Regulation of actin dynamics during morphogenesis and wound healing

Morphogenesis involves a complex set of cell movements. Similar cell movements are also required during the repair of damaged tissues. While cell movement has been extensively studied in culture, we currently have a relatively poor understanding of how cells move within in vivo environments and how their movements are controlled to generate complex tissues.

Our aim is to understand how cell movement in achieved and regulated during tissue morphogenesis and repair. In particular, we are interested in the role and regulation of the actin cytoskeleton during cell movement. The main model system that we use for this research is the Drosophila embryo. One advantage of using Drosophila embryos for this research is that we can readily image cell movement with high resolution in live embryos, and we have developed fluorescent probes that allow us to follow the dynamics of a range different cytoskeletal components and regulators during cell movement. A second advantage of using Drosophila is the ease with which genetic techniques can be used to dissect the function of individual genes in cell movement.

A major focus of the lab is the formation and repair of epithelial cell sheets. To investigate the formation of epithelial sheets, we study dorsal closure, a morphogenetic process in which a large hole in the epidermis of the embryo is closed. The actin cytoskeleton plays multiple roles during dorsal closure and its activity must be precisely regulated to ensure the process occurs correctly. We are particularly interested in the role and regulation of dynamic cell protrusions called filopodia that ‘stitch’ together the epidermal edges when they meet. To study the repair of epithelial sheets, we wound the epidermis of Drosophila embryos with a laser and observe the healing process in live embryos. Using a laser for wounding allows us to make very precise wounds and also allows us to observe the cellular events that occur immediately after wounding. We are interested in understanding how epithelia detect damage and how the cells surrounding the wound subsequently reorganise their actin cytoskeleton in order to become motile and thus close the wound.

In addition to investigating actin dynamics during epithelial sheet movement, we are also interested in actin dynamics during single cell movement. To study this we use haemocytes, the Drosophila equivalent of macrophages. Haemocytes undergo stereotypic migrations within the embryo, but also migrate to epidermal wounds. We can therefore use our wound model to study actin dynamics in both the epidermis and in immune cells during tissue repair.

Our research will lead to a better understanding of how cell movement is achieved and regulated within the organism, which has implications for a range for medically important processes including immune responses and tumour metastasis. In addition our work will improve our understanding of birth defects such as spina bifida and will assist in the development of therapies to improve the ability of our bodies to heal wounds.

Mechanistic analysis of neurodevelopmental diseases caused by altered RAC1 function

RAC1 is a member of the Rho family of small GTPases. RAC1 is an important signalling protein with diverse roles, notably in regulating the actin cytoskeleton and cell movement, but also in controlling cell survival and proliferation. RAC1 is known to play a variety of roles in human development, in particular in development of the central nervous system. In 2017 we established that de novo mutations in RAC1 cause a neurodevelopmental disorder (NDD) with an unusually large phenotypic spectrum, including patients both with severe microcephaly and severe macrocephaly. We are carrying out functional analysis using biochemistry, cellular assays and an in vivo Drosophila model to determine the mechanistic basis for the NDD caused by RAC1 mutations. We recently established that mutations affecting the switch II region of RAC1 result in increased RAC1 activity and showed that suppressing one particular downstream pathway can reduce the cellular effects of one such mutation, thus suggesting a possible target for therapeutic intervention. Our ultimate aim is to improve the diagnosis and treatment of patients with NDDs caused by altered RAC1 function.
 

Regulation of cell movement in development and disease

The formation of our tissues during embryonic development involves a complex set of cell movements as each cell manoeuvres itself into the correct location. Similar movements are also required in adults when tissues are repaired following an injury. We are investigating how these cell movements occur, how they are controlled to ensure that each cell movement occurs correctly and how defects in cell movement lead to disease. Cell movement is driven by the continual remodelling of a structural network within the cell called the cytoskeleton. We are interested in understanding how remodelling of the cytoskeleton is controlled to achieve precise cell movements. As it is extremely difficult to study cell movement in complex organisms such as humans, we are using cell culture and a simple organism, the fruit fly Drosophila for our research. Drosophila embryos are transparent meaning we can image cell movement with high resolution in live embryos. In addition, we can use genetic techniques to study the function of individual genes in cell movement and how genetic mutations can lead to changes cell movement and and developmental diseases. Our research will lead to a better understanding cell movement which will help in the development of treatments for genetic diseases and injury. It will also improve our understanding of cancer metastasis, which occurs when tumour cells inappropriately acquire the ability to move.

Unit co-ordinator for The Dynamic Cell (BIOL21121)

Programme Director for Medical Biochemistry