Molecular diagnosis of inherited disorders: lessons from hemoglobinopathies

Abstract

Hemoglobinopathies constitute a major health problem worldwide, with a high carrier frequency, particularly in certain regions where malaria has been endemic. These disorders are characterized by a vast clinical and hematological phenotypic heterogeneity. Over 1,200 different genetic alterations that affect the DNA sequence of the human alpha-like (HBZ, HBA2, HBA1, and HBQ1) and beta-like (HBE1, HBG2, HBG1, HBD, and HBB) globin genes are mainly responsible for the observed clinical heterogeneity. These mutations, together with detailed information about the resulting phenotype, are documented in the globin locus-specific HbVar database. Family studies and comprehensive hematological analyses provide useful insights for accurately diagnosing thalassemia at the DNA level. For this purpose, numerous techniques can provide accurate, rapid, and cost-effective identification of the underlying genetic defect in affected individuals. The aim of this article is to review the diverse methodological and technical platforms available for the molecular diagnosis of inherited disorders, using thalassemia and hemoglobinopathies as a model. This article also attempts to shed light on issues closely related to thalassemia diagnostics, such as prenatal and preimplantation genetic diagnoses and genetic counseling, for better-quality disease management.

Elucidating the spectrum of -thalassemia mutations in Iran

“…α-thalassemia disorder is characterized by a wide clinical and hematologic phenotypic heterogeneity. 8 Undetected cases could also be due to situations like antisense RNA transcription which was clarified in long-range analysis of chromosome structures.…”

Mutation screening in the human ɛ-globin gene using single-strand conformation polymorphism analysis

“…This technique has been previously employed for the human a-and b-globin genes [reviewed in ref. 9] to screen for a-and b-thalassemia mutations, respectively. Using this technique to screen for e-globin gene sequence alterations in healthy adults would allow us to determine those eglobin gene regions that, even when mutated, do not affect the physiological properties of the e-globin chain and the assembly of the embryonic Hb fractions.…”

A versatile denaturing HPLC approach for human β‐globin gene mutation screening

“…In Greece, six b-globin gene mutations account for almost 90% of the observed molecular heterogeneity leading to b-thalassemia [4,5]. Molecular screening for the b-globin mutations currently relies on several conventional methods [6], while the golden standard of full-gene sequencing is both time consuming and costly.…”

“…Denaturing high-performance liquid chromatography (DHPLC) is a cost-effective methodology that has been successfully applied for mutational detection of several genes [7], including the a-and b-globin genes [6,8,9], approaching 90-100% in sensitivity and specificity. However, the earlier-mentioned protocols are based on the Transgenomic Wave TM DHPLC system, which is expensive and therefore poses a hurdle for its implementation in low-budget laboratories, particularly those in developing countries.…”