Zhicen Liu | PubMed Health

PubMed2007

Improved method for visualizing cells revealed dynamic morphological changes of ventral neuroblasts during ventral cleft closure of Caenorhabditis elegans.

The formation of intricate and functional biological structures depends on the dynamic changes of cellular morphology. Confocal laser scanning microscopy (CLSM) is a widely used method to reveal the three-dimensional (3-D) structure of cells during the development of Caenorhabditis elegans (C. elegans) and other model organisms. Improving the efficiency and image quality of CLSM would benefit studies using this method. We found that CED-10::GFP::CED-10, a green fluorescent protein (GFP) marker, is intensely expressed beneath the cell surface, facilitating visualization of cellular morphology in C. elegans embryos. By combining the unique properties of this marker, and with the help of direct 3-D rendering of images obtained by CLSM, we developed a simple but powerful method for investigating cellular morphology in developing embryos. Using this method we, for the first time, document the dynamic changes in the morphology of ventral neuroblasts in vivo during ventral cleft closure.

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PubMed2005

C. elegans PlexinA PLX-1 mediates a cell contact-dependent stop signal in vulval precursor cells.

PLX-1 is a PlexinA transmembrane protein in Caenorhabditis elegans, and the transmembrane-type semaphorin, SMP-1, is a ligand for PLX-1. The SMP-1/PLX-1 system has been shown to be necessary for proper epidermal morphogenesis in the male tail and seam cells. Here, we show that the SMP-1/PLX-1 system also regulates vulval morphogenesis. In plx-1 and smp-1 mutants, hermaphrodites sometimes exhibit a protruding vulva or multiple vulva-like protrusions. Throughout the vulval development of plx-1 and smp-1 mutants, the arrangement of vulval cells is often disrupted. In the initial step of vulval morphogenesis, vulval precursor cells (VPCs) are generated normally but are subsequently arranged abnormally in mutants. Continuous observation revealed that plx-1 VPC fails to terminate longitudinal extension after making contact with neighbor VPCs. The arrangement defects of VPCs in plx-1 and smp-1 mutants are rescued by expressing the respective cDNA in VPCs. plx-1::egfp and smp-1::egfp transgenes are both expressed in all vulval cells, including VPCs, throughout vulval development. We propose that the SMP-1/PLX-1 system is responsible for a cell contact-mediated stop signal for VPC extension. Analyses using cell fate-specific markers showed that the arrangement defects of VPCs also affect cell fate specification and cell lineages, but in a relatively small fraction of plx-1 mutants.

Animals↗