RESUMO
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.
Assuntos
Corpo Estriado/citologia , Proteína Forkhead Box O1/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Proteínas com Homeodomínio LIM/metabolismo , Neurônios/metabolismo , Transdução de Sinais/genética , Fatores de Transcrição/metabolismo , Fatores Etários , Animais , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Diferenciação Celular/fisiologia , Corpo Estriado/embriologia , Corpo Estriado/metabolismo , Embrião de Mamíferos , Proteína Forkhead Box O1/genética , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteínas com Homeodomínio LIM/genética , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos , Camundongos Transgênicos , Vias Neurais/fisiologia , Receptores de Dopamina D1/genética , Receptores de Dopamina D1/metabolismo , Transativadores/metabolismo , Fatores de Transcrição/genéticaRESUMO
Mice lacking phosphodiesterase 1B (PDE1B) exhibit an exaggerated locomotor response to D-methamphetamine and increased in vitro phosphorylation of DARPP32 (dopamine- and cAMP-regulated phosphoprotein, M r 32 kDa) at Thr34 in striatal brain slices treated with the D1 receptor agonist, SKF81297. These results indicated a possible regulatory role for PDE1B in pathways involving DARPP32. Here, we generated PDE1B x DARPP32 double-knockout (double-KO) mice to test the role of PDE1B in DARPP32-dependent pathways in vivo. Analysis of the response to d-methamphetamine on locomotor activity showed that the hyperactivity experienced by PDE1B mutant mice was blocked in PDE1B-/- x DARPP32-/- double-KO mice, consistent with participation of PDE1B and DARPP32 in the same pathway. Further behavioral testing in the elevated zero-maze revealed that DARPP32-/- mice showed a less anxious phenotype that was nullified in double-mutant mice. In contrast, in the Morris water maze, double-KO mice showed deficits in spatial reversal learning not observed in either single mutant compared with wild-type mice. The data suggest a role for PDE1B in locomotor responses to psychostimulants through modulation of DARPP32-dependent pathways; however, this modulation does not necessarily impact other behaviors, such as anxiety or learning. Instead, the phenotype of double-KOs observed in these latter tasks may be mediated through independent pathways.
Assuntos
Estimulantes do Sistema Nervoso Central/farmacologia , Fosfoproteína 32 Regulada por cAMP e Dopamina/metabolismo , Metanfetamina/farmacologia , Atividade Motora/efeitos dos fármacos , Diester Fosfórico Hidrolases/metabolismo , Comportamento Espacial/efeitos dos fármacos , Análise de Variância , Animais , Ansiedade/metabolismo , Nucleotídeo Cíclico Fosfodiesterase do Tipo 1 , Fosfoproteína 32 Regulada por cAMP e Dopamina/genética , Feminino , Hipercinese/enzimologia , Hipercinese/genética , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora/fisiologia , Diester Fosfórico Hidrolases/genética , Transdução de Sinais/fisiologia , Comportamento Espacial/fisiologiaRESUMO
Several families of regulatory genes have been implicated in anteroposterior patterning of gastrulation-stage vertebrate embryos. Members of the Drosophila caudal family of homeobox genes (Cdx) are among the earliest regulators of posterior cell fates. The regulatory cascade initiated by the caudal homologue, cCdx-B, was examined in avian embryos. During gastrulation, cCdx-B is expressed with other posterior patterning genes. In the posterior primitive streak, cCdx-B expression coincides with posteriorly expressed Hox cluster genes and Wnt family members such as Wnt-8c. The hierarchical relationship between these patterning genes was examined after anterior ectopic expression of cCdx-B. cCdx-B expression in anterior cardiogenic cells by means of adenoviral infection leads to the induction of Wnt-8c and the posterior Hox genes, Hoxa-7, Hoxc-6, and Hoxc-8. Cardiogenesis is not inhibited in cCdx-B expressing anterior lateral mesoderm, indicating that anterior cell fates are not respecified with the activation of posterior patterning genes after gastrulation. These results support an important role for cCdx-B in initiating a posterior program of gene expression that includes Wnt signaling molecules and the Hox cluster genes.