oko meduzy and related crumbs genes are determinants of apical cell features in the vertebrate embryo.
BACKGROUND
Polarity is an essential attribute of most eukaryotic cells. One of the most prominent features of cell polarity in many tissues is the subdivision of cell membrane into apical and basolateral compartments by a belt of cell junctions. The proper formation of this subdivision is of key importance. In sensory cells, for example, the apical membrane compartment differentiates specialized structures responsible for the detection of visual, auditory, and olfactory stimuli. In other tissues, apical specializations are responsible for the propagation of fluid flow. Despite its importance, the role of genetic determinants of apico-basal polarity in vertebrate embryogenesis remains poorly investigated.


RESULTS
We show that zebrafish oko meduzy (ome) locus encodes a crumbs gene homolog, essential for the proper apico-basal polarity of neural tube epithelia. Two ome paralogs, crb2b and crb3a, promote the formation of apical cell features: photoreceptor inner segments and cilia in renal and auditory systems. The motility of cilia is defective following the impairment of crb2b function. Apical surface defects in ome- and crb2b-deficient animals are associated with profound disorganization of neuronal architecture and with the formation of pronephric cysts, respectively. Unexpectedly, despite differences in their structure and expression patterns, crumbs genes are, at least partially, functionally interchangeable.


CONCLUSIONS
ome and related crumbs genes are necessary for the formation of gross morphological features in several organs, including the CNS and the renal system. On the cellular level, crumbs genes regulate the formation of both ciliary and nonciliary apical membrane compartment.
Omori
Yoshihiro
Y
Department of Ophthalmology, Harvard Medical School, MEEI, R513, 243 Charles Street, Boston, Massachusetts 02114, USA.
Malicki
Jarema
J
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology*; D002923:Cilia / Q000502:physiology / Q000648:ultrastructure; D029721:Drosophila Proteins / Q000235:genetics; D050437:Genes, Developmental; D006198:Hair Cells, Auditory / Q000196:embryology; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D009399:Nephrons / Q000196:embryology; D009419:Nerve Tissue Proteins / Q000502:physiology*; D046569:Neuroepithelial Cells / Q000166:cytology*; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology; D012689:Sequence Homology, Nucleic Acid; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins / Q000502:physiology*
C517151:Crb1 protein, zebrafish; C513141:Crb2a protein, zebrafish; D029721:Drosophila Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D029961:Zebrafish Proteins; C064360:crb protein, Drosophila; C513142:crb2b protein, zebrafish; C513143:crb3a protein, zebrafish