Worm Breeder's Gazette 16(1): 55 (October 1, 1999)

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.

Characterizing Body Size of TGF-b Mutants

Rafal Tokarz, Cathy Savage-Dunn

Department of Biology, Queens College/CUNY, Flushing NY 11367

We are interested in understanding why TGF-b small mutants have decreased body size. We first characterized the growth rates of all sma mutants. We set up synchronous populations of worms by washing them off the plate and adding decontaminating solution. After spinning, the pellet containing only eggs was put on a plate and placed in the incubator. We then photographed and measured the length of the worms at 24 hour intervals. We did this for N2 and an allele of every TGF-b sma mutant, as well as sma-9, a novel gene we are currently studying, which shows the characteristics of other sma mutants.

The experiment showed that the sma mutants posses a post-embryonic growth defect. They all hatch at about the same size as N2 and then proceed to grow at a reduced rate. Sma-9 was a notable exception, as it possesses an early defect, followed by normal growth at later stages.

We also wanted to see if all or only some cells are smaller in the sma mutants. We used Su93 strain which expresses at sites of MH 27 staining to measure seam cells immediately after division in the L3 stage. It is in the L3 stage that the sma mutants begin to show a distinct size difference as compared to N2. We photographed and measured the length and area of seam cells, the length of the pharynx, and the overall worm length. We did this for the wild type strain as well as the dbl-1 mutant, which is the ligand in the pathway, and sma-9.

Our results showed that the seam cells in the wild type strain are longer than in the sma mutants. The difference in cell length is approximately the same as the difference in the overall body size. The ratio of overall body length and cell length in N2 to sma mutants is approximately 1.2 to 1 at this stage. The area of the cells is also larger in N2. The pharynx length, however, is not significantly bigger in N2 than in the sma mutants. We concluded that some but probably not all cells are smaller in the sma mutants. To address this further we will use mosaic analysis and misexpression of sma genes.