence variations of the ?-globin genes: Scanning of high CG content genes with DHPLC and DG-DGGE

“…DNA was purified from peripheral blood leukocytes by a saltingout procedure [Miller et al, 1988]. Carriers and patients had previously been screened for deletions of the a-globin gene cluster with restriction mapping of genomic DNA [Lacerra et al, 1991] or with gap-PCR [Dodé et al, 1993;Bowden et al, 1992]. Identification of variant alleles was carried out by restriction analysis with HphI and NcoI enzymes [Orkin et al, 1981;Pirastu et al, 1984], manual PCR-direct-sequencing of DNA [Lacerra et al, 1991], or DNA sequencing with automated cycle sequencing (3100 Genetic analyzer; Applied Biosystems, Foster City, CA).…”

β+45 G → C: a novel silent β‐thalassaemia mutation, the first in the Kozak sequence

“…α ‐Globin gene rearrangements were detected by the digestion of genomic DNA with restriction enzymes, Southern blot and hybridization with an α ‐globin gene probe as previously reported (Lacerra et al , 1991).…”

Human α‐Thalassemia syndromes:Detection of molecular defects

“…(a)a5.3 is an a-thalassemia-2 deletion which was described in a family from Southern Italy and probably arose from an intrachromatid illegitimate recombination event involving AZu repeats [53]. -(a)'.2 is the smallest in different areas of the Mediterranean basin, while aTa was described in a familiy from Turkey [ 151.…”