RESETTING AND SCULPTING THE NOTCH RESPONSE

Lead Research Organisation: University of Cambridge
Department Name: Physiology Development and Neuroscience

Abstract

Communication between cells, the building blocks of the body, is essential to build and maintain our tissues. Failures in this communication are the cause of many diseases, especially many types of cancers. One key way cells communicate is via the Notch receptor. When a signal is received by Notch, the instructions are interpreted differently depending on the previous history of the cell. For example, whether or not a cell will go on to multiply will be based on how its genome is set up to receive the signal. Under normal conditions there are checks and balances in the system to ensure that the cells respond correctly. However, in several types of cancers Notch signalling doesn't function properly. In many of these conditions, including T-cell acute lymphoblastic leukaemia and breast cancers, too much signal is produced causing the cells to multiply excessively, forming tumours. Surprisingly, in some other types of cancer the converse is the case. This makes it important to know how the cells will be interpreting the Notch signal in a particular tissue context. It also makes it more difficult to use drug treatments that simply shut off the Notch signal as they could have damaging effects in some tissues.

By answering two key questions we will acquire a better understanding of cell circumstances that will increase the probability that Notch activity will be oncogenic. This information will be valuable in working out the best strategies for patient treatments and to identify avenues that could be used to develop targeted drugs or drug combinations to avoid problems with current treatments. First we aim to discover what normally resets the way that cells interpret Notch signals, to ensure that they do not behave inappropriately by dividing unchecked and becoming cancer stem cells. Second, we will find out what architectural features of the genome help guide the signal so that the right types of product are made when the genes are turned on. To do this we will use both the fruit fly and human cells and will use strategies that enable us visualize in real time the way the genome is reset to help Notch to pick out which genes to turn on and to find the components in cells that facilitate this. We will also undertake large-scale analysis that allows us to detect global changes in the genome architecture in normal tissue and in tissues that grow too much because they have extra Notch activity. We use fruit flies because they have a simpler system that we can easily study in the living organism, making it more straightforward to decipher the information, yet they have over 75% of the human disease-causing genes. We then translate our discoveries from fruit-flies into the more complex human cancer cells to show their relevance for disease and to identify the best routes towards uses in the clinic.

Technical Summary

The highly conserved Notch signalling pathway functions in diverse developmental and homeostatic processes. Likewise, disease implications from aberrant Notch programmes differ depending on the tissue: Notch activity promotes tumourigenesis in many contexts, including T-cell acute lymphoblastic leukaemia and breast cancers, whereas in others it is protective. Discovering how the appropriate responses to Notch are configured is therefore vital for deciphering when combinations of genetic abnormalities are likely to be oncogenic, and for informing strategies for targeted therapies. Our goal is to use a combination of live-imaging, genetic, biochemical and genomic approaches in Drosophila and in human cells to discover the fundamental mechanisms that reset and sculpt transcriptional responses to Notch. These mechanisms are essential to bring about different outcomes and to avoid inappropriate gene expression programmes being turned on. We have two major aims: (1) to discover what mechanisms ensure that enhancers are correctly remodelled during cell state transitions so that appropriate responses to Notch signals occur and emergence of cancerous cells is avoided; and (2) to learn how Notch-regulated enhancers select and communicate with promoters to produce RNA isoforms with the right regulatory features for the physiological context.

Our results will uncover general principles that explain how the diverse effects of Notch activation arise in tissue development They will also provide important insights for distinguishing the likelihood that disrupted Notch signalling will be oncogenic, by helping to decode contexts where other mutations will affect key components or regulatory mechanisms and will provide new paradigms to aid design of therapeutic strategies.

Planned Impact

Beneficiaries:
-Industry involved in pharmaceutical research and drug development.
-Medical profession involved in treating Notch related diseases including cancers
-Business, industrial and public sector recruiting graduate level staff.
-The general public and schools, through our involvement in public engagement.

Benefits to industry will come from the scientific results and the methodologies we develop:
Notch pathway is a major target for cancer and other therapeutics. Increased knowledge about the mechanisms can lead to novel approaches for targeting the pathway and can be important in informing about unforeseen side effects. For example, our results can inform whether patient mutations could be synergistic with Notch in a particular disease context and/or causing very different outcomes (e.g. tumour promoting versus tumour suppressing). They could also identify novel protein:protein interactions that would be a good substrate for drug developments.
Benefit is likely to be realized in the longer term and it would impact especially on enhancing quality of health.

Benefits to medicine will come from the scientific results and the insights into clinically relevant mechanisms:
A better understanding of how different targets are selected could be extremely valuable in diagnostic strategies because classical Notch targets (e.g., HES1) do not necessarily appear to be modulated in patient tissues. Results will also suggest new possibilities to improve on therapies targeting the Notch pathway. Currently, the main strategies use small molecule inhibitors of gamma-secretase and have serious side effects such as goblet cell metaplasia, as well as off target effects. The discovery of novel regulatory mechanisms in a subset of tissues could lead to strategies for developing more targeted therapies to overcome these problems. They can also be harnessed to manipulate Notch for directed differentiation of stem cells.

Benefits to business, industrial and public sector recruiting graduate level staff will come from the development of relevant research sills and professional skills:
The project's diverse nature ensures that the staff will acquire a broad range of technical skills (high-end imaging, genomic and molecular biology techniques, computational approaches for working with large data sets and modelling), which will be applicable in wide range of life sciences, pharmaceutical, computational employment. Further gains come from our international collaborations, enhancing the skills training and exposure. Alongside technical skills, staff will at the same time develop generic professional skills e.g. presentational skills; writing skills; data handling, including statistics; generic computational skills; project management. Evidence of our track record in this aspect comes from subsequent employment of staff from our groups (e.g. investment banking, parliamentary advisor, publishing, venture capital advisor).

Benefits to the general public and schools, through our involvement in public engagement:
We have been involved in communicating modern scientific ideas, methodologies and approaches to the wider community. These activities will be extended to encourage scientific understanding and to extend the concepts from our research into other fields. The University of Cambridge provides excellent support for public dissemination of research through the Office of Community Affairs, including the Cambridge Science Festival, and we will continue to encourage our researchers to participate in these activities.

Publications

10 25 50