Kisliouk, T., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Ziv, M., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Meiri, N., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel

Thermal control set point is regulated by thermosensitive neurons of the preoptic anterior hypothalamus (PO/AH) and completes its development during postnatal critical sensory period. External stimuli, like increase in environmental temperature, influence the neuronal protein repertoire and, ultimately, cell properties via activation or silencing of gene transcription, both of which are regulated by the "histone code." Here, we demonstrated an increase in global histone H3 lysine 9 (H3K9) acetylation as well as H3K9 dimethylation in chick PO/AH during heat conditioning at the critical period of sensory development. In contrast to the global profile of H3K9 modifi-cations, acetylation and dimethylation patterns of H3K9 at the promoter of the catalytic subunit of eukaryotic translation initiation factor 2B (Eif2b5) were opposite to each other. During heat conditioning, there was an increase in H3K9 acetylation at the Eif2b5 promoter, simultaneously with decrease in H3K9 dimethylation. These alterations coincided with Eif2b5 mRNA induction. Moreover, exposure to excessive heat during the critical period resulted in longterm effect on both H3K9 tagging at the Eif2b5 promoter and Eif2b5 mRNA expression. These data suggest a role for dynamic H3K9 post-translational modi-fications in global translation regulation during the thermal control establishment. © 2009 Wiley Periodicals, Inc.