Overlapped and differential expression of cAMP-dependent kinase-inhibitor isoforms during avian organogenesis period.

Although cAMP-dependent kinase (PKA) has been known to regulate many biological systems, including patterning, cell differentiation and proliferation, it is not well understood how the spatial-temporal specificity of the PKA signaling is generated. While the PKA signal activation is regulated in many ways, a direct visualization of PKA activity in situ is not possible. Thus, examinations of PKA regulators will provide indirect, but nonetheless important information to elucidate the distribution of PKA activity. In the present study, three isoforms of PKA-inhibitor (PKI) genes were identified from avian genome, and their expression patterns were examined during the organogenesis period. PKI genes were strongly expressed in muscle, liver, and nervous system primordia, suggesting their inhibitory roles on the PKA signaling in the development of these tissues.