Genomic analyses of familial autoimmune Addison's disease

Lead Research Organisation: Newcastle University
Department Name: Institute of Human Genetics

Abstract

Autoimmune Addison‘s disease (AAD) is a rare condition in which the immune system attacks the adrenal glands which normally produce essential steroid hormones. People with AAD are dependent lifelong on taking daily steroid medication for survival.

Like AAD, type I diabetes is an autoimmune disorder and results from an immune attack targeted, in part, against insulin in pancreatic cells. We know that variations in the insulin gene contribute to susceptibility to type I diabetes. In AAD, the target of the immune attack is an adrenal enzyme called 21-hydroxylase. Our hypothesis is that variations around the 21-hydroxylase gene might predispose an individual to AAD.

We already know that a complex series of variations exist around the 21-hydroxylase gene. The first part of my project is to see if these variations contribute towards AAD susceptibility. For the second part of my study, I will use gene-chips containing more than a million DNA markers scattered regularly across all the chromosomes to look for markers that are transmitted with Addison‘s disease in 25 families with 2 or 3 members affected by the condition. These studies should enhance our understanding of why AAD is so strongly inherited and will shed light on the mechanisms behind the disease.

Technical Summary

Autoimmune Addison‘s disease (AAD) is amongst the rarest of the autoimmune diseases and has a high genetic load, with a lambda-sib of more than 150. However little of the genetic susceptibility has so far been accounted for, suggesting that there may be one, or a small number, of aetiological variants exerting very strong effects. Investigating AAD is important, as more than half of patients will develop a second autoimmune condition, suggesting that the alleles responsible for AAD will also contribute to susceptibility to other autoimmune conditions e.g. type I diabetes.

The major autoantigen for AAD is the steroidogenic enzyme, 21-hydroxylase. Variations at the insulin gene and thyrotropin receptor gene predispose to type 1 diabetes and Graves‘ disease, respectively. Therefore, it is plausible that variations in or around the gene encoding 21-hydroxylase will predispose to AAD. The 21-hydroxylase gene (CYP21B) is located in the MHC class III region, adjacent to the complement factor 4 gene, both contained within a known copy number variation. CYP21B is close to its own pseudogene, which also exists in several copy number states. In the first part of my study, I will use PCR-based approaches to determine whether structural variations at the CYP21 locus predispose to AAD, including quantitative real-time PCR, long range PCR and paralogue ratio testing. To pursue these studies, a unique sample resource is available to me, comprising 25 multiplex AAD families, 320 unrelated UK AAD probands and matching healthy controls.

In the second part of my project, I plan to perform a genome-wide linkage and association study, using SNP-chips containing 900,000 markers in members of the 25 UK and German kindreds with more than one affected AAD individual. I will analyse the data under the expert direction of genetic statistician Prof. Cordell, looking for the strength of the linkage signal and evidence for conserved haplotypes across different families. I will then takrward a series of the 200 most linked and associated markers to a replication experiment using a case-control design in the 320 unrelated AAD probands and 450 controls. This series of experiments should yield an unbiased insight into the genetic architecture of AAD for the first time.

This project provides a scientific opportunity to gain a greater understanding of autoimmune disease pathogenesis, and offers a medical opportunity since AAD has fatal consequences if the diagnosis is missed. A high penetrance AAD allele that predicts disease would be valuable in screening at risk individuals, such as children with type 1 diabetes.

