The Caenorhabditis elegans muscle mutants, pat-10 and unc-15, cause abnormal distal tip cell migration
Hiroaki Kagawa, Tomohide Takaya, Bunsho Ito, Daisuke Fujii, Katsuyuki Tamai, Ryota Adachi, Kiyoji Nishiwaki.
Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
The 15th International C. elegans Meeting (Los Angels, USA), 2005/06/27 (Talk).
Abstract
The pat-10(st568) mutant has two mutations in body wall troponin C, CeTnC-1; D64 to N and W153 to stop. Mutated proteins produced in bacteria shows that the D64 site is necessary for Ca2+-dependent conformation change and the C-terminal H-helix is essential for troponin I- and Ca2+-bindings. (J. Cell Biol. 1999, 146: 193-202).We constructed genomic vectors having m1: D64N or m2: W153stop in the CeTnC-1 gene. Mutant analysis of transgenic animals suggests that Pat phenotype comes from m2 mutation. Transgenic animal of m1 was almost similar phenotype to the wild type by young adult stage but showed abnormal phenotype in adult as follows. Structure and pumping of pharyngeal muscle were normal but Pvl (protruding vulva), expanded intestine and weak Unc phenotypes. Interestingly gonad was extended irregular direction. Both of anterior and posterior gonads were extended and migrated abnormal directions. Even U-shaped gonads at young adult detached from body wall muscles and deformed at adult. Locomotion, egg-laying and defecation of the m1 animals were dramatically decreased. These results indicate that Ca2+ binding to site II of CeTnC-1 is necessary to regulate muscle contraction and to keep surrounding cell structure. The mutant animal of paramyosin, unc-15(k178) isolated as a mutant of the distal tip cells migration, had a mutation at the C-terminal hot spot, which is important for the first interaction site of filament assembly. This mutant animal isolated by Tc1 insertion and excision had five base pairs deletion in the unc-15 gene that causes amino acid residue addition including proline residue, which rose to change the direction the helical rod of paramyosin. Other unc-15 mutant animals had also show similar phenotypes of uncoordinated motility and migration defect of the distal tip cells. These results combined together suggest that muscle filament stiffness or normal function is important not only for muscle contraction of body wall muscle but also migration of the distal tip cells. This result will be useful to understand how cell sociology related to cell biology and developmental biology.