Investigator: Katherine A. Siminovitch, M.D.
Location: Mount Sinai Hospital, Toronto, Ontario, Canada
Timeline: March 1, 2004 – ongoing
PATIENTS MAY STILL ENROLL IN STUDY.
For more information please contact:
Jennifer or Stephanie, Clinical Research Coordinators
Phone: 416-946-4501 x. 3297
Fax: 416-946-4531
Email: clinicalgenet.research@gmail.com
Abstract
Wegener’s granulomatosis (WG) is a multisystem, necrotizing, granulomatous vasculitis that affects about 3 in every 100,000 people in the United States and is equally prevalent in males and females. Diagnosis of WG is difficult, and many physicians are unfamiliar with the condition. Thus, there is a significant unmet medical need for improved diagnostic tests. Development of new diagnostic and therapeutic approaches to WG has been substantially impeded by lack of understanding of the causes of WG.
Many lines of evidence suggest that a major cause of WG is infectious insult of genetically susceptible individuals. A handful of susceptibility genes have been examined as possible etiologic factors, but to date both the genetic and infectious factors underlying WG remain unknown. Identification of WG susceptibility genes would, however, provide a very promising avenue to the development of improved diagnostic and prognostic tests as well as new targets for therapeutic management. Although technologies for disease gene discovery are radically improving, the application of such technologies is highly dependent on the availability of collections of DNA samples from affected individuals and their family members.
This proposal describes a strategy to collect blood samples and prepare DNA from individuals with WG and their immediate family members, and to conduct comprehensive clinical chart review in order to obtain powerful data for results stratification and analysis. The obtained samples and clinical information will lay the foundation, and be absolutely required for, future studies to identify WG susceptibility genes.
Specific aims and goals contained within this grant:
a) To collect blood samples for DNA analysis from 500 WG patients and family members where available;
b) To review and document clinical data from these WG patients, including demographic data;
c) To prepare DNA samples for banking from the blood samples;
d) To lay the groundwork for future genetic analysis of the WG patient/family cohort
Larger goals within the framework of our WG research program (anticipated to be funded by additional national granting programs)
e) To understand the fundamental causes of WG by using genetic association and family-based linkage studies (where possible) to focus on identification of the full complement of WG susceptibility genes;
f) To develop gene-based (DNA) diagnostic assays for early identification of susceptible individuals, in conjunction with established ANCA blood testing and other diagnostic procedures;
g) To elucidate the molecular pathophysiology of WG and the nature of environmental-genetic interactions that trigger disease, and;
h) To design improved strategies for prevention and treatment of WG, including the diagnostic applications mentioned above.
Relevance to WG:
The exact cause(s) of WG are unknown, but it is generally thought to result from infection of individuals with an underlying genetic susceptibility. A variety of gene variants have been shown to be associated with WG susceptibility, including the immunologically relevant IL-10 (Interlukin 10), transforming growth factor-beta (TGFB) and the cytoxic T lymphocyte associated antigen-4 (CTLA-4) genes. Additionally, some other genes have been associated with WG, including those for the angiotensin-converting enzyme (ACE), proteinase-3 and alpha-1-antitrypsin. The tendency to relapse among WG patients has also been associated with variants of the Fcgamma receptor gene. Despite these data, the molecular and biochemical pathways underlying WG onset and progression remain largely uncharacterized.
Recent studies of the genetics of Crohn’s Disease, an inflammatory disease of the gastrointestinal tract, and of the rare Blau syndrome, have demonstrated an association with variants of the NOD2 gene bacterial species. Because both Crohn’s Disease and Blau syndrome are associated with granuloma development, and because granulomatous disease in Crohn’s Disease patients are specifically associated with NOD2 gene variants, we recently undertook a genetic study in WG patients (Newman et al. (2003)., J. Rheuma. 30(2):305-7. While we did not detect any association between WG and the NOD2 gene, our results illustrate our general strategy in examining candidate genes that may be involved in WG, and further emphasize the necessity of much larger, family-based genetic studies in research into the genetic underpinnings of this disease. Accordingly, we propose to greatly expand our current collection of DNA samples from WG patients and their family members, in order to lend greater power to future genetic association and family-based linkage studies. We anticipate working closely with the WGA to achieve these goals.
Long-range objective:
The long-range goal of our WG research program is to identify genes that confer susceptibility to WG.
Progress to date:
Over the past three years, our group has focused on collection of patient and family samples required to map and isolate genes that cause and/or modulate WG. To date, patients have been ascertained mainly from the Canadian Wegener’s Granulomatosis Support Group (WGSG), and the relevant family members have been ascertained via telephone contact initiated with the probands’ consent. To allow for case-control and family-based association as well as linkage analysis, we have collected the following types of materials: individual patients for whom no other family members are available (singletons) and who can be used for case-control association studies; patients and their parents and/or unaffected siblings (trio families), who can be used for family-based association studies; and multicase families such as affected siblings and their parents (sib-pair family) or patient and affected as well as unaffected parent (relative-pair family), who can be used for linkage analysis.
Collection involves obtaining blood samples for DNA and lymphoblastoid cell line preparation and detailed demographic data on all study participants and detailed clinical data on all affected individuals.
Research Plan
The objective of this proposal is to collect sufficient numbers of WG patients and family members to lay the groundwork for identifying WG susceptibility genes. This proposal is therefore entirely focused on patient recruitment. However, in the future we will use these patient materials to carry out a genome wide scan of WG families and to examine and analyze any other genes that are discovered in the future to be associated with granulomatous disease and/or granuloma formation. Data from these studies will provide the framework for further studies aimed at identifying candidate and ultimately the relevant WG susceptibility genes.
As noted above, the patient collections possible in eastern Canada are largely completed. However, significant additional patient sample resources are required to ensure that sufficient clinical materials are available, for example, for large-scale case-control association and linkage analyses. We propose to work closely with, and seek the assistance of, the WGA in ascertaining and recruiting volunteer patients and family members interested in participating in this study.
To allow for the use of several complementary methods for WG gene identification, we will continue to collect WG patients/families of varying pedigree structures. These include:
• Multicase families: These families, which will be used for linkage analysis, contain a minimum of two affected siblings and their parents (sib-pair family) or an affected parent-child combination and an unaffected parent and/or sibling (relative-pair family).
• Trio families: These families include patients and their parents (or minimally, a patient and a single parent) as well as patients and unaffected siblings.
• Singletons: Individual patients, for whom family members cannot be recruited are also being collected and will be used for case-control association studies to facilitate candidate gene analysis once chromosomal regions of interest are identified. As most of the patients collected represent singletons, we anticipate that at least 500 such individuals will be recruited to the study by the end of year 1 and these individuals, together with any individuals drawn from the trio and multicase families, will provide a substantive resource for analysis of the association between selected SNPs/genes and WG.
Conclusion:
The identification of disease susceptibility genes has attracted considerable interest in recent years, an interest that builds upon the wealth of genetic information and improved genotyping technologies emanating from the Human Genome Project research. Definition of WG susceptibility genes will not only elucidate the combination of genes which influence disease progression, severity and response to treatment, but will also pave the way for identifying individuals at risk, delineating the specific environmental factors which help convert genetic susceptibility to disease, and designing strategies for intervention and disease prevention. Even in advance of development of new therapeutic drugs, our investigations should provide DNA-based diagnostic tools that will complement and enhance current ANCA and other clinical testing procedures, resulting in earlier diagnosis of WG and the opportunity to widen the opportunity for therapy.