Publications

10 25 50

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Mitchell AL (2012) Autoimmune Addison disease: pathophysiology and genetic complexity. in Nature reviews. Endocrinology

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Mitchell AL (2011) Genetic basis and variable phenotypic expression of Kallmann syndrome: towards a unifying theory. in Trends in endocrinology and metabolism: TEM

 
Description ADSHG Alfred Potter Award
Amount £5,000 (GBP)
Organisation Addison's Disease Self Help Group (ADSHG) 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2017 
End 12/2019
 
Description British Thyroid Association Travel Grant
Amount £400 (GBP)
Organisation British Thyroid Association 
Sector Charity/Non Profit
Country United Kingdom
Start 09/2010 
End 09/2010
 
Description Simon Wolff Charitable Foundation Travel Grant
Amount £300 (GBP)
Organisation The Simon Wolff Charitable Foundation 
Sector Charity/Non Profit
Country United Kingdom
Start 06/2011 
End 06/2011
 
Description Society for Endocrinology International Travel grant
Amount £750 (GBP)
Organisation Society for Endocrinology 
Sector Charity/Non Profit
Country United Kingdom
Start 06/2011 
End 06/2011
 
Description Society for Endocrinology Travel Grant
Amount £500 (GBP)
Organisation Society for Endocrinology 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2014 
End 03/2014
 
Description Collaboration with molecular genetics group in Bergen Norway 
Organisation Haukeland University Hospital
Department Endocrine Genetics Group
Country Norway 
Sector Hospitals 
PI Contribution Collaboration to gather samples from families with autoimmune Addison's disease for a linkage study. We identified, characterised and gathered DNA from UK families. All genotying was carried out in the UK. The data was analysed by myself, with Prof Cordell
Collaborator Contribution Our collaborators identified, characterised and gathered DNA from Norwegian families.
Impact 1 manuscript under review at present - PlosONE. Collaboration comprises scientists, technicians and clinicians
Start Year 2010
 
Description Expression of CYP21A2 and CYP21A1P in tissues 
Organisation University College London
Department MRC/Wellcome Trust Human Developmental Biology Resource
Country United Kingdom 
Sector Private 
PI Contribution Studies of the expression of CYP21A2 and CYP21A1P in human tissues. Collaboration with the Newcastle HBDR and Birmingham HBRC for collection of human thymus and adrenal tissue. All studies (tissue in situ hybridisation, northern blotting, quantitative PCR, Western blotting) conceived and planned by myself and Prof Pearce. All analyses performed by me.
Collaborator Contribution Tissue provided by Newcastle and Birmingham HDBRs
Impact Ongoing studies - future publication envisaged
Start Year 2012
 
Description Addison's Disease Self Help Group Twitter chat 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Addison's Disease Self Help Group Twitter chat - Twitter chat focussing on dentistry for patients with adrenal insufficiency including considerations for additional steroids. Social media engagement event for people with Addison's disease and those interested (members of the public, carers, professionals etc). Genetic research into Addison's disease highlighted, leading to requests from individuals to participate in ongoing genetic research
Year(s) Of Engagement Activity 2018
 
Description Addison's Disease Self Help Group Twitter chat 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Addison's Disease Self Help Group Twitter chat - Twitter chat to coincide with Rare Disease Day - the role of paramedics in recognising and managing Addison's disease. Social media engagement event for people with Addison's disease and those interested (members of the public, carers, professionals etc). Research into Addison's disease highlighted, leading to requests from individuals to participate in ongoing genetic research
Year(s) Of Engagement Activity 2018
 
Description Addison's Disease Self Help Group Twitter chat 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Addison's Disease Self Help Group Twitter chat - Twitter chat focussing on exercise and nutrition for individuals with adrenal insufficiency. Social media engagement event for people with Addison's disease and those interested (members of the public, carers, professionals etc). Genetic research into Addison's disease highlighted, leading to requests from individuals to participate in ongoing genetic research
Year(s) Of Engagement Activity 2018
 
Description Addison's disease self help group "Medic in the pub" engagement event 15/2/19 7-9pm 
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 Addison's disease self help group "Medic in the pub" engagement event 15/2/19 7-9pm. Over 60 people (mostly patients and their families) attended for a "question and answer" session. Our genetic research was discussed and patients volunteered to participate
Year(s) Of Engagement Activity 2019
URL https://www.addisons.org.uk/calendar/event/324-medic-in-a-pub-newcastle-15th-february-7-830pm/