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PubMed2003

Gene-environment interactions and the etiology of common complex disease.

Genetic epidemiology has greatly expanded its scope as a result of major technological innovations in the past decade. Laboratory capacity to determine DNA variation and archival information on the human genome sequence are now readily available. A wide range of research projects have been launched on chronic disease and health problems of aging, on the assumption that a better understanding of mechanisms will improve treatment and prevention. In many instances, the actions of genes are known to be modified by environmental conditions, and considerable emphasis has now been placed on finding specific interactions between genes and the environment. Studies in agriculture and animals provide clear empirical evidence on the importance of this concept. Describing gene-environment interactions in studies of humans is still very challenging, however, given the difficulties in study design and measurement. Despite the theoretical value of characterizing both intrinsic and extrinsic components of the causal process in the development of disease, the argument can also be made that main effects of each component separately are much more important. For these reasons, gene-environment interactions are likely to remain a conceptual framework for health research rather than a practical goal for the foreseeable future.

Animals↗
PubMed1999

[Cystic fibrosis: a complex disease and a paradigm for biomedical research].

Cystic fibrosis (CF) is a genetic disease, particularly frequent among northern Europeans and northern Americans which affects, often lethally, the function of exocrine organs (including the respiratory, digestive, genital and cutaneous mucosae). Despite its pioneering role in areas as diverse as genetics, physiology or pharmacology, CF research still faces essential unsolved questions. In particular, the factors involved in the appearance and severity of CF airway disease remain mostly unraveled so far. This review aims at presenting current views on the pathophysiological processes involved in CF, whether these views are firmly demonstrated or still hypothetical. The various experimental models, central to CF research, are also examined. Finally, emerging therapeutic options for CF (e.g. gene and protein therapy), which raise many hopes among patients, are described.

Animals↗
PubMed2001

Simulation studies of detection of a complex disease in a partially isolated population.

Simulation studies were undertaken with POPGEN, a new population simulation program, to explore strategies for detecting loci underlying rare and common disorders in a small population that has been partially isolated for 10 generations. Haplotype-sharing analysis (HSA) and non-parametric linkage analysis (NPL) were applied to the simulated haplotype and pedigree data for 100 cases, 100 controls, and an average of 28 multiplex pedigrees from cases' families, for a 2-5 cM map of markers. When identity by descent (IBD) status was known (using unique founder marker allele designations assigned during simulation), a linkage disequilibrium (LD) signal could be detected under disease-generating models predicting relative risk to sibs of 11.8 (high-RR) or 2.67 (mod-RR). Detection was more difficult when marker alleles were down-coded to resemble microsatellites (heterozygosities 0.75-0.80). False-positive peaks on nondisease chromosomes were uncommon. NPL analysis was more powerful than HSA at this marker density using down-coded alleles and assuming availability of all affected relatives. LD mapping of common disorders is likely to require denser maps of highly polymorphic markers to approximate full IBD information. LD and linkage mapping provide independent information, and strategies that combine these two methods could be useful in studies of small isolated populations.

Computer Simulation↗
PubMed2002

[Use of case-parents trio for epidemiological studies of association between genetic polymorphisms and complex diseases].

In case-control studies, spurious associations between allelic variants in candidate genes and disease may arise as a result of population stratification by ethnicity. In epidemiological terms, the ethnic group would act as a confounding factor if both the genotype frequency and the incidence/prevalence of a given chronic disease vary across ethnic groups. Population stratification is a key element in the study of population dynamics and the knowledge of the disparity in health-related conditions among strata has important social and public health implications. However, it would not be scientifically correct to conclude a causal gene-disease association in situations in which the association arises as a consequence of a particular population structure. Although the relevance and magnitude of the bias derived from this confounding, effect would be different depending on the population considered, there has been an increased use of study designs such as the case-parent study, that avoids the effect of population stratification by ethnicity. In this article, we review the analysis of case-parent trios using unrelated affected cases as an epidemiological study design for testing association between genetic polymorphisms and disease.

Alleles↗
PubMed2003

[A case of pulmonary Mycobacterium avium complex disease complicated by interstitial pneumonia with collagen vascular disease].

A 45-year-old woman with scleroderma for 15 years duration, rheumatoid arthritis in the past five years, and interstitial pneumonia in the past two years had been followed at OPD. Although sputum had appeared and cough had increased since January 2002, there was no obvious abnormal findings on chest X-ray. Later, as a chest X-ray revealed an infiltrative shadow with cavity in the right lower lung field, we suspected pulmonary tuberculosis and performed the direct smear examination of sputum immediately. As acid-fast bacilli were positive (Gaffky 10) and the polymerase chain reaction (PCR) test was positive for only Mycobacterium avium, we diagnosed the case as pulmonary nontuberculous mycobacterial disease. This case was thought to be pulmonary nontuberculous mycobacterial disease complicated with interstitial pneumonia with collagen vascular disease as a secondary infectious type, and as the cause of the disease, the decrease of the local pulmonary defence mechanism due to pre-existing pulmonary lesions was suspected.

Collagen Diseases↗