ABSTRACT
Krox-24 is an immediate early gene encoding a zinc-finger transcription factor implicated in several adaptive responses, and its induction by cannabinoids has been reported. We used mice targeted in the Krox-24 gene to specifically dissect the role of this protein in the acute and chronic central actions of cannabinoids. We report here on the ability of cannabinoids to activate G-proteins and to inhibit adenylyl cyclase, and to elicit behavioral responses in wild-type and mutant mice. The behavioral parameters and the biochemical correlates of abstinence after delta9-THC withdrawal were evaluated. We show that Krox-24 is not involved in the acute analgesic effects of delta9-THC and in the SR precipitated delta9-THC withdrawal syndrome.
Subject(s)
Adenylyl Cyclases/drug effects , Behavior, Animal/drug effects , Cannabinoids/pharmacology , Cyclic AMP/genetics , DNA-Binding Proteins/drug effects , GTP-Binding Proteins/drug effects , Immediate-Early Proteins , Mice, Knockout/metabolism , Transcription Factors/drug effects , Adenylyl Cyclases/metabolism , Animals , Behavior, Animal/physiology , Binding, Competitive/drug effects , Binding, Competitive/physiology , Cerebellum/drug effects , Cerebellum/metabolism , Cyclic AMP/metabolism , Cyclic AMP Response Element-Binding Protein/drug effects , Cyclic AMP Response Element-Binding Protein/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Early Growth Response Protein 1 , GTP-Binding Proteins/metabolism , Male , Marijuana Abuse/metabolism , Marijuana Abuse/physiopathology , Mice , Mice, Knockout/genetics , Phosphorylation/drug effects , Receptors, Cannabinoid , Receptors, Drug/drug effects , Receptors, Drug/metabolism , Spleen/drug effects , Spleen/metabolism , Substance Withdrawal Syndrome/drug therapy , Substance Withdrawal Syndrome/metabolism , Substance Withdrawal Syndrome/physiopathology , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
The induction of long-term potentiation (LTP) in the dentate gyrus of the hippocampus is associated with a rapid and robust transcription of the immediate early gene Zif268. We used a mutant mouse with a targeted disruption of Zif268 to ask whether this gene, which encodes a zinc finger transcription factor, is required for the maintenance of late LTP and for the expression of long-term memory. We show that whereas mutant mice exhibit early LTP in the dentate gyrus, late LTP is absent when measured 24 and 48 hours after tetanus in the freely moving animal. In both spatial and non-spatial learning tasks, short-term memory remained intact, whereas performance was impaired in tests requiring long-term memory. Thus, Zif268 is essential for the transition from short- to long-term synaptic plasticity and for the expression of long-term memories.
Subject(s)
DNA-Binding Proteins/deficiency , DNA-Binding Proteins/genetics , Dentate Gyrus/metabolism , Genes, Immediate-Early/physiology , Immediate-Early Proteins , Long-Term Potentiation/genetics , Memory/physiology , Neuronal Plasticity/genetics , Transcription Factors/deficiency , Transcription Factors/genetics , Anesthetics/pharmacology , Animals , Avoidance Learning/physiology , Dentate Gyrus/cytology , Discrimination Learning/physiology , Early Growth Response Protein 1 , Excitatory Postsynaptic Potentials/physiology , Maze Learning/physiology , Memory Disorders/genetics , Memory Disorders/metabolism , Memory, Short-Term/physiology , Mice , Mice, Knockout , Neurons/cytology , Neurons/metabolism , RNA, Messenger/metabolismABSTRACT
Facial branchiomotor (fbm) neurones undergo a complex migration in the segmented mouse hindbrain. They are born in the basal plate of rhombomere (r) 4, migrate caudally through r5, and then dorsally and radially in r6. To study how migrating cells adapt to their changing environment and control their pathway, we have analysed this stereotyped migration in wild-type and mutant backgrounds. We show that during their migration, fbm neurones regulate the expression of genes encoding the cell membrane proteins TAG-1, Ret and cadherin 8. Specific combinations of these markers are associated with each migratory phase in r4, r5 and r6. In Krox20 and kreisler mutant mouse embryos, both of which lack r5, fbm neurones migrate dorsally into the anteriorly positioned r6 and adopt an r6-specific expression pattern. In embryos deficient for Ebf1, a gene normally expressed in fbm neurones, part of the fbm neurones migrate dorsally within r5. Accordingly, fbm neurones prematurely express a combination of markers characteristic of an r6 location. These data suggest that fbm neurones adapt to their changing environment by switching on and off specific genes, and that Ebf1 is involved in the control of these responses. In addition, they establish a close correlation between the expression pattern of fbm neurones and their migratory behaviour, suggesting that modifications in gene expression participate in the selection of the local migratory pathway.
