RESEARCH

PROJECTS

There are currently three interrelated research themes in the laboratory:

  1. The assembly of human cortical circuits in vivo
  2. Human axon and synaptic dysfunction in the early stages of neurodegenerative conditions
  3. Enhancement of human cortical axon and synaptic regeneration

PROJECTSPAST WORK
PROJECTS

Human cortical circuit development, degeneration and regeneration

We study the regulation of neural network connectivity in the brain with the ultimate goal of using this knowledge to develop new strategies to tackle human neurological diseases.

We recently established a new approach to study the dynamics of human cortical synaptic networks using transplanted donor-derived cells (from various academic collaborators and commercial sources) and intravital longitudinal imaging.  This experimental design, inspired by previous pioneering transplantation work from Anders Björklund (University of Lund, Sweden), Rusty Gage (Salk Institute, La Jolla, USA), Su-Chun Zhang (University of Wisconsin-Madison, USA), Pierre Vanderhaeghen (KU Leuven, Belgium), Oliver Brüstle (University of Bonn, Germany), Lorenz Studer (Sloan Kettering Institute, New York, USA), Magdalena Götz (Ludwig Maximilian University of Munich, Germany), Ole Isacson (Harvard University, Boston, USA) and others, led to the discovery of reduced neural activity and reduced turnover of synaptic connections in Down syndrome (Real et al., 2018), which could explain the development of cognitive symptoms in this condition. We are now working hard to figure out why these Down syndrome cellular phenotypes arise and how they can be rescued.

Using this new in vivo imaging approach to gain insights into the dynamics of human cortical circuits, we are tackling three research areas, or problems.

1. Human Cortical circuit wiring and neurodevelopmental conditions

Proper assembly of cortical circuitry is a critical step in human brain development and maturation of high-order cognitive abilities (Fernández et al., 2016).  Despite its pivotal role, we do not yet clearly understand how human cortical circuits develop in vivo, and why this process can fail, leading to cognitive disturbances in neurodevelopmental conditions.  Cellular analyses in the immature human brain rely on scarce foetal material and focus on post-mortem fixed samples, which cannot provide direct observation of dynamic events such as axon and synaptic remodelling and patterned network activity.  This limitation raises the question of how to study the cellular mechanisms of human cortical circuit assembly and their dysfunction in the many incurable disorders affecting the developing cortex.

Building on our recent work on Down syndrome (Real et al., 2018), we now want to tackle other complex genetic conditions such as autism and schizophrenia.  Our aim is to catalyze new treatment strategies by increasing our understanding of the synaptic basis and potential common pathophysiological principles underlying cognitive impairment.

Related work from the Group

The effects of haloperidol on microglial morphology and translocator protein levels: An in vivo study in rats using an automated cell evaluation pipeline.
Bloomfield, P. S., Bonsall, D., Wells, L., Dormann, D., Howes, O.*, De Paola, V.*
Journal of Psychopharmacology 32, 1264-1272 (2018).
*Co-senior authors

In vivo modeling of human neuron dynamics and Down syndrome
Real, R.*, Peter, M.*, Trabalza, A.*, Khan, S., Smith, M. A., Dopp, J., Barnes, S. J., Momoh, A., Strano, A., Volpi, E., Knott, G., Livesey, F. J.†, De Paola, V.
Science 362, eaau1810 (2018).
*Co-first authors, †Corresponding authors
Neuron Spotlight | F1000Prime | Nature Reviews Neurology Research Highlight | MRC London Institute of Medical Science News | MRC News | Spectrum | Adnkronos (Italian) | Público (Portuguese) | Imperial College London Podcast | Imperial College London News |

Microglial activity in people at ultra high risk of psychosis and in schizophrenia: an [11C]PBR28 PET brain imaging study.
Bloomfield, P. S., Selvaraj, S., Veronese, M., Rizzo, G., Bertoldo, A., Owen, D. R., Bloomfield, M. A. P., Bonoldi, I., Kalk, N., Turkheimer, F., McGuire, P., de Paola, V.*, Howes, O. D.* (2016).
The American Journal of Psychiatry 173, 44-52 (2016).
*Co-senior authors
Cover article | Editor Spotlight | Editorial | BBC News | Imperial College London News | MRC News | New Scientist |

