Expression of cadherin10, a type II classic cadherin gene, in the nervous system of the embryonic zebrafish

Cadherins are cell surface adhesion molecules that play important roles in development of tissues and organs. In this study, we analyzed expression pattern of cadherin10, a member of the type II classic cadherin subfamily, in the embryonic zebrafish using in situ hybridization methods. cadherin10 message (cdh10) is first and transiently expressed by the notochord. In the developing nervous system, cdh10 was first detected in a subset of the cranial ganglia, then in restricted brain regions and neural retina. As development proceeds, cdh10 expression domain and/or expression levels increased in the embryonic nervous system. Our results show that cdh10 expression in the zebrafish developing nervous system is both spatially and temporally regulated.     

LPA in neural cell development

Lysophosphatidic acid (LPA) elicits diverse cellular responses through cell surface LPA receptors in nervous system-derived cells and cell lines. The developing nervous system is one of the major loci for LPA receptor expression. Recent studies have also revealed that metabolic pathways of LPA are present in the nervous system. A growing body of literature suggests a crucial role for LPA in neuronal development processes, including neurogenesis, neuronal migration, neuritogenesis, and myelination.     

The cell cycle associated protein, HTm4, is expressed in differentiating cellsof the hematopoietic and central nervous system in mice

HTm4 is a member of a newly defined family of human and murine proteins, the MS4 (membrane-spanning four) protein group, which has a distinctive four-transmembrane structure. MS4 protein functions include roles as cell surface signaling receptors and intracellular adapter proteins. We have previously demonstrated that HTm4 regulates the function of the KAP phosphatase, a key regulator of cell cycle progression. In humans, the expression of HTm4 is largely restricted to cells of the hematopoietic lineage, possibly reflecting a causal role for this molecule in differentiation/proliferation of hematopoietic lineage cells. In this study, we show that, like the human homologue, murine HTm4 is also predominantly a hematopoietic protein with distinctive expression patterns in developing murine embryos and in adult animals. In addition, we observed that murine HTm4 is highly expressed in the developing and adult murine nervous system, suggesting a previously unrecognized role in central and peripheral nervous system development.JLK and XY contributed equally to this work     

The zinc finger transcription factor Gfi1, implicated in lymphomagenesis,is required for inner ear hair cell differentiation and survival

Gfi1 was first identified as causing interleukin 2-independent growth in T cells and lymphomagenesis in mice. Much work has shown that Gfi1 and Gfi1b, a second mouse homolog, play pivotal roles in blood cell lineage differentiation. However, neither Gfi1 nor Gfi1b has been implicated in nervous system development, even though their invertebrate homologues, senseless in Drosophila and pag-3 in C. elegans are expressed and required in the nervous system. We show that Gfi1 mRNA is expressed in many areas that give rise to neuronal cells during embryonic development in mouse, and that Gfi1 protein has a more restricted expression pattern. By E12.5 Gfi1 mRNA is expressed in both the CNS and PNS as well as in many sensory epithelia including the developing inner ear epithelia. At later developmental stages, Gfi1 expression in the ear is refined to the hair cells and neurons throughout the inner ear. Gfi1 protein is expressed in a more restricted pattern in specialized sensory cells of the PNS, including the eye, presumptive Merkel cells, the lung and hair cells of the inner ear. Gfi1 mutant mice display behavioral defects that are consistent with inner ear anomalies, as they are ataxic, circle, display head tilting behavior and do not respond to noise. They have a unique inner ear phenotype in that the vestibular and cochlear hair cells are differentially affected. Although Gfi1-deficient mice initially specify inner ear hair cells, these hair cells are disorganized in both the vestibule and cochlea. The outer hair cells of the cochlea are improperly innervated and express neuronal markers that are not normally expressed in these cells. Furthermore, Gfi1 mutant mice lose all cochlear hair cells just prior to and soon after birth through apoptosis. Finally, by five months of age there is also a dramatic reduction in the number of cochlear neurons. Hence, Gfi1 is expressed in the developing nervous system, is required for inner ear hair cell differentiation, and its loss causes programmed cell death.     

Differential expression of alternate forms of a Drosophila src protein during embryonic and larval tissue differentiation

The Dsrc28C gene encodes two major proteins, p66 and p55, each of which contains a tyrosine kinase domain. Using monoclonal antibodies we have completed a detailed investigation of the spatial expression of Dsrc28C proteins during embryonic and larval development. Differentiation of a number of embryonic tissues is accompanied by the induction of Dsrc28C expression. With the exception of the developing salivary glands which express high levels of p66, developing tissues express the p55 form of Dsrc28C. Notable examples are cells of the and peripheral nervous systems which express p55 from the early stages of neurogenesis through the remainder of embryogenesis and pole cells which transiently express p55 during portions of embryonic stages 10 and 11. Nervous system expression includes the cell bodies and neuronal fibers of the central nervous system, the anterior sensory organs, and the peripheral sensory neurons. During larval development, p55 levels within the central nervous system remain high but substantial changes in the pattern of expression take place. p55 gradually disappears from the neuronal fibers of the central nervous system and from embryonic cell bodies. During the third larval instar, the birth of immature neuroblasts within the ventral and midbrain ganglia, but not within the optic ganglia, is marked by a transient high level of p55 expression. All imaginal cells that have been observed within the larva express the p66 protein. The patterns of expression that we have noted suggest that expression of the p55 form of Dsrc28C protein is an early event in the differentiation of neuronal cells, while expression of the p66 form is characteristic of cells committed to ectodermal cell differentiation.     

