Worm Breeder's Gazette 10(3): 158
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.
I'm interested in zygotically expressed genes that control embryogenesis, and may have identified the product of one such gene by staining embryos with a monoclonal antibody that recognizes the Drosophila engrailed (en) protein. Nipam Patel (Corey Goodman's lab) and Kevin Colman (Tom Kornberg's lab) made and characterized this antibody (called 4D9D4), and found that it reacts to antigens in most organisms examined, from brittle stars to vertebrates. This antibody has been shown to react with a 6-7 amino acid epitope residing between the two helices in the homeodomain of en. In insects, the early staining pattern is characteristic of the Drosophila en pattern, lighting up nuclei in the posterior compartment of each segment. 4D9D4 also recognizes antigens in the hindbrain of vertebrates, a repeating pattern in the nervous system of earthworms, and one head segmental ganglion in leeches. I've found that 4D9D4 recognizes an antigen expressed in a subset of nuclei in C. elegans embryos. This antigen is first detectable in a couple of nuclei when the embryos contain fewer than 70 cells. In more advanced embryos, the antibody recognizes two bilateral rows of 10 nuclei that appear to be seam cell nuclei, and lights up all of the hypodermal nuclei by the beginning of morphogenesis, although seam cell nuclei exhibit the most intense signal. The assignment of hypodermal nuclei was confirmed by double- staining with 4D9D4 and Ross Francis' and Bob Waterston's desmosomal antibody MH27. In adults, the hypodermal pattern is not readily apparent, but a number of (as yet unidentified) nuclei stain in the head and pharynx. The 4D9D4 cross-reaction is interesting because of the early onset and nuclear location of the antigen. Moreover, since the en product plays a critical role in fly embryogenesis, it is conceivable that this immunologically related protein is important in regulating early worm development, in which case it would be of interest to identify the gene encoding it. The 4D9D4 antibody may also be useful as an early cell-type specific marker in screens of mutants defective in embryogenesis. I plan to characterize further the expression of the protein(s) recognized by this antibody and perhaps try to isolate it by affinity-chromotography. Thanks to Tom Kornberg who sent 4D9D4 to Peter Lawrence from whom I obtained it.