Evidence for a gene conversion in a Hb Arya Carrier [α codon 47 Asp&gt;Asn, Hb A1(or Hb A2):c.142 G&gt;A]

Pécriaux, Adrien; Paillard, Catherine; Galoisy, Anne; Riou, Jean; Metayer, Nathalie Le; Wajcman, Henri; Pissard, Serge

doi:10.1111/ijlh.12609

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…9 One possible mechanism would involve Hb Lepore which arises from an illegitimate recombination between the δ and β genes, resulting in a fusion 5 0 δ- other examples of hybrids between the δ and β chains, 9 as the anti-Lepore variants, which are the counterpart of the Lepore recombination and produce a 5 0 β-3 0 δ fusion gene and a variant protein which migrates as Hb A2 but is expressed as a beta chain because it is driven by a β promoter. 10 In our variant, the sequence of the beta gene showed that the only DNA trace of the delta gene found are 3 codons within 10 bases (exon 2B), which is the most frequent Hb Lepore found worldwide. [11][12][13] The fusion gene is driven by a beta promoter and the IVS2 is of beta type since in Hb LBW the delta gene stops after codon 87 and, as expected, expression should be normal, which is consistent with our RP-HPLC findings showing that the two proteins are expressed at the same level (28.7% W/Y/30.8%…”

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confidence: 49%

A high level of Hb F unmasks a new case of Hb Wanjiang (β (F3‐F4) Ala87_Thr88delinsSer_Gln (HBB:c.255_264 delinsTTTTTCTCAG)) in a pregnant woman of African ancestry

Pissard,

Moyrand,

Peron

et al. 2023

Int J Lab Hematology

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Blood count and hemoglobin (Hb) analysis are mandatory steps in the laboratory testing of a patient belonging to a community at high risk for hemoglobinopathies, especially during pregnancy, the aim being to detect possible transmission of a harmful variant and, eventually, to propose a prenatal diagnosis. When evidence for an unexpected peak is found, a thorough Hb analysis is required. We describe a patient in whom thorough molecular studies and Hb analysis unmasked a rare complex variant and demonstrated pitfalls of Hb analysis. 1,2 The 23-year-old patient born in Yogoupon (Ivory Coast) was followed up for a twin pregnancy. She had to be hospitalized briefly because of gestational hypertension, hepatic cytolysis and renal dysfunction. She was not known to suffer from any red cell abnormality, but because of her origin, hemoglobinopathies investigations were proposed to confirm the absence of any such abnormality. Laboratory tests during hospitalization revealed hematologic data in the normal range for her pregnancy, except for an additional Hb peak detected using capillary electrophoresis (eCap) (Capillarys, Sebia, Lisses, France) in the D-zone which was suspected to be Hb F (Figure 1A). Since this Hb fraction was estimated at 8%, which is higher than the slightly increased Hb F value expected during pregnancy (below 5%), genetic counseling was offered and informed consent was obtained to perform the full identification of the variant with a complete Hb study and globin gene analysis, in order to ensure there was no rare variant harmful for the twins. Biochemical analysis during hospitalization and 4 months after delivery revealed no constitutive abnormality (all laboratory are presented in Table 1). After delivery, the twins were included in a scheme for neonatal detection of hemoglobinopathies and dried blood spots were collected on cardboard for analysis. To the full Hb study we added cation exchange HPLC (CE-HPLC) (Variant 2, Bio-Rad, Hercules CA) and isoelectric focusing (Figure 1B), which showed that the peak was not, in fact, Hb F, but an unknown variant amounting to around 8% according to E cap. We thus studied the isolated globin chains by reverse-phase HPLC (RP-HPLC) 2 and mass spectrometry analysis using the Maldi-8020 (Shimadzu, Kyoto, Japan), combined with Neohemog ® , 3 a dedicated solution for hemoglobinopathy screening (Biomaneo, Dijon, France). This demonstrated that:(1) the variant was a beta variant and not Hb F, since no γ-chains could be resolved using RP-HPLC, and (2) the variant was expressed in the same quantity as the normal chain (RP-HPLC and MALDI TOF mass spectrometry analysis Figure 1C,D). RP-HPLC analysis demonstrated that the twins were free of the variant. We then performed molecular identification of this variant using Sanger analysis of the β-globin gene and multiplex ligation-dependent probe amplifica-

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confidence: 49%

A high level of Hb F unmasks a new case of Hb Wanjiang (β (F3‐F4) Ala87_Thr88delinsSer_Gln (HBB:c.255_264 delinsTTTTTCTCAG)) in a pregnant woman of African ancestry

Pissard,

Moyrand,

Peron

et al. 2023

Int J Lab Hematology

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“…These results should be reconsidered by the researchers for the proper classification of the variant in α-globin genes. Analytic tools and HbVar database should updated for the gene conversions reported between the HBA1 and HBA2 genes [ 6 , 14 , 15 , 16 ].…”

Section: Resultsmentioning

confidence: 99%

Impact of annotation error in α-globin genes on molecular diagnosis

Borgio

2017

PLoS ONE

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BackgroundRecent studies on the variants in duplicated human alpha globin genes (HBA2 and HBA1) actively target the α-globin gene as molecular modulators for the treatment of β-thalassemia major. Identification of the exact position of variant in HBA1, HBA2 or its patchworks is mandatory to support the therapeutic aims in β-thalassemia major, by identifying specific modulators for the reactivation of fetal hemoglobin production. Hence, accurate identification of the variants in α-globin genes is crucial for the proper diagnosis, treatment and genetic counseling.MethodThe objective was to reveal the annotation errors produced in α-globin gene sequence analysis while using different analytic tools. An HBA2 gene sequence with the HBA2:c.95+2_95+6delTGAGG variant and a recently reported HBA12 gene convert have been taken as examples to prove annotation error in α-globin gene from different analytic tools.Results and discussionAlthough various bioinformatics tools used to predict variants are usually of high reliability, the current study using the an alpha globin 2 sequence with the HBA2:c.95+2_95+6delTGAGG variant and a recently reported HBA12 gene convert, has showcased ambiguous outputs among the three bioinformatics tools used and against the manual analytical method adopted.ConclusionsThis report emphasizes the necessity for caution in the usage of DNA sequence analysis tools during molecular diagnosis and the importance of the selection of more appropriate tools for analysis. Furthermore, ethnic specific sequences should be considered as reference sequence for the analysis to bypass sequence dissimilarities among diverse populations.

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Evidence for a gene conversion in a Hb Arya Carrier [α codon 47 Asp>Asn, Hb A1(or Hb A2):c.142 G>A]

Cited by 2 publications

References 8 publications

A high level of Hb F unmasks a new case of Hb Wanjiang (β (F3‐F4) Ala87_Thr88delinsSer_Gln (HBB:c.255_264 delinsTTTTTCTCAG)) in a pregnant woman of African ancestry

A high level of Hb F unmasks a new case of Hb Wanjiang (β (F3‐F4) Ala87_Thr88delinsSer_Gln (HBB:c.255_264 delinsTTTTTCTCAG)) in a pregnant woman of African ancestry

Impact of annotation error in α-globin genes on molecular diagnosis

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