I joined the Thompson Lab in October 2015, having completed my PhD in limb development (Davey Lab) and a subsequent post-doctoral position studying canine skull morphology (Schoenebeck Lab) at the Roslin Institute (University of Edinburgh). During this time, I investigated the physical and genetic dynamics that underlie the patterning of digits, polydactyly, and evolutionary digit loss (employing chick, mouse, rat, and emu(!) models), and identifying loci associated with brachycephaly in multiple dog breeds.
Both the developing limb and skull are classic examples of position-based differentiation, whereby the relative position of a given cell in a developing mass plays a significant role in eventual cell fate. Having studied these structures in vertebrates for some time, I sought a new challenge – to study pattern formation in a system where spatial information during differentiation is largely irrelevant (known as “salt and pepper patterning”). Vegetative cells of Dictyostelium discoideum represent such a system, whereby genetically identical cells respond to a uniform concentration of DIF in a heterogeneous manner.
I am currently investigating the dynamics that underlie heterogeneous Dicty differentiation into stalk and spore fates; with a particular interest how various sources of extracellular and intracellular “noise” interact and buffer each other to achieve a suitable spore:stalk cell ratio (~80:20). We have identified several sources of heterogeneity that affect cell fate, and as such my work involves studies into cell cycle length and phase occupation within single cells, examination of cell fate upon metabolic changes, organelle proportioning, and investigation of RasD-dependent intracellular DIF responses.
Marchant, T M., Johnson, E J., McTeir, L., Johnson, C I., Gow, A., Liuti, T., Kuehn, D., Svenson, K., Bermingham, M L., Drögemüller, M., Nussbaumer, M., Davey, M G., Argyle, D J., Powell, R M., Guilherme, S., Lang, J., Ter Haar, G., Leeb, T., Schwarz, T., Mellanby, R J., Clements, D N & Schoenebeck, J J. (2017) Canine brachycephaly is associated with a retrotransposon-mediated mis-splicing of SMOC2. Current Biology. DOI: 10.1016/j.cub.2017.04.057
Johnson, E J., Neely, D M., Dunn, I C., Lam, W, L., Davey, M G. (2014) The pathogenesis of preaxial polydactyly: anatomical insights using a Silkie chicken model with Sonic Hedgehog mutation enhancement. Journal of Plastic Reconstructive and Aesthetic Surgery. 67 (11) 1611. DOI: 10.1016/j.bjps.2014.09.027.
Johnson, E J., Neely, D M., Dunn, I C., Davey, M G. (2014) Direct functional consequences of ZRS enhancer mutation combine with secondary long range SHH signalling effects to cause preaxial polydactyly. Developmental Biology. 392 (2) 209-220. DOI: 10.1016/j.ydbio.2014.05.025.
Stephen, L A., Johnson, E J., Davis, G M., McTeir, L., Pinkham, J., Jaberi, N., Davey, M G. (2014) The chicken left right organiser has nonmotile cilia which are lost in a stage-dependent manner in the talpid3 ciliopathy. Genesis. DOI: 10.1002/dvg.22775
Dunn, I C., Paton, I R., Clelland, A K., Sebastian, S., Johnson, E J., McTeir, L., Windsor, D., Sherman, A., Sang, H., Burt, D W., Tickle, C., Davey, M G. (2011) The chicken polydactyly (Po) locus causes allelic imbalance and ectopic expression of Shh during limb development. Developmental Dynamics. 240 (5) 1163-72. DOI: 10.1002/dvdy.22623