Table 1.
Cytological distribution of emb-30(tn377ts) embryos
| Parental genotype | Chromatin morphologya | Spindle morphology
|
n | |||
|---|---|---|---|---|---|---|
| Meioticb | Disorganizedc | Multipolard | No staininge | |||
| emb-30(tn377ts) | Condensed DNA | 20% | 25% | 2% | 3% | 175 |
| Less condensed DNA | 1% | 31% | 16% | 3% | 178 | |
| Total | 353 | |||||
| fog-2(q71); emb-30(tn377ts) ♀ × wild-type ♂ | Condensed DNA | 12% | 9% | 0% | 1% | 73 |
| Less condensed DNA | 0% | 53% | 17% | 8% | 264 | |
| Total | 337 | |||||
Embryos were dissected from adult worms 16 h after transfer to 25°C. The cytology of the meiotic spindle and chromatin was analyzed in fixed samples stained with anti-tubulin antibodies and DAPI (see MATERIALS AND METHODS). All meiotic stages were observed in the wild-type control (see RESULTS). In contrast, not all meiