Analysis of a Novel Mexican Variant of the HBB Gene Associated with β-Thalassemia Using Bioinformatic Tools

Abstract

We present a study performed on 54 unrelated subjects, with and without thalassemic features. Two primer pairs were proposed to perform Sanger sequencing of the complete HBB gene. The bioinformatic analysis was performed taking advantage of the availability of free online tools. In the sample, we found 11 variants, 10 reported, and one novel. Among the variants found, six are clinically important: three encode a premature stop codon [codon 39 (C>T) (HBB: c.118C>T); IVS-II-1 (G>A) (HBB: c.315+1G>A), and one not reported], a double substitution within the same allele [Hb Borås (HBB: c.266T>G) and Hb Santa Giusta Sardegna (HBB: c.282T>C)], and one whose pathogenicity is not yet defined [Hb Fannin-Lubbock I (HBB: c.359G>A)]. Even though the variants Hb Borås and Hb Santa Giusta Sardegna have been described, there is no report of their combined occurrence on the same allele, which could cause hemolytic anemia. Although the p.Leu88Arg and p.Cys93Trp variants do not alter the final length of the protein, the bioinformatic results suggest that there are differences in the tertiary structure of β-globin genes, mainly affecting helices E and F, being the motifs of interaction with the heme group. The novel variant is a 4 bp insertion that modifies the open reading frame, changing the last amino acid residue and causing a premature stop codon (HBB: c.291-294insGCAC). The variant was associated with β-thalassemia (β-thal). Bioinformatic analysis made it possible to predict the consequences that the new variant of the HBB gene caused on the β-globin tertiary structure.

Keywords:

• β-Thalassemia (β-thal)
• bioinformatic
• Hb A
• HBB
• gene

Acknowledgments

We would like to thank Patricia Bouchan Valencia (MSc.) and Georgina C. Coeto Barona (Biol), Department of Perinatal Hematology, National Institute of Perinatology, Mexico City, Mexico, for their technical collaboration in this study. We would like to thank the patients participating in this study. In memory of our colleague and friend Leonardo Ibarra Zuñiga (QFB), Ortho Clinical Diagnostics, Mexico City, Mexico, who passed away during the preparation of this manuscript.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

This study was supported by a grant [212250–3101-10808–02-15] with federal funds assigned to the National Institute of Perinatology, Mexico City, Mexico.