Genome-wide expression profiling of mid-gestation placenta and embryo using a 15,000 mouse developmental cDNA microarray

cDNA microarray technology has been increasingly used to monitor global gen e expression patterns in Various tissues and cell types. However, applicati ons to mammalian development have been hampered by the lack of appropriate cDNA collections, particularly for early developmental stages. To overcome this problem, a PCR-based cDNA library construction method was used to deri ve 52,374 expressed sequence tags from pre- and peri-implantation embryos, embryonic day (E) 12.5 female gonad/mesonephros, and newborn ovary. From th ese cDNA collections, a microarray representing 15,264 unique genes (78% no vel and 22% known) was assembled. In initial applications, the divergence o f placental and embryonic: gene expression profiles was assessed. At stage E12,5 of development, based on triplicate experiments, 720 genes (6.5%) dis played statistically significant differences in expression between placenta and embryo. Among 289 more highly expressed in placenta, 61 placenta-speci fic genes encoded, for example, a novel prolactin-like protein. The number of genes highly expressed land frequently specific) for placenta has thereb y been increased 5-fold over the total previously reported, illustrating th e potential of the microarrays for tissue-specific gene discovery and analy sis of mammalian developmental programs.