Molecular reconstitution of cellular machinery essential for neuronal development

When you were a child, did you ever get lost amidst the towering shelves of a supermarket? That sense of something very small in a huge and complex environment is reminiscent of the challenge faced by cells of the developing brain. The adult human brain is built from billions of specialised cells called neurons. During embryonic growth, immature neurons undertake an amazing journey that involves finding their way from the centre of the developing brain, pushing past many other neurons to get to specific locations in the brain's complex structure. Successful migration enables the formation of the network of mature neurons that are essential for memory and thought. Severe human diseases including epilepsy and mental retardation, and early death, can be caused if the neurons get lost on their journey. Work in my lab is beginning to provide understanding about components of the machinery that enable neurons to navigate the complex maze of the developing brain.

In the same way as our body has a skeleton, neurons have a skeleton - called the cytoskeleton - which also provides support and strength. The cytoskeleton is involved in many important aspects of the life of the cell, including cell shape and movement and it is essential for brain development. Studying the cytoskeleton is important so we can understand both how healthy cells work and malfunctions of the cytoskeleton in disease. My research team studies the three-dimensional structure of the cytoskeleton, because knowing what the cytoskeleton looks like contributes to our understanding of how it works within the cell. We use a very powerful microscope to take pictures of individual cytoskeleton molecules and then use computers to combine these pictures and calculate their three-dimensional shape. Our current research focuses on a part of the cytoskeleton called microtubules, long cylindrical structures that act as scaffolds to help neurons on the move.

In this project, we will be studying a family of proteins that provide extra stability for microtubules in neurons. These proteins are called the doublecortin family of microtubule associated proteins, and they are essential for human brain development. We have had some exciting recent results from our microscope studies and we want to know more about how these proteins interact with microtubules to provide strength for migrating neurons. We also want to know how microtubule stabilisation by the doublecortin family affects the neuron's transporter motors that use microtubules as tracks to carry cargo around the cell.

With this information, we hope to provide insight into how diseases of brain development occur. Our research should also provide essential clues about how immature brain cells might be used to treat brain damage later in life, for example in stroke patients or in sufferers of neurodegenerative diseases like Alzheimer's disease.

Human brain development involves the coordinated movement of billions of neurons. Microtubules (MTs) are crucial for this, acting as both a dynamic framework for motility and forming tracks for intracellular trafficking by molecular motors. Disruption of these functions causes aberrant migration, resulting in developmental neurological defects and brain malformations. Understanding neuronal migration is also critical in the context of brain repair therapies for adult diseases, for example in the treatment of stroke and neurodegeneration. MT-associated proteins (MAPs) are essential for regulating and organising MTs. However, our mechanistic understanding of MAP function is limited by a lack of integrated structural and functional information. The aim of this research programme is to shed light on the doublecortin (DCX) family of essential neuronal MAPs (DCX-MAPs). We will elucidate the molecular mechanisms by which they regulate MTs and control cargo trafficking through interactions with molecular motors. Using state-of-the-art cryo-electron microscopy and image processing, we will solve sub-nanometre resolution structures of DCX-MAP-MT complexes to precisely reveal their mechanisms of MT regulation. We will also reconstitute complexes of motor-bound DCX-MAP-MT complexes and determine these structures by cryo-electron microscopy, revealing the molecular details of motor-track cross-talk. Biochemical and biophysical assays will provide a functional context for our structural discoveries and allow us to test our hypotheses using protein engineering. To place our molecular discoveries in a cellular context, we will study the function of DCX-MAPs in neurons using cryo-electron tomography. We will visualise the organisation of MTs in neurons and elucidate the impact of depletion of DCX-MAPs on neuronal MTs. Through this integrated programme of research, we will discover regulatory mechanisms of MT dynamics and trafficking, with important implications for human health.

Who will benefit from this research?
- Patients with genetic disorders of neuronal development
- Patients with brain damage due to mechanical injury or neurodegeneration
- UK economy
- The wider public
- Women in science

How will they benefit from this research?
The work described will lead to a greater understanding of essential mechanisms involved in human brain development. DCX-MAPs are regulators of MTs and disruption of their function causes human diseases including epilepsy, intellectual disability and blindness. The molecular insight that will arise from our studies will, first, contribute to improved diagnosis of particular syndromes associated with these diseases. There is emerging evidence that groups of symptoms cluster with particular types of mutations and our studies will provide greater clarity as to the molecular basis of these phenotypes. Once the molecular basis of these diseases are fully understood, novel treatments for these often devastating conditions can be contemplated. Our work will contribute to this, particularly in bridging the gap between molecular function of DCX-MAPs and their regulation of MTs within neurons. In the future, it is also hoped that the understanding that our work will bring concerning general mechanisms of neuronal development can be brought to bear on treatment of extremely common neurological phenomena such as brain injury and neurodegenerative diseases. Science and technology will lie at the heart of global economic recovery, and we will liase with Birkbeck College Business Relations Department to maximise the impact of our discoveries. This will ultimately have benefits for the economic competitiveness of the United Kingdom.

It is essential to retain talented young researchers in the UK, and the proposed research programme will provide an attractive research opportunity for excellent young scientists looking for multi-disciplinary areas of discovery. In addition, transferable skills - such as time- and project-management, presentation and collaboration - that can be applied in all employment sectors will be acquired, particularly through transferable skills training within the Institute of Structural and Molecular Biology.

We will aim to make the discoveries of our research available not only to the academic community, but also to the general public. I have a proven track-record of public communication of science. The appointed PDRAs and I will undertake to design web-pages for my lab which are accessible for the general public and will seek to participate in other public understanding of science activities, for example by inviting sixth-form students to visit our lab and experience the day-to-day life of scientists. During the project period, I will arrange to visit my former school to inspire future scientists and will seek to become involved in advancing gender equality in science, engineering and technology through involvement with The UKRC and WISE campaign.