Patrick J. Concannon
Harrison Professor of Biochemistry & Molecular Genetics
Ph.D., University of California, Los Angeles
Cellular DNA Damage Responses; Genetics of Type 1 Diabetes

 

Research in our laboratory builds upon our prior genetic studies intended to map and identify the genes responsible for two very different types of inherited genetic disorders: rare recessive disorders such as ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) that are characterized by hypersensitivity to ionizing radiation, and the common, but genetically complex disorder type 1 diabetes (T1D) that disrupts the body's ability to metabolize glucose. Nijmegen Breakage Syndrome (NBS) is a recessive inherited childhood disease characterized by microcephaly from birth, immunodeficiency, an increased incidence of malignancy and hypersensitivity to ionizing radiation. We positionally cloned the gene NBS1, which is mutated in this disorder. Subsequently, we have used cell biology studies to develop an understanding the role of NBS1 in the complex signaling cascade that is elicited in mammalian cells when exposed to agents, such as ionizing radiation, that cause double strand breaks in DNA. These studies have demonstrated that the product of the NBS1 gene, nibrin, acts in the same pathway as ATM, the gene mutated in A-T, and is both an activator of ATM and a substrate for ATM's kinase activity.

Many of the DNA damage response proteins that take part in the signaling cascade elicited by cellular exposure to ionizing radiation, such as NBS1 and ATM, are also implicated in predisposition to cancer in the general population. For potential cancer susceptibility genes such as these, the low prevalence of mutation carriers and of exposure to environmental risk factors such as radiation limits the informativeness of standard case-control studies as a means of defining cancer risk. To investigate the joint roles of mutations in DNA damage response genes and radiation exposure in cancer, we participate in the Women's Environment, Cancer and Radiation Epidemiology (WECARE) Study. The primary hypothesis of the WECARE Study is that women who carry a deleterious allele in a DNA damage response gene, and who received radiation therapy as treatment for their first primary breast cancer, have an increased risk of developing a second primary breast cancer. This design is based on the premise that by restricting consideration to women with a first primary breast cancer and then studying the determinants of developing a second primary breast cancer, the power to detect main effects of relatively rare genetic mutations and/or their interactions with environmental factors is considerably enhanced. Currently, we are examining the roles of variation in the ATM, BRCA1, BRCA2 and CHEK2 genes in the WECARE Study population. Using cell lines from WECARE subjects, we are also exploring the functional consequences of variation in these genes for cellular radiation sensitivity.

Positional cloning of the mutated genes is relatively straightforward in a disorder like NBS where the disease alleles are highly penetrant, the disease follows a clear mode of inheritance, and there is little heterogeneity. The genetics of a disorder such as type 1 diabetes (T1D) is considerably more complex and involves the actions and likely the interactions of multiple genes as well as unknown environmental factors, all of which conspire to drive the autoimmune destruction of the insulin-secreting Beta cells of the pancreas. Loss of these cells results in a complete dependence on exogenously administered insulin for survival. Identification of the genetic component of this disorder holds the promise of better disease prediction and a better understanding of the underlying pathology. These factors are crucial to developing treatments for T1D that are preventive, rather than simply supportive. Our current studies on T1D are focused on mapping and identifying the major susceptibility genes for this disorder. Some of these genes, such as PTPN22 a tyrosine phosphatase that acts to modulate T cell receptor signaling, are known, and, in these cases, we are pursuing translational studies to connect risk genotypes with patient phenotypes.


Selected References

Saidi A, Li T, Weih F, Concannon P, Wang ZQ. (2010) "Dual functions of Nbs1 in the repair of DNA breaks and proliferation ensure proper V(D)J recombination and T-cell development." Mol Cell Biol. 30(23):5572-81. Epub 2010 Oct 4. [PubMed]

Bernstein JL, Haile RW, Stovall M, Boice JD Jr, Shore RE, Langholz B, Thomas DC,Bernstein L, Lynch CF, Olsen JH, Malone KE, Mellemkjaer L, Borresen-Dale AL,Rosenstein BS, Teraoka SN, Diep AT, Smith SA, Capanu M, Reiner AS, Liang X,Gatti RA, Concannon P; WECARE Study Collaborative Group. (2010) "Radiation exposure, the ATM Gene, and contralateral breast cancer in the women's environmental cancer and radiation epidemiology study." J Natl Cancer Inst. Apr 102:475-83. Epub 2010 Mar 19. [PubMed]

Barrett JC, Clayton DG, Concannon P, Akolkar B, Cooper JD, Erlich HA, Julier C,Morahan G, Nerup J, Nierras C, Plagnol V, Pociot F, Schuilenburg H, Smyth DJ,Stevens H, Todd JA, Walker NM, Rich SS; Type 1 Diabetes Genetics Consortium. (2009) "Genome-wide association study and meta-analysis find that over 40 loci affect risk of type 1 diabetes." Nat Genet. 41:703-7. Epub 2009 May 10. [PubMed]

Concannon P, Rich SS, Nepom GT. (2009) "Genetics of type 1A diabetes." N Engl J Med. Apr 360(16):1646-54. [PubMed]