Wading into the genomic pool to unravel acute lung injury genetics

Acute lung injury (ALI) is a common and often devastating illness characterized by acute hypoxemia, alveolar flooding, and an unacceptably high morbidity and mortality. Because only a fraction of the patients exposed to ALI-inciting events progress to development of the syndrome, there is significant interest in the identification of genetic factors potentially contributing to ALI susceptibility or prognosis. Two complementary strategies used to elucidate ALI genetics formulate the "candidate gene approach," whereby genes are identified by either global gene expression profiling in humans or animal models of ALI, often yielding highly conserved candidates across multiple species, or by related literature searches. Relevant variants or single nucleotide polymorphisms (single base pair substitutions) in these ALI candidate genes are tested for differences in allelic frequency for both ALI susceptibility and outcome between ALI cases and control patients at risk for ALI. This approach has yielded important variants in a number of genes (angiotensin converting enzyme, surfactant protein B, heat shock protein 70, pre-B-cell colony enhancing factor, myosin light chain kinase, and macrophage migration inhibitory factor) contributing toward an ALI phenotype. An alternative strategy not yet used in ALI genetic studies includes genomewide analyses to locate "hot" genomic segments harboring several hundred genes, with potential ALI candidate genes embedded within these segments. Overall, the detailing of specific ALI-associated polymorphisms will continue to provide new insights in the understanding of ALI pathogenesis, reveal novel molecular targets, and promote the development of individualized therapies to reduce morbidity and mortality from this devastating disease.