Chromosome Breakage Induced by DEB in Thai Patients with Fanconi Anemia

Abstract

Abstract: Finding of chromosome breakage is a diagnostic hallmark of Fanconi anemia (FA), a hereditary bone marrow failure syndrome with autosomal recessive inheritance. A defect in DNA repair mechanism leading to genome instability is an important etiology of FA. One strategic methodology to detect instability within chromosomes is a clastagenic introduction into the cell
culture. Since the chromosome breakage analysis among Thai FA patients and standardized condition of the optimum clastagenic concentration used for the test among Thai patients and Thai normal subjects have never been reported, we then initiated this work in order to improve diagnostic accuracy of this rare but important genetic disease. Lymphocytes from patients and their first degree relatives of seven families as well as lymphocytes from thirty normal Thais were cultured using modified standard culture procedure for chromosome preparation. Chromosome breaks were induced by different concentration of a clastagenic agent diepoxybutane (DEB) from 0.0 to 0.2 Mg/mL. Chromosome analysis were determined in the total of 2,400 metaphases from normal control subjects and 1,260 metaphases from FA patients and their family members. Result shows that chromosome breaks were easily observed when induced by low concentration of DEB (0.01 to 0.1 Mg/mL) or even in uninduced culture (spontaneous breaks) in the majority FA patients. Five out of seven FA families exhibited chromosome breakage in various number of chromosomes. In contrast, no chromosome break was detectable in all thirty normal Thai samples eventhough DEB was used at the concentration as high as 0.2 Mg/mL. We propose herein that chromosome breakage analysis is a useful technique and should be performed in all Thai patients suspicious of FA to confirm clinical diagnosis. DEB concentration at 0.1 Mg/mL should be suitable for chromosome breakage analysis for FA in Thai people.