| 1. |
- Stjernberg (Zetterblad), Jenny
(författare)
-
Knock Knock Knock, Who is there? - Cell Crosstalk within the Bone Marrow
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is focused on the subject of cell-cell interaction. Our body is composed of cells, most of them are integrated in a network with other cells that together forms tissues and organs. Every cell type in these complex organs has its special task and location. This is true whether we are doing research on humans or, as we have been, investigating mice. Mice are excellent models for studies of blood cell development since this process in mice resembles human blood cell generation in many regards.Cells communicate with each other by sending out small molecules or by directly binding to surrounding cells; to cells of the same kind as well as to cells with different origins and tasks. A cell is surrounded by hundreds of different signal-carrying entities; soluble, bound to the extra cellular matrix or bound to its surface. Every cell has to distinguish and respond to the environment according to its own specific nature.In the first article interleukin 7 (IL-7) a growth factor expressed by the stroma cells was studied. Results show that IL-7 is crucial for the immature progenitor cell in its development towards antibody producing B-lymphocytes. The second article is about stroma cells and their ability to support the development of B-cells. It is a comparative study on two different cell lines, where we focus on transcription factors and their regulation of protein induction of factors supporting B-cells. This study increased our knowledge of stroma cells. In the third paper we combined our knowledge from the first two papers in regard to stroma cells as well as B-cell development by testing if there is a possibility to theoretically find new factors of importance for the maturing B-cell. We achieved this by the development of GCINT, a database investigating possible receptorligand interactions between two cells, verifying these results in vitro with cell lines as well as primary cells. This revealed a two way communication between blood cells and stroma cells, highlighting the complexity of the bone marrow environment. In the last article we continued this work with primary FACS sorted stroma cells investing the potential connections between each of the stroma cell populations with primary blood cells in different stages of development. This work supports a model where hematopoietic cells can interact with stroma cells in a stage-specific manner and that the exchange between cells is of importance for their maturation.
|
|
| 2. |
- Zandi, Sasan
(författare)
-
What’s in a name? : Sub-fractionation of common lymphoid progenitors
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The hematopoietic system is a highly dynamic organ developed in many multi-cellular organisms to provide oxygen, prevent bleeding and to protect against microorganisms. The blood consist of many different specialized cells that all derive from rare hematopoietic stem cells (HSCs) located in the bone marrow in mice and humans. Blood cell production from HSCs occurs in a stepwise manner through development of intermediate progenitors that gradually loose lineage potentials. This is a tightly regulated process with complex regulatory mechanisms and many checkpoints that ensure a high and balanced production of blood cells. One of the fundamental questions in hematopoiesis relates to how the maturation of the cells is controlled and driven towards defined cell fates. The understanding of these processes is largely facilitated by isolation of intermediate populations of cells at defined stages of development.This thesis is focused on the regulatory mechanisms that regulate the maturation of B-lymphocytes constituting an important part of adaptive immunity by being responsible for the production of antibodies. It has been suggested that all the lymphoid cells have a common lineage restricted ancestor defined as a Lin-KitloSca1loFlt3+IL7R+ common lymphoid progenitor (CLP). These cells are believed retain the combined potentials for B, T and NK cells and it has been presumed that commitment of CLPs to B lineage is associated with expression of CD19 and B220 on progenitor B-cells.The aim of this thesis has been to identify the point of no return in B-cell development in order to allow for a better understanding of lineage restriction events in early lymphopoesis.To this end, we have used reporter transgenic mice where marker gene expression has been controlled by the transcription regulatory elements from one early lymphoid marker (Rag1) and one B-lymphoid restricted gene (λ5, Igll1). This allowed us to identify three functionally distinct sub-populations within the conventional CLP compartment. The cells were identified as CLPRaglowλ5- cells retaining B, T, Nk and a limited myeloid potential while up-regulation of Rag1 to generate CLPRaghighλ5- cells, was associated with loss of Nk potential as well as of the residual myeloid potential. Ultimately expression of λ5 in the CLPRag1highλ5+ compartment identifies the first committed B cells. Hence, our data suggest that the point of no return in B-cell development can be found within the CD19- CLP compartment. Using this new model for B-cell development, we investigated the instructive vs. permissive role of IL7 signaling in B cell commitment. Our results show that in absence of IL7, CLP maturation is impaired and generation of the earliest committed B-lineage cells is severely impaired. CLP maturation could not be rescued by ectopic expression of the anti-apoptotic Bcl2 protein even though the cells were able to generate normal B lineage cells after restoration of the IL7 signal. These findings suggest that Il7 is crucial for the maturation of lineage restricted CLPs and provide support for an instructive role of IL7 in early Bcell development.This thesis highlights the importance of precise identification of the point of commitment in B cell development and provides insight to the hematopoietic hierarchical model with the potential to serve as a map to better understand the mechanisms of hematopoietic disorders.
|
|
| 3. |
- Åhsberg, Josefine
(författare)
-
Molecular mechanisms in lymphoid restriction : securing the B lineage fate
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the work in this thesis I have aimed to deepen the understanding of the mechanisms behind the development of different blood cell lineages with a specific focus on B cell development.To understand the interplay between extracellular signaling and transcription factor networks in early lymphoid development we investigated the functional collaborations of FLT3 and IL7R. We found that signaling via FLT3 and IL7R act in powerful synergy on proliferation of common lymphoid progenitors (CLPs). In addition to a role in expansion of progenitor cells we provided evidence for that IL7R signaling play a crucial role in B-cell commitment. IL7 deficient mice display a dramatic block in development before functional lineage restriction in the Ly6D+ CLP-compartment. The few Ly6D+CLPs that do develop have reduced mRNA levels of transcription factor EBF1, a protein with crucial functions in lineage restriction and activation of the B-lymphoid program. One crucial function of EBF1 is to activate Pax5. Even though Pax5 deficient fetal liver cells upon transplantation to congenic hosts will generate an abundance of cells with an activated B-lineage transcriptional program, the pro-B cells have disrupted regulation of non-B-lineage transcripts and a propensity to develop into T- and NK-cells in vitro. Both the activation of the B-lineage program and lineage restriction was dependent on the dose of transcription factors. Mice carrying a heterozygous mutation for the transcription factor E2A had slightly reduced relative frequency of progenitor cells and an impaired B-lineage specification in CLPs. Loss of one allele of Ebf1 resulted in reduced surface expression of IL2Rα and pre-B cell receptor (BCR), reduced IL7-response in vitro, and disrupted cell cycle dynamics in pro- and pre-B cells. While heterozygous loss of Pax5 did not result in any dramatic phenotype, the combined loss of one allele of Pax5 and one allele of Ebf1 (Pax5+/-Ebf1+/-) had a dramatic effect on lineage plasticity in B-cell progenitors compared to the single heterozygotes. Furthermore, these Pax5+/-Ebf1+/- mice developed spontaneous, transplantable pro-B cell tumors and had a significantly reduced probability to survive over time. The transformed cells show high in vitro plasticity and tumor cells with induced overexpression of intracellular Notch1 can transform into T-lineage cell in vivo.The data presented in this thesis add important pieces of information to the field of developmental hematopoiesis. By increasing the analytical depth of development in normal circumstances, and by understanding the consequence of genetic mutations in relation to cell type, we hope to contribute to the understanding of hematopoietic development in health and disease.
|
|
