Sox neuro, a new Drosophila Sox gene expressed in the developing central nervous system

We describe the identification and detailed expression pattern of a second Drosophila Sox gene, SoxNeuro (SoxN), highly related to mammalian group B Sox1, 2, 3 genes. SoxN is expressed in a highly dynamic pattern during embyogenesis, being associated with the development of the central nervous system (CNS), from the early steps onwards. We present strong evidence that the early SoxN neuroectoderm expression is controlled by the zygotic dorso-ventral patterning genes (dpp, sog, brk, twi).     

Identification and characterization of Veph, a novel gene encoding a PH domain-containing protein expressed in the developing central nervous system of vertebrates

We isolated Veph, a novel gene encoding a pleckstrin homology (PH) domain-containing protein from a mouse. Veph was strongly expressed in the embryonic brain, and its expression level gradually decreased in later stages. In situ hybridization analysis of sectioned embryo brains revealed that Veph was expressed exclusively in the ventricular zone. We then isolated a zebrafish orthologue of Veph (zVeph). As observed in the mouse gene, zVeph was expressed in the ventricular zone of developing brain and spinal cord. Blockage of zVeph expression by injection of zVeph-specific morpholino antisense oligo into zebrafish fertilized eggs resulted in a defect in the midbrain-hindbrain boundary and otic vesicle formation, suggesting the important function of zVeph in central nervous system (CNS) development. On the other hand, homozygous knockout mice of Veph showed no significant defect in the CNS, pointing to possible different functions of Veph between the zebrafish and mouse.     

Formin-2, a novel formin homology protein of the cappuccino subfamily, is highly expressed in the developing and adult central nervous system

Formin-1 is the founding member of a family of genes of emerging biological and medical importance that share specific domains of homology, allowing them to be classified together as the formin homology proteins. Although deficiency mutations in formin-1 lead to profound developmental defects in limb and kidney formation, similar deficiency mutations in more distantly related members of this family (diaphanous and cappuccino in Drosophila and BNI1 in yeast) have ostensibly unrelated phenotypes. Here we describe murine and human formin-2 (Fmn2), a gene which bears a high degree of similarity to formin-1 and cappuccino. The mouse gene, which encodes a putative 1567-amino-acid open reading frame and maps to mouse Chromosome 1, is expressed almost exclusively in the developing and mature central nervous system. Expression begins at embryonic day 9. 5 in the developing spinal cord and brain structures and continues in neonatal and adult brain structures including the olfactory bulb, cortex, thalamus, hypothalamus, hippocampus and cerebellum. Human formin-2 has a similar expression pattern.     

Identification of a novel neuromedin U receptor subtype expressed in the central nervous system

Neuromedin U is a neuropeptide prominently expressed in the upper gastrointestinal tract and central nervous system. Recently, GPR66/FM-3 (NmU-R1) was identified as a specific receptor for neuromedin U. A BLAST search of the GenBank(TM) genomic database using the NmU-R1 cDNA sequence revealed a human genomic fragment encoding a G protein-coupled receptor that we designated NmU-R2 based on its homology to NmU-R1. The full-length NmU-R2 cDNA was subsequently cloned, stably expressed in 293 cells, and shown to mobilize intracellular calcium in response to neuromedin U. This response was dose-dependent (EC(50) = 5 nm) and specific in that other neuromedins did not induce a calcium flux in receptor-transfected cells. Expression analysis of human NmU-R2 demonstrated its mRNA to be most highly expressed in central nervous system tissues. Based on these data, we conclude that NmU-R2 is a novel neuromedin U receptor subtype that is likely to mediate central nervous system-specific neuromedin U effects.     

