Mutation of the Zebrafish glass onion Locus Causes Early Cell-Nonautonomous Loss of Neuroepithelial Integrity Followed by Severe Neuronal Patterning Defects in the Retina

Abstract

Mutation of the glass onion locus causes drastic neuronal patterning defects in the zebrafish retina and brain. The precise stratified appearance of the wild-type retina is absent in the mutants. The glass onion phenotype is first visible shortly after the formation of optic primordia and is characterized by the rounding of cells and disruption of the ventricular surface in the eye and brain neuroepithelia. With exception of the dorsal- and ventral-most regions of the brain, neuroepithelial cells lose their integrity and begin to distribute ectopically. At later stages, the laminar patterning of retinal neurons is severely disrupted. Despite the lack of lamination, individual retinal cell classes differentiate in the glass onion retina. Mosaic analysis reveals that the glass onion mutation acts cell nonautonomously within the retina and brain, as neuroepithelial cell morphology and polarity in these tissues are normal when mutant cells develop in wild-type hosts. We conclude that the glass onion mutation affects cell-cell signaling event(s) involved in the maintenance of the neuroepithelial cell layer shortly after its formation. The disruption of neuroepithelial integrity may be the cause of the neuronal patterning defects following neurogenesis. In addition, the expression of the glass onion phenotype in a subset of neuroepithelial cells as well as its onset following the initial formation of the neuroepithelial sheets indicate the presence of genetically distinct temporal and spatial subdivisions in the development of this histologically uniform tissue.

Zebrafish protocadherin 10 is involved in paraxial mesoderm development and somitogenesis

“…Mice lacking cdh2 had small, irregular, and less-cohesive somites (Radice et al, 1997). A zebrafish cdh2 mutant, glass onion, showed disorganized somite boundaries (Pujic and Malicki, 2001) as well as neural and retinal malformations, although another cdh2 mutant, parachute, had no apparent somite defects (Lele et al, 2002).…”

Analysis of the retina in the zebrafish model

“…mRNA Probes-In situ hybridization with most RNA probes works very well on whole embryos (Oxtoby and Jowett, 1993). Following hybridization, embryos are gradually dehydrated in a series of ethanol solutions of increasing concentration, and embedded in plastic as described above (Pujic and Malicki, 2001). An additional fixation step prior to dehydration reduces the leaching of in situ signal (Westerfield, 2000).…”

“…A disadvantage of transgene use in this context is that it takes one generation to in-cross an FP transgene into a mutant line. In summary, mosaic analysis is an important approach that has been widely used to study zebrafish retinal mutants (Avanesov et al, 2005;Cerveny et al, 2010;Doerre and Malicki, 2001;Goldsmith et al, 2003;Jensen et al, 2001;Jing and Malicki, 2009;Krock et al, 2007;Link et al, 2000;Malicki and Driever, 1999;Malicki et al, 2003;Pujic and Malicki, 2001;Wei and Malicki, 2002;Yamaguchi et al, 2010).…”

“…Determination of expression pattern on protein level Pujic and Malicki (2001), Wei and Malicki (2002) In situ hybridization-double labeling Parallel determination of two expression patterns on transcript level Hauptmann and Gerster (1994), Jowett (2001), Jowett and Lettice (1994), Strahle et al (1994) In situ hybridization-frozen sections Determination of expression pattern on transcript level Barthel and Raymond (1993), Hisatomi et al (1996) In situ hybridization-whole mount Determination of expression pattern on transcript level Oxtoby and Jowett (1993), Thisse et al (2004) Gene function analysis Implantation Test of function for a factor (most often diffusible) via the implantation of a bead saturated with this substance Hyatt et al (1996), Martinez-Morales et al (2005) Morpholino knockdown Test of gene function based on antisense inhibition of its activity Eisen and Smith (2008), Nasevicius and Ekker (2000), Tsujikawa and Malicki (2004a) Overexpression (DNA injections) Test of gene function based on enhancement of its activity through DNA injections Koster and Fraser (2001), Mumm et al (2006) Overexpression (light-mediated RNA/DNA uncaging) Identification of gene function through enhancement of its activity in selected tissues at specific developmental stages Ando et al (2001), …”

“…Identification of direct and indirect protein binding partners Omori et al (2008) Chemical screens Screens of small-molecule libraries Identification of chemicals that affect a developmental process Kitambi et al (2008) Genetic screens Behavioral Detection of mutant phenotypes by behavioral tests Muto et al (2005), Neuhauss et al (1999) Histological Detection of mutant phenotypes via histological analysis of sections Mohideen et al (2003) Marker/tracer labeling Detection of mutant phenotypes via staining with antibodies, RNA probes, or lipophilic tracers Baier et al (1996), Guo et al (1999) Morphological Detection of mutant phenotypes by morphological criteria Malicki et al (1996) Transgene guided Detection of mutant phenotypes in transgenic lines expressing fluorescent proteins in specific cell populations Xiao et al (2005) In this Kikuchi et al (1997), , Covance PRB-276P rx1 (zrx1) RNA probe Anterior neural keel, optic primordia (≤11 hpf) Chuang et al (1999), Pujic and Malicki (2001) rx2 (zrx2) RNA probe Anterior neural keel, optic primordia (≤11 hpf) Chuang et al (1999), Pujic and Malicki (2001) rx3 (zrx3) RNA probe Anterior neural plate (≤9 hpf); optic primordia (≤12 hpf) Chuang et al (1999), Pujic and Malicki (2001) six3a (six3) RNA probe Neural keel, optic primordia (≤11 hpf) …”