Worm Breeder's Gazette 14(2): 68 (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||HHMI and Division of Biology, 156-29, California Institute of Technology, Pasadena, CA 91125|
|2||Laboratory of Molecular Biology and Department of Anatomy, University of Wisconsin, Madison, WI 53704|
We have followed the uterine nuclei from the completion of the lineages in early L4 (Kimble and Hirsh, 1979) through the beginning of L4 lethargus. Differentiated uterine cell types have been defined by EM reconstruction (White, Southgate, and Kershaw, WBG 11(3) p.75); they are the toroidal ut cells that make structural epithelium and specialized utse and uv cells that make the connection between the uterus and the vulva. Comparison of Nomarski and EM data enabled us to correlate differentiated fate with lineal position. The 60 uterine cells are produced by the dorsal uterine (DU) and ventral uterine (W) precursor cells. The anchor cell (AC) induces adjacent W granddaughters (which are intermediate precursor cells) to adopt the fate rather than the ground state p (Newman, White, and Sternberg, Development 1995). For convenience, we have assigned names to the DU and W great grandprogeny: Dl-8 (from anterior to posterior) and Vl-12 (see diagram). The cells that contribute to each of the differentiated cell types are as follows: ut toroids Following the final uterine divisions during the beginning of L4, the uterus largely consists of two epithelial rows, ventral and dorsal, consisting of all DU descendants except the most distal and most proximal and all of the p cell progeny. These nuclei do not undergo any appreciable movements during L4. Each ut toroid is formed when the four or six cells at that anterior-posterior position fuse (N.B. double the number shown in the diagram to account for left and right). Thus, for the ut toroids, the lineage puts cells where they are needed. utse The utse (previously called "use") is an H-shaped cell containing 9 nuclei (utse: uterine-seam cell). The two sides of the "H" run along the seam on each side of the animal, attaching the uterus to it. The central portion crosses the animal transversely, passing above the vulva and forming a thin laminar process between the uterus and the vulva. The utse is formed by fusion of four of the six progeny on both sides of the animal and the AC. (7 cells divide along a dorsal-ventral axis; all the dorsal progeny plus the middle ventral ones make utse). Following their fusion, the nuclei migrate (or are squeezed) to the distal lateral corners of the utse. Late in L4, a lateral line slightly ventral to the seam that Ed Hedgecock has previously proposed to represent attachment of the utse to the seam forms with these nuclei at its corners. uv1 The uv1 cells are mononucleate cells that make adherens junctions with the most dorsal vulval cells, vulF and with the utse. These cells are made by the ventral outer 7 progeny. Thus, cells produce both uterine cell types (uv1 and utse) that connect the uterus to the vulva and the AC induces both the vulva and all uterine cells that connect to it. du, uv2, uv3 These are the cells that make uterine epithelium dorsal to the vulva where there is no toroid. The uv2 cells are mononucleate cells that contact the uterine lumen ventrally, and the du cell (containing four nuclei) forms the epithelium dorsal to the lumen. The uv3 cells are just distal to uv2. Surprisingly, all of these cells are made by the most proximal DU progeny, D4 and D5, although they are ventral as well as dorsal. This may compensate for the absence of W-derived cells dorsal to the vulva capable of forming uterine epithelium since, as discussed above, all 7 progeny make the uterine-vulval connection. (A figure accompanies the original article.)