GLUTX1, a novel mammalian glucose transporter expressed in the central nervous system and insulin-sensitive tissues

Based on homology with GLUT1-5, we have isolated a cDNA for a novel glucose transporter, GLUTX1. This cDNA encodes a protein of 478 amino acids that shows between 29 and 32% identity with rat GLUT1-5 and 32-36% identity with plant and bacterial hexose transporters. Unlike GLUT1-5, GLUTX1 has a short extracellular loop between transmembrane domain (TM) 1 and TM2 and a long extracellular loop between TM9 and TM10 that contains the only N-glycosylation site. When expressed in Xenopus oocytes, GLUTX1 showed strong transport activity only after suppression of a dileucine internalization motif present in the amino-terminal region. Transport activity was inhibited by cytochalasin B and partly competed by D-fructose and D-galactose. The Michaelis-Menten constant for glucose was approximately 2 mM. When translated in reticulocytes lysates, GLUTX1 migrates as a 35-kDa protein that becomes glycosylated in the presence of microsomal membranes. Western blot analysis of GLUTX1 transiently expressed in HEK293T cells revealed a diffuse band with a molecular mass of 37-50 kDa that could be converted to a approximately 35-kDa polypeptide following enzymatic deglycosylation. Immunofluorescence microscopy detection of GLUTX1 transfected into HEK293T cells showed an intracellular staining. Mutation of the dileucine internalization motif induced expression of GLUTX1 at the cell surface. GLUTX1 mRNA was detected in testis, hypothalamus, cerebellum, brainstem, hippocampus, and adrenal gland. We hypothesize that, in a similar fashion to GLUT4, in vivo cell surface expression of GLUTX1 may be inducible by a hormonal or other stimulus.     

Identification of chick frizzled-10 expressed in the developing limb and the central nervous system

We have identified chick frizzled (Fz)-10, encoding a Wnt receptor, and examined the expression pattern during embryogenesis. Fz-10 is expressed in the region posterior to the Hensen's node at stage 6. Fz-10 expression is detected in the dorsal domain of the neural tube and the central nervous system of the developing embryo. In the developing limb, Fz-10 expression starts at stage 18 in the posterior-dorsal region of the distal mesenchyme, and gradually expands to the anterior-distal region. Fz-10 is also expressed in the feather bud and branchial arch. Implantation of Sonic hedgehog (Shh)-expressing cells into the anterior margin of the limb bud resulted in the induction of Fz-10 expression in anterior-dorsal mesenchyme.     

Eos: a novel member of the Ikaros gene family expressed predominantly in the developing nervous system

We identified a novel member of the Ikaros gene family, which has critical roles in the development of lymphoid lineages. This gene, which we named Eos, was expressed predominantly in the developing central and peripheral nervous system. Eos protein could interact with itself and Ikaros protein through its C-terminal portion in the yeast two hybrid assay. These findings suggested that Eos may have important roles in neural development similarly to the Ikaros family in the development of hemolymphoid tissue.     

Gap junctional communication in the developing central nervous system

The development of the central nervous system is a complex process involving multiple interactions between various cell types undergoing mitosis, migration, differentiation, axonal outgrowth, synaptogenesis and programmed cell death. For example, neocortical development is characterized by a series of transient events that ultimately leads to the formation of a discrete pattern of laminar and columnar organization. While neuron-glial cell-cell interactions have been shown to be involved in neuronal migration, recent observations that neurons are extensively coupled by gap junctions in the developing neocortex have implicated this phenomenon in the process of neocortical differentiation. The present review will examine the putative role of gap junctional intercellular communication in development of the central nervous system, with specific reference to recent studies in the development of the cerebral cortex.     

Cell fate control in the developing central nervous system

The principal neural cell types forming the mature central nervous system (CNS) are now understood to be diverse. This cellular subtype diversity originates to a large extent from the specification of the earlier proliferating progenitor populations during development. Here, we review the processes governing the differentiation of a common neuroepithelial cell progenitor pool into mature neurons, astrocytes, oligodendrocytes, ependymal cells and adult stem cells. We focus on studies performed in mice and involving two distinct CNS structures: the spinal cord and the cerebral cortex. Understanding the origin, specification and developmental regulators of neural cells will ultimately impact comprehension and treatments of neurological disorders and diseases.     

A novel POU homeodomain gene specifically expressed in cells of the developing mammalian nervous system.

