ABSTRACT
BACKGROUND: The homeobox containing transcription factor Uncx4.1 is, amongst others, expressed in the mouse midbrain. The early expression of this transcription factor in the mouse, as well as in the chick midbrain, points to a conserved function of Uncx4.1, but so far a functional analysis in this brain territory is missing. The goal of the current study was to analyze in which midbrain neuronal subgroups Uncx4.1 is expressed and to examine whether this factor plays a role in the early development of these neuronal subgroups. RESULTS: We have shown that Uncx4.1 is expressed in GABAergic, glutamatergic and dopaminergic neurons in the mouse midbrain. In midbrain dopaminergic (mDA) neurons Uncx4.1 expression is particularly high around E11.5 and strongly diminished already at E17.5. The analysis of knockout mice revealed that the loss of Uncx4.1 is accompanied with a 25% decrease in the population of mDA neurons, as marked by tyrosine hydroxylase (TH), dopamine transporter (DAT), Pitx3 and Ngn2. In contrast, the number of glutamatergic Pax6-positive cells was augmented, while the GABAergic neuron population appears not affected in Uncx4.1-deficient embryos. CONCLUSION: We conclude that Uncx4.1 is implicated in the development of mDA neurons where it displays a unique temporal expression profile in the early postmitotic stage. Our data indicate that the mechanism underlying the role of Uncx4.1 in mDA development is likely related to differentiation processes in postmitotic stages, and where Ngn2 is engaged. Moreover, Uncx4.1 might play an important role during glutamatergic neuronal differentiation in the mouse midbrain.
Subject(s)
Cell Differentiation/genetics , Dopaminergic Neurons/physiology , Gene Expression Regulation, Developmental/genetics , Homeodomain Proteins/metabolism , Mesencephalon , Age Factors , Animals , Animals, Newborn , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Bromodeoxyuridine/metabolism , Cell Count , Cell Death/genetics , Dopamine Plasma Membrane Transport Proteins/metabolism , Embryo, Mammalian , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Homeodomain Proteins/genetics , Immunoprecipitation , In Situ Nick-End Labeling , Mesencephalon/cytology , Mesencephalon/embryology , Mesencephalon/growth & development , Mice , Mice, Transgenic , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Tyrosine 3-Monooxygenase/metabolismABSTRACT
Lmx1a is a member of the LIM homeodomain containing transcription factors and plays an important role during embryonic development. Specifically, it is required for the proper formation of several structures in the central nervous system, such as the roof plate, the cerebellum, and the inner ear. All these defects may contribute to the neurological phenotype observed in dreher mice, lacking functional Lmx1a protein. Interestingly, this factor was also found to promote midbrain dopaminergic neuron fate. We have introduced Green fluorescent protein (GFP) coding sequences into the Lmx1a locus by homologous recombination, and created knockout mice where GFP recapitulates the Lmx1a endogenous expression pattern.
Subject(s)
Genes, Reporter/genetics , Green Fluorescent Proteins/genetics , Homeodomain Proteins/genetics , Animals , Embryo, Mammalian/metabolism , Female , Genetic Loci , Green Fluorescent Proteins/metabolism , Homeodomain Proteins/metabolism , LIM-Homeodomain Proteins , Mice , Mice, Knockout , Neurons/metabolism , Transcription FactorsABSTRACT
BACKGROUND: The forebrain consists of multiple structures necessary to achieve elaborate functions. Proper patterning is, therefore, a prerequisite for the generation of optimal functional areas. Only a few factors have been shown to control the genetic networks that establish early forebrain patterning. RESULTS AND CONCLUSION: Using conditional inactivation, we show that the transcription factor Sp8 has an essential role in the molecular and functional patterning of the developing telencephalon along the anteroposterior axis by modulating the expression gradients of Emx2 and Pax6. Moreover, Sp8 is essential for the maintenance of ventral cell identity in the septum and medial ganglionic eminence (MGE). This is probably mediated through a positive regulatory interaction with Fgf8 in the medial wall, and Nkx2.1 in the rostral MGE anlage, and independent of SHH and WNT signaling. Furthermore, Sp8 is required during corticogenesis to sustain a normal progenitor pool, and to control preplate splitting, as well as the specification of cellular diversity within distinct cortical layers.
Subject(s)
Body Patterning/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation, Developmental/genetics , Homeodomain Proteins/metabolism , Prosencephalon/embryology , Prosencephalon/metabolism , Transcription Factors/metabolism , Animals , Cell Differentiation/physiology , Cell Polarity/genetics , DNA-Binding Proteins/genetics , Down-Regulation/genetics , Eye Proteins/genetics , Eye Proteins/metabolism , Fibroblast Growth Factor 8/genetics , Fibroblast Growth Factor 8/metabolism , Homeodomain Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Neurons/cytology , Neurons/metabolism , Nuclear Proteins/genetics , PAX6 Transcription Factor , Paired Box Transcription Factors/genetics , Paired Box Transcription Factors/metabolism , Prosencephalon/cytology , Repressor Proteins/genetics , Repressor Proteins/metabolism , Stem Cells/cytology , Stem Cells/metabolism , Thyroid Nuclear Factor 1 , Transcription Factors/genetics , Transcriptional Activation/geneticsABSTRACT
The specification of neuronal cell types in the developing neural tube is orchestrated by signaling centers. However, how patterned territories of the central nervous system (CNS) are organized into structures with appropriate size and shape is still unclear. We report that in the absence of the mouse transcription factor mBtd/Sp8, a posterior shift of the isthmic organizer (IsO) occurs, suggesting a crucial role for Sp8 in this process. In addition, large patches of cells ectopically expressing Fgf8, Otx2 and/or Wnt1 in the rostral hindbrain are detected in Sp8 mutant embryos. In this context, midbrain dopaminergic neurons are found posterior to the IsO. Furthermore, we provide evidence that cell proliferation in the mid- and hindbrain is tightly controlled by Sp8 activity. Our observations are consistent with a role for Sp8 in restricting Fgf8 expression at the IsO.
Subject(s)
Body Patterning , DNA-Binding Proteins/metabolism , Gene Expression Regulation, Developmental , Mesencephalon/embryology , Rhombencephalon/embryology , Transcription Factors/metabolism , Animals , Body Patterning/genetics , DNA-Binding Proteins/genetics , Mesencephalon/metabolism , Mice , Mice, Knockout , Rhombencephalon/metabolism , Transcription Factors/geneticsABSTRACT
Embryonic stem cells (ES) are pluripotent and may therefore serve as a source for the generation of specific cell types required for future therapies based on cell replacement. The isolation of defined cell populations from a certain lineage or tissue is a prerequisite for the analysis of the potential of such ES-derived cells in animal transplantation studies. Here, using the Cre/loxP system, we report the generation of murine ES cells conditionally expressing the hrGFP gene at the cell surface. Such ES cells can be differentiated in vitro into neurons displaying GFP activity in neurites. Transgenic mice derived from these ES cells permit the targeting of GFP-expression to specific tissues and provide material from the three germ layers suitable for molecular and biochemical analysis.
