AbstractUnderstanding the gene regulatory networks driving the differentiation of the distinct cell types in embryos is a key component of understanding development. Amongst the first types of cell to differentiate during vertebrate development are blood cells, and haematopoiesis is tightly regulated by proteins known as haematopoietic transcription factors (HTFs). Although the mRNA expression patterns of many HTFs are now well characterised, little is known about their protein expression patterns or how their transcription regulation activity is controlled during early development. Knowledge of their spatial and temporal expression patterns and their post-translational regulation would greatly enhance our understanding of the genetic regulatory networks that produce blood.
Antibodies have been successfully raised and characterised that recognise Xenopus Hex, fli1 and Tal1. Western blot experiments have shown that Hex and fli1 are expressed in oocytes and expression continues throughout development. This maternal expression is unexpected but is reminiscent of another embryonic HTF, Gata2. At stage VI of oogenesis the majority of fli1 and all Hex protein was localised within the cytoplasm, suggesting an alternative second function for each of these proteins. An intensively sampled developmental time-course carried out for fli1 between stages 24 and 31, revealed striking post-transcriptional control over fli1 expression. Neither Hex or fli1 proteins have been shown to be absent from the regions containing sites of haematopoiesis and both proteins were eluted in the same fractions following size exclusion chromatography using Xenopus extract, suggesting the possibility that they may be in complex together. Finally, either Tal1 protein is undetectable during early Xenopus embryogenesis, or is heavily modified.
Since, at least for fli1, knockdown of the zygotic protein specifically affects blood development a number of questions are raised. What is different about the maternal and zygotic proteins, which means that the zygotic form is needed for haematopoiesis? What is the function of the maternal proteins – are they even capable of transcription
|Date of Award||Feb 2011|
|Supervisor||Suzannah Jayne Page (Supervisor), Matt Guille (Supervisor) & Garry Scarlett (Supervisor)|