How do carbohydrates instruct brain development?
APPLICATION DEADLINE 16th January 2015
The emergence of a brain at the front-end of a growing embryo requires very precise orchestration to make sure that the right structures form in the right place at the right times. Central to this process is not only the giving of instructions but also their proper transmission and reception. Over the past few years scientists have made considerable strides in identifying the protein signals, or ‘signalling proteins’, which transmit instructions between cells. Signalling proteins are produced by a source and move to their target where they are sensed by receptors on the surface of the target cell. The target cell then changes its behaviour in response to the signal. A puzzling conundrum is that, despite intense efforts, only a relatively small number of signalling proteins have been identified compared to the complexity of instructions needed to produce the brain. We have focused our attention on the role played by a completely different class of molecules, the carbohydrates, in cell signalling. We are particularly interested in the idea that interactions between carbohydrates and proteins expand the diversity of instructions.
This project will employ state-of-the-art confocal microscopy in combination with live cell imaging to look in detail at the interaction between biologically powerful signalling proteins called ‘morphogens’ and a structurally diverse type of carbohydrate called ‘Heparan sulphate’ (HS), a linear polysaccharide which is modified by differential sulphation. Morphogens are a class of signalling protein important for brain development as cells are very sensitive to the amount they encounter such that even small changes in level can have a dramatic effect on brain development including developmental defects. We have discovered that the pattern of HS sulphation regulates morphogen gradient emergence and signalling in the developing brain and that mouse mutants with abnormal HS structure have brain malformations (Conway et al., 2011; Clegg et al., 2014). In order to investigate the molecular mechanism in more detail, we are developing a novel culture system, which allows us to apply a source of morphogen labelled with green fluorescent protein (morphogen-GFP) to developing brain tissue and then track its movement over time. By comparing the behaviour of morphogen-GFP when presented with normal and abnormal HS we can build up a picture of how HS normally functions and how the process can go awry. The overarching goal of the project is a deeper understanding of how carbohydrates and proteins coordinate to instruct biological processes.
This project will provide training in advanced confocal microscopy and image analysis as well as more standard molecular biology techniques involved in building GFP expression constructs, gene expression analysis, and working with transgenic mice. Live cell imaging is an area of rapidly-growing importance in both academia and commercial environments, because only this technology delivers results with high temporal and spatial resolution of molecular events such as the in vivo distribution of morphogens etc. The skills acquired will be of great value and transferrable to many other research areas, either in academia or the biotechnology / pharmaceutical sector.
This project is part of the BBRSC EASTBIO Doctoral Training Partnership. For information on this scheme please see http://www.eastscotbiodtp.ac.uk/
Clegg, J. M., Conway, C. D., Howe, K. M., Price, D. J., Mason, J. O., Turnbull, J. E., Basson, M. A. and Pratt, T. (2014) ‘Heparan sulfotransferases hs6st1 and hs2st keep erk in check for mouse corpus callosum development’, The Journal of neuroscience 34(6): 2389-401.
Conway, C. D., Howe, K. M., Nettleton, N. K., Price, D. J., Mason, J. O. and Pratt, T. (2011) ‘Heparan sulfate sugar modifications mediate the functions of slits and other factors needed for mouse forebrain commissure development’, The Journal of neuroscience 31(6): 1955-70.