Microarray identification of novel downstream targets of FoxD4L1/D5, a critical component of the neural ectodermal transcriptional network.

FoxD4L1/D5 is a forkhead transcription factor that functions as both a transcriptional activator and repressor. FoxD4L1/D5 acts upstream of several other neural transcription factors to maintain neural fate, regulate neural plate patterning, and delay the expression of neural differentiation factors. To identify a more complete list of downstream genes that participate in these earliest steps of neural ectodermal development, we carried out a microarray analysis comparing gene expression in control animal cap ectodermal explants (ACs), which will form epidermis, to that in FoxD4L1/D5-expressing ACs. Forty-four genes were tested for validation by RT-PCR of ACs and/or in situ hybridization assays in embryos; 86% of those genes up-regulated and 100% of those genes down-regulated in the microarray were altered accordingly in one of these independent assays. Eleven of these 44 genes are of unknown function, and we provide herein their developmental expression patterns to begin to reveal their roles in ectodermal development.