The Experts below are selected from a list of 54843 Experts worldwide ranked by ideXlab platform
Peter Gruss - One of the best experts on this subject based on the ideXlab platform.
-
retinal pigmented epithelium determination requires the redundant activities of pax2 and PAX6
Development, 2003Co-Authors: Nicole Bäumer, Till Marquardt, Anastassia Stoykova, Dieter Treichel, Ruth Asherypadan, Derek Spieler, Peter GrussAbstract:The transcription factors Pax2 and PAX6 are co-expressed in the entire optic vesicle (OV) prior and concomitant with the establishment of distinct neuroretinal, retinal, pigmented-epithelial and optic-stalk progenitor domains, suggesting redundant functions during retinal determination. Pax2; PAX6 compound mutants display a dose-dependent reduction in the expression of the melanocyte determinant Mitf, accompanied by transdifferentiation of retinal pigmented epithelium (RPE) into neuroretina (NR) in Pax2 -/- ; PAX6 +/- embryos, which strongly resembles the phenotype of Mitf -null mutants. In Pax2 -/- ; PAX6 -/- OVs Mitf fails to be expressed and NR markers occupy the area that usually represents the Mitf + RPE domain. Furthermore, both, Pax2 and PAX6 bind to and activate a MITF RPE - promoter element in vitro, whereas prolonged expression of PAX6 in the Pax2-positive optic stalk leads to ectopic Mitf expression and RPE differentiation in vivo. Together, these results demonstrate that the redundant activities of Pax2 and PAX6 direct the determination of RPE, potentially by directly controlling the expression of RPE determinants.
-
ifn γ overexpression within the pancreas is not sufficient to rescue pax4 PAX6 and pdx 1 mutant mice from death
Pancreas, 2000Co-Authors: Michelle Krakowski, Peter Gruss, Luc Stonge, Beatriz Sosapineda, Brian Yeung, Robin Abdelmalik, A Good, Lorraine Mocnik, Nora SarvetnickAbstract:In the presence of interferon-γ (IFN-γ), pancreatic ductal epithelial cells grow continuously, and islets undergo neogenesis. To determine whether these new islets are derived from conventional precursors, we tested whether IFN-γ can complement the loss of transcription factors known to regulate pancreatic development. We analyzed the effect of a transgene on lethality in mice lacking the transcription factors Pax4, PAX6, or Pdx-1, by intercrossing such mice with transgenic mice whose pancreatic cells make IFN-γ (ins-IFN-γ mice). However, IFN-γ expression did not rescue these mice from the lethal mutations, because no homozygous knockout mice carrying the IFN-γ transgene survived, despite the survival of all other hemizygous gene combinations. This outcome demonstrates that the pathway for IFN-γ regeneration requires the participation of Pax4, PAX6, and Pdx-1. We conclude that the striking islet regeneration observed in the ins-IFN-γ NOD strain is regulated by the same transcription factors that control initial pancreatic development.
-
spatial specification of mammalian eye territories by reciprocal transcriptional repression of pax2 and PAX6
Development, 2000Co-Authors: Martin K. Schwarz, Nicole Andrejewski, Birgitta Kammandel, Gilbert Bernier, Francesco Cecconi, Martin Wagner, Peter GrussAbstract:We have studied the molecular basis of the Pax2 and PAX6 function in the establishment of visual system territories. Loss-of-function mutants have revealed crucial roles for Pax2 in the generation of the optic stalk and for PAX6 in the development of the optic cup. Ectopic expression of PAX6 in the optic stalk under control of Pax2 promoter elements resulted in a shift of the optic cup/optic stalk boundary indicated by the presence of retinal pigmented cells on the optic stalk. By studying mouse embryos at early developmental stages we detected an expansion of Pax2 expression domain in the PAX6(−/−) mutant and of PAX6 expression domain in the Pax2(−/−) embryo. These results suggest that the position of the optic cup/optic stalk boundary depends on Pax2 and PAX6 expression, hinting at a possible molecular interaction. Using gel shift experiments, we confirmed the presence of Pax2- and PAX6-binding sites on the retina enhancer of the PAX6 gene and on the Pax2 upstream control region, respectively. Co-transfection experiments revealed a reciprocal inhibition of Pax2 promoter/enhancer activity by PAX6 protein and vice versa. Based on our findings, we propose a model for Pax gene regulation that establishes the proper spatial regionalization of the mammalian visual system.
