Studies on Molecular Genetics of B cell Development

Abstract: The development of immature progenitor cells into highly differentiated effector cells is a process central in modern medicine with applications in the fields of cell therapy as well as oncology. This thesis is focused on the molecular mechanisms that control the development of B lymphocytes. This is a complex and tightly regulated process involving several stages proceeding from stem cells to antibody-secreting plasma cells. B cell development is regulated through the action of transcription factors and cytokines that act in concert to control the pathway. Some of the work presented herein utilized broad RNA expression analysis of several mouse B cell-lines representing different stages of B cell development, to identify genes with restricted expression pattern in B cell development. It also revealed that B cell-lines arrested at a certain stage of B cell development display high similarity in overall expression pattern allowing the usage of this experimental system to define genetically linked genes. Based on these experiments, mathematical methods to analyze the linkage of genes in a complex data set were developed. The efficiency of this approach was shown by the verified identification of genetic targets for the transcription factor EBF. The integration of intracellular and extracellular signals was investigated using the Ialpha promoter, involved in class switch recombination to IgA, to investigate how sterile transcription from this promoter is stimulated by TGFbeta1. This revealed a functional synergy between the intracellular mediators of TGFbeta signaling, SMAD proteins, and the transcription factor AML1. This study provides explanations for how extracellular signals can be integrated into the transcriptional regulatory pathways in the cell in terminal B cell development.