The relative levels of α2-, α1-, and ζ-mRNA in HB H patients with different deletional and nondeletional α-thalassemia determinants

Smetanina, N.S.; Öner, Cihan; Baysal, E.; Öner, Reyhan; Bozkurt, G.; Altay, Çiğdem; Gürgey, Aytemiz; Adekile, Adekunle; Gu, Lihao; Huisman, T. H. J.

doi:10.1016/0925-4439(96)00024-5

Cited by 11 publications

(4 citation statements)

References 23 publications

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“…Interestingly, the AAUAGA motif was reported as functional solely in flatworms (Wahlberg and Johnson 1997), while its presence in human ␤-globin mRNA in replacement of the canonical signal is a known cause of ␤-thalassemia (Jankovic et al 1990;van Solinge et al 1996). Mutations in poly(A) signals causing ␣-and ␤-thalassemia result in elongated mRNAs (Orkin et al 1985;Smetanina et al 1996), meaning the poly(A) signal either is not functional or is used inefficiently. The situation is similar for the AAGAAA and AAUGAA motifs.…”

Section: Discussionmentioning

confidence: 99%

Patterns of Variant Polyadenylation Signal Usage in Human Genes

Beaudoing¹,

Freier²,

Wyatt³

et al. 2000

Genome Res.

623

615

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The formation of mature mRNAs in vertebrates involves the cleavage and polyadenylation of the pre-mRNA, 10-30 nt downstream of an AAUAAA or AUUAAA signal sequence. The extensive cDNA data now available shows that these hexamers are not strictly conserved. In order to identify variant polyadenylation signals on a large scale, we compared over 8700 human 3Ј untranslated sequences to 157,775 polyadenylated expressed sequence tags (ESTs), used as markers of actual mRNA 3Ј ends. About 5600 EST-supported putative mRNA 3Ј ends were collected and analyzed for significant hexameric sequences. Known polyadenylation signals were found in only 73% of the 3Ј fragments. Ten single-base variants of the AAUAAA sequence were identified with a highly significant occurrence rate, potentially representing 14.9% of the actual polyadenylation signals. Of the mRNAs, 28.6% displayed two or more polyadenylation sites. In these mRNAs, the poly(A) sites proximal to the coding sequence tend to use variant signals more often, while the 3Ј-most site tends to use a canonical signal. The average number of ESTs associated with each signal type suggests that variant signals (including the common AUUAAA) are processed less efficiently than the canonical signal and could therefore be selected for regulatory purposes. However, the position of the site in the untranslated region may also play a role in polyadenylation rate.The 3Ј untranslated regions (UTRs) of eukaryotic mRNAs contain regulatory elements affecting mRNA translation, stability, and transport. Mature 3Ј UTRs are formed by polyadenylation of the pre-mRNA, a coupled reaction involving endonucleolytic cleavage followed by poly(A) synthesis. A significant fraction of mRNAs display multiple polyadenylation sites (Gautheret et al. 1998). The choice of poly(A) sites may influence the stability, translation efficiency, or localization of an mRNA in a tissue-or disease-specific manner (Edwalds-Gilbert et al. 1997). In the mammalian system, effective polyadenylation requires two main sequence components: a highly conserved AAUAAA signal located 10-30 nucleotide 5Ј to the cleavage site and a more variable GU-rich element, 20-40 bases 3Ј of the site (see Proudfoot 1991; Colgan and Manley 1997 for reviews). Although the AAUAAA signal is often considered to be present in 90% of the mRNAs and replaced by a AUUAAA variant in the other 10% (Wahle and Keller 1996; Colgan and Manley 1997), alternate signals are certainly present in a significant fraction of the 3Ј ends (Claverie 1997;Gautheret et al. 1998;Tabaska and Zhang 1999;Graber et al. 1999).The expressed sequence tag (EST) database, dbEST (Boguski et al. 1993), which contains highly redundant partial cDNAs, especially from the 3Ј UTRs, is a rich source of information on mRNA 3Ј ends. Analyzing clustered EST sequences, we previously identified multiple cases of alternate polyadenylation in mRNA (Gautheret et al. 1998). Based on a public EST collection now containing over 1.4 million human sequences, the present work focuses on the region immediatel...

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Section: Discussionmentioning

confidence: 99%

Patterns of Variant Polyadenylation Signal Usage in Human Genes

Beaudoing¹,

Freier²,

Wyatt³

et al. 2000

Genome Res.