-
Pax genes and the differentiation of hormone-producing endocrine cells in the pancreas
Mechanisms of Development, 2000Co-Authors: Cord E. Dohrmann, Peter Gruss, Lydia LemaireAbstract:Despite the pivotal role of the pancreas in hormonally-regulated pathways in the body, e.g. glucose homeostasis, the genetic mechanisms defining it have for many years remained largely enigmatic. After years out of the spotlight, pancreas development has once again come to centre stage. To a large extent, this is due to recent advances made through the detailed analysis of transgenic mice which have been engineered to carry mutations in specific developmental control genes. This review specifically focuses on the specification of the endocrine pancreas lineage and in particular on the role of the developmental control genes Pax4 and PAX6 in the generation of specific endocrine cell types. The comparison of various phenotypes of different mouse mutants affecting endocrine development supports a model in which Pax4 and PAX6 are required for the differentiation of certain endocrine cell lineages and implies a potential for acting at different levels of endocrine development.
-
pax2 5 and PAX6 subdivide the early neural tube into three domains
Mechanisms of Development, 1999Co-Authors: Martin K. Schwarz, Gonzalo Alvarezbolado, Gregory R. Dressler, Meinrad Busslinger, Pavel Urbánek, Peter GrussAbstract:The nested expression patterns of the paired-box containing transcription factors Pax2/5 and PAX6 demarcate the midbrain and forebrain primordium at the neural plate stage. We demonstrate that, in Pax2/5 deficient mice, the mesencephalon/metencephalon primordium is completely missing, resulting in a fusion of the forebrain to the hindbrain. Morphologically, in the alar plate the deletion is characterized by the substitution of the tectum (dorsal midbrain) and cerebellum (dorsal metencephalon) by the caudal diencephalon and in the basal plate by the replacement of the midbrain tegmentum by the ventral metencephalon (pons). Molecularly, the loss of the tectum is demonstrated by an expanded expression of PAX6, (the molecular determinant of posterior commissure), and a rostral shift of the territory of expression of Gbx2 and Otp (markers for the pons), towards the caudal diencephalon. Our results suggest that an intact territory of expression of Pax2/5 in the neural plate, nested between the rostral and caudal territories of expression of PAX6, is necessary for defining the midbrain vesicle.
Meinrad Busslinger - One of the best experts on this subject based on the ideXlab platform.
-
nephric lineage specification by pax2 and pax8
Genes & Development, 2002Co-Authors: Maxime Bouchard, Abdallah Souabni, Markus Mandler, Annette Neubuser, Meinrad BusslingerAbstract:The mammalian kidney develops in three successive steps from the initial pronephros via the mesonephros to the adult metanephros. Although the nephric lineage is specified during pronephros induction, no single regulator, including the transcription factor Pax2 or Pax8, has yet been identified to control this initial phase of kidney development. In this paper, we demonstrate that mouse embryos lacking both Pax2 and Pax8 are unable to form the pronephros or any later nephric structures. In these double-mutant embryos, the intermediate mesoderm does not undergo the mesenchymal-epithelial transitions required for nephric duct formation, fails to initiate the kidney-specific expression of Lim1 and c-Ret, and is lost by apoptosis 1 d after failed pronephric induction. Conversely, retroviral misexpression of Pax2 was sufficient to induce ectopic nephric structures in the intermediate mesoderm and genital ridge of chick embryos. Together, these data identify Pax2 and Pax8 as critical regulators that specify the nephric lineage.
