RESUMEN
Background: The Lewis (Le) blood group system, unlike most other blood groups, is not defined by antigens produced internally to the erythrocytes and their precursors but rather by glycan antigens adsorbed on to the erythrocyte membrane from the plasma. These oligosaccharides are synthesized by the two fucosyltransferases FUT2 and FUT3 mainly in epithelial cells of the digestive tract and transferred to the plasma. At their place of synthesis, some Lewis blood group carbohydrate antigen variants also seem to be involved in various gastrointestinal malignancies. However, relatively little is known about the transcriptional regulation of FUT2 and FUT3. Summary: To address this question, we screened existing literature and additionally used in silico prediction tools to identify novel candidate regulators for FUT2 and FUT3 and combine these findings with already known data on their regulation. With this approach, we were able to describe a variety of transcription factors, RNA binding proteins and microRNAs, which increase FUT2 and FUT3 transcription and translation upon interaction. Key Messages: Understanding the regulation of FUT2 and FUT3 is crucial to fully understand the blood group system Lewis (ISBT 007 LE) phenotypes, to shed light on the role of the different Lewis antigens in various pathologies, and to identify potential new diagnostic targets for these diseases.
The Lewis (Le) blood group system, in contrast to the majority of blood groups, is not able to synthesize its antigens itself. It depends on the attachment of different oligosaccharides to the erythrocyte membrane, which are adsorbed from the plasma. These glycans are modified by the fucosyltransferases 2 and 3 enzymes (FUT2/3). Beside their role in defining the Lewis blood group, FUT2 and FUT3 are also known to be involved in the susceptibility and progression of various gastrointestinal pathologies, like inflammatory bowel diseases (IBD) or colorectal cancer (CRC). Even though different expression levels of FUT2 and FUT3 have been described in these malignancies, relatively little is known about the mechanisms behind their transcriptional regulation. In this review, we aim to shed light on transcription factors (TFs) responsible for FUT2 and FUT3 expression as well as on post-transcriptional regulators by the means of RNA binding proteins (RBPs) and microRNAs (miRNAs). To achieve our goal, we combined previous knowledge on FUT2 and FUT3 expression regulation with a computational analysis to predict additional novel regulators. On this way, we are able to broaden our knowledge on FUT2 and FUT3 expression regulation and consequently might be able to transfer our findings into diagnostics or therapeutics in the future.