Profile

Career

Research

Overview

My research centres on the role of the endosome in regulating signals controlling synapse growth. Appropriate regulation of synaptic growth is a key mechanism in regulating the fidelity of synaptic communication. Many neurodegenerative diseases show abnormal function of endosomal compartments. My previous work has suggested that in one form of neurodegenerative disease, a lysosomal storage disorder, endosomal perturbation leads to an excessive growth of the synapse most likely due to the failure to regulate growth signals appropriately. Working with the larval neuromuscular junction of Drosophila as a model synapse, I will model the lysosomal storage diseases to further understand the cellular perturbations that give rise to the profound neurodegeneration produced by this set of devastating genetic conditions.

Discoveries

Identification of the endosomal protein spinster as a key regulator of synapse growth and function. Identification of other key membrane trafficking steps essential to synaptic transmission and growth such n-synaptobrevin, and Dap160. I have also developed key tools in common use for the silencing of synapses in Drosophila.

In recent work we have identified oxidative stress as a regulator of synapse growth. A potentially critical insight into the signalling activated in the brain both during ageing and neurodegenerative disease.

Current projects

• Oxidative stress and the regulation of synapse function (Funding body: BBSRC, 1/08/11 to 31/07/14)
•  A Drosophila model of Frontotemporal Dementia (Alzheimer’s Society)

Research group(s)

Lab Alumni

• Laura Briggs (post-doc) Schoolteacher
• Matthew Oswald (PhD student) Post-Doc in lab of Dr Matthias Landgraf, Department of Zoology, University of Cambridge
• Samantha Hindle (PhD student) Post-Doc in lab of Dr Roland Bainton, Department of Anesthesia, University of California, San Francisco
• Valerie Milton (PhD student) Postgraduate Medical student, Queen Mary’s University, London

Collaborators

Dr Matthias Landgraf, Department of Zoology, University of Cambridge (Oxidative stress and synapse growth)

Dr Keith Stubbs, Department of Chemistry, University of Western Australia (Using Drosophila models of mucopolysaccharidosis as a therapeutic screening tool)

Dr Fen-Biao Gao, Department of Neurology, University of Massachusetts, Worcester (A Drosophila model of Frontotemporal Dementia)

Dr Sarita Hebbar and Dr Dominik Schwudke, NCBS, Bangalore, India (Using Drosophila to model Lysosomal Storage Disease).

Available PhD research projects

Generating a Drosophila model of Valosin-containing-peptide induced Frontotemporal Dementia (for 2012 - 13)

 Frontotemporal Dementia (FTD) is a major cause of early onset dementia.  Characterised by atrophy of the frontal and temporal lobes with a loss in language and social function, FTD incidence has a strong genetic component and a number of loci have been mapped. Amongst these loci is the Valosin-containing-peptide (VCP) gene. VCP is a known regulator of cellular traffic but little is known about how mutations in VCP can lead to neurodegeneration.

We have successfully generated Drosophila models of known neurodegenerative diseases and these models are providing insights into the mechanisms of disease onset and effect. We currently work with a model of CHMP2B related FTD that has been successful in identifying a role for immune response in this disease. Using the advanced genetics of Drosophila, we will generate a model of VCP related FTD in order to identify signalling pathways  induced by loss of function of VCP. We will use the fly eye model as the basis for an enhancer/suppressor screen to identify loci important for the progression of the neurodegenerative phenotype. This will generate a genetic model and cellular description of VCP induced FTD which will improve our understanding of the pathology of this poorly characterised disease.

Identifying signaling responses governing synapse growth and function in aging neurons: defining responses to different cellular sources of oxidative stress (For 2012 - 13)

Supervisors:  Dr Sean Sweeney and Dr David Ashford

Background: Aging results from the cumulative cellular damage incurred during lifetime. Reactive oxygen species (ROS) are a recognised source of damage during aging. High metabolic demand and terminal developmental state in neurons renders neural tissue vulnerable to ROS. How neurons, and in particular synapses, respond to ROS during ageing remains unclear. At low levels, ROS can act as a signal promoting learning and memory processes potentially through the conserved Jun-kinase (JNK)/AP-1 signaling cascade. Our recent work (Milton et al., 2011, PNAS) has identified ROS as an upstream activator of JNK/AP-1 activation and synaptic growth in the Drosophila neuromuscular synapse, with pathological levels of ROS leading to overgrowth and functional failure. We observe that mitochondrial or cytoplasmic sources of ROS lead to differential signaling activation and synapse growth. Identifying and defining the mechanisms of this differential signal activation during an ageing process is the major aim of this project.

Objectives: We find cytoplasmic ROS activates Fos, while mitochondrial ROS activates Fos and Jun to drive synapse growth. We will use the genetic toolbox of Drosophila to define upstream signaling from JNK, and a targeted expression of a transgenic Tandem-Affinity-Purification tagged versions of Fos and Jun (followed by mass spectrometry) to identify the phosphorylation code that allows homo- or heterodimerisation of these factors. Our findings will be confirmed by the introduction of mutant genes by homologous recombination bearing appropriate phospho-mimetic and non-phosphorylatable mutations. This work will define the JNK pathway outputs regulating synapse growth and function in response to pathological levels of ROS from different cellular sources during the ageing process.

Novelty and Timeliness: With an increasingly ageing UK population, how age exerts effects on the brain is almost completely unknown. The Sweeney lab is first to identify ROS as an ageing signal to affect synapse growth and function. This project will build on our published work.

Publications

Selected publications

Milton, V.J., Jarrett, H.E., Gowers, K., Chalak, S., Briggs, L., Robinson, I.M. and Sweeney, S.T. (2011) Oxidative stress induces overgrowth of the Drosophila neuromuscular junction. P.N.A.S. in press

Sweeney ST and Davis GW (2002) Unrestricted growth in spinster: regulation of synapse development from an endosomal/lysosomal compartment. Neuron 36: 403-416

Sanyal S and Ramaswami M (2002) Spinsters, synaptic defects, and amaurotic idiocy. Neuron 36: 335-8

Marie, B., Sweeney, S.T., Poskanzer, K.E., Roos, J., Kelly, R.B. and Davis, G.W. ( (2004) Dap160/Intersectin Scaffolds the Peri-Active Zone to Achieve High-Fidelity Endocytosis and Normal Synaptic Growth Neuron 43: 207-219

External activities

Memberships

• Member of the Biochemical Society

Editorial duties

• Editorial board member for Intertebrate Neuroscience
• Outreach: Biotechnology and Biological Sciences Research Council (BBSRC) Regional Schools Champion for Northeast England.