623

615

View full text Add to dashboard Cite

show abstract

“…Prior to 2008, α-thalassemia mutations were identified with previously described methods [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. After 2008, mutation analyses for the α-globin gene were evaluated with the α-Globin Strip-Assay (ViennaLab, Austria), based on the reverse-hybridization technique used for detection of the 21 most common α-thalassemia mutations in the Mediterranean region.…”

Section: Methodsmentioning

confidence: 99%

The Hematological and Molecular Spectrum of α-Thalassemias in Turkey: The Hacettepe Experience

Ünal¹,

Gümrük²

2015

Tjh

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Objective:The spectrum of α-thalassemias correlates well with the number of affected α-globin genes. Additionally, combinations of the several non-deletional types of mutations with a large trans deletion comprising the 2 α-globin genes have an impact on the clinical severity. The objective of this study was to analyze the hematological and molecular data of 35 patients with Hb H disease from a single center in order to identify the genotypes of Hb H disease and genotype-phenotype correlations.Materials and Methods:Herein, we report the hematological and mutational spectrum of patients with Hb H disease (n=35). Additionally, genotypes of α-gene mutations of 78 individuals, who were referred to our institution for α-gene screening, were analyzed. Results:Supporting the previous data from Turkey, -α3.7 was the most common mutation among patients with Hb H disease (62.8%) and in the other 78 subjects (39.7%). Of the patients with Hb H disease, the most common genotypes were -α3.7/--20.5, -α3.7/--26.5, and -α3.7/--17.5 in 10 (28.6%), 6 (17.1%), and 6 (17.1%) patients, respectively. Another small deletion, -4.2 alpha, and several non-deletional types of α-gene mutations, namely α (-5nt): IVS-I donor site (GAG.GTG.AGG->GAG.G-----); α (PA-2): AATAAA>AATGGA, and α (cd59): GGC->GAC, were found to be associated with Hb H disease when present at trans loci of one of the large deletions given above. The combinations consisting of 1 non-deletional and 1 of the large deletional types of mutations (αTα/--) at trans loci were found to result in a more severe phenotype compared to the genotypes composed of 1 small trans deletion of a large deletion (-α/--). The combination of α (Cd59) and -- in trans was associated with severe phenotype and the disease was associated with an increase in Hb Bart’s level with null Hb H. In spite of the presence of 2 intact α-globin genes, homozygosity for PA-2 mutation resulted in severe Hb H disease. Conclusion:This study indicated that Hb H disease is not rare in Turkey and its genotype is quite heterogeneous.

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“…Ayrıca yedi olgunun bu mutasyonu heterozigot olarak taşıdığı belirlenmiştir (Tablo 1 ve Şekil 1b) Aynı olgular 5nt delesyonel mutasyonunu Gap-PCR yöntemine göre standardize edilerek tekrar çalışılmıştır. Nondelesyonel mutasyon grubuna giren 5 nt'lik delesyonel mutasyonlar RNA 'splicing' mekanizmasını etkilediklerinden bu talasemilerin heterozigotları α-talaseminin "trait" fenotipine, homozigotları ise α talasemilerin daha ciddi formlarına neden olurlar [20]. Heterozigot olguların hematolojik verilerinin normale yakın oldukları gözlenmiştir.…”

Section: Introductionunclassified

The first observation of two alpha globin mutations in Turkey: Hb Stanleyville II and a homozygous 5nt deletion

Güzelgül¹

2014

Turk J Bioch

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Objective: In this study, we aimed to contribute prenatal diagnosis in the Çukurova region having high prevalence of hemoglobinopathies by implementing DNA sequencing analysis for the mutations undetectable by conventional methods. Methods: Hematological parameters of two families applied to Cukurova University Prenatal Diagnosis Center were analyzed. Hb variants were screened by cellulose acetate electrophoresis and by HPLC. DNA samples of cases were isolated using automatic DNA extraction machine. Microarray, RFLP, ARMS and Gap-PCR molecular methodologies carried out for determinations of hemoglobin mutations. Unidentified mutations were resolved by means of DNA Sequence Analysis. Results: We identified a previously unreported homozygous 5 nt deletional mutation [α2 IVS-1 134.-138. nt (TGAGG)] in Turkey by DNA Sequence Analysis. When we investigated twelve cases of this family by Gap-PCR and DNA Sequence Analysis it is observed that seven cases were heterozygous for 5nt deletion, a case found to be heterozygous 20.5 kb deletional mutation and four cases were found to be having no mutation. In the other family applied for prenatal diagnosis was observed to having Hb Stanleyville II [α2 78 (EF 7) Asn→ Lys (AAC→AAA)] mutation which is also a novel mutaion in Turkey. Mutations of eleven members of this family were determined by ARMS, RFLP, Gap-PCR and DNA Sequence Analysis, resulting in two cases heterozygous Hb Stanleyville II, five cases heterozygous 3.7 kb deletion, a case with heterozygous IVS-1-110 (G→C) mutation on β globin gene and three cases do not have any mutation. Conclusion: In this study, two types of mutations observed for the first time in Turkey have been identified.

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The relative levels of α2-, α1-, and ζ-mRNA in HB H patients with different deletional and nondeletional α-thalassemia determinants

Cited by 11 publications

References 23 publications

Patterns of Variant Polyadenylation Signal Usage in Human Genes

Patterns of Variant Polyadenylation Signal Usage in Human Genes

The Hematological and Molecular Spectrum of α-Thalassemias in Turkey: The Hacettepe Experience

The first observation of two alpha globin mutations in Turkey: Hb Stanleyville II and a homozygous 5nt deletion

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