Dr. rer. nat. Alexej Knaus    

Research interest

On all eukaryotic cells a specific glycolipid functions as an anchor to attach proteins to the plasma membrane: The glycosylphosphatidylinositol (GPI) anchor. There are more than 150 proteins that are attached to the cell surface via the GPI anchor. It therefore plays important roles in signal transduction, cell adhesion, antigen presentation and complement regulation. So far 29 genes have been identified in the synthesis and maturation of the GPI anchor, and attachment and transport of GPI anchored proteins (GPI-APs). Defects in the synthesis and maturation pathway of the GPI anchor, which lead to reduction of GPI-APs, are a subclass of congenital disorders of glycosylation (CDG). Disease-causing mutations have been described for 17 of these genes. Among the most common features in GPI biosynthesis defects (GPIBDs) are intellectual disability, epilepsies, and elevated alkaline phosphatase activity. However, the expressivity of the clinical features varies from severe syndromic forms with multiple organ malformations to mild non-syndromic intellectual disability. Yet, the pathophysiological implications of GPI deficiencies that lead to the broad phenotypic spectrum are only poorly understood. The objectives of my study are: 1st functional characterization of pathogenic mutations in genes of the GPI synthesis pathway, 2nd investigation of the underlying pathophysiological mechanism of GPI deficiencies, 3rd correct diagnosis of exome data based on facial gestalt recognition and flow cytometry in cases with suspected GPIBDs.