Epithelial bending in mammalian morphogenesis

Genes drive and control the embryonic development of tissues and organs of the body in the way that software drives a computer. We are beginning to understand "gene programmes" written in the genome. However, we know much less about how the software drives the hardware: how do genes drive the physical shapes that we see? This question needs to be answered if we want one day to fix the hardware using biological methods. To answer this question, the extremely complicated and elaborate process of physical construction of the body (known as "morphogenesis") needs to be broken down into more easily analysed sub-processes. One of these is the bending of a sheet of cells to make a groove or pit. This is called "invagination". Invagination is medically important because it occurs in making the brain and spinal cord and its failure is a major class of birth defects (which includes, for example, spina bifida). We propose to look at something simpler but that will give answers about several different kinds of invagination. We will examine the formation of teeth, salivary glands, hair follicles and mammary ducts ("ectodermal organs") in mice. Each of these organs begins with an invagination that becomes gradually deeper. We will use some new techniques to detect more precisely than ever before the outlines of cells that make up the invaginating sheet so that we can get good, engineering-style measurements of their structures. Finally, we can grow these tissues in a dish and see which kinds of chemical "inhibitors" (which interfere with certain known proteins in the cell) will block which parts of the morphogenesis. This will link the cell movements and shape changes to particular proteins. Since proteins come from known genes, these studies, together with the mutant studies. will link cell shapes and movements to genes and be able to fit them in with the genetic software written in the DNA. comparing multiple small organs of this type, we can get an idea of the rules that make them similar but different. Ultimately this kind of knowledge should make it possible to use chemical signals (software) to drive structural repairs (hardware).

Epithelial invagination is a fundamental and widespread morphogenetic motif during development of embryos and their organs. The ectodermal organs tooth, hair follicle, mammary duct and salivary gland provide good models for studying mammalian invagination because they are amenable to in vivo and ex-vivo (explant culture) analysis as well as being of interest in their own right. This project will first compare cell behaviours and pathways in common, and different, between these organs using cell shape, actomyosin staining, nuclear deformation analysis and live imaging, which we previously used to demonstrate the mechanism of tooth placode invagination. This will enable detailed quantitative correlation between the cellular phenotype and the resulting tissue architecture. We will then characterise the chemotactic versus permissive activity of Hh signalling, which we previously showed to be critical in tooth for driving the centripetal cell migration required for placode invagination, using gain- and loss-of-function approaches and spatial mapping of expression and cell movement. We will also determine the effects of known inhibitors of non-canonical Hh signalling previously implicated in Hh-dependent chemotaxis. We shall apply similar cell-level analysis to salivary gland invagination, testing in particular a mechanism we have called "vertical telescoping" and which may be involved in other pseudostratified-epithelial bending events in development. Together, these investigations will link cellular mechanisms with the genetics and evolutionary development of an important panel of epithelial bending events in development, establishing the basic biology that is an essential foundation for future phenotypic analyses and regenerative interventions.

Who will benefit from this research?
This is basic research and does not pretend to being translatable in the very short term. However, it is also critical strategically for translational purposes because it will provide a part of the crucial foundation for the morphogenetic aspects of regenerative medicine that are currently in a very primitive state.
Beneficiaries will include:
(i) Tissue engineers in diverse areas engaged in using biomaterials to constrain or enhance tissue shape.
(iii) Biotechnology companies interested in developing histologically faithful tissues and organoids for the purposes of drug testing

How will they benefit from this research?

Health will be improved if regenerative therapies are successfully developed and this research will provide the basic foundations for such therapies to be applied to real structures rather than just amorphous clumps of cells or poorly self-assembled organoids.

Wealth will be improved by building knowledge in this area and its ultimate application as above within the UK biotechnology and tissue engineering sectors, but also by developing training and expertise at the interface of biology and engineering that can be applied in related enterprises. This kind of research will further establish the UK as one of the top places in the world for regenerative medicine, and so attract companies and talent.

Culture will benefit because the understanding of biological form is fundamental to the understanding of nature in general, freeing the public from mystical or superstitious ideas about the "miracle" of evolution while sustaining and appreciation of the beauty of biological processes and structures.

Health and wealth impacts will be long term. The nearest parallel is the early use of growth factors in tissue specification from embryonic cells in the early 1990s that is now being applied in clinical trials with embryonic stem cells, i.e. 20-25 years.

Staff working on the project will develop research and professional skills that they could apply in all employment sectors since in addition to lab work, they will be trained in oral and written presentational skills and computer skills with wide and general relevance.

What will be done to ensure that they benefit from this research?

This investigator is very active in publishing and presenting the group's work through active ongoing contact with regenerative medicine/tissue engineering groups and companies within King's College London Dental Institute and King's Health Partnerships, and to the UK and worldwide health sectors.

The proposed research project will be managed to engage users and beneficiaries and increase the likelihood of impacts with public engagement via talks given to schools, presentations on the media, including radio and the World Wide Web.