We report the isolation of a novel human POU domain encoding gene named RDC-1. The POU domain of the RDC-1 encoded protein is highly related to the POU domain potentially encoded by the rat brain-3 sequence and to that of the Drosophila I-POU protein; outside of the POU region, RDC-1 is unrelated to any previously characterized protein. The RDC-1 gene is expressed almost exclusively in normal tissues and transformed cells of neural origin. In the developing mouse and human fetus, RDC-1 is expressed in a spatially and temporally restricted pattern that suggests a critical role in the differentiation of neuronal tissues. In addition, RDC-1 is expressed in a unique subset of tumors of the peripheral nervous system including neuroepitheliomas and Ewing's sarcomas but not neuroblastomas. Based on its unique structural characteristics and expression pattern, we discuss potential functions for the RDC-1 protein.     

CIP98, a novel PDZ domain protein,is expressed in the central nervous system and interacts with calmodulin-dependent serine kinase

Receptors and various molecules in neurons are localized at precise locations to perform their respective functions, especially in synaptic sites. Among synaptic molecules, PDZ domain proteins play major roles in scaffolding and anchoring membrane proteins for efficient synaptic transmission. In the present study, we isolated CIP98, a novel protein (98 kDa) consisting of three PDZ domains and a proline-rich region, which is widely expressed in the central nervous system. In situ hybridization and immunohistochemical staining patterns demonstrate that CIP98 is expressed strongly in certain types of neurons, i.e. pyramidal cells in layers III-V of the cerebral cortex, projecting neurons in the thalamus and interneurons in the cerebellum. The results of immunocytochemical staining and electron microscopy revealed that CIP98 is localized both in dendrites and axons. Interestingly, CIP98 interacts with CASK (calmodulin-dependent serine kinase), a member of the membrane-associated guanylate kinase (MAGUK) family that plays important roles in the molecular organization of proteins at synapses. CIP98 was shown to co-localize with CASK along the dendritic processes of neurons. In view of its direct association with CASK, CIP98 may be involved in the formation of CASK scaffolding proteins complex to facilitate synaptic transmission in the CNS.     

Gsh-4 encodes a LIM-type homeodomain, is expressed in the developing central nervous system and is required for early postnatal survival.

We present an initial characterization of the murine Gsh-4 gene which is shown to encode a LIM-type homeodomain. Genes in this category are known to control late developmental cell-type specification events in simpler organisms. Whole mount and serial section in situ hybridizations show transient Gsh-4 expression in ventrolateral regions of the developing neural tube and hindbrain. Mice homozygous for a targeted mutation in Gsh-4 suffer early postnatal death resulting from immature lungs which do not inflate. Prenatal administration of progesterone and glucocorticoid, to extend gestational term and accelerate maturation, resulted in lung inflation at birth. Nevertheless, the hormonally treated mutants generally failed to survive beyond an hour after birth, due to ineffective breathing efforts. It is concluded that Gsh-4 plays a critical role in the development of respiratory control mechanisms and in the normal growth and maturation of the lung.     

CSMD1 is a novel multiple domain complement-regulatory protein highly expressed in the central nervous system and epithelial tissues

In this study, we describe the identification and in vitro functional activity of a novel multiple domain complement regulatory protein discovered based on its homology to short consensus repeat (SCR)-containing proteins of the regulators of complement activation (RCA) gene family. The rat cDNA encodes a predicted 388-kDa protein consisting of 14 N-terminal CUB domains that are separated from each other by a SCR followed by 15 tandem SCR domains, a transmembrane domain, and a short cytoplasmic tail. This protein is the homolog of the human protein of unknown function called the CUB and sushi multiple domains 1 (CSMD1) protein. A cloning strategy that incorporates the two C-terminal CUB-SCR domains and 12 of the tandem SCR repeats was used to produce a soluble rat CSMD1 protein. This protein blocked classical complement pathway activation in a comparable fashion with rat Crry but did not block alternative pathway activation. Analysis of CSMD1 mRNA expression by in situ hybridization and immunolabeling of neurons indicates that the primary sites of synthesis are the developing CNS and epithelial tissues. Of particular significance is the enrichment of CSMD1 in the nerve growth cone, the amoeboid-leading edge of the growing neuron. These results suggest that CSMD1 may be an important regulator of complement activation and inflammation in the developing CNS, and that it may also play a role in the context of growth cone function.