Novel β‐thalassemia trait (IVS I‐1 G→C) in a Japanese family

Abstract

A rare ␤-thalassemia mutation at the splicing junction [namely, G→C in intervening sequence (IVS) I-1] was found in a Japanese family. The proband and his mother were heterozygous for the mutation. Analysis of mRNA extracted from the reticulocyte-rich fraction obtained from the proband's mother revealed that the mutant ␤-globin gene did not produce any detectable, stable mRNA including exon 1 and exon 2, since the polymorphism in exon 1 on her mutant gene was not detected in the RT-PCR products. Am.

Microcytosis and Alpha and Beta Thalassaemia in Prospective Blood Donors of East Indian Descent in Trinidad and Tobago

“…IVS I-5 G/C is the most common beta thalassaemia mutation in these areas and can lead to severe β+ thalassaemia. However the IVS II-666 T/C is a neutral polymorphism previously found in Saudi Arabia and in a Japanese family [5,6]. Lin in a larger study, (where microcytosis was defined as MCV<82 FL), in China showed a high prevalence of thalassaemia carriers (both alpha and beta, with heterozygote frequency ranging from 2.63% to 9.49% in different parts of one province [7].…”

In vitro expression of β-thalassaemia gene (IVS1-1G>C) reveals complete inactivation of the normal 5' splice site and alternative aberrant RNA splicing

“…Some cases of mRNA-de¢cient b-thalassaemia involve large deletions 7 or rearrangements of the b-globin genes; however, most cases are reported to be caused by other genetic mutations that a¡ect transcription, 1 RNA processing, 2 RNA transport (nucleus to cytoplasm), 3 mRNA stability in the cytoplasm, 4 nonsense-mediated mRNA decay, 5 or a combination of these factors. In this study to examine the cause of the drastically reduced mutant mRNA level in the reticulocytes from a patient with a G4C splicing junction mutation in IVS1--1of the b-globin gene, 6 we analysed the mRNA encoded by the cloned mutant gene in COS-1 cells. Our transient expression system using COS-1 cells indicated that the mutant gene containing IVS1--1C was transcribed at a similar level to the normal gene (analysed by RT-PCR), and this transcription was followed by the splicing and processing of the mutant RNA.…”

“…However, we did not observe these minor bands of mRNAs in vivo in the reticulocytes from the normal control or the proband. 6 The nucleotide sequences of these 5 0 and 3 0 'cryptic' splice sites are listed in Figure 2, and compared with the sequences of the normal 5 0 splice site of IVS1 or the 3 0 splice site in the 3 0 -£anking region as well as the consensus sequence of the 5 0 or 3 0 splice site.We think that unexpected splicing products from the normal (W2 and W3) and mutant (T3 and T4) b-globin gene might be produced by excess transcription occurring in the COS-1 cell expression system (gene dosage e¡ect caused by the combination of the T-antigen in the cells and the SV40-ori on the vector) and the highly e⁄cient promoter derived from cytomegalovirus in the pcDNAI. Furthermore, the excess expression may lead to aberrant RNA processing, including aberrant transportation, degradation of RNA and so on.…”

“…We previously reported a case of a heterozygous genetic mutation with a G4C mutation in IVS1--1 and a non-detectable level of mutant mRNA in the patient's reticulocytes by reverse transcription-polymerase chain reaction (RT-PCR). 6 In the present study, to determine whether the transcription and RNA splicing and processing of the mutant gene occurred, we cloned the mutant gene into an expression vector, transfected it into mammalian cells, and analysed the expressed mRNA.…”

“…6 In the present study, to determine whether the transcription and RNA splicing and processing of the mutant gene occurred, we cloned the mutant gene into an expression vector, transfected it into mammalian cells, and analysed the expressed mRNA.…”