-
functional equivalence of the transcription factors pax2 and pax5 in mouse development
Development, 2000Co-Authors: Maxime Bouchard, Peter Pfeffer, Meinrad BusslingerAbstract:Pax2 and Pax5 arose by gene duplication at the onset of vertebrate evolution and have since diverged in their developmental expression patterns. They are expressed in different organs of the mouse embryo except for their coexpression at the midbrain-hindbrain boundary (MHB), which functions as an organizing center to control midbrain and cerebellum development. During MHB development, Pax2 expression is initiated prior to Pax5 transcription, and Pax2(−/−) embryos fail to generate the posterior midbrain and cerebellum, whereas Pax5(−/−) mice exhibit only minor patterning defects in the same brain regions. To investigate whether these contrasting phenotypes are caused by differences in the temporal expression or biochemical activity of these two transcription factors, we have generated a knock-in (ki) mouse, which expresses a Pax5 minigene under the control of the Pax2 locus. Midbrain and cerebellum development was entirely rescued in Pax2(5ki/5ki) embryos. Pax5 could furthermore completely substitute for the Pax2 function during morphogenesis of the inner ear and genital tracts, despite the fact that the Pax5 transcript of the Pax2(5ki)allele was expressed only at a fivefold lower level than the wild-type Pax2 mRNA. As a consequence, the Pax2(5ki)allele was able to rescue most but not all Pax2 mutant defects in the developing eye and kidney, both of which are known to be highly sensitive to Pax2 protein dosage. Together these data demonstrate that the transcription factors Pax2 and Pax5 have maintained equivalent biochemical functions since their divergence early in vertebrate evolution.
-
pax2 and homeodomain proteins cooperatively regulate a 435 bp enhancer of the mouse pax5 gene at the midbrain hindbrain boundary
Development, 2000Co-Authors: Peter L Pfeffer, Maxime Bouchard, Meinrad BusslingerAbstract:Pax and homeodomain transcription factors are essential for the formation of an organizing center at the midbrain-hindbrain boundary (mhb) which controls the genesis of the midbrain and cerebellum in the vertebrate embryo. Pax2 and Pax5 are sequentially activated in this brain region, with Pax2 expression preceding that of Pax5. Using a transgenic reporter assay, we have now identified a conserved 435 bp enhancer in the 5′ flanking region of mammalian Pax5 genes which directs lacZ expression in the correct temporal and spatial pattern at the mhb. This minimal enhancer is composed of two distinct elements, as shown by protein-binding assays with mhb-specific extracts. The proximal element contains overlapping consensus binding sites for members of the Pax2/5/8 and POU protein families, whereas a distal element is bound by homeodomain and zinc finger transcription factors. Expression analysis of transgenes carrying specific mutations in these recognition motifs identified the Pax- and homeodomain-binding sites as functional elements which cooperatively control the activity of the mhb enhancer. lacZ genes under the control of either the minimal enhancer or the endogenous Pax5 locus were normally expressed at the mhb in Pax5 mutant embryos, indicating that this enhancer does not depend on autoregulation by Pax5. In Pax2 mutant embryos, expression of the endogenous Pax5 gene was, however, delayed and severely reduced in lateral aspects of the neural plate which, on neural tube closure, becomes the dorsal mhb region. This cross-regulation by Pax2 is mediated by the Pax-binding site of the minimal enhancer which, upon specific mutation, resulted in severely reduced transgene expression in the dorsal part of the mhb. Together these data indicate that Pax2 and homeodomain proteins directly bind to and cooperatively regulate the mhb enhancer of Pax5.
-
pax2 5 and PAX6 subdivide the early neural tube into three domains
Mechanisms of Development, 1999Co-Authors: Martin K. Schwarz, Gonzalo Alvarezbolado, Gregory R. Dressler, Meinrad Busslinger, Pavel Urbánek, Peter GrussAbstract:The nested expression patterns of the paired-box containing transcription factors Pax2/5 and PAX6 demarcate the midbrain and forebrain primordium at the neural plate stage. We demonstrate that, in Pax2/5 deficient mice, the mesencephalon/metencephalon primordium is completely missing, resulting in a fusion of the forebrain to the hindbrain. Morphologically, in the alar plate the deletion is characterized by the substitution of the tectum (dorsal midbrain) and cerebellum (dorsal metencephalon) by the caudal diencephalon and in the basal plate by the replacement of the midbrain tegmentum by the ventral metencephalon (pons). Molecularly, the loss of the tectum is demonstrated by an expanded expression of PAX6, (the molecular determinant of posterior commissure), and a rostral shift of the territory of expression of Gbx2 and Otp (markers for the pons), towards the caudal diencephalon. Our results suggest that an intact territory of expression of Pax2/5 in the neural plate, nested between the rostral and caudal territories of expression of PAX6, is necessary for defining the midbrain vesicle.
