The purpose of this proposal is to discover genetic variants that are central to the development of fibrosing interstitial lung diseases (fILD). Since both genetic variants and the environment increase the risk of disease development in fILD, we seek to comprehensively identify genetic variants associated with fILD by considering environmental exposures while studying the genetics of this group of complex diseases. The fILD study populations included in this proposal (familial interstitial pneumonia (FIP), sporadic idiopathic interstitial pneumonia (IIP), and asbestosis) will enable us to discover genetic variants that are associated with fILD while spanning a spectrum of genes that confer susceptibility to fILD and are increasingly likely to be influenced by environmental exposures. Evidence for a genetic basis of fILD is substantial. fILD has been associated with pleiotropic genetic disorders, and at least 3% of cases of IIP have a first degree relative with a similar illness. Rare mutations in genes that maintain telomere length (TERT and TERC) have been reported to be associated with the development of FIP (defined as e 2 cases of IIP in one family) and idiopathic pulmonary fibrosis (IPF), the most common form of IIP. Two families with FIP have been shown to have disease-associated mutations in surfactant protein C. We have performed a linkage study in 82 families with FIP, and have identified linked regions on chromosomes 10, 11, and 12. Furthermore, we have found common variants in MUC5AC (chr11 positional candidate) that are associated with both FIP and IPF. Approximately 40% of families with FIP have discordant types of IIP among family members, suggesting that IIP may be caused by common gene variants that are altered phenotypically by environmental exposures. In fact, FIP and IPF can be influenced by environmental exposures, occurring more frequently in males (probably due to occupational exposures), and among cigarette smokers. IPF is also associated with exposure to metal or wood dust. Occupational exposure to asbestos can cause fILD that is indistinguishable from the histology of IPF (usual interstitial pneumonia, UIP). We have found that among patients with FIP, the chr11 LOD score is strongly influenced by cigarette smoking. Thus, we hypothesize that fILDs are caused by multiple genetic variants, acting independently or in combination with environmental exposures, and that the same genetic variants can lead to different forms of fILD. We plan to identify the genetic causes of fILDs by performing a genome-wide association study in familial and sporadic IIP and asbestosis, and determining the genetic variants associated with these diseases. In addition, we will examine the generalizability of these fILD genetic variants to other ethnic groups and in families of individuals with FIP. These approaches will identify genetic variants that are common to lung fibrosis, and genetic variants that are more unique to asbestos exposure and/or cigarette smoke.
Idiopathic interstitial pneumonia (IIP) represents a broad spectrum of chronic fibrosing lung conditions that can lead to untreatable respiratory failure. While substantial progress has been made in understanding the clinical, radiological, and pathological manifestations of these disorders, it remains difficult for the clinician to predict the clinical course or the response to therapy for the subtypes of IIP, particularly from individual to individual with the same diagnosis. The purpose of this proposal is to discover genes and gene variants that are central to the development of fibrosing interstitial lung diseases (fILD);once established these genetic risks for fILD could be tested in future studies to enhance early detection, to predict outcome, and to mould personalized therapeutic strategies.
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