HBB gene mutation spectrum of beta-thalasemia patients from Turkey.

European Human Genetics Conference 2014, Milan, İtalya, 31 Mayıs - 03 Haziran 2014, cilt.22, sa.1, ss.140

Beta-thalasemia is de􀏐ined by the absence or decrease of beta globin via

mutations of the HBB gene and is one of the most common hereditary disorders

existing in Turkey. With the mean carrier frequency of β-thalassemia

being 2.1% in the general population, and rates as high as 10% concentrated

in certain regions of the country, hemoglobin electrophoresis of the individuals

at premarital stage and molecular diagnosis of the carrier individuals

for genetic counseling cannot be overstated. Targeted diagnosis of the

HBB gene mutations can be readily obtained using commercially available

reverse dot blotting kits. A sequence analysis of the complete HBB gene covering

UTR and near-gene regions provides a 99% mutation detection rate.

We report here a summary 􀏐inding of HBB gene analysis for 163 Turkish

patients, along with their family members totaling 248 individuals, referred

with beta-thalassemia indications covering the period of 2010-2014. 39

were found to have homozygous, 31 possessed compound heterozygous and

63 possessed heterozygous mutations. Overall, a total of 205 alleles were

found to have mutations. The 􀏐irst 15 frequented mutations covered 88%

of the entirety of all mutations. The summary range is as follows: c.93-21-

G>A (IVS1+110G>A) 30.7%; c.135delC (p.ser45fs) 7.8%; c.92+1G>A (IVSI-

1) 7.8%; c.25_26delAA (p.Lys9Valfs) 5.9%; c.20A>T (p.Glu7Val) 4.9%;

c.92+6T>C (IVS-I-6) 4.9%. We discuss that the commercial targeted kits

detect up to 80% of the HBB mutations for our patients. Sequence analysis

of the HBB gene from 5’ promoter (-250bp) to 3’ promoter region (*250bp)

contributes 15% to the mutation detection rate.