Relationships between constitutive and acute gene regulation, and physiological and behavioral responses, mediated by the neuropeptide PACAP

• Published in: Psychoneuroendocrinology 2022-01, Vol.135, p.105447-105447, Article 105447
• Main Authors: Bakalar, Dana, Sweat, Sean, Drossel, Gunner, Jiang, Sunny Z., Samal, Babru B., Stroth, Nikolas, Xu, Wenqin, Zhang, Limei, Zhang, Haiying, Eiden, Lee E.
• Format: Article
• Language: English
• Subjects: Animals; Behavior, Animal - physiology; Gene Expression Regulation - physiology; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide; PACAP; Pituitary Adenylate Cyclase-Activating Polypeptide - genetics; Pituitary Adenylate Cyclase-Activating Polypeptide - metabolism; Stress responding; Transcriptomics
• ISSN: 0306-4530; 1873-3360
• DOI: 10.1016/j.psyneuen.2021.105447

Since the advent of gene knock-out technology in 1987, insight into the role(s) of neuropeptides in centrally- and peripherally-mediated physiological regulation has been gleaned by examining altered physiological functioning in mammals, predominantly mice, after genetic editing to produce animals deficient in neuropeptides or their cognate G-protein coupled receptors (GPCRs). These results have complemented experiments involving infusion of neuropeptide agonists or antagonists systemically or into specific brain regions. Effects of gene loss are often interpreted as indicating that the peptide and its receptor(s) are required for the physiological or behavioral responses elicited in wild-type mice at the time of experimental examination. These interpretations presume that peptide/peptide receptor gene deletion affects only the expression of the peptide/receptor itself, and therefore impacts physiological events only at the time at which the experiment is conducted. A way to support ‘real-time’ interpretations of neuropeptide gene knock-out is to demonstrate that the wild-type transcriptome, except for the deliberately deleted gene(s), in tissues of interest, is preserved in the knock-out mouse. Here, we show that there is a cohort of genes (constitutively PACAP-Regulated Genes, or cPRGs) whose basal expression is affected by constitutive knock-out of the Adcyap1 gene in C57Bl6/N mice, and additional genes whose expression in response to physiological challenge, in adults, is altered or impaired in the absence of PACAP expression (acutely PACAP-Regulated Genes, or aPRGs). Distinguishing constitutive and acute transcriptomic effects of neuropeptide deficiency on physiological function and behavior in mice reveals alternative mechanisms of action, and changing functions of neuropeptides, throughout the lifespan. •Constitutive PACAP KO results in transcriptomic and behavioral changes distinct from acute effects of PACAP KO in stress.•Some developmentally mediated effects of constitutive PACAP knockout are not phenocopied by PAC1 knockout.•Later conditional PACAP KO does not phenocopy behavioral and transcriptional changes in constitutive KO.•Neuropeptides have fundamentally distinct roles as trophic factors and later as neurotransmitters.