Defining the role of ciliary BBS proteins in neuroplasticity

Lead Research Organisation: University College London
Department Name: Institute of Child Health

Abstract

Neuronal plasticity is among the most important areas of modern neuroscience research and one of the best existing cellular models for learning and memory. The hippocampus is a brain structure important for learning and the storage of memories. It has been shown that there is an area in hippocampus where new neurons are born even during adult life. New neurons integrate into existing networks and are important for developing new skills and memory. It has also recently emerged that memories and learning skills are "stored" in dendritic spines, mushroom like protrusions on the dendrites of nerve cells. Dendritic spines are very "plastic", that is, they change significantly in shape, volume, and number over a short time course. Because spines mostly comprise an actin cytoskeleton, they are dynamic, with the majority of spines able to change their shape within seconds to minutes following actin remodelling. New experiences and learning lead to the formation of new spines. It has been observed that malformed spines or reduced spine number can be associated with learning disabilities.

Recently, an exciting link between cilia/ciliary proteins and adult neurogenesis has emerged. Cilia are hair-like projections from the cell membrane. They are found on almost all eukaryotic cells. In the last decade it has been shown normal human functions such as ability to see, hear, smell, breathe, excrete, reproduce critically depend on correct ciliary function. It has been also shown that cilia are important for normal brain functions such as learning and memory. Normal cilia function depends on integrity of many proteins including BBS.
We have generated preliminary data indicating that there is a reduction in formation of adult new born neurons as well as reduction in dendritic spine number and density in Bbs mice model. These mice lack a functional BBS protein and therefore recapitulates the main features of human BBS and thus, will provide Here we propose to investigate how mutation in a single BBS protein might lead to the changes in neuroplasticity. We hypothesise that the absence of a fully functioning Bbs protein affects the formation of dendritic spines thus reducing the hippocampal capacity for information storage and effective learning.

Technical Summary

Neuronal plasticity is among the most important areas of modern neuroscience research and one of the best existing cellular models for learning and memory. Dynamic changes in axon and dendritic growth, integration of adult new-born neurons into existing networks, synaptogenesis, and dendritic spine formation are just some examples of the molecular and cellular underpinnings of neuronal plasticity.
Recently, an exciting link between cilia and adult neurogenesis has emerged. Loss of cilia in adult progenitor cells leads to significant decrease of proliferation in hippocampal amplifying progenitors. Moreover, loss of ciliary protein Arl13b causes aberrant polarity of radial progenitors leading to the disruption of neuron organisation in cortex.
Cilia are microtubule-based, centriole-derived projections from the apical cell membrane. In the last decade it has been identified that normal human functions such as ability to see, hear, smell, breathe, excrete, reproduce and learn/remember critically depend on correct ciliary function.
Bardet-Biedl syndrome, BBS, proteins play an important role in cilia function being a core facilitators of ciliogenesis and cilia receptor trafficking. We, and others have previously shown that the BBS4 protein is involved in microtubular stabilisation suggesting involvement of BBS proteins in the regulation of the cytoskeleton and protein trafficking. In spite a well-defined role in ciliagenesis, the role of BBS proteins in neurogenesis and dendritic spine formation has not been investigated. In our preliminary experiments we have determined that Bbs4 and Bbs5 null mice have significantly reduced neurogenesis and dendritic spine formation in the dentate gyrus suggesting that there is an overall reduction in neuronal plasticity. Here we propose to investigate the molecular mechanisms of BBS proteins involvement in adult neurogenesis and synaptogenesis.

