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.

Embryonic Expression of a Nuclear Antigen Immunologically Related to the Drosophila Engrailed Product

Joel H. Rothman

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.