Long-term, high-resolution imaging in the mouse neocortex through a chronic cranial window.
Holtmaat, A.*, Bonhoeffer, T., Chow, D. K., Chuckowree, J., De Paola, V.*, Hofer, S. B., Hübener, M.*, Keck, T., Knott, G.*, Lee, W.-C. A., Mostany, R., Mrsic-Flogel, T. D., Nedivi, E.*, Portera-Cailliau, C.*, Svoboda, K., Trachtenberg, J. T.*, Wilbrecht, L.
Nature Protocols 4, 1128-1144 (2009).
Except for first author, authors listed alphabetically; *Corresponding authors

Cell type-specific structural plasticity of axonal branches and boutons in the adult neocortex.
De Paola, V., Holtmaat, A., Knott, G., Song, S., Wilbrecht, L., Caroni, P., Svoboda, K.
Neuron 49, 861-875 (2006).
Neuron News and Views | F1000Prime |

Diverse modes of axon elaboration in the developing neocortex.
Portera-Cailliau, C., Weimer, R. M., De Paola, V., Caroni, P., Svoboda, K.
PLoS Biology 3, e272 (2005).
Nature Reviews Neuroscience Research Highlight | F1000Prime |


2. Human cortical circuit dysfunction in the early stages of neurodegenerative diseases

We focus on the physiological roles of amyloid precursor protein (APP) and Tau. These are two key proteins that when altered can accumulate in the brain as the main components of amyloid plaques and neurofibrillary tangles in many neurodegenerative diseases such as Alzheimer’s disease (AD) and frontotemporal dementia (FTD). Usually these protein aggregates can be found in the late stages of disease progression. Yet, this fact needs to be reconciled with the frequent observation of abundant amyloid plaques in normal aged, non-demented people (Gold et al., 2001), as well as with the much stronger correlation of clinical severity of dementia with synapse density, rather than plaque density (Chen et al., 2018). In the early stages of AD there is neural network dysfunction and loss of axons and synapses leading to progressive and relentless impairment of cognitive abilities (Palop and Mucke, 2010, Benilova and De Strooper, 2013). So, elucidating the role of APP and Tau in these early steps of disease progression may provide fundamental insights into pathomechanisms, which could be helpful to develop potential treatment strategies for AD and FTD.

To study the role of APP and Tau alterations in human axon and synaptic dysfunction, we have teamed up with the labs of Dean Nizetic (Nanyang Technological University, Singapore) and Maria Grazia Spillantini (University of Cambridge, UK), who have developed iPSC lines from people with APP copy number changes (e.g. from DS people, dupAPP or via genome editing) and with Tau point mutations linked to frontotemporal dementia (e.g. P301L). Importantly, after transplantation these neurons survive and mature by forming long range axons and boutons (unpublished), opening the way for in vivo imaging studies of their structure and function in the context of human neurodegenerative conditions.

Related work from the Group

Impaired axon regeneration and heightened synaptic dynamics in the injured aged mouse cortex.
Bass, C., Clopath, C., Bharath, A. A., De Paola, V.
(2019, in preparation)

Single-axon-resolution intravital imaging reveals a rapid onset form of Wallerian degeneration in the adult neocortex.
Canty, A. J., Jackson, J. S., Huang, L., Trabalza, A., Bass, C., Little, G. De Paola, V.
BMC Biology (2019, submitted).

