ABSTRACT
Development of the vertebrate cerebellum is unusual compared to most other regions of the brain since it involves two germinal regions. Most cell types arise from the luminal, ventricular zone as in other brain regions, but granule cells arise from the second germinal layer, the external granular layer (EGL). Our analysis of the temporal and positional expression of three members of the Sox gene family of transcription factors in the cerebellum shows that granule cell development is unusual compared to most other neurons of the central nervous system (CNS). We show that granule cell precursors lose expression of cSox2 and cSox3 as they migrate to form the EGL. The EGL is the first example of a germinal layer in the CNS which does not exhibit expression of these genes. Throughout most of the CNS cSox11 expression is very low in the ventricular zone but increases dramatically as cells cease proliferation and migrate to form the subventricular zone. We also find that cSox11 expression increases when cells of the cerebellum migrate to form the EGL, but levels of expression as high as that in the subventricular zone are only seen when cells cease proliferation and migrate inwards to form the deep EGL. These observations demonstrate that cells of the proliferative superficial EGL differ qualitatively from cells of the ventricular zone in their expression of Sox genes whereas the post-proliferative cells of the deep EGL appear analogous, in their expression of Sox genes, to cells of the subventricular zone.
Subject(s)
Cerebellar Cortex/cytology , Gene Expression Regulation, Developmental , High Mobility Group Proteins/biosynthesis , Nerve Tissue Proteins/biosynthesis , Animals , Cell Division , Cell Lineage , Cell Movement , Cerebellar Cortex/embryology , Cerebellar Cortex/metabolism , Chick Embryo , High Mobility Group Proteins/genetics , High Mobility Group Proteins/physiology , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/physiology , Pons/cytology , Pons/embryology , Rhombencephalon/cytology , Rhombencephalon/embryologyABSTRACT
The chick genes, cSox2 and cSox3, are members of a large family of genes that encode transcription factors. Previous studies have shown that these genes are predominantly expressed in the central nervous system during embryonic development. We show that cSox3 is expressed throughout the ectoderm that is competent to form nervous tissue before neural induction. The expression of cSox3 is lost from cells as they undergo gastrulation to form nonectodermal tissues; the transcription factor, Brachyury, appears in cells about to undergo gastrulation a short time before cSox3 transcripts are lost. Therefore, Brachyury expression may act functionally upstream of cSox3 downregulation. cSox3 expression is also lost from non-neuronal ectoderm shortly after the neural plate becomes morphologically apparent. cSox2 expression increases dramatically in the central nervous system as neural ectoderm is established. The appearance of cSox2 in neural ectoderm represents one of the earliest molecular responses to neural induction documented thus far.
Subject(s)
DNA-Binding Proteins/genetics , Ectoderm/chemistry , High Mobility Group Proteins/genetics , Nervous System/embryology , Nuclear Proteins/genetics , T-Box Domain Proteins , Animals , Chick Embryo , DNA-Binding Proteins/analysis , Embryo, Nonmammalian/chemistry , Embryo, Nonmammalian/embryology , Embryonic Induction/genetics , Epithelium/chemistry , Fetal Proteins/analysis , Fetal Proteins/genetics , Gene Expression Regulation, Developmental/physiology , Genes, Homeobox/physiology , HMGB Proteins , Immunohistochemistry , In Situ Hybridization , Nervous System/chemistry , RNA, Messenger/analysis , SOXB1 Transcription Factors , Transcription Factors/geneticsABSTRACT
The advent of non-isotopic in situ hybridisation allows the possibility to detect the presence of both mRNAs and other markers in cells. We have established conditions for simultaneous analysis of gene expression and a variety of other immunohistochemical markers in tissue sections. We report the analysis of expression of a family of transcription factors (Sox genes) in combination with detection of: (1) protein antigens (using both monoclonal and polyclonal antibodies); (2) bromodeoxyuridine to mark cells which are proliferating; and (3) acetylcholinesterase activity. The approaches we describe, which demonstrate the compatibility of non-isotopic in situ hybridisation with a range of other treatments, should be generally applicable and open to many variations of probe, antibodies and colour detection systems.
