ABSTRACT
ß-Thalassemia is a genetic disease caused by a defect in the production of the ß-like globin chain. More than 200 known different variants can lead to the disease and are mainly found in populations that have been exposed to malaria parasites. We recently described a duplication of four nucleotides in the first exon of ß-globin gene in several families of patients living in Nord-Pas-de-Calais (France). Using the genotypes at 12 microsatellite markers surrounding the ß-globin gene of four unrelated variant carriers plus an additional one recently discovered, we found that they shared a common haplotype indicating a founder effect that was estimated to have taken place 225 years ago (nine generations). In order to determine whether this variant arose in this region of Northern Europe or was introduced by migrants from regions of the world where thalassemia is endemic, we genotyped the first 4 unrelated variant carriers and 32 controls from Nord-Pas-de-Calais for 97 European ancestry informative markers (EAIMs). Using these EAIMs and comparing with population reference panels, we demonstrated that the variant carriers were very similar to the controls and were closer to North European populations than to South European or Middle-East populations. Rare ß-thalassemia variants have already been described in patients sampled in non-endemic regions, but it is the first proof of a founder effect in Northern Europe.
Subject(s)
Codon , Founder Effect , Mutation , beta-Globins/genetics , beta-Thalassemia/diagnosis , Bayes Theorem , Exons , France , Gene Expression , Haplotypes , Heterozygote , Humans , Microsatellite Repeats , Pedigree , beta-Thalassemia/genetics , beta-Thalassemia/pathologyABSTRACT
A 37-year-old man presented a slight debility. The hemogram showed a phenotype of beta-thalassemia minor: Hb (13.1 g/dL), mean corpuscular volume (MCV) (62 fL) with low mean corpuscular hemoglobin (MCH) (20.8 pg), associated with a high level of Hb A(2) of 5.3%. The serum ferritin level was 1,072 ng/mL. The sequencing of the mutated fragment revealed a duplication of four bases of codons 7/8 involving a shift in the open reading frame starting from codon 9 with a TGA stop codon at codon 23: codons 7/8/9 (+AGAA); GAG.AAG.TCT(Gly-Lys-Ser)>GAG.AAAGAAG. The human hemoglobin (Hb) instability tests were negative. The patient did not present the high iron Fe (HFE) mutation (C282Y, H63D). The same mutation was found in five other unrelated families (representing a total of 23 patients). All of their ancestors came from the north of France. This mutation has not been described before and could have its origins in the native populations of Northern France.
Subject(s)
Codon/genetics , Mutation , beta-Globins/genetics , beta-Thalassemia/genetics , Adult , Amino Acid Sequence , Base Sequence , DNA Mutational Analysis , Family Health , Female , France , Humans , Male , Middle Aged , Phenotype , Sequence Homology, Amino Acid , Sequence Homology, Nucleic Acid , Siblings , beta-Thalassemia/pathologyABSTRACT
BACKGROUND: Most screening programs for sickle cell disease (SCD) utilize isoelectric focusing (IEF) or high performance liquid chromatography (HPLC) to detect haemoglobin (Hb) variants. The first method is not automated and becomes too tedious when many samples have to be investigated. The aim of this work is to explore the capacity of an automated capillary electrophoresis (CE) system, with full traceability, as a tool for newborn screening of SCD. METHODS: The Capillarys neonat fast automated system has been developed by Sebia for newborn screening. We performed separate studies using different types of samples to evaluate the utility of the Capillarys for (i) separating Hb S and other variants, and (ii) for performing the routine activity of our laboratory for 20 working days. RESULTS: A throughput of 48 samples per hour with a loading capacity of 192 samples was achieved. Migration times of the major Hb variants were distinct. There were few variants showing similar migration times to Hb S and Hb C and thalassaemia could be detected. In addition, late screening, screening of premature or transfused babies and screening performed using poor quality Guthrie's cards did not interfere with reporting of accurate phenotypes. CONCLUSIONS: Sebia Capillarys neonat fast automated system is a reliable tool for haemoglobinopathy neonatal screening.