In vivo modeling of human neuron dynamics and Down syndrome
Real, R.*, Peter, M.*, Trabalza, A.*, Khan, S., Smith, M. A., Dopp, J., Barnes, S. J., Momoh, A., Strano, A., Volpi, E., Knott, G., Livesey, F. J.†, De Paola, V.
Science 362, eaau1810 (2018).
*Co-first authors, †Corresponding authors
Neuron Spotlight | F1000Prime | Nature Reviews Neurology Research Highlight | MRC London Institute of Medical Science News | MRC News | Spectrum | Adnkronos (Italian) | Público (Portuguese) | Imperial College London Podcast | Imperial College London News |

Laser-mediated microlesions in the mouse neocortex to investigate neuronal degeneration and regeneration.
Jackson, J., Canty, A. J., Huang, L., De Paola, V.
Current Protocols in Neuroscience 73, 2.24.1-2.24.17. (2015)

Pharmacogenetic stimulation of cholinergic pedunculopontine neurons reverses motor deficits in a rat model of Parkinson’s disease.
Pienaar, I. S., Gartside, S. E., Sharma, P., De Paola, V., Gretenkord, S., Withers, D., Elson, J. L., Dexter, D. T.
Molecular Neurodegeneration 10, 47 (2015).

Increased axonal bouton dynamics in the aging mouse cortex.
Grillo, F. W., Song, S., Teles-Grilo Ruivo, L. M., Huang, L., Ge, G., Knott, G. W., Maco, B., Ferretti, V., Thompson, D., Little, G. E., De Paola, V.
Proceedings of the National Academy of Sciences of the United States of America 110, E1514-E1523 (2013).
Nature Research Highlights | F1000Prime |


3. In vivo modeling and enhancement of human cortical axon regeneration

Recovery from brain damage is incomplete and slow, causing irreversible disabilities for millions of people every year. One of the main reasons for this is the limited regeneration of lesioned brain circuitry. To achieve effective recovery following brain injury, re-growth of injured axons either towards their original or new synaptic targets is a necessary process towards re-establishment of functional neural circuits. An important unresolved question is to what extent the principles of cell type-dependent axon and presynaptic plasticity we uncovered in the mouse brain (Portera-Cailliau et al., 2005, De Paola et al., 2006, Allegra Mascaro et al., 2013, Canty et al., 2013, Canty et al., 2013, Grillo et al., 2013) apply to humans. Indeed, mechanistic insights from model systems still need to be validated in humans to advance translational therapies. Therefore, there is a pressing need for new experimental models that can mimic human-specific features to (i) characterise differences in axon regeneration of major CNS neuronal subclasses e.g. long-range cortical projection neurons (such as the cortico-spinal tract) and (ii) develop strategies to enhance axon regeneration of mature human neurons.

We previously found that human axons grew for up to 5 months post-transplantation towards their cortical and subcortical targets. To enhance human axon regeneration, we are now 1) characterising human axon regeneration after injury and 2) testing the efficacy of temporally interfering electrical fields (Grossman et al,. 2017), a technology with clinical potential that allows non-invasive transcranial stimulation of cortical neural networks (in collaboration with Nir Grossman, Imperial College London, UK).

Related work from the Group

Impaired axon regeneration and heightened synaptic dynamics in the injured aged mouse cortex.
Bass, C., Clopath, C., Bharath, A. A., De Paola, V.
(2019, in preparation)

Single-axon-resolution intravital imaging reveals a rapid onset form of Wallerian degeneration in the adult neocortex.
Canty, A. J., Jackson, J. S., Huang, L., Trabalza, A., Bass, C., Little, G. De Paola, V.
BMC Biology (2019, submitted).

In vivo modeling of human neuron dynamics and Down syndrome
Real, R.*, Peter, M.*, Trabalza, A.*, Khan, S., Smith, M. A., Dopp, J., Barnes, S. J., Momoh, A., Strano, A., Volpi, E., Knott, G., Livesey, F. J.†, De Paola, V.
Science 362, eaau1810 (2018).
*Co-first authors, †Corresponding authors
Neuron Spotlight | F1000Prime | Nature Reviews Neurology Research Highlight | MRC London Institute of Medical Science News | MRC News | Spectrum | Adnkronos (Italian) | Público (Portuguese) | Imperial College London Podcast | Imperial College London News |

In vivo imaging of CNS injury and disease.
Akassoglou, K.*, Merlini, M., Rafalski, V. A., Real, R., Liang, L.*, Jin, Y., Dougherty, S. E., De Paola, V.*, Linden, D. J.*, Misgeld, T.*, Zheng, B.*
The Journal of Neuroscience 37, 10808-10816 (2017).
*Contributed equally to work
Cover article |

