α-Thalassemia in The Netherlands: a heterogeneous spectrum of both deletions and point mutations

Abstract

In this article we describe the molecular characterization of 104 independent alpha-thalassemia patients identified by hematological analysis and family studies. During the study, another six chromosomes were identified with rearrangements of the alpha-cluster or point mutations in the alpha 2-globin gene, not associated with alpha-thalassemia, in healthy relatives of the patients. The molecular defects were established by Southern blot analysis and, if no deletions could be identified, the alpha-globin genes were investigated by denaturing gradient gel electrophoresis and single strand conformation analysis for the presence of point mutations. Following this strategy, we were able to identify the molecular basis of 131 independent alpha-thalassemia chromosomes. In two individuals, the alpha-thalassemia determinant could not be demonstrated at the molecular level. We identified eight different deletion and five non-deletion alpha-thalassemias, three rearrangements in the alpha-cluster, two alpha-chain variants, and a silent mutation in the alpha 2-globin gene not associated with alpha-thalassemia. The large heterogeneity of alpha-thalassemia mutations seen in the Dutch population might be typical for northern European countries where, besides the more common mutations introduced by migration, a variety of sporadic mutations was also found in the autochthonous population. The screening strategy as described here, capable of identifying a wide spectrum of both deletions and point mutations, identified 98% of the alpha-thalassemia determinants present in 133 chromosomes.

Molecular spectrum of α-globin gene mutations in the Aegean region of Turkey: first observation of three α-globin gene mutations in the Turkish population

“…The −α 3.7 mutation results from a reciprocal recombination, between highly homologous regions, called Z boxes, removing a single α-globin gene [10]. It is also reported to be the most prevalent mutation in many populations across various continents including Europe [14][15][16][17][18]. Another single α-gene deletion mutation is −α 4.2 mutation which is more prevalent in south Asia [17,19].…”

A complex haemoglobinopathy diagnosis in a family with both βo- and αo/+-thalassaemia homozygosity

“…6 The α-gene deletion was identified by standard Southern blot procedure, using Eco-RI and Bgl-II endonucleases and hybridisation with a 32 P-labelled α and gene probe. 7 The α gene point mutation was characterised by DGGE and sequence analysis as previously described. 8 The molecular analysis of the gene was done by selective amplification from genomic DNA of overlapping gene fragments followed by denaturing gradient gel electrophoresis (DGGE) as previously described.…”

Nine unknown rearrangements in 16p13.3 and 11p15.4 causing - and -thalassaemia characterised by high resolution multiplex ligation-dependent probe amplification

“…Six showed no resemblance to previously described deletions and were considered to be new (--GZ , --OH , (aa) L , (aa) ZW , --AB , --MK ). One has been described (Dutch II a 0 -thalassaemia) but the breakpoint position and deletion length could not be determined at the time 31 ; FISH analysis performed in John Radcliff Hospital in Oxford revealed an approximate deletion length of 300 kb (Higgs, personal communication). Four deletions show similarity with previously described deletions (fig 1B, last four deletions).…”