The production of adult blood initiates from the haematopoietic stem cell (HSC). This clinically important cell has the capacity to maintain all blood lineages throughout the lifetime of an organism. HSCs emerge de novo from the haemogenic endothelium in the ventral wall of the embryonic dorsal aorta, from where they go on to seed adult sites of haematopoiesis. We have shown that Lmo4a is required for the emergence of HSCs in the zebrafish, and go on to demonstrate that Lmo4a regulates expression of the critical transcription factor, gata2a. Strikingly, both over- and under-expression of gata2a in the dorsal aorta severely diminishes HSC production. The LIM-only domain protein Lmo4 has previously been shown to interact with the known haematopoietic regulator, Ldb1. Together with our collaborators, we have identified novel binding partners of Lmo4 in mouse erythroleukaemic cells. Our functional analysis shows that many of these partners are also necessary for HSC emergence, thus revealing several new potential regulators of HSC formation. Given that these proteins were identified in an in vitro model of definitive erythropoiesis, it is remarkable that they also appear to act together in vivo at the level of HSC formation, and our data suggests that a transcriptional complex containing Lmo4 and these partners may directly repress gata2a. The related protein Lmo2 is also known to bind Ldb1. Together with Scl, Lmo2 is a master regulator of the haemangioblast programme. We have been utilising this activity, together with recent structural studies, to identify functionally important residues in the Lmo2 molecule. As a cell’s transcriptional programme drives both normal and pathological development, and misexpression of both Lmo2 and Lmo4 is involved in a variety of oncogenic states, the work presented in this thesis is likely to inform efforts to develop therapeutically relevant reagents.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:581005 |
| Date | January 2012 |
| Creators | Tuladhar, Kapil |
| Contributors | Patient, Roger |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:d6b73e89-7095-402f-9d9f-4d7837a4db00 |
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