Family studies and positional cloning of genes for asthma and related phenotypes

Although it is not yet known how many genes may contribute to the susceptibility or the severity of asthma and related phenotypes, genome-wide screens and positional cloning techniques have been successful in identifying contributing genes in multiple populations. The results of these studies provide additional insight into the molecular mechanisms responsible for the development of a variety of phenotypes. Replication with additional populations-particularly in large-scale studies-has been used to distinguish between false positive results or population-specific effects or to further quantify the conferred risk. Even when individual markers do not replicate in multiple population, association of the same region or gene has been useful in directing future studies. As further understanding of the linkage disequilibrium patterns within the genome has allowed greater efficiency for genetic studies, advances in high-throughput genotyping technology, genetic analysis methodologies, and a more in-depth understanding of clinical phenotypes has made genome-wide studies more accessible and cost-effective. In the future, identification of function variants with clinical relevance may be used to influence the diagnosis and treatment of asthma.