NK1R knockout mouse model and human genetics of Attention Deficit Hyperactivity Disorder

Lead Research Organisation: University College London
Department Name: Neuroscience Physiology and Pharmacology

Abstract

Attention Deficit Hyperactivity Disorder (ADHD) affects about 2-5% of children and adults in the UK. Its main features are hyperactivity, impulsivity and inattentiveness. ADHD is heritable and often co-exists with other psychiatric problems, especially alcoholism and bipolar disorder (manic depression). Front-line medication includes drugs that are described as ?psychostimulants? (e.g amphetamine). However, little is known about their long-term effects, especially in children, and there is a pressing need for alternative drug treatments. Recently, we discovered that a mutant mouse, which lacks so-called NK1 receptors (?NK1R knockout?), is hyperactive. Moreover, this striking behaviour is prevented by drugs used to treat humans with ADHD. Arising from these findings, we are developing the NK1R knockout mouse as an animal model of ADHD. In this project, we shall refine this model by investigating whether these mice are impulsive and/or inattentive, as well as hyperactive. We shall also test our proposal that their abnormal behaviour is explained by disrupted regulation of the neurotransmitters, dopamine and acetylcholine, in two brain regions that have been linked with ADHD.
Prompted by these studies in mice, we have also discovered mutations (single nucleotide polymorphisms) in the human equivalent of the NK1R gene (known as TACR1) in DNA from patients with ADHD. Our evidence suggests that these polymorphisms can be used as a diagnostic marker for ADHD. It is also possible that certain mutations in the TACR1 gene increase susceptibility of ADHD patients to alcoholism and/or bipolar disorder. In this project, we shall map the TACR1 gene in DNA from ADHD patients and confirm which of the mutations we have identified are associated with ADHD and/or alcoholism or bipolar disorder.
The combined results of these experiments will help to refine the use of both mutant (NKR1 /-) mice, as a much needed animal model of ADHD, and mutations in the TACR1 gene as a diagnostic test for ADHD. They will also cast light on the functional abnormalities in the brain arising from a deficit in NK1R/TACR1 function. All this information will inform future investigations aimed at developing novel treatment strategies (including the potential for a new class of drug treatment) for ADHD.

Technical Summary

Mice with functional ablation of the NK1 receptor (NK1R-/-) express hyperactivity, which is prevented by psychostimulants. They also have deficits in dopaminergic transmission in the prefrontal cortex and dorsal striatum. All these abnormalities are consistent with NK1R /- mice being a model of Attention Deficit Hyperactivity Disorder (ADHD). This proposal was confirmed in studies in which we found an association between four single nucleotide polymorphisms in the TACR1 (the human NK1R) gene and a diagnosis of ADHD. We have further evidence for polymorphisms in the TACR1 gene and increased susceptibility to alcoholism and/or bipolar disorder (BPAD). One aim of this project is to refine this mouse model of ADHD. We shall use the 5-Choice Serial Reaction Time task to establish whether NK1R-/- mice express other core features of ADHD, namely, impulsivity / inattentiveness, as well as hyperactivity. We shall also use microdialysis to test our hypothesis that, as well as disruption of dopaminergic transmission in NK1R-/- mice, there is a deficit in acetylcholine release from striatal interneurones: these neurons govern striatal output and so have a key role in regulating behaviour. We shall go on to investigate whether behavioural and neurochemical abnormalities are abolished by psychostimulants, which are used to treat ADHD, and mimicked by giving an NK1R antagonist to wild type mice. All these experiments will have a multifactorial design and the mice will be assigned randomly to the different groups. In parallel studies, we shall carry out genotyping of human DNA to test whether a clinical subgroup of ADHD is strongly associated with NKR1/TACR1 polymorphisms, as our evidence suggests. This will involve association studies using DNA from patients with ADHD, BPAD, alcoholism and healthy controls. We shall look for allelic and haplotype associations and identify region(s) of NK1R/TACR1 to be screened for mutations in the exons and promoter regions of NK1R/TACR1. We shall then genotype the entire sample to assess the likely role of novel mutations in susceptibility to ADHD, BPAD and alcoholism. This work will guide bioinformatics and in vitro studies of the functional consequences of promising mutations. The combined results of this translational project will help to develop the NK1R-/- mice as a much-needed mouse model of ADHD, provide essential information on TACR1 polymorphisms as a causal factor in this disorder and its comorbidity, and could open up new avenues of research in the hunt for novel treatments.