-
characterization of three novel members of the zebrafish pax2 5 8 family dependency of pax5 and pax8 expression on the pax2 1 noi function
Development, 1998Co-Authors: Peter Pfeffer, Thomas Gerster, Michael Brand, Meinrad BusslingerAbstract:The mammalian Pax2, Pax5 and Pax8 genes code for highly related transcription factors, which play important roles in embryonic development and organogenesis. Here we report the characterization of all members of the zebrafish Pax2/5/8 family. These genes have arisen by duplications before or at the onset of vertebrate evolution. Due to an additional genome amplification in the fish lineage, the zebrafish contains two Pax2 genes, the previously known Pax[b] gene (here renamed as Pax2.1) and a novel Pax2.2 gene. The zebrafish Pax2.1 gene most closely resembles the mammalian Pax2 gene in its expression pattern, as it is transcribed first in the midbrain-hindbrain boundary region, then in the optic stalk, otic system, pronephros and nephric ducts, and lastly in specific interneurons of the hindbrain and spinal cord. Pax2.2 differs from Pax2.1 by the absence of expression in the nephric system and by a delayed onset of transcription in other Pax2.1 expession domains. Pax8 is also expressed in the same domains as Pax2.1, but its transcription is already initiated during gastrulation in the primordia of the otic placode and pronephric anlage, thus identifying Pax8 as the earliest developmental marker of these structures. The zebrafish Pax5 gene, in contrast to its mouse orthologue, is transcribed in the otic system in addition to its prominent expression at the midbrain-hindbrain boundary. The no isthmus (noi) mutation is known to inactivate the Pax2.1 gene, thereby affecting the development of the midbrain-hindbrain boundary region, pronephric system, optic stalk and otic region. Although the different members of the Pax2/5/8 family may potentially compensate for the loss of Pax2.1 function, we demonstrate here that only the expression of the Pax2.2 gene remains unaffected in noi mutant embryos. The expression of Pax5 and Pax8 is either not initiated at the midbrain-hindbrain boundary or is later not maintained in other expression domains. Consequently, the noi mutation of zebrafish is equivalent to combined inactivation of the mouse Pax2 and Pax5 genes with regard to the loss of midbrain-hindbrain boundary development.
Nerea Moreno - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal patterns of pax3 PAX6 and pax7 expression in the developing brain of a urodele amphibian pleurodeles waltl
The Journal of Comparative Neurology, 2013Co-Authors: Alberto Joven, Ruth Morona, Agustín González, Nerea MorenoAbstract:The onset and developmental dynamics of Pax3, PAX6, and Pax7 expressions were analyzed by immunohistochemical techniques in the central nervous system (CNS) of embryos, larvae, and recently metamorphosed juveniles of the urodele amphibian Pleurodeles waltl. During the embryonic period, the Pax proteins start being detectable in neuroepithelial domains. Subsequently, they become restricted to subsets of cells in distinct brain regions, maintaining different degrees of expression in late larvae and juvenile brains. Specifically, PAX6 is broadly expressed all along the urodele CNS (olfactory bulbs, pallium, basal ganglia, diencephalon, mesencephalic tegmentum, rhombencephalon, and spinal cord) and the developing olfactory organ and retina. Pax3 and Pax7 are excluded from the rostral forebrain and were usually observed in overlapping regions during embryonic development, whereas Pax3 expression is highly downregulated as development proceeds. Thus, Pax3 is restricted to the roof plate of prosomere 2, pretectum, optic tectum, rhombencephalon, and spinal cord. Comparatively, Pax7 was more conspicuous in all these regions. Pax7 cells were also found in the paraphysis, intermediate lobe of the hypophysis, and basal plate of prosomere 3. Our data show that the expression patterns of the three Pax genes studied are overall evolutionarily conserved, and therefore could unequivocally be used to identify subdivisions in the urodele brain similar to other vertebrates, which are not clearly discernable with classical techniques. In addition, the spatiotemporal sequences of expression provide indirect evidence of putative migratory routes across neuromeric limits and the alar-basal boundary.
