Molecular dissection of B-lymphocyte signalling using expression profiling

Abstract: Gene expression profiling and bioinformatics have emerged into playing a large and diverse role in many aspects of both the clinical and molecular research. These two approaches have in this thesis work been used in combination in order to shed light to the role of Bruton's tyrosine kinase (Btk) in B-lymphocyte development and signal transduction. When Btk is found to be defective andlor non-functional, e.g. due to mutations, these processes are disrupted, giving rise to the primary immunodeficiency disease X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Gene expression profiling has been used on both resting, primary splenic B-cells, with Btk-defective mice in comparison to a normal strain, as well as Epstein-Barr Virus (EBV) transformed peripheral B-lymphocytes from both XLA patients and healthy individuals. Differences as well as similarities in gene expression pattern not only within experiments, but also between B-cell lines compared to resting B-cells and whole primary splenic B-lymphocytes compared to purified transitional type 1 (T1) B-cell splenocytes, have been distinguished. Several potentially interesting genes, both of known and unknown character, have been discovered to be differentially expressed in a Btk dependent manner. Microsomal epoxide hydrolase (mEH), Ionized Ca2+ type 1 (lba1) and CD9 are three examples of genes found in the gene profile from Btk-defective mice. These genes have also been confirmed on protein level. Also, four Expressed Sequence Tags (ESTs) have been annotated and characterised by the use of bioinformatics tools. The gene expression profiling technology, in combination with bioinformatics and conventional biochemistry, has enabled the search for new target molecules in B-lymphocyte development and signalling in the context of Btk.