Publications

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Al Eissa MM (2019) Genetic association and functional characterization of MCPH1 gene variation in bipolar disorder and schizophrenia. in American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics

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Pillidge K (2014) Atomoxetine reduces hyperactive/impulsive behaviours in neurokinin-1 receptor 'knockout' mice. in Pharmacology, biochemistry, and behavior

 
Description Chairman: NC3Rs working group on Experimental Design and Data Analysis
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact On-line EDA now launched: use being monitored but premature to comment
URL https://www.nc3rs.org.uk/experimental-design-assistant-eda
 
Description Co-ordinated LASA's responses to (3) consultations on transposition into UK lawof EU Directive governing use of animals in scientific experiments
Geographic Reach National 
Policy Influence Type Participation in a national consultation
Impact Impact cannot be measured
 
Description Contribution to FELASA working group on rodent identification
Geographic Reach Europe 
Policy Influence Type Participation in a advisory committee
Impact I wrote and led LASA's response to the FELASA / WG proposal that toe amputation of neonates should be the PREFERRED method for identification of laboratory rodents within the EU. We had strong welfare concerns, especially when the animals reached adulthood. This view was accepted and the EU commission decided that toe amputation, although permitted, should not be recommended as the preferred method.
URL http://www.felasa.eu/recommendations/reports/report-of-the-felasa-working-group-on-animal-identifica...
 
Description Director (until 2012) of course leading to the BAP Certificate in Preclinical Psychopharmacolgy
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Impact Better training and appreciation of need for CPD for scientists engaged in psychopharmacolgy
 
Description Member of NC3Rs PhD scholarship panel
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Policy Influence Type Participation in a advisory committee
Impact Better training of scientists engaged in preclinical psychopharmacology
 
Description Member of NC3Rs working group on Experimental Design and Data Analysis.
Geographic Reach Multiple continents/international 
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Impact The ARRIVE guidelines were developed through the discussions of this working group. They define information that must be included in manuscripts describing laboratory animal science and have been adopted by leading journals that publish work in this field.
 
Description Regular contributor to European Summer School in Whole Animal Pharmacology (held at University of Utrecht)
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact Course aimed at resolving the skills deficit in in vivo pharmacology research
URL https://www.linkedin.com/pulse/esswap-behavioural-pharmacology-now-on-line-joop-s-de-graaf
 
Description Responses to Home Office Consultations on implementation of EU Directive on use of animals in scientific procedures:A(SP)A
Geographic Reach National 
Policy Influence Type Participation in a national consultation
Impact New law in the UK now implemented
URL https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291350/Guidance_on_the_Ope...
 
Description Industrial
Amount £41,000 (GBP)
Funding ID N/A 
Organisation Neumedix Health Group 
Sector Private
Country Australia
Start 05/2010 
End 06/2011
 
Description MRC Industrial CASE scheme
Amount £75,268 (GBP)
Funding ID G1001602 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 09/2011 
End 09/2014
 
Description Proof of Concept
Amount £29,000 (GBP)
Funding ID 37-005 - POC 
Organisation UCL Business 
Sector Private
Country United Kingdom
Start 01/2010 
End 07/2011
 