Subject(s)
Avian Proteins , Cell Adhesion Molecules, Neuronal , Drosophila Proteins , Facial Nerve/embryology , Motor Neurons/cytology , Oncogene Proteins , Animals , Cadherins/genetics , Cadherins/physiology , Cell Movement , Contactin 2 , DNA-Binding Proteins/genetics , DNA-Binding Proteins/physiology , Early Growth Response Protein 2 , Facial Nerve/cytology , Gene Expression Regulation, Developmental , In Situ Hybridization , Lac Operon , MafB Transcription Factor , Membrane Glycoproteins/genetics , Membrane Glycoproteins/physiology , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Mice, Knockout , Mice, Transgenic , Neural Pathways/cytology , Neural Pathways/embryology , Proto-Oncogene Proteins , Proto-Oncogene Proteins c-ret , Receptor Protein-Tyrosine Kinases , Transcription Factors/genetics , Transcription Factors/physiologyABSTRACT
The developing vertebrate hindbrain is transiently subdivided along the anterior-posterior axis into metameric units, called rhombomeres (r). These segments constitute units of lineage restriction and display specific gene expression patterns. The transcription factor gene Krox-20 is restricted to r3 and r5, and is required for the development of these rhombomeres. We present evidence that Krox-20 transcriptional activity is under the control of a negative feedback mechanism in the hindbrain. This regulatory loop involves two closely related proteins, Nabl and Nab2, previously identified as antagonists of Krox-20 transcriptional activity in cultured cells. Here we show that in the mouse hindbrain, Nab1 and Nab2 recapitulate the Krox-20 expression pattern and that their expression is dependent on Krox-20 function. Furthermore, misexpression of Nab1 or Nab2 in zebrafish embryos leads to alterations in the expression patterns of several hindbrain markers, consistent with an inhibition of Krox-20 activity. Taken together, these data indicate that Krox-20 positively regulates the expression of its own antagonists and raise the possibility that this negative feedback regulatory loop may play a role in the control of hindbrain development.
Subject(s)
DNA-Binding Proteins/genetics , Gene Expression Regulation, Developmental , Neoplasm Proteins , Repressor Proteins/genetics , Rhombencephalon/embryology , Transcription Factors/genetics , 3T3 Cells , Animals , DNA-Binding Proteins/physiology , Early Growth Response Protein 2 , Feedback , Mice , Rhombencephalon/pathology , Transcription Factors/physiology , ZebrafishABSTRACT
Ebf1/Olf-1 belongs to a small multigene family encoding closely related helix-loop-helix transcription factors, which have been proposed to play a role in neuronal differentiation. Here we show that Ebf1 controls cell differentiation in the murine embryonic striatum, where it is the only gene of the family to be expressed. Ebf1 targeted disruption affects postmitotic cells that leave the subventricular zone (SVZ) en route to the mantle: they appear to be unable to downregulate genes normally restricted to the SVZ or to activate some mantle-specific genes. These downstream genes encode a variety of regulatory proteins including transcription factors and proteins involved in retinoid signalling as well as adhesion/guidance molecules. These early defects in the SVZ/mantle transition are followed by an increase in cell death, a dramatic reduction in size of the postnatal striatum and defects in navigation and fasciculation of thalamocortical fibres travelling through the striatum. Our data therefore show that Ebf1 plays an essential role in the acquisition of mantle cell molecular identity in the developing striatum and provide information on the genetic hierarchies that govern neuronal differentiation in the ventral telencephalon.
Subject(s)
Corpus Striatum/embryology , Corpus Striatum/pathology , DNA-Binding Proteins/genetics , Trans-Activators/genetics , Animals , Atrophy/genetics , Cadherins/genetics , Cell Compartmentation/genetics , Cell Death/genetics , Cell Differentiation/genetics , DNA-Binding Proteins/metabolism , Fetal Proteins/genetics , Gene Expression Regulation, Developmental , Gene Silencing , Homeodomain Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Mutation , Nerve Fibers/pathology , Octamer Transcription Factor-6 , Receptor Protein-Tyrosine Kinases/genetics , Receptor, EphA4 , Receptors, Retinoic Acid/genetics , Retinoic Acid Receptor alpha , Trans-Activators/metabolism , Transcription Factors/geneticsABSTRACT
Two novel mouse genes, Ebf2 and Ebf3, have been identified which show high similarity to the rodent Ebf/Olf-1 and the Drosophila collier genes. The strong conservation of the protein regions corresponding to the DNA binding and dimerisation domains previously defined in Ebf strongly suggests that Ebf2 and Ebf3 also constitute DNA sequence-specific transcription factors. Determination of the chromosomal locations of the two genes indicated that the different members of this novel mouse multigene family are not clustered. A detailed analysis of the expression of each of the three Ebf genes in the developing central nervous system revealed partially overlapping patterns with two salient features: 1) In the region extending from the midbrain to the spinal cord, the expression of the three genes correlated with neuronal maturation, with a general activation in early post-mitotic cells, followed by specific patterns of extinction also consistent with the neurogenic gradient. 2) In the forebrain area, although the patterns of expression of the Ebf genes also reflected neuronal maturation, they appeared in addition to be region specific. These data suggest that Ebf genes may be involved in the control of neuronal differentiation in the CNS and in enforcing regional diversity in populations of post-mitotic forebrain neurons.