-
expression patterns of PAX6 and pax7 in the adult brain of a urodele amphibian pleurodeles waltl
The Journal of Comparative Neurology, 2013Co-Authors: Alberto Joven, Nerea MorenoAbstract:Expression patterns of PAX6, Pax7, and, to a lesser extent, Pax3 genes were analyzed by a combination of immunohistochemical techniques in the central nervous system of adult specimens of the urodele amphibian Pleurodeles waltl. Only PAX6 was found in the telencephalon, specifically the olfactory bulbs, striatum, septum, and lateral and central parts of the amygdala. In the diencephalon, PAX6 and Pax7 were distinct in the alar and basal parts, respectively, of prosomere 3. The distribution of PAX6, Pax7, and Pax3 cells correlated with the three pretectal domains. Pax7 specifically labeled cells in the dorsal mesencephalon, mainly in the optic tectum, and PAX6 cells were the only cells found in the tegmentum. Large populations of Pax7 cells occupied the rostral rhombencephalon, along with lower numbers of PAX6 and Pax3 cells. PAX6 was found in most granule cells of the cerebellum. PAX6 cells also formed a column of scattered neurons in the reticular formation and were found in the octavolateral area. The rhombencephalic ventricular zone of the alar plate expressed Pax7. Dorsal Pax7 cells and ventral PAX6 cells were found along the spinal cord. Our results show that the expression of PAX6 and Pax7 is widely maintained in the brains of adult urodeles, in contrast to the situation in other tetrapods. This discrepancy could be due to the generally pedomorphic features of urodele brains. Although the precise role of these transcription factors in adult brains remains to be determined, our findings support the idea that they may also function in adult urodeles.
Markus Noll - One of the best experts on this subject based on the ideXlab platform.
-
origin of pax and six gene families in sponges single paxb and six1 2 orthologs in chalinula loosanoffi
Developmental Biology, 2010Co-Authors: April Hill, Werner Boll, Carolin Ries, Lisa Warner, Marisa Osswalt, Malcolm Hill, Markus NollAbstract:Pax genes play an important role in networks of transcription factors that determine organogenesis, notably the development of sensory organs. Other members of this regulatory network include transcription factors encoded by the Six gene family. Sponges lack organs and a nervous system, possibly because they have not evolved a Pax/Six network. Here we show that the demosponge Chalinula loosanoffi encodes only one Pax and one Six gene, representatives of the PaxB and Six1/2 subfamilies. Analysis of their temporal transcription patterns during development shows no correlation of their mRNA levels while their spatial patterns show some overlap of expression in adult tissue, although cellular resolution was not achieved. These results do not suggest that these genes form a major network in this basal phylum, although its existence in a minor fraction of cells is not excluded. We further show that sponge PaxB can substitute for some of the Pax2, but not of the PAX6 functions in Drosophila. Finally, we have analyzed the phylogeny of Pax and Six genes and have derived a model of the evolution of the Pax gene subfamilies in metazoans. It illustrates a diversification of Pax genes into subfamilies mostly in triploblasts before the protostome-deuterostome split, whereas few subfamilies were lost in various phyla after the Cambrian explosion.
-
role of pax genes in eye evolution a cnidarian paxb gene uniting pax2 and PAX6 functions
Developmental Cell, 2003Co-Authors: Zbynek Kozmik, Michael Daube, Erich Frei, Markus Noll, Barbara Norman, Larry J Dishaw, Joram PiatigorskyAbstract:Abstract PaxB from Tripedalia cystophora , a cubomedusan jellyfish possessing complex eyes (ocelli), was characterized. PaxB , the only Pax gene found in this cnidarian, is expressed in the larva, retina, lens, and statocyst. PaxB contains a Pax2/5/8-type paired domain and octapeptide, but a PAX6 prd -type homeodomain. Pax2/5/8-like properties of PaxB include a DNA binding specificity of the paired domain, activation and inhibitory domains, and the ability to rescue spa pol , a Drosophila Pax2 eye mutant. Like PAX6, PaxB activates jellyfish crystallin and Drosophila rhodopsin rh6 promoters and induces small ectopic eyes in Drosophila . PAX6 has been considered a "master" control gene for eye development. Our data suggest that the ancestor of jellyfish PaxB, a PaxB-like protein, was the primordial Pax protein in eye evolution and that PAX6-like genes evolved in triploblasts after separation from Cnidaria, raising the possibility that cnidarian and sophisticated triploblastic eyes arose independently.
