Worm Breeder's Gazette 15(4): 33 (October 1, 1998)
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku Nagoya JAPAN
Transmembrane proteins, such as adhesion molecules, receptors, and channels, are often associated with the actin-filament. The association between the actin-filament and the plasma membrane plays crucial roles in various cellular events, such as cell adhesion, cell motility, and cell shape determination. Neurabin-I and -II are novel actin-filament binding proteins purified from rat brain. Neurabin-I is localized at the synapse in the mature nervous system, and implicated in neurite formation. On the other hand, Neurabin-II is enriched at synapse and cadherin-based cell-cell adhesion sites. We isolated a Neurabin homolog from C. elegans genomic database, and termed it nab-1(Neurabin homolog-1). Similar to rat Neurabins, NAB-1 has one PDZ domain, one protein phosphatase1(PP1)-binding domain, and several domains predicted to form coiled-coil structures(see below). [Figure 1] We created a nab-1::gfp translational fusion construct to investigate the nab-1 expression pattern. The nab-1::gfp was expressed in the hypodermal progenitor cells during gustrulation. GFP-staining persisted in the hypodermal cells through L2. In young adult stage, expression was detected in a pair of the amphid chemosensory neurons. To investigate the role of nab-1, we performed RNA-mediated interference(RNAi) experiment. Most of nab-1(RNAi) worms were embryonic lethal. These lethal embryos arrested before organogenesis. A few embryos survived, and all of them showed dumpy and left-handed roller phenotypes. Some of them also showed the defects in the germ-line formation and vulval formation (such as protreuding-vulva). These data suggest that nab-1 is essential for embryogenesis. The hypodermal cells from embryo to L2 stage do the most active morphogenetic movement in development. One possibility is that NAB-1 may participate in the migration or cell-shape determinmation of hypodermal cells during embryogenesis.