Patterns of gene expression in the developing chick thymus.

Gene expression in thymic T cells during late embryogenesis and early growth in chicks was examined using cDNA microarrays. Gene expression patterns were profiled into nine clusters by using self-organizing maps (SOM) clustering analysis. The expression patterns for a set of genes confirmed current information on the development of immune response. Expression of cell surface markers (MHC class I alpha chain, MHC class II associated invariant chain, CD8 beta chain, CD18, and beta2-microglobulin), and genes involved in the innate immune response (NK lysin-like) increased with age, and these patterns were consistent with an increase in the immune responsiveness of the young chick. The expression of cytokine receptor common gamma chain (gammac), death receptor-3 (DR3), and TCR alpha chain increased up to 1 day of age and then decreased. DR3 could play a role in the apoptosis during T-cell maturation, while the differential expression of TCR genes could reflect regulation of the rearrangement of TCR genes and TCR-mediated signal transduction during T cell development. Three genes coding for previously uncharacterized proteins are included in the clusters. These gene expression profiling studies provide background information on the developing chick immune system and provide preliminary functional information on unknown proteins.