Abstract The neurodevelopmentally regulated microRNA miR-137 was strongly implicated as risk locus for schizophrenia in the most recent genome wide association study coordinated by the Psychiatric Genome Consortium (PGC). This molecule is highly conserved in vertebrates enabling the investigation of its function in the developing zebrafish. We utilized this model system to achieve overexpression and suppression of miR-137, both transiently and stably through transgenesis. While miR-137 overexpression was not associated with an observable specific phenotype, downregulation by antisense morpholino and/or transgenic expression of miR-sponge RNA induced significant impairment of both embryonic and larval touch-sensitivity without compromising overall anatomical development. We observed miR-137 expression and activity in sensory neurons including Rohon–Beard neurons and dorsal root ganglia, two neuronal cell types that confer touch-sensitivity in normal zebrafish, suggesting a role of these cell types in the observed phenotype. The lack of obvious anatomical or histological pathology in these cells, however, suggested that subtle axonal network defects or a change in synaptic function and neural connectivity might be responsible for the behavioral phenotype rather than a change in the cellular morphology or neuroanatomy.
Die Expressionsmuster der Homeoboxgene Nkx5-1, Nkx5-2 und des 'paired box' Gens Pax2 sowie des Tyrosinkinase Rezeptorgens sek wurden zu unterschiedlichen Zeitpunkten der Innenohrmorphogenese, wahrend der normalen Entwicklung und unter veranderten in vivo und in vitro Situationen, untersucht. Die Expressionsmuster im sich entwickelnden Innenohr von Wildtyp Embryonen stellen die Basis fur vergleichende Analysen in verschiedenen Innenohrmutanten der Maus dar. Die fidget Maus, eine Gleichgewicht-Mutante, die mit der Transkriptverteilung des Nkx5-1 Gens im vestibularen Apparat korrelierende Innenohrdefekte aufweist, wurde untersucht. Um Hinweise auf externe, die Innenohrentwicklung steuernde Signale, die insbesondere die Aktivitat des Nkx5-1 Gens regulieren, zu erhalten, wurden auch Mutanten, deren Innenohrdefekte auf Hinterhirnmisbildungen zuruckzufuhren sind (splotch, Hoxa-1), analysiert. Es wurde keine Veranderung in der Expression der untersuchten Gene detektiert. Mittels des Expressionsnachweises des Melanoblasten-spezifischen Markergens Trp2 konnte gezeigt werden, das in splotch Mausmutanten keine Melanoblasten aus der Neuralleiste in das Innenohrepithel einwandern. In einem hier optimierten Innenohr in vitro Kultursystem wurden einzelne Schritte der Innenohrmorphogenese nachgestellt und demonstriert, das die in vivo charakterisierten Genexpressionsmuster unter in vitro Bedingungen in Organ- und Organ-ahnlichen Kulturen nachvollziehbar sind. Verschiedene, modifizierende Bedingungen und funktionelle Anwendungen dieses in vitro Modellsystems wurden untersucht und diskutiert.
Correct morphogenesis and differentiation are critical in development and maintenance of the lens, which is a classic model system for epithelial development and disease. Through germline genomic analyses in patients with lens and eye abnormalities, we discovered functional mutations in the Signal Induced Proliferation Associated 1 Like 3 (SIPA1L3) gene, which encodes a previously uncharacterized member of the Signal Induced Proliferation Associated 1 (SIPA1 or SPA1) family, with a role in Rap1 signalling. Patient 1, with a de novo balanced translocation, 46,XY,t(2;19)(q37.3;q13.1), had lens and ocular anterior segment abnormalities. Breakpoint mapping revealed transection of SIPA1L3 at 19q13.1 and reduced SIPA1L3 expression in patient lymphoblasts. SIPA1L3 downregulation in 3D cell culture revealed morphogenetic and cell polarity abnormalities. Decreased expression of Sipa1l3 in zebrafish and mouse caused severe lens and eye abnormalities. Sipa1l3−/− mice showed disrupted epithelial cell organization and polarity and, notably, abnormal epithelial to mesenchymal transition in the lens. Patient 2 with cataracts was heterozygous for a missense variant in SIPA1L3, c.442G>T, p.Asp148Tyr. Examination of the p.Asp148Tyr mutation in an epithelial cell line showed abnormal clustering of actin stress fibres and decreased formation of adherens junctions. Our findings show that abnormalities of SIPA1L3 in human, zebrafish and mouse contribute to lens and eye defects, and we identify a critical role for SIPA1L3 in epithelial cell morphogenesis, polarity, adhesion and cytoskeletal organization.
The original article to which this Erratum refers was published in Developmental Dynamics 237:2195–2208 In the original published version of this article, the Results section contained a numerical error. The sentence reading, “Mapping of the retroviral insertion 3 kb downstream of hoxb4a was described previously (Hadrys et al., 2006).” was incorrect. The correct sentence should read, “Mapping of the retroviral insertion 0.6 kb downstream of hoxb4a was described previously (Hadrys et al., 2006).” The authors regret this error.
The formation of the vascular network requires a tightly controlled balance of pro-angiogenic and stabilizing signals. Perturbation of this balance can result in dysregulated blood vessel morphogenesis and drive pathologies including cancer. Here, we have identified a novel gene, ARHGAP18, as an endogenous negative regulator of angiogenesis, limiting pro-angiogenic signaling and promoting vascular stability. Loss of ARHGAP18 promotes EC hypersprouting during zebrafish and murine retinal vessel development and enhances tumor vascularization and growth. Endogenous ARHGAP18 acts specifically on RhoC and relocalizes to the angiogenic and destabilized EC junctions in a ROCK dependent manner, where it is important in reaffirming stable EC junctions and suppressing tip cell behavior, at least partially through regulation of tip cell genes, Dll4, Flk-1 and Flt-4. These findings highlight ARHGAP18 as a specific RhoGAP to fine tune vascular morphogenesis, limiting tip cell formation and promoting junctional integrity to stabilize the angiogenic architecture.
The inner ear, also called the membranous labyrinth, contains the cochlea, which is responsible for the sense of hearing, and the vestibular apparatus, which is necessary for the sense of balance and gravity. The inner ear arises in the embryo from placodes, which are epithelial thickenings of the cranial ectoderm symmetrically located on either side of hindbrain rhombomeres 5 and 6. Placode formation in mice is first visible at the 12-somite stage and is controlled by surrounding tissues, the paraxial mesoderm and neural ectoderm. Diffusible molecules such as growth factors play an important role in this process. The activity of several genes confers the identity to the placodal cells. Subsequent cellular proliferation processes under influences from the adjacent hindbrain cause the inner ear epithelium to invaginate and form a vesicle called the otocyst. Combinatorial expression of several genes and diffusible factors secreted from the vesicle epithelium and hindbrain control specification of distinct inner ear compartments. Transplantation studies and inner ear in vitro cultures show that each of these compartments is already committed to develop unique inner ear structures. Later developmental periods are principally characterized by intrinsic differentiation processes. In particular, sensory patches differentiate into fully functional sensory epithelia, and the semicircular canals along with the cochlear duct are elaborated and ossified.
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