Abstract
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 selfโorganizing 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 ฮฑ chain, MHC class II associated invariant chain, CD8 ฮฒ chain, CD18, and ฮฒ2โmicroglobulin), and genes involved in the innate immune response (NK lysinโlike) 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 (ฮณc), death receptorโ3 (DR3), and TCR ฮฑ chain increased up to 1 day of age and then decreased. DR3 could play a role in the apoptosis during Tโcell maturation, while the differential expression of TCR genes could reflect regulation of the rearrangement of TCR genes and TCRโmediated 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. Developmental Dynamics 229:480โ488, 2004. ยฉ 2004 WileyโLiss, Inc.