The anterior pituitary is comprised of five major hormone-secreting cell types which differentiate during embryonic development in a temporally distinct manner. Microarrays containing 5,128 unique cDNAs expressed in the neuroendocrine system were produced and used to identify genes with potential involvement in onset of thyroid-stimulating hormone beta-subunit, growth hormone, and prolactin gene transcription during chick embryonic development. We identified 352 cDNAs that were differentially expressed (P < 0.05 and the highest mean at least 1.6-fold greater than the lowest mean) on embryonic day 10, 12, 14, or 17, the period of thyrotroph, somatotroph, and lactotroph differentiation in the chicken. Consistent with cellular ontogeny in the chick anterior pituitary gland, thyroid-stimulating hormone beta-subunit mRNA increased steadily between embryonic day 10 and embryonic day 17, growth hormone mRNA increased between embryonic day 12 and embryonic day 17, and PRL mRNA did not increase until embryonic day 17. Expression of 149 cDNAs increased in a manner similar to thyroid-stimulating hormone beta-subunit mRNA and 67 decreased between embryonic day 10 and embryonic day 17, and some of these are likely associated with thyrotroph differentiation. Similarly, expression of 74 and 66 genes changed in a manner over the 4 ages that is consistent with them having a potential role in induction of growth hormone and prolactin mRNA, respectively. Among these candidate genes are numerous transcription factors and signaling molecules that have not previously been implicated in pituitary development. Keywords: time course during development (4 ages)
Overall design
Four biological replicates each of chicken pituitary embryonic day 10, embryonic day 12, embryonic day 14, and embryonic day 17 amplified antisense RNA were analyzed using neuroendocrine cDNA microarrays in a reference design. Each experimental sample (embryonic day 10, 12, 14, or 17) was labeled with Cy3 and hybridized with an aliquot of the Cy5 reference pool, which was generated from all sixteen RNA samples.