The present invention relates to the field of mucins and isoforms thereof, more in particular for use in the diagnosis, monitoring, prevention and/or treatment of a disease characterized by barrier dysfunction, such as but not limited to a gastrointestinal disorder (e.g. Inflammatory Bowel Disease (IBD), Irritable Bowel Syndrome (IBS), cancer, gastro-intestinal infections, obesitas, non-alcoholic fatty liver disease (NAFLD)), neurodegenerative disorders, respiratory infections,... more in particular coronaviral infections In a specific embodiment, said mucins and/or isoforms thereof are ...