-
the pax2 homolog sparkling is required for development of cone and pigment cells in the drosophila eye
Genes & Development, 1997Co-Authors: Weimin Fu, Markus NollAbstract:The Drosophila compound eye is a hexagonal array of ∼750 facets or ommatidia, each of which consists of eight photoreceptor cells (R1–R8), four non-neuronal cone cells, three types of pigment cells, and bristle cells arranged in a stereotyped pattern (for review, see Wolff and Ready 1993). The fate of cells in the eye disc is determined during the progressive assembly of individual ommatidia, which is initiated in the morphogenetic furrow sweeping from posterior to anterior across the eye disc during the third larval instar and early pupal stage. Undifferentiated cells are recruited in a fixed sequence to adopt a particular developmental fate based on temporally and spatially restricted signals from previously recruited neighboring cells (for reviews, see Dickson and Hafen 1993; Zipursky and Rubin 1994). In late third instar larvae and early pupae, after the assembly of the eight photoreceptor cells, the four cone cells are recruited into each growing ommatidium. In early pupae, anterior and posterior cone cells induce their neighboring undifferentiated cells to become primary pigment cells (Cagan and Ready 1989). Subsequently, secondary and tertiary pigment cells are incorporated into each ommatidium, followed by elimination of all surplus cells through programmed cell death (Wolff and Ready 1993). Incorrect determination of these cell fates disrupts the ommatidial assembly, leading to a rough appearance of the adult eye as a consequence of irregularly spaced ommatidia. The retinal precursor cells are recruited by signals that emanate from already differentiating ommatidial cells and that activate the Ras signaling pathway (for review and model, see Freeman 1997). It appears that these signals play a permissive rather than an instructive role (Dickson et al. 1992): They trigger the differentiation of recruited cells in a time-dependent manner as cell fate hinges critically on the specific set of susceptible transcription factors present, whose activity states are modified by selective phosphorylation in response to the signal (Freeman 1997). As a result, these transcription factors activate genes, some of which also encode transcription factors that determine the next steps of a cell’s developmental pathway. Therefore, it is important to identify transcription factors that are expressed differentially in ommatidial cells. While a number of such factors have been characterized to be essential for the correct determination of photoreceptors (for review, see Dickson 1995), relatively few genes are known that encode transcription factors required for the specification of the subsequently recruited cone and pigment cells. Two genes encoding paired-domain transcription factors, Pax2 and PAX6, have been shown to play crucial roles in vertebrate eye development (for review, see Macdonald and Wilson 1996). Homozygous Sey mice, which are deficient for PAX6 activity, develop no eyes because they fail to initiate retinal development. In Pax2 null mutant mice, no glial cells develop in the optic nerve, and the optic chiasma fails to form as all retinal axons project ipsilaterally, which indicates that Pax2 is required for proper guidance of the retinal axons along the optic stalk and across the ventral diencephalon (Torres et al. 1996). In addition, the optic fissure fails to close in these mice, which produces optic nerve coloboma (Torres et al. 1996). In agreement with the mutant phenotypes, PAX6 is expressed in the optic cup, whereas Pax2 expression is restricted to the optic stalk epithelium from which all glial cells of the optic nerve develop. Thus, in wild-type eyes PAX6 and Pax2 expression is mutually exclusive, which results in a sharp boundary between eye and optic stalk, whereas in the absence of Pax2, PAX6 expression extends from the pigmented retina into the optic stalk epithelium, causing it to differentiate into pigmented retina instead of glial cells (Torres et al. 1996). Although PAX6 plays an essential role in the initiation of eye development in Drosophila (Quiring et al. 1994; Halder et al. 1995a) and probably all metazoa (Halder et al. 1995b), as yet no Pax2 homolog has been identified in invertebrates (Macdonald and Wilson 1996). Because evolution tends to conserve networks of functionally related genes (Noll 1993), it was logical to postulate that, in addition to the PAX6 homolog eyeless (ey) (Quiring et al. 1994), a homolog of the Pax2, Pax5, Pax8 subgroup existed in Drosophila and played a conserved role in eye development. Indeed, as we report here and show by isolation and molecular characterization, the paired-box gene sparkling (spa) is the Drosophila homolog of the mammalian Pax2 gene. In addition to its structural conservation, spa appears to be conserved functionally in eye development. It is required for proper specification and differentiation of cone and primary pigment cells. Spa may partly exert its function through the activation of cut in cone cells and of both Bar genes in primary pigment cells.
