Carrier screening and prenatal diagnosis of hemoglobinopathies. A study of indigenous and immigrant couples in northern Greece, over the last 5 years.

Hemoglobinopathies constitute the most frequent monogenic disorders worldwide and thalassemias are the most frequent genetic disorders in Greece. Over a 5-year period (2002-2006), 1,375 couples were screened for hemoglobinopathies and counseled at our Thalassaemia Prevention Unit, Hippokration Hospital, Thessaloniki, Greece. In 148 cases (10.7%), both partners carried an abnormal hemoglobin (Hb) gene and genetic counseling was offered. One hundred out of 116 pregnancies were at-risk of giving birth to an offspring carrying either the homozygous or double heterozygous forms of the mutations under discussion. The remaining 16 pregnancies involved couples who were heterozygous for mutations that did not cause severe clinical disease, and were exempted from prenatal diagnosis. Twenty-six fetuses were found to be homozygotes or double heterozygotes for clinically significant mutations. These couples were informed of the danger of having an affected child but the termination or continuation of the pregnancy was left to the couples to decide. Nevertheless, all the couples preferred to terminate the pregnancies. The National Thalassaemia Prevention Programme has effectively decreased the incidence of thalassemia major and sickle cell syndromes in Greece.

G gamma-196 C-->T, A gamma-201 C-->T: two novel mutations in the promoter region of the gamma-globin genes associated with nondeletional hereditary persistence of fetal hemoglobin in Greece.

The increased level of fetal hemoglobin in nondeletional hereditary persistence of fetal hemoglobin (nd-HPFH) is associated with several single base substitutions in the promoter region of either the (G)gamma- or the (A)gamma-globin genes. In this study, we report two new forms of nd-HPFH found in two unrelated Greek adults with high HbF production (8.6% and 10.2% respectively) and positive for the (G)gamma-158 C-->T substitution. Scanning by DGGE analysis and direct sequencing of the gamma-globin gene 5' promoter region revealed the presence of a (G)gamma-196 C-->T in the first case and an (A)gamma-201 C-->T in the second. These mutations seem to reactivate gamma-genes and cause their high expression in the adult period.

The molecular heterogeneity of beta-thalassemia in Greece.

Beta-thalassemia is the most predominant genetic defect in Greece. In this study, we investigated the heterogeneity and the frequency of beta-thalassemia mutations among 3796 heterozygotes detected in the course of DNA based diagnoses. The diagnostic strategy included Denaturing Gradient Gel Electrophoresis (DGGE), Allele Specific Oligonucleotide Hybridization (ASO), GAP PCR, Restriction Enzyme (RE) analysis and direct sequencing and led to 100% identification of the underlying molecular lesion. Six out of 33 different beta-globin defects identified accounted for more than 91.4% of the total beta-thalassemia chromosomes in Greece. The beta-globin gene mutations cd29 C-->T, IVS-I-2 T-->C, IVS-I-5 G-->T, cd37 G-->A and poly A Kurdish AATAAA-->AATAAG are for the first time reported in Greece, whereas cd7 GAG-->TAG is a new beta(0)-thalassemia mutation detected in an adult man from Albania residing in Greece. Three DNA single nucleotide polymorphisms (IVS-I-85 T-->C, IVS-I-91 C-->T and IVS-I-108 T-->C) were also revealed; among these, IVS-I-85 T-->C and IVS-I-91 C-->T are new and described for the first time worldwide.