Planned Impact

The proposed research will likely have immediate and long term impact on academic communities and clinical researchers. Even though it is not our primary goal to investigate a Bardet-Biedl syndrome patients neurophysiology, this study will have an impact on BBS patients, their clinicians, and the National Health and Social services
Academic community:
Although the proposed research project is multi-disciplinary in nature, we predict that the greatest impact for researchers will be in the cilia and neuro-biology fields. Cilia is a organell which is recognised to be vital for many normal human functions such as hearing, vision, taste, reproduction and learning and memory. The evidence of cilia profound significance lies in the fact that defects in cilia lead to a broad range of organ specific disorders: situs inversus, polycystic kidneys, retinal degeneration, obesity etc. However, little is known as to how defects in cilia function affect learning, memory and even psychiatric disease. This project will help to evaluate the potential link between neuronal plasticity and its impact on learning, memory and behaviour. Bbs mice might provide an excellent tool for the neurobiological studies of neuronal plasticity.
Bardet-Biedl patients and their clinicians
In this study we propose to investigate the role of BBS proteins in neuroplasticity. BBS proteins when mutated, cause Bardet-Biedl syndrome (BBS) which is a highly debilitating autosomal-recessive genetic disorder in which patients present with early-onset blindness, polydactyly, renal disease, obesity, diabetes and cognitive impairment. There is no cure. In addition to learning disabilities, the neuropsychiatric component of BBS comprises behavioural difficulties such as disinhibition, an inability to recognise social cues, obsessive-compulsive tendencies, anxiety and depression, autism and even psychosis. Most adult patients experience short-term memory deficits but relatively well-preserved long term memory.
For the clinicians, the knowledge of the underlying aetiology of the cognitive impairment in BBS patients is critical for how clinicians regard the intellectual development of these patients who currently have no strategy for improvement. For example, early recognition of the disorder by GPs, mid-wives or health visitors, and subsequent correct diagnosis by paediatricians and clinical geneticists is vital if affected children are to be given the appropriate and timely therapy.
National Health Service and Social Services
Approximately 500 patients attend the NHS nationally commissioned clinical service (led by P. Beales). Each BBS patient requires input from multiple services including ophthalmology, nephrology, urology, dietetics, endocrinology, clinical genetics, psychology and neurology. The BBS specialised service provides a one-stop shop clinic visit delivered by four NHS trusts; Birmingham Children's Hospital, Queen Elizabeth Hospital (Birmingham), Guys Hospital and Great Ormond Street Hospital (London). Genetic testing for each patient is also provided through this service. BBS patients require lifelong monitoring of their disease and treatment of organ-specific problems which is partly delivered through this service.
An important observation from the service is that learning disabilities and memory deficits are much less pronounced in the early years than during adolescence and adulthood indicating that these are not likely due to defects in embryonic development but decline with age. By investigating the role of BBS proteins in learning and memory, we could potentially develop early intervention programmes and targeted educational approaches for BBS syndrome patients.

Publications

10 25 50
 
Description We have shown a global reduction of dendritic spines in a BBS mouse model. We find that the spine loss occurs within the first 3 postnatal weeks and that it results from the increased autophagy during this period. This suggest that we may be able to modify/restore spine density through autophagy interventions in future. Now we show that BBS cognitive impairment phenotype is probably caused by defects in dendritic spine formation and maintenance of principal neurons. We have found that loss of Bbs proteins results in significant dendritic spine loss in hippocampal, basolateral amygdala and Layer V pre-frontal cortex neurons, that loss of spines occurs only postnatally and is spine sub-type dependent. Moreover, we show that these dendritic spine deficit is correlated with impaired IGF-1R signalling and autophagy. Finally, we demonstrate that a number of Bbs proteins are expressed in the neuronal synapses. Based on our date, we propose a model in which Bbs proteins, similarly to their role in primary cilia, regulate receptor trafficking to the membrane of dendritic spines.
Exploitation Route This work demonstrates that the fundamental process of autophagy might play a significant role in neuroplasticity, thereby permitting the development of therapies or other interventions to reverse defects found in other conditions such as autism.
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology

 
Description Newlife Foundation Project Grant
Amount £119,000 (GBP)
Organisation Newlife 
Sector Charity/Non Profit
Country United Kingdom
Start 12/2016 
End 11/2017
 
Title Development of reagents and resources for studying Bardet-Biedl syndrome 
Description We have generated gene modified cells, GPCR libraries, MRI assays, physical exercise protocols, applied RNASeq techniques and Proteomics to the study of Bardet-Biedl syndrome. We have implemented CRISPR gene editing in cells to model disease, established ELISA assays, new Immmunohistochemistry tools, developed FACS sorting methods for studying ciliopathies and new cloning strategies. 
Type Of Material Technology assay or reagent 
Year Produced 2015 
Provided To Others? Yes  
Impact Part of this resource was published in JOVE. 
 
