Noncompensation in peptide/receptor gene expression and distinct behavioral phenotypes in VIP- and PACAP-deficient mice.

TitleNoncompensation in peptide/receptor gene expression and distinct behavioral phenotypes in VIP- and PACAP-deficient mice.
Publication TypeJournal Article
Year of Publication2006
AuthorsGirard, BA, Lelievre V, Braas KM, Razinia T, Vizzard MA, Ioffe Y, El Meskini R, Ronnett GV, Waschek JA, May V
JournalJournal of neurochemistry
Volume99
Issue2
Pagination499-513
Date Published2006 Oct
ISSN0022-3042
KeywordsAging, Animals, Animals, Newborn, Behavior, Animal, Brain, Female, Gene Expression Regulation, Developmental, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Phenotype, Pituitary Adenylate Cyclase-Activating Polypeptide, Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Receptors, Vasoactive Intestinal Peptide, RNA, Messenger, Time Factors, Up-Regulation, Vasoactive Intestinal Peptide
Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are closely related neurotrophic peptides of the secretin/glucagon family. The two peptides are derived from a common ancestral gene and share many functional attributes in neuronal development/regeneration which occur not only from overlapping receptor subtype signaling but also through common mechanisms regulating their expression. Although PACAP or VIP null mice have been generated for study, it is unclear whether the expression of the complementary peptide or their receptor systems are altered in a compensatory manner during nervous system development. By radioimmunoassay and quantitative PCR measurements, we first show that PACAP and VIP have very different temporal patterns of expression in developing postnatal mouse brain. In wild-type animals, PACAP transcript and peptide levels increased rapidly 2- and 5-fold, respectively, within 1 week of age. These levels at 1 week of age were maintained through adulthood. VIP transcript and peptide levels, by contrast, increased 25- and 50-fold, respectively, over a later time course. In parallel studies of development, there were no apparent compensatory increases in brain VIP expression in the PACAP knockout animals, PACAP expression in the VIP-deficient animals, or receptor mRNA levels in either genotype. To the contrary, there was evidence for developmental delays in the expression of peptide and receptor transcripts in the knockout animals. A series of behavioral and neurological tests demonstrated differences between the knockout genotypes, revealing some functional distinctions between the two genes. These results suggest that the PACAP and VIP have evolved to possess distinct biological activities and intimate that the respective knockout phenotypes represent deficits unmitigated by the actions of the complementary related peptide.

Alternate JournalJ. Neurochem.