Ontogeny of semaphorins 3A and 3F and their receptors neuropilins 1 and 2 in the kidney

Semaphorins 3A and 3F are axon guidance proteins during nervous system development. Their expression pattern and function outside the nervous system are unknown. Neuropilin 1 and 2 (NP-1, NP-2) are natural ligands for semaphorins 3A and 3F, respectively. NP-1 is also a co-receptor for vascular endothelial growth factor (VEGF) required for normal vascular development. We showed that VEGF is a direct chemoattractant for glomerular endothelial cells towards developing nephrons. To examine whether semaphorins could modulate VEGF endothelial cell guidance cues in the developing kidney, we studied the expression of semaphorin 3A and semaphorin 3F and their receptors NP-1 and NP-2 in the kidney during ontogeny using Northern blot analysis, in situ hybridization, Western blot analysis and immunohistochemistry. All four genes are developmentally regulated, with abundant expression during organogenesis and downregulation in the adult kidney. Semaphorin 3A and 3F are expressed by podocytes and tubules whereas their receptors NP-1 and NP-2 are localized to endothelial cells. In vitro, renal tubular epithelial cell lines (tsMPT, IRPT and MDCK) and glomerular endothelial cells express both semaphorins and their receptors, suggesting the presence of an autocrine system. The distribution of the receptors NP-1 and NP-2 in endothelial cells and developing vessels is complementary to that of the ligands in adjacent epithelial cells during kidney development. The sum of the guidance cues provided by VEGF and semaphorins 3A and 3F may be important determinants of the pattern of endothelial cell migration during kidney morphogenesis.     

Grasshopper Lazarillo, a GPI-anchored Lipocalin, increases Drosophila longevity and stress resistance, and functionally replaces its secreted homolog NLaz

Lazarillo (Laz) is a glycosyl-phosphatidylinositol (GPI)-linked glycoprotein first characterized in the developing nervous system of the grasshopper Schistocerca americana. It belongs to the Lipocalins, a functionally diverse family of mostly secreted proteins. In this work we test whether the protective capacity known for Laz homologs in flies and vertebrates (NLaz, GLaz and ApoD) is evolutionarily conserved in grasshopper Laz, and can be exerted from the plasma membrane in a cell-autonomous manner. First we demonstrate that extracellular forms of Laz have autocrine and paracrine protecting effects for oxidative stress-challenged Drosophila S2 cells. Then we assay the effects of overexpressing GPI-linked Laz in adult Drosophila and whether it rescues both known and novel phenotypes of NLaz null mutants. Local effects of GPI-linked Laz inside and outside the nervous system promote survival upon different stress forms, and extend lifespan and healthspan of the flies in a cell-type dependent manner. Outside the nervous system, expression in fat body cells but not in hemocytes results in protection. Within the nervous system, glial cell expression is more effective than neuronal expression. Laz actions are sexually dimorphic in some expression domains. Fat storage promotion and not modifications in hydrocarbon profiles or quantities explain the starvation-desiccation resistance caused by Laz overexpression. This effect is exerted when Laz is expressed ubiquitously or in dopaminergic cells, but not in hemocytes. Grasshopper Laz functionally restores the loss of NLaz, rescuing stress-sensitivity as well as premature accumulation of aging-related damage, monitored by advanced glycation end products (AGEs). However Laz does not rescue NLaz courtship behavioral defects. Finally, the presence of two new Lipocalins with predicted GPI-anchors in mosquitoes shows that the functional advantages of GPI-linkage have been commonly exploited by Lipocalins in the arthropodan lineage.     

Ontogeny of semaphorins 3A and 3F and their receptors neuropilins 1 and 2 in the kidney