Laser-mediated microlesions in the mouse neocortex to investigate neuronal degeneration and regeneration.
Jackson, J., Canty, A. J., Huang, L., De Paola, V.
Current Protocols in Neuroscience 73, 2.24.1-2.24.17. (2015)

In vivo single branch axotomy induces GAP-43-dependent sprouting and synaptic remodeling in cerebellar cortex.
Allegra-Mascaro, A. L., Cesare, P., Sacconi, L., Grasselli, G., Mandolesi, G., Maco, B., Knott, G., Huang, L, De Paola, V., Strata, P., Pavone, F. S.
Proceedings of the National Academy of Sciences of the United States of America 110, 10824-10829 (2013).

In-vivo single neuron axotomy triggers axon regeneration to restore synaptic density in specific cortical circuits.
Canty, A. J., Huang, L., Jackson, J..S., Little, G. E., Knott, G., Maco, B., De Paola, V.
Nature Communications 4, 2308 (2013).
Nature Research Highlights |

Synaptic elimination and protection after minimal injury depend on cell type and their prelesion structural dynamics in the adult cerebral cortex.
Canty, A. J., Teles-Grilo Ruivo, L., Nesarajah, C., Song, S., Jackson, J. S., Little, G. E., De Paola, V.
The Journal of Neuroscience 33, 10374-10383 (2013).

Publications
PAST WORK

1. Axon and synaptic remodelling underlying aging and learning / memory

Learning deficits with age are thought to arise from a progressive loss of synapses and synaptic plasticity, but in vivo evidence has been lacking. We have imaged diverse types of excitatory axons and their boutons in the somatosensory cortex of aged (> 22 months) mice with impaired long-term recognition memory. We have combined two-photon microscopy with behavioural assessment and a novel, computer-based, method to rigorously track the size (i.e., strength) and location of large populations of synaptic boutons over extended periods of time, which we have extensively validated including with correlated two-photon-serial section electron microscopy. Axonal arbors and their boutons continue to remodel in the aged brain. Unexpectedly, the aged cortex shows circuit-specific increased rates of axonal bouton addition, elimination and destabilization. Compared to the young adult brain, large (i.e., strong) boutons show 10-fold higher rates of destabilization and 20-fold higher turnover in the aged cortex. Size fluctuations of persistent boutons, believed to encode long-term memories, are larger in the aged brain, while bouton size and density are not affected. Our study suggests that increased synaptic plasticity in specific cortical circuits is a novel mechanism for age-related cognitive decline. Since large boutons are thought to encode long-term memories, and are stabilized at the same rate as in young adults, their increased destabilization suggests that learning deficits in the aged brain arise because of a higher probability of forgetting rather than a failure to learn.

Related work from the Group

Single-axon-resolution intravital imaging reveals a rapid onset form of Wallerian degeneration in the adult neocortex.
Canty, A. J., Jackson, J. S., Huang, L., Trabalza, A., Bass, C., Little, G. De Paola, V.
BMC Biology (2019, submitted).

Laser-mediated microlesions in the mouse neocortex to investigate neuronal degeneration and regeneration.
Jackson, J., Canty, A. J., Huang, L., De Paola, V.
Current Protocols in Neuroscience 73, 2.24.1-2.24.17. (2015)

Pharmacogenetic stimulation of cholinergic pedunculopontine neurons reverses motor deficits in a rat model of Parkinson’s disease.
Pienaar, I. S., Gartside, S. E., Sharma, P., De Paola, V., Gretenkord, S., Withers, D., Elson, J. L., Dexter, D. T.
Molecular Neurodegeneration 10, 47 (2015).

