Coinheritance of Hb A₂-Melbourne (HBD: c.130G>A) and Hb E (HBB: c.79G>A) in Laos and Simultaneous High Resolution Melt Detection of Hb A₂-Melbourne and Hb A₂-Lampang (HBD: c.142G>A) in a Single Tube

Abstract

We report the molecular and hematological identifications of a Hb A₂ variant [coinheritance of Hb A₂-Melbourne (HBD: c.130G>A) and Hb E (HBB: c.79G>A)] found for the first time in the Lao People’s Democratic Republic (PDR). The subject was a 29-year-old pregnant Laotian woman who was a foreign worker in Thailand and was diagnosed with thalassemia and hemoglobinopathies. Capillary electrophoresis (CE) demonstrated 1.6% of Hb A₂, with a minor unknown peak at the initial Z1 zone (1.7%). Identification of abnormal hemoglobin (Hb) using direct DNA sequencing showed a genetic defect causing a δ-globin gene missense mutation at codon 43 (GAG>AAG) causing a glutamic acid to lysine substitution corresponding to Hb A₂-Melbourne. The origin of Hb A₂-Melbourne in Lao PDR may be similar to a case found in Thailand with the [+ – – – – + +] haplotype. We developed a method that could clearly detect Hb A₂-Melbourne and Hb A₂-Lampang (HBD: c.142G>A) mutations in a single tube using high resolution melt (HRM) analysis. The HRM analysis is a more effective method for rapid detection than conventional polymerase chain reaction (PCR), as there is no need for a post-PCR step, and no exposure to ethidium bromide. This new method would be a useful addition for the first investigation of a suspected Hb A₂ variant in the routine molecular setting.

Keywords:

• δ-Globin gene mutation
• Hb A2-Melbourne
• hemoglobin (Hb) variant
• high resolution melt (HRM) analysis

Acknowledgments

The researchers thank Mr. Dave Patterson (Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand) who is a native English speaker for helpful comments on the 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 Maha Chakri Sirindhorn Medical Center, Faculty of Medicine, Srinakharinwirot University, Ongkharak, Nakhon Nayok, Thailand.