Title NK1R-/- mouse model of ADHD 
Description The behavioural abnormalities expressed by the NK1R-/- ('knockout') mouse resemble those seen in humans with ADHD and include hyperactivity with deficits in cognitive performance. Neurochemical abnormalities in the brain are also consistent with our understanding of the brain mechanisms underlying this disorder and the mechanism of action of drugs used to treat ADHD. 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Year Produced 2008 
Provided To Others? Yes  
Impact Granting of patent 17.06.2011 [EP2114130] 
 
Title ANIMAL MODEL FOR ADHD 
Description NK1 receptor 'knockout' mouse model of Attention Deficit Hyperactivity Disorder 
IP Reference EP2114130 
Protection Patent granted
Year Protection Granted 2009
Licensed Yes
Impact EU Company is marketing the mouse for study of ADHD and screening of candidate novel treatments
 
Title NK1R-/- mouse model of ADHD 
Description The colony of mice has been maintained by the commercial partner since 2008. However, the colony is currently being expanded to enable detailed phenotyping and distribution. The costs are being paid by the licensee under the terms agreed with UCL- Business. 
Type Support Tool - For Fundamental Research
Current Stage Of Development Small-scale adoption
Year Development Stage Completed 2012
Development Status Under active development/distribution
Impact Growing interest in the role of NK1 receptors in ADHD. Our paper, published in PLoS ONE in May, 2011, has received 1900 'hits'. 
 
Description BBC Radio 4 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview for 'Inside Science' discussing research findings suggesting that sex of experimenter influenced rodent behaviour

Further requests for interview via UCL press office
Year(s) Of Engagement Activity 2014
 
Description LASA Winter meeting (Care and Welfare section) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I was invited to speak about our research of the NK1R-/- mouse model of ADHD, with particular emphasis on our contribution to refinement of the behavioural phenotyping of mutant mice and evaluation of their neurochemical status. There were a few research scientists in the audience but most came from other professions concerned with animal science: e.g. animal technicians and breeders, veterinary surgeons, Home Office Inspectorate, Certificate Holders, ethicists, representatives from Animal Charities (e.g. RSPCA) and managers from the industrial sector.

Too soon to identify long-term impact.
Year(s) Of Engagement Activity 2009
 
Description Public Understanding of Psychopharmacology 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? Yes
Type Of Presentation Paper Presentation
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Too soon to measure
Year(s) Of Engagement Activity 2012
 
Description Publication of full article in The Times 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Much positive feedback (from laboratory animal scientists and lay public) on my comments about the merits of some scientific research

request to contribute an article on my research to the UCL BSU website
Year(s) Of Engagement Activity 2014
 
Description RSPCA: Lay Members' Forum 2011 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I was invited to give a talk on the ethical / welfare aspects and validity of behavioural laboratory animal science. Approximately 100 people attended the meeting, which was was open to anyone (from the general public) with an interest in the process of ethical review of the use of animals in medical and scientific research.

Much positive feedback from delegates. Some commented that it would help their input into their role on ER panels.
Year(s) Of Engagement Activity 2011
 
Description Request for comment on scientific publication 
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Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact My comments on the publication were publsihed in The Daily telegraph, The Times, daily Mail and on many websites, internationally

Closer links with UCL Press Office
Year(s) Of Engagement Activity 2014
 
Description Scientific advice to media 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? Yes
Type Of Presentation Paper Presentation
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Responding to specific questions from the programme Producer in respect of the design, objectives and scientific validity of programme content

Unknown
Year(s) Of Engagement Activity 2009
 
Description Talk at the Royal Society for BIology 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A talk on the Neurobiology of mental health and wellbeing - on World Mental Health Day
Year(s) Of Engagement Activity 2017
URL https://www.facebook.com/biochemicalsociety/videos/vb.99242639743/10155851651909744/?type=2&theater
 
Description Television (International) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Lead scientific contributor to two full-length television programs, about the effects of cocaine and MPTP on the brain, to be broadcast on the Discovery channel in the autumn of 2012

Not yet broadcast
Year(s) Of Engagement Activity 2012