Worm Breeder's Gazette 14(2): 47 (February 1, 1996)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
|1||DNA Research Center, Natl. Inst. Genet., Mishima, Shizuoka-ken 411, Japan and Dept. Biophysics, Kyoto University, Kyoto 606, Japan|
|2||DNA Research Center, Natl. Inst. Genet., Mishima, Shizuoka-ken 411, Japan|
|3||Dept. Bioengineering, Soka Univ., Hachioji, Tokyo 192, Japan|
|4||DNA Research Center, Natl. Inst. Genet., Mishima, Shizuoka-ken 411, Japan|
hch-1 gene is necessary for two quite different developmental processes in C. elegans: hatching and cell migration (Hedgecock et al., Development 100:365-382, 1987). The mutant embryos cannot digest proteins in the eggshell and consequently show delayed hatching. hch-1 mutations also cause the QL neuroblast and its descendants to migrate in a wrong direction (anteriorly instead of posteriorly). Previously we reported the isolation of a hch-1 Tc1-insertion mutation (ut110) and the cloning of hch-1 gene by Tc1 tagging and by transformation rescue experiments (WBG 12(2)p.108, 13(3)p.87). We then isolated hch-1 cDNA by screening embryonic and mixed-stage cDNA libraries (kindly provided by P. Okkema) and sequenced the longest cDNA clone. HCH-1 deduced from this sequence data is an extracellular protein with 605 amino acids. Data base searches revealed HCH-1 is a Zn protease related to the tolloid / BMP-1 family (See Figure). Members of this family are known to play important roles in cell differentiation and morphogenesis, and several members are thought to interact with TGF-b-like growth factors. The EGF domain and CUB domain in those proteins are thought to act in protein-protein interaction. The protease domain seems to process other proteins to regulate their activity. In both amino acid sequence and domain arrangement, HCH-1 resembles sea urchin BP10, SpAN and C. elegans toh-1, toh-2 which were named by C. Savage et al. as a tolloid homolog found in the data of genome sequencing project (WBG 13(4)p.64). We investigated the expression pattern of hch-1 gene in embryos by in situ hybridization. It was expressed in hypodermal cells at early stages of morphogenesis. The transcript was detectable from the time just before elongation (about 350 min after the first cleavage), through the comma stage, and until the 1.5-fold or 2-fold stages (about 430 min to 450 min). The signal is localized first in the dorsal and lateral surface area of the middle and posterior region of the embryos. At later stages (1.5-fold stage), the signal was restricted to lateral surface regions, probably hypodermal seam cells. These hypodermal cells have 2 faces: exterior face and interior face. From exterior face hatching enzymes could be secreted, and from interior face the proteins that control QL migration could be secreted. Our questions are as follows: (1) Is HCH-1 a hatching enzyme? We plan to examine whether the hatching fluid of HCH-1 depleted with anti-HCH-1 antibodies can rescue the delayed hatching phenotype of hch-1 mutant embryos. (2) What is a role of HCH-1 in QL migration? We plan to investigate whether hch-1 acts upstream or downstream to mab-5, which also affects QL migration (Salser & Kenyon, Nature 355:255-258, 1992). We will also check the presence and pattern of hch-1 expression in L1 larvae. It is also intriguing if HCH-1 forms complex with a TGF-b-like protein. (3) Does HCH-1 have other roles in morphogenesis? The dorsal expression of hch-1 gene at early stages of embryogenesis suggests this gene may have a role in morphogenesis like tolloid and BP10, which show a similar dorsal expression pattern in embryos. Functionally redundant genes, if any, may prevent hch-1 mutants to show any obvious phenotype in embryogenesis. If HCH-1 functions through protein-protein interaction, overexpression of a dominant negative hch-1 gene that has a mutation in the protease domain may affect the morphogenesis. Figure. Members of tolloid / BMP-1 family