Worm Breeder's Gazette 13(2): 39 (February 1, 1994)
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.
daf-4 encodes a TGFß ( BMP-4 )receptor that is involved in the regulation of dauer development (Estevez et al., Nature 345: 644-649, 1993). Unlike other daf genes, daf-4 also is required for the proper development of male copulatory structures; daf-4 males have abnormal patterns of sensory rays (fusions of rays 4 and 5 and of rays 6 and 7) and short crumpled spicules.
The ray pattern defects result from defects in ray identity specification. In mutant males, rays 5 and 7 express traits characteristic of the wild-type rays 4 and 6, respectively. The spicule defects result from the failure of the proctodeum to elongate during L4 .This may be due to defects in proctodeal cells (B.a(1)/r(appv)) and/or to defects in the spicules retractors (Sulston et al., Dev. Biol . 78: 542-576,1980).
To further characterize the daf-4 requirement for male development, I have determined daf-4 temperature critical periods (tcps) for the rays and spicules. This was accomplished using daf-4 ( m592 )(provided by D. Riddle) which is temperature sensitive for ray and spicule defects.
The daf-4 tcp for ray development is during late L3 .This stage corresponds to the period from the division of the ray precursor cells (Rn cells) to the division of the ray neuroblast (Rn.a) (stages are based primarily on the T-cell lineage and were determined by microscopic observation at 1,000x). This result is consistent with ray identities being determined in the ray neuroblasts.
The daf-4 tcp for spicule development is broader than that observed for ray development (figure 2). The primary effect is during early L4 .This stage immediately follows the completion of both proctodeal (B and F) sex mesoblast (SM1-SM3) cell lineages at the end of L3 ,indicating that daf-4 may be required for the specification of individual muscle or proctodeal cell fates, or to direct the attachment of the spicule retractors to B.a(1)/r(appv.)
In downshifted animals, there also is a slight effect from mid to late L3 . daf-4 may be required for a single function during this time span with defects being partially reversible until L4 .Alternatively, daf-4 may be required for multiple functions with earlier functions being less important than later functions for spicule development.