Description Characterisation of neuroplasticity in the brain of Bardet-Biedl Syndrome mice 
Organisation University College London
Department London Centre for Nanotechnology
Country United Kingdom 
Sector Academic/University 
PI Contribution We have worked closely with Dr Christoph Schmied -Hieber, Prof Michael Hausser and Prof Patricia Salinas to develop a unqiue program of research aimed at understanding the role of neurplasticity in the brain. We have provided mouse mutants (e.g. Bbs5, Bbs4) and reagents to this collaboration.
Collaborator Contribution Dr Christoph Schmied -Hieber, Prof Michael Hausser and Prof Patricia Salinas have provided both intellectual expertise and resources/skills (neurophysiology) toward the characterisation of BBS mouse mutants.
Impact This is multidisciplinary whereby Prof Salinas has providing training in aspect of neuronal cell culture. Dr Christoph Schmied -Hieber did electrophysiology experiments on brain sections. Prof Hausser has provided valuable insights and advice into the study design and data analysis.
Start Year 2015
 
Description Collaboration with Christoph Schmidt-Hieber, Institut Pasteur, Paris 
Organisation Pasteur Institute, Paris
Country France 
Sector Academic/University 
PI Contribution We have made key neuroplasticity discoveries in ciliopathies using neuronal cultures
Collaborator Contribution Christoph has been working with on neuroplasticity by undertaking electrophysiological studies in neuronal cultures
Impact None yet. Paper in preparation
Start Year 2017
 
Description Elucidating the role of GPCRs in ciliopathy neurocognitive phenotypes 
Organisation Heptares Therapeutics Ltd
Country United Kingdom 
Sector Private 
PI Contribution We are providing staff, resources and expertise in Bardet-Biedl syndrome experimental modelling.
Collaborator Contribution Heptares will provide funding for a PhD studenship beginning in May 2017 for 3 years. They will also provide expertise in GPCR biology, compounds and an industrial placement for the student.
Impact We are currently agreeing an MTA and collaboration agreement between UCL and Heptares. There are no outcomes yet to report.
Start Year 2016
 
Title A study of the value of exercise intervention on hippocampal volume and function in children with Bardet-Biedl syndrome 
Description We are perfoming a pilot trial of 20 children under 16 years with Bardet-Biedl syndrome. Each child is randomly assigned to the intervention/non-intervention arm whereupon each child receives a brain MRI at day 1. Half the group go onto undertake a prescribed routine of exercises supervised by a trainer at their local gym for sixth months. On completion each child (both arms) is rescanned and analysed for changes in hippocampal, volume, blood flow, memory and cognitive changes. 
Type Diagnostic Tool - Imaging
Current Stage Of Development Initial development
Year Development Stage Completed 2017
Development Status Actively seeking support
Clinical Trial? Yes
UKCRN/ISCTN Identifier UCL Clinical Trials Unit
Impact The study ia ongoing and no results have been analysed yet. 
 
Description Bardet-Biedl Syndrome UK Annual Family Conference 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Patients, carers and/or patient groups
Results and Impact Over 200 delegates made up of Bardet-Biedl syndrome patients, their relatives and friends as well as healthcare professionals and scientists, attended the residential weekend. Beales chairs and presents a round of the latest medical and scientific advance relating to Bardet-Biedl syndrome patients. There is always a patient perspective and involved public debate. New and old patients alike value this occasion for its information content and social engagement.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
URL http://www.lmbbs.org
 
Description CILIA2016 Amsterdam 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Organisation and support for the premier international conference of Cilia and disease held biennially. Beales chaired opening scientific session and assisted in patient facing activity and panel debate.
Year(s) Of Engagement Activity 2016
URL http://events.embo.org/16-cilia/
 
Description Patient Support Group Patient Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Patients, carers and/or patient groups
Results and Impact 120 families attended the annual support group weekend conference of BBSUK in Northampton where they listened to a programme of talks on patient care and research. Later they participated in workshops providing further interaction with researchers and medical workers.

Patients have been willing to take part in further studies and surveys.
The support scoiety has also received further financial support from bodies such as the lottery to support these PPEs.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
URL http://www.lmbbs.org.uk
 
Description Presentations/abstracts at Volga Neuroscience conference 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presented early stage research findings in the form of a poster and discussion groups.
Year(s) Of Engagement Activity 2016