ABSTRACT
Patients with Down syndrome (DS) are commonly affected by a pre-leukemic disorder known as transient abnormal myelopoiesis (TAM). This condition usually undergoes spontaneous remission within the first two months after birth, however in children under 5, 20 – 30% of cases evolve to myeloid leukemia of DS (ML-DS). TAM and ML-DS are caused by co-operation between trisomy 21 and acquired mutations in the GATA1 gene. Currently, only NGS-based methodologies are sufficiently sensitive for diagnosis in samples with small GATA1 mutant clones (≤ 10% blasts). Alternatively, this article presents research on a new, fast, sensitive and inexpensive HRM-based diagnostic approach that allows the detection of most cases of GATA1 mutations, including silent TAM. The algorithm first uses flow cytometry for blast count, followed by high resolution melting (HRM) and Sanger sequencing to search for mutations on exons 2 and 3 of GATA1. We analyzed 138 samples of DS patie nts: 110 of asymptomatic neonates, 10 suspected of having TAM, and 18 suspected of having ML-DS. Our algorithm enabled the identification of 33 mutant samples, among them 5 cases of silent TAM (5/110) and 7 cases of ML-DS (7/18) with blast count ≤ 10%, in which GATA1 alterations were easily detected by HRM. Depending on the type of genetic variation and its location, our methodology reached sensitivity similar to that obtained by NGS (0.3%) at a considerably reduced time and cost thus making it accessible worldwide.
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