Increased axonal bouton dynamics in the aging mouse cortex.
Grillo, F. W., Song, S., Teles-Grilo Ruivo, L. M., Huang, L., Ge, G., Knott, G. W., Maco, B., Ferretti, V., Thompson, D., Little, G. E., De Paola, V.
Proceedings of the National Academy of Sciences of the United States of America 110, E1514-E1523 (2013).
Nature Research Highlights | F1000Prime |

 


 

2. Cellular mechanisms of axon and synaptic regeneration in the brain

Major efforts in the field of axon regeneration have so far concentrated on the spinal cord and white matter injury models. As a consequence, whether, how and when axons regenerate in the brain is not fully understood, leaving open basic questions regarding its endogenous repair capacity. For example, can axons regenerate in the absence of glial scar-mediated inhibition? Can axons elongate for distances sufficient to cover the lost output in the highly interconnected grey matter? Does the pattern of re-growth recapitulate developmental axon growth or does it employ a distinct growth program? And, finally, can axons reach the pre-lesion targets and form synapses? These questions are particularly important now that many experimental manipulations can successfully initiate axon regeneration in the adult injured CNS. Here we have used a combination of two-photon microscopy, femtosecond laser micro-surgery and a variety of post-hoc techniques including novel retrospective focused ion beam-electron microscopy. This enabled us, for the first time, to assess the real-time reorganization of injured axons for periods up to a year in the brain of living mice and in the absence of glial scars. We report four main findings: i. Many severed cortical axons in the grey matter can spontaneously regrow within weeks depending on cell type. ii. Axons can extend for distances larger than the amount cut (i.e. distances unseen in the adult cortex) at speeds comparable to peripheral nerves. iii. Injured axons grow monotonically, a unique pattern of growth which surprisingly differs from developmental axon growth. iv. Regenerating axons consistently form new boutons to re-establish the pre-lesion synaptic densities but never reconnect to the original targets. Our data unequivocally provide in vivo evidence for spontaneous axon regeneration in the mature brain and identify key underlying cellular and synaptic mechanisms. Moreover, we provide evidence for a rapid and lasting process of synaptic elimination, which depends on cell type and their recent history, while synapse formation rates are globally unaffected. Recent work in Caenorhabditis elegans and mouse spinal cord has highlighted the power of in vivo optical imaging to dissect the axonal response to injury (Bradke et al., 2012), and we provide the first quantitative analysis of axonal regeneration and synaptic reorganization in the cortex and cerebellum of living mice by combining longitudinal in vivo 2-photon imaging with precise laser micro-surgery.

Related work from the Group

In vivo imaging of CNS injury and disease.
Akassoglou, K.*, Merlini, M., Rafalski, V. A., Real, R., Liang, L.*, Jin, Y., Dougherty, S. E., De Paola, V.*, Linden, D. J.*, Misgeld, T.*, Zheng, B.*
The Journal of Neuroscience 37, 10808-10816 (2017).
*Contributed equally to work
Cover article |

Laser-mediated microlesions in the mouse neocortex to investigate neuronal degeneration and regeneration.
Jackson, J., Canty, A. J., Huang, L., De Paola, V.
Current Protocols in Neuroscience 73, 2.24.1-2.24.17. (2015)

In vivo single branch axotomy induces GAP-43-dependent sprouting and synaptic remodeling in cerebellar cortex.
Allegra-Mascaro, A. L., Cesare, P., Sacconi, L., Grasselli, G., Mandolesi, G., Maco, B., Knott, G., Huang, L, De Paola, V., Strata, P., Pavone, F. S.
Proceedings of the National Academy of Sciences of the United States of America 110, 10824-10829 (2013).

In-vivo single neuron axotomy triggers axon regeneration to restore synaptic density in specific cortical circuits.
Canty, A. J., Huang, L., Jackson, J..S., Little, G. E., Knott, G., Maco, B., De Paola, V.
Nature Communications 4, 2308 (2013).
Nature Research Highlights |

Synaptic elimination and protection after minimal injury depend on cell type and their prelesion structural dynamics in the adult cerebral cortex.
Canty, A. J., Teles-Grilo Ruivo, L., Nesarajah, C., Song, S., Jackson, J. S., Little, G. E., De Paola, V.
The Journal of Neuroscience 33, 10374-10383 (2013).

Unpublished article

Window on the brain – Researchers look into the living brain.
Lewis, A. (2013).

All Publications