-
the pax2 homolog sparkling is required for development of cone and pigment cells in the drosophila eye
Genes & Development, 1997Co-Authors: Markus NollAbstract:A new Drosophila Pax gene, sparkling (spa), implicated in eye development, was isolated and shown to encode the homolog of the vertebrate Pax2, Pax5, and Pax8 proteins. It is expressed in the embryonic nervous system and in cone, primary pigment, and bristle cells of larval and pupal eye discs. In spa(pol) mutants, a deletion of an enhancer abolishes Spa expression in cone and primary pigment cells and results in a severely disturbed development of non-neuronal ommatidial cells. Spa expression is further required for activation of cut in cone cells and of the Bar locus in primary pigment cells. We suggest close functional analogies between Spa and Pax2 in the development of the insect and vertebrate eye.
Alberto Joven - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal patterns of pax3 PAX6 and pax7 expression in the developing brain of a urodele amphibian pleurodeles waltl
The Journal of Comparative Neurology, 2013Co-Authors: Alberto Joven, Ruth Morona, Agustín González, Nerea MorenoAbstract:The onset and developmental dynamics of Pax3, PAX6, and Pax7 expressions were analyzed by immunohistochemical techniques in the central nervous system (CNS) of embryos, larvae, and recently metamorphosed juveniles of the urodele amphibian Pleurodeles waltl. During the embryonic period, the Pax proteins start being detectable in neuroepithelial domains. Subsequently, they become restricted to subsets of cells in distinct brain regions, maintaining different degrees of expression in late larvae and juvenile brains. Specifically, PAX6 is broadly expressed all along the urodele CNS (olfactory bulbs, pallium, basal ganglia, diencephalon, mesencephalic tegmentum, rhombencephalon, and spinal cord) and the developing olfactory organ and retina. Pax3 and Pax7 are excluded from the rostral forebrain and were usually observed in overlapping regions during embryonic development, whereas Pax3 expression is highly downregulated as development proceeds. Thus, Pax3 is restricted to the roof plate of prosomere 2, pretectum, optic tectum, rhombencephalon, and spinal cord. Comparatively, Pax7 was more conspicuous in all these regions. Pax7 cells were also found in the paraphysis, intermediate lobe of the hypophysis, and basal plate of prosomere 3. Our data show that the expression patterns of the three Pax genes studied are overall evolutionarily conserved, and therefore could unequivocally be used to identify subdivisions in the urodele brain similar to other vertebrates, which are not clearly discernable with classical techniques. In addition, the spatiotemporal sequences of expression provide indirect evidence of putative migratory routes across neuromeric limits and the alar-basal boundary.
-
expression patterns of PAX6 and pax7 in the adult brain of a urodele amphibian pleurodeles waltl
The Journal of Comparative Neurology, 2013Co-Authors: Alberto Joven, Nerea MorenoAbstract:Expression patterns of PAX6, Pax7, and, to a lesser extent, Pax3 genes were analyzed by a combination of immunohistochemical techniques in the central nervous system of adult specimens of the urodele amphibian Pleurodeles waltl. Only PAX6 was found in the telencephalon, specifically the olfactory bulbs, striatum, septum, and lateral and central parts of the amygdala. In the diencephalon, PAX6 and Pax7 were distinct in the alar and basal parts, respectively, of prosomere 3. The distribution of PAX6, Pax7, and Pax3 cells correlated with the three pretectal domains. Pax7 specifically labeled cells in the dorsal mesencephalon, mainly in the optic tectum, and PAX6 cells were the only cells found in the tegmentum. Large populations of Pax7 cells occupied the rostral rhombencephalon, along with lower numbers of PAX6 and Pax3 cells. PAX6 was found in most granule cells of the cerebellum. PAX6 cells also formed a column of scattered neurons in the reticular formation and were found in the octavolateral area. The rhombencephalic ventricular zone of the alar plate expressed Pax7. Dorsal Pax7 cells and ventral PAX6 cells were found along the spinal cord. Our results show that the expression of PAX6 and Pax7 is widely maintained in the brains of adult urodeles, in contrast to the situation in other tetrapods. This discrepancy could be due to the generally pedomorphic features of urodele brains. Although the precise role of these transcription factors in adult brains remains to be determined, our findings support the idea that they may also function in adult urodeles.