title: Molecular and cellular analysis of three novel alpha2-globin gene promoter mutations [HBA2: c.-59C>T], [HBA2: c.-81C>A] and [HBA2: c.-91G>A] reveal varying patterns of transcriptional and translational activities.
abstract: While point mutations affecting the promoter region of β-globin gene are widely described, there are no well characterised reports of any point mutations currently found in the promoter of the α2-globin (HBA2) gene. We present clinical and experimental data for three novel HBA2 gene core and proximal promoter mutations. Using an in vitro system designed to assess the impact of point mutations, the three novel [HBA2:c.-59C>T], [HBA2:c.-81C>A] and [HBA2:c.-91G>A] promoter mutations identified in three unrelated patients were analysed for HBA2 gene transcriptional and translational activities. Following the generation and transfection of expression vectors carrying each mutation, the HBA2 transcription activity of the promoters from each mutant was analysed with quantitative real time-PCR (qReTi-PCR) technique. Immunofluorochemistry (IFC) was used to analyse HBA2 protein synthesis. The analyses showed that [HBA2:c.-59C>T] and [HBA2:c.-91G>A] mutant constructs caused significant reduction in the HBA2 transcription levels by 53.7% (p = 0.0008) and 36.2% (p = 0.004), respectively, resulting in markedly lower HBA2 protein labelling when compared to the wild type as shown with subsequent IFC analysis. Conversely, the [HBA2:c.-81C>A] construct showed no significant changes in either transcription (p = 0.089) or in protein labelling when compared to the wild type. The equal pAmp transcription levels found in each group confirmed that the observed labelling differences were not due to varying transfection efficiencies. This study emphasises the importance of in vitro studies to establish the impact of base substitutions on the level of gene expression, and the value of these studies in clinicopathological correlation so that appropriate advice can be given in genetic counselling.
authors.affiliation: 1Department of Haematology, PathWest Laboratory Medicine, QEII Medical Centre, Nedlands 2Department of Haematology, Sir Charles Gairdner Hospital, Nedlands 3School of Pathology and Laboratory Medicine, University of Western Australia, Nedlands 4School of Biomedical Sciences, Curtin University, Bentley, Western Australia, Australia 5Department of Medical Technology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Talal
authors.initials: T
authors.lastname: Qadah
authors.forename: Jill
authors.initials: J
authors.lastname: Finlayson
authors.forename: Maxine
authors.initials: M
authors.lastname: Dennis
authors.forename: Reza
authors.initials: R
authors.lastname: Ghassemifar
mesh_terms: D000328:Adult; D001483:Base Sequence; D001665:Binding Sites; D045744:Cell Line, Tumor; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics*; D006443:Hemoglobin A2 / Q000235:genetics*; D006801:Humans; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014176:Protein Biosynthesis; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D017931:DNA Primers; D006443:Hemoglobin A2