Semaphorins 3A and 3F are axon guidance proteins during nervous system development. Their expression pattern and function outside the nervous system are unknown. Neuropilin 1 and 2 (NP-1, NP-2) are natural ligands for semaphorins 3A and 3F, respectively. NP-1 is also a co-receptor for vascular endothelial growth factor (VEGF) required for normal vascular development. We showed that VEGF is a direct chemoattractant for glomerular endothelial cells towards developing nephrons. To examine whether semaphorins could modulate VEGF endothelial cell guidance cues in the developing kidney, we studied the expression of semaphorin 3A and semaphorin 3F and their receptors NP-1 and NP-2 in the kidney during ontogeny using Northern blot analysis, in situ hybridization, Western blot analysis and immunohistochemistry. All four genes are developmentally regulated, with abundant expression during organogenesis and downregulation in the adult kidney. Semaphorin 3A and 3F are expressed by podocytes and tubules whereas their receptors NP-1 and NP-2 are localized to endothelial cells. In vitro, renal tubular epithelial cell lines (tsMPT, IRPT and MDCK) and glomerular endothelial cells express both semaphorins and their receptors, suggesting the presence of an autocrine system. The distribution of the receptors NP-1 and NP-2 in endothelial cells and developing vessels is complementary to that of the ligands in adjacent epithelial cells during kidney development. The sum of the guidance cues provided by VEGF and semaphorins 3A and 3F may be important determinants of the pattern of endothelial cell migration during kidney morphogenesis.     

Teneurins: a novel family of neuronal cell surface proteins in vertebrates, homologous to the Drosophila pair-rule gene product Ten-m

We have characterized chicken teneurin-1 and teneurin-2, two homologues of the Drosophila pair-rule gene product Ten-m and Drosophila Ten-a. The high degree of conservation between the vertebrate and invertebrate proteins suggests that these belong to a novel family. We propose to name the vertebrate members of this family teneurins, because of their predominant expression in the nervous system. The expression of teneurin-1 and -2 was investigated by in situ hybridization. We show that teneurin-1 and -2 are expressed by distinct populations of neurons during the time of axonal growth. The most prominent site of expression of chicken teneurins is the developing visual system. Recombinant teneurin-2 was expressed to assay its molecular and functional properties. We show that it is a type II transmembrane protein, which can be released from the cell surface by proteolytic cleavage at a furin site. The expression of teneurin-2 in neuronal cells led to a significant increase in the number of filopodia and to the formation of enlarged growth cones. The expression pattern of teneurins in the developing nervous system and the ability of teneurin-2 to reorganize the cellular morphology indicate that these proteins may have an important function in the formation of neuronal connections.     

Lack of correspondence between mRNA expression for a putative cell death molecule (SGP-2) and neuronal cell death in the central nervous system

Neuronal death during nervous system development, a widely observed phenomenon, occurs through unknown mechanisms. Recent evidence suggests an active, destructive process requiring new gene expression. Sulfated glycoprotein-2 (SGP-2), a secretory product of testicular Sertoli cells has been shown to up-regulate in several nonneural tissues undergoing programmed cell death and in several types of neuronal degeneration. In order to determine if this message up-regulates in neurons undergoing developmentally determined cell death, we have studied the expression of SGP-2 mRNA in the developing and adult rat central nervous system (CNS) with in situ hybridization. We also report on the expression of this message in nonneural tissues from several regions of the developing embryo. The developing and adult rat central nervous system as well as widely varied tissues in the rat embryo express SGP-2 mRNA in a pattern that does not correlate with regions undergoing developmental cell death. In the nervous system, SGP-2 mRNA is expressed in neuronal populations including motor neurons, cortical neurons, and hypothalamic neurons at ages when the period of developmental cell death has passed. In a nonneural tissue (palatal shelve epithelium) for which a developmental cell death period has been described, SGP-2 mRNA was not present in the region where cell death occurs. We conclude that SGP-2 mRNA expression cannot be correlated with programmed cell death in neural or nonneural tissues. The results of this study as well as recently reported SGP-2 homologies indicate a possible role for this protein in secretion and lipid transport.     

Fas and Fas ligand in embryos and adult mice: ligand expression in several immune-privileged tissues and coexpression in adult tissues characterized by apoptotic cell turnover

The cell surface receptor Fas (FasR, Apo-1, CD95) and its ligand (FasL) are mediators of apoptosis that have been shown to be implicated in the peripheral deletion of autoimmune cells, activation-induced T cell death, and one of the two major cytolytic pathways mediated by CD8+ cytolytic T cells. To gain further understanding of the Fas system., we have analyzed Fas and FasL expression during mouse development and in adult tissues. In developing mouse embryos, from 16.5 d onwards, Fas mRNA is detectable in distinct cell types of the developing sinus, thymus, lung, and liver, whereas FasL expression is restricted to submaxillary gland epithelial cells and the developing nervous system. Significant Fas and FasL expression were observed in several nonlymphoid cell types during embryogenesis, and generally Fas and FasL expression were not localized to characteristic sites of programmed cell death. In the adult mouse, RNase protection analysis revealed very wide expression of both Fas and FasL. Several tissues, including the thymus, lung, spleen, small intestine, large intestine, seminal vesicle, prostate, and uterus, clearly coexpress the two genes. Most tissues constitutively coexpressing Fas and FasL in the adult mouse are characterized by apoptotic cell turnover, and many of those expressing FasL are known to be immune privileged. It may be, therefore, that the Fas system is implicated in both the regulation of physiological cell turnover and the protection of particular tissues against potential lymphocyte-mediated damage.