The aim of my research is to understand the early lineage decisions of embryonic stem (ES) cells. I am interested in how cells communicate with each other through the Notch pathway to influence these decisions. A related interest is to understand why seemingly homogenous populations of ES cells differentiate at different rates, or into different lineages, even under simple, fully defined differentiation protocols.
At present, most ES cell differentiation protocols generate heterogeneous mixtures of different cell types (see figure 1). We aim to understand why it is that some ES cells in a population respond differently from their neighbours.
Figure 1. Even under fully defined neural differentiation protocols, differentiating cultures contain a heterogenous mixture of neural cells intemingled with undifferentiated ES cells. In this picture, a Sox1-GFP reporter line of mouse embryonic stem cells allows us to identify neural progenitors in green, while ES cells are identified by staining for the ES cell marker Oct4, in red.
Notch signalling is used in many different tissues to regulate differentiation decisions by mediating signalling between adjacent cells. This pathway is classically deployed to restrict the spread of cell differentiation, a process called lateral inhibition . In other contexts, however, Notch promotes neighbouring cells to adopt the same fate, lateral ind uction.
We have recently shown that manipulation of Notch activity alters lineage choice of both mouse and human embryonic stem cells, with Notch activation steering ES cells towards the neural fate and away from non-neural fates (see figure 2).
Figure 2. A high proportion of neural progenitors can be generated from embryonic stem cells through activation of the Notch pathway. In this picture, neural cells are identified by staining for the neural marker BLBP, in green, and cell nuclei are stained blue.
Approaches and progress
We are working to understand the mechanism by which Notch is acting during ES cell differentiation. What limits Notch activity during neural differentiation? How does Notch interact with the other pathways that are known to influence lineage choice? What are the targets that mediate the effects of Notch on neural differentiation and are these the same or different from those that suppress non-neural differentiation?
Another goal is to improve our ability to direct ES cell differentiation. To this end, we are refining and extending the range of tools available for manipulation of Notch activity, with particular emphasis on those methods that do not depend upon genetic manipulation and can easily be applied to human ES cells.
We are also interested in whether ES cells can become biased to a particular fate even before the onset of differentiation. We are testing the idea that levels of Notch activity could predict this lineage bias.
We are collaborating with Stuart Forbes' group to investigate whether Notch signalling regulates stem cell function in the liver.
MultiCell3D image analysis software
We have developed an image analysis software which is intended to quantify and analyse the immunostainings of nuclei in cells. You can download the application free here.