Aiming to understand the roles and the mechanisms of temporal and spatial dynamics of cellular structure during embryogenesis, we are analyzing early embryonic cell lineages of RNAi-treated embryos.L3-L4 stage worms were placed onto plates containing seeded bacteria expressing dsRNA (provided from J. Ahringer through UK MRC HGMP Resource Centre) and were incubated for 40-48 h at 22C. Then, the worm was bisected and an embryo was obtained just after the sperm entry. Development of the embryo was recorded at 22C by 4D DIC microscope system with 56 different focal planes at a distance of 0.5 m between two focal planes, at intervals of 40 sec for 2 h. The recorded images were processed by our automatic cell lineage acquisition system (Onami et al. 2001; Hamahashi et al. this meeting), which detects nucleus regions in each image, groups regions that represent the same nucleus at each time point, connects those groups that represent the same nucleus in adjacent time points and outputs cell lineage that consists of 3D positions of nucleus at each time point and their lineage from 1 cell stage to 24 cell stage.First, cell lineage was measured for 20 individual wild-type worms. The shape of the resulted lineage was similar to that of Sulston et al.'s. Variation of the lineage among different embryos was rather small, e.g. the standard deviation for cell-cycle length of each cell was less than 6 min (less than 2.5 min in most cases). Thus, we established a standard wild-type cell lineage that consists of the mean and the SD for each cell-cycle length and direction of each cell division.Then, cell lineage of RNAi-treated embryos was measured. Genes on the chromosome I whose RNAi phenotypes were reported as 100% embryonic lethal (Fraser et al. 2000) were chosen as targets. All 18 genes with 3-letter gene name (
dad-1,
dhc-1,
eft-2,
gsk-1,
hlh-2,
hmp-1,
lam-1,
mei-1,
mei-2,
mel-26,
mex-1,
rba-1,
par-6,
pfn-1,
pop-1,
rba-2,
tba-1 and
tba-2) and 15 out of 229 hypothetical genes have been examined. Unexpectedly, more than 25% (5/18) genes did not show 100% embryonic lethality in our experiments. Cell lineage measurement for the remaining genes is in progress. Detailed analysis of measured cell lineages will be presented.