Asymmetric localization of Numb:EGFP in dividing neuroepithelial cells during neurulation in Danio rerio

Institut für Entwicklungsbiologie, Universität zu Köln, 50923 Köln, Germany.
Developmental Dynamics (Impact Factor: 2.38). 04/2006; 235(4):934-48. DOI: 10.1002/dvdy.20699
Source: PubMed


In the neural plate and tube of the zebrafish embryo, cells divide with their mitotic spindles oriented parallel to the plane of the neuroepithelium, whilst in the neural keel and rod, the spindle is oriented perpendicular to it. This change is achieved by a 90 degrees rotation of the mitotic spindle. We cloned zebrafish homologues of the gene for the Drosophila cell fate determinant Numb, and analyzed the localization of EGFP fusion proteins in vivo in dividing neuroepithelial cells during neurulation. Whereas Numb isoform 3 and the related protein Numblike are localized in the cytoplasm, Numb isoform 1 is localized to the cell membrane. Time-lapse analyses showed that Numb 1 is distributed uniformly around the cell cortex in dividing cells during plate and keel stages, but becomes localized at the basolateral membrane of some dividing cells during the transition from neural rod to tube. Using in vitro mutagenesis and Numb:EGFP deletion constructs, we showed that the first 196 amino acids of Numb are sufficient for this localization. Furthermore, we found that an 11-amino acid insertion in the PTB domain is essential for localization to the cortex, whereas amino acids 2-12 mediate the basolateral localization in the neural tube stage.

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Available from: Nico Scheer, Jan 27, 2015
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    • "There are several lines of evidence supporting an evolutionary conservation of Numb function. Vertebrate Numb proteins are asymmetrically distributed in dividing neural progenitors [10,15-18] and can rescue the Numb mutant phenotype in Drosophila[9,10]. Moreover, mammalian Numbs have been demonstrated to inhibit Notch signaling in the developing Drosophila outer optic anlage [19] and chick neuroepithelium [15]. "
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    ABSTRACT: Members of the vertebrate Numb family of cell fate determinants serve multiple functions throughout early embryogenesis, including an essential role in the development of the nervous system. The Numb proteins interact with various partner proteins and correspondingly participate in multiple cellular activities, including inhibition of the Notch pathway. Here, we describe the expression characteristics of Numb and Numblike (NumbL) during Xenopus development and characterize the function of NumbL during primary neurogenesis. NumbL, in contrast to Numb, is expressed in the territories of primary neurogenesis and is positively regulated by the Neurogenin family of proneural transcription factors. Knockdown of NumbL afforded a complete loss of primary neurons and did not lead to an increase in Notch signaling in the open neural plate. Furthermore, we provide evidence that interaction of NumbL with the AP-2 complex is required for NumbL function during primary neurogenesis. We demonstrate an essential role of NumbL during Xenopus primary neurogenesis and provide evidence for a Notch-independent function of NumbL in this context.
    Full-text · Article · Oct 2013 · BMC Developmental Biology
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    • "These diverse splicing patterns dictate important regulatory decisions in many steps of neuronal development. By affecting proteins such as growth factors (e.g., FGF8) (Gemel et al., 1996; Ghosh et al., 1996; Li et al., 2007; MacArthur et al., 1995; Olsen et al., 2006) and cell-adhesion molecules (e.g., DSCAM, NLGNs, and NRXNs) (Nie et al., 2004; Ullrich et al., 1995), alternative splicing shapes processes such as cell-fate determination (via Numb proteins) (Dho et al., 1999; Dho et al., 2006; Reugels et al., 2006), axon guidance (via DSCAM) (Schmucker et al., 2000; Zipursky et al., 2006), and synaptogenesis (Li et al., 2007). In adult neurons, synaptic remodeling or strengthening is regulated by alternative splicing and the relative expression levels of ASVs. "
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    ABSTRACT: Alternative pre-mRNA splicing is a major mechanism by which the proteomic diversity of eukaryotic genomes is amplified. Much akin to neuropsychiatric disorders themselves, alternative splicing events can be influenced by genetic, developmental, and environmental factors. Here, we review the evidence that abnormalities of splicing may contribute to the liability toward these disorders. First, we introduce the phenomenon of alternative splicing and describe the processes involved in its regulation. We then review the evidence for specific splicing abnormalities in a wide range of neuropsychiatric disorders, including psychotic disorders (schizophrenia), affective disorders (bipolar disorder and major depressive disorder), suicide, substance abuse disorders (cocaine abuse and alcoholism), and neurodevelopmental disorders (autism). Next, we provide a theoretical reworking of the concept of "gene-focused" epidemiologic and neurobiologic investigations. Lastly, we suggest potentially fruitful lines for future research that should illuminate the nature, extent, causes, and consequences of alternative splicing abnormalities in neuropsychiatric disorders.
    Full-text · Article · Jun 2011 · American Journal of Medical Genetics Part B Neuropsychiatric Genetics
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    • "Numb and Numblike homologs have been identified and cloned in zebrafish. Numb is ubiquitously expressed during blastula and gastrula stages [13]. Its expression becomes concentrated at the midline at the beginning of somitogenesis and, by the 18-ss, a strong signal is found at the midline from the head to the tail region, and in the retina. "
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    ABSTRACT: Notch signaling is an evolutionarily conserved regulatory circuitry implicated in cell fate determination in various developmental processes including hematopoietic stem cell self-renewal and differentiation of blood lineages. Known endogenous inhibitors of Notch activity are Numb-Nb and Numblike-Nbl, which play partially redundant functions in specifying and maintaining neuronal differentiation. Nb and Nbl are expressed in most tissues including embryonic and adult hematopoietic tissues in mice and humans, suggesting possible roles for these proteins in hematopoiesis. We employed zebrafish to investigate the possible functional role of Numb and Numblike during hematopoiesis, as this system allows a detailed analysis even in embryos with severe defects that would be lethal in other organisms. Here we describe that nb/nbl knockdown results in severe reduction or absence of embryonic erythrocytes in zebrafish. Interestingly, nb/nbl knocked-down embryos present severe downregulation of the erythroid transcription factor gata1. This results in erythroblasts which fail to mature and undergo apoptosis. Our results indicate that Notch activity is increased in embryos injected with nb/nbl morpholino, and we show that inhibition of Notch activation can partially rescue the hematopoietic phenotype. Our results provide the first in vivo evidence of an involvement of Numb and Numblike in zebrafish erythroid differentiation during primitive hematopoiesis. Furthermore, we found that, at least in part, the nb/nbl morphant phenotype is due to enhanced Notch activation within hematopoietic districts, which in turn results in primitive erythroid differentiation defects.
    Full-text · Article · Dec 2010 · PLoS ONE
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