Importance of the 3'UTR region in globin synthesis: identification of two novel HBA1 mutations causing α-Thalassemia

Alpha-thalassemia is primarily caused by large deletions in the HBA1 and HBA2 genes, but a minority of cases result from non-deletional mutations, including variants in untranslated regions (UTRs) that affect mRNA regulation. The 3'UTR is crucial for post-transcriptional control, influencing mRNA stability, localization, and translation via binding elements for RNA-binding proteins and microRNAs. We describe two patients with persistent microcytosis and normal iron levels. Standard hematological analyses were complemented by high-performance liquid chromatography (HPLC) and capillary electrophoresis to rule out common hemoglobinopathies. Molecular analysis was performed using multiplex PCR and direct sequencing of the HBA1 3'UTR. Patient 1, a 3-year-old Nigerian boy, carried a novel insertion mutation (HBA1:c.*119_120insT) five nucleotides downstream of the transcription termination signal. Patient 2, a 31-year-old Moroccan woman, exhibited a missense variant (HBA1:c.*150C > A) located 40 nucleotides downstream of the TTS. Both variants are located within regulatory regions of the HBA1 3'UTR. In silico analyses suggest disruption of RNA secondary structure, impaired interactions with HuR and AUF1 proteins, altered microRNA binding (e.g., miR-16-5p), and potential interference with polyadenylation signals, resulting in mRNA instability and reduced alpha-globin synthesis. These two novel mutations in the 3'UTR of HBA1 expand the spectrum of non-deletional alpha-thalassemia variants and highlight the importance of regulatory regions in globin gene expression. Their inclusion in routine molecular screening may enhance diagnostic accuracy in cases of unresolved microcytic anemia.