title: Foxo1 is a downstream effector of Isl1 in direct pathway striatal projection neuron development within the embryonic mouse telencephalon.
abstract: Recent studies have shown that the LIM-homeodomain transcription factor Isl1 is required for the survival and differentiation of direct pathway striatonigral neurons during embryonic development. The downstream effectors of Isl1 in these processes are presently unknown. We show here that Foxo1, a transcription factor that has been implicated in cell survival, is expressed in striatal projection neurons (SPNs) that derive from the Isl1 lineage (i.e. direct pathway SPNs). Moreover, Isl1 conditional knockouts (cKOs) show a severe loss of Foxo1 expression at E15.5 with a modest recovery by E18.5. Although Foxo1 is enriched in the direct pathway SPNs at embryonic stages, it is expressed in both direct and indirect pathway SPNs at postnatal time points as evidenced by co-localization with EGFP in both Drd1-EGFP and Drd2-EGFP BAC transgenic mice. Foxo1 was not detected in striatal interneurons as marked by the transcription factor Nkx2.1. Conditional knockout of Foxo1 using Dlx5/6-CIE mice results in reduced expression of the SPN marker Darpp-32, as well as in the direct pathway SPN markers Ebf1 and Zfp521 within the embryonic striatum at E15.5. However, this phenotype improves in the conditional mutants by E18.5. Interestingly, the Foxo family members, Foxo3 and Foxo6, remain expressed at late embryonic stages in the Foxo1 cKOs unlike the Isl1 cKOs where Foxo1/3/6 as well as the Foxo1/3 target Bach2 are all reduced. Taken together, these findings suggest that Foxo-regulated pathways are downstream of Isl1 in the survival and/or differentiation of direct pathway SPNs.
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA; Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. Electronic address: ronald.waclaw@cchmc.org.
authors.forename: R R
authors.initials: RR
authors.lastname: Waclaw
authors.affiliation: Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Ehrman
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
authors.forename: P
authors.initials: P
authors.lastname: Merchan-Sala
authors.affiliation: Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
authors.forename: V
authors.initials: V
authors.lastname: Kohli
authors.affiliation: Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
authors.forename: D
authors.initials: D
authors.lastname: Nardini
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA; Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. Electronic address: kenneth.campbell@cchmc.org.
authors.forename: K
authors.initials: K
authors.lastname: Campbell
mesh_terms: D000367:Age Factors; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D003342:Corpus Striatum / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D004622:Embryo, Mammalian; D000071161:Forkhead Box Protein O1 / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D017447:Receptors, Dopamine D1 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C102109:Bach2 protein, mouse; D050976:Basic-Leucine Zipper Transcription Factors; C100597:Dlx6 protein, mouse; C583261:Drd1 protein, mouse; C489921:Ebf1 protein, mouse; C472572:Evi3 protein, mouse; D000071161:Forkhead Box Protein O1; C467200:Foxo1 protein, mouse; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D008164:Luminescent Proteins; D017447:Receptors, Dopamine D1; D015534:Trans-Activators; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1
keywords: Basal ganglia; Cell survival; Neuronal subtype differentiation; Striatum