title: Pituitary adenylyl cyclase-activating peptide counteracts hedgehog-dependent motor neuron production in mouse embryonic stem cell cultures.
abstract: Pituitary adenylyl cyclase-activating peptide (PACAP; ADCYAP1) is a neuropeptide that regulates a wide array of functions within the brain and periphery. We and others have previously demonstrated that PACAP and its high-affinity receptor PAC1 are expressed in the embryonic mouse neural tube, suggesting that PACAP plays a role in early brain development. Moreover, we previously showed that PACAP antagonizes the mitotic action of Sonic hedgehog (Shh) in postnatal cerebellar granule precursors. In the present study, we demonstrate that PACAP completely blocked Shh-dependent motor neuron generation from embryonic stem cell cultures and reduced mRNA levels of the Shh target gene Gli-1 and several ventral spinal cord patterning genes. In vivo examination of motor neuron and other patterning markers in embryonic day 12.5 spinal cords of wild-type and PACAP-deficient mice by immunofluorescence, on the other hand, revealed no obvious alterations in expressions of Islet1/2, MNR2, Lim1/2, Nkx2.2, or Shh, although the Pax6-positive area was slightly expanded in PACAP-deficient spinal cord. Caspase-3 staining revealed low, and similar, numbers of cells undergoing apoptosis in embryonic wild-type vs. PACAP-deficient spinal cords, whereas a slight but significant increase in number of mitotic cells was observed in PACAP-deficient mice. Thus, although PACAP has a strong capacity to counteract Shh signaling and motor neuron production in vitro, corresponding patterning defects associated with PACAP loss may be obscured by compensatory mechanisms.
authors.affiliation: Department of Psychiatry, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, CA 90095-7332, USA.
authors.forename: Megumi
authors.initials: M
authors.lastname: Hirose
authors.forename: Pawel
authors.initials: P
authors.lastname: Niewiadomski
authors.forename: Gary
authors.initials: G
authors.lastname: Tse
authors.forename: Gloria C
authors.initials: GC
authors.lastname: Chi
authors.forename: Hongmei
authors.initials: H
authors.lastname: Dong
authors.forename: Alice
authors.initials: A
authors.lastname: Lee
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Carpenter
authors.forename: James A
authors.initials: JA
authors.lastname: Waschek
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000378:metabolism*; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism*; D009687:Nuclear Proteins; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D014157:Transcription Factors; D000071676:Zinc Finger Protein GLI1
chemical_list: C498520:Gli1 protein, mouse; D053823:Hedgehog Proteins; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins; D051741:Kruppel-Like Transcription Factors; C000715631:NKX2-2 protein, human; C000715627:Nkx2-2 protein, mouse; D009687:Nuclear Proteins; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; C465570:Shh protein, mouse; D014157:Transcription Factors; D000071676:Zinc Finger Protein GLI1