Worm Breeder's Gazette 8(2): 23
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.
Mutants of unc-33 (IV) are paralyzed and have axonal abnormalities in many classes of neurons (WBG, Vol. 5., No. 1; Hedgecock, Culotti, Perkins, and Thomson, unpublished). While examining the labial sensilla of unc-33 (e204) by electron microscopy, we discovered that the distal processes of the sensory neurons and the sheath and socket cells have a superabundance of microtubules. Moreover, these microtubules were sometimes larger than normal in diameter (called 'macrotubules') or formed abnormal hooks, doublets, or even triplets. We have not yet examined the proximal region of the afferent processes or any part of the efferent axons for abnormal microtubules. The microtubules in muscle and hypodermal cells appeared normal in number and structure. The normal unc-33 product may be a component of the neuronal cytoskeleton, and, more specifically, a protein that limits the assembly or stability of axonal microtubules. The guidance defects in unc-33 mutants, which include ectopic branching, incorrect turning, and premature termination, may be the consequence of this cytoskeletal defect rather than a direct disruption of surface recognition. The means and standard deviations of the number of microtubules and neurofilaments observed in cross sections of amphidial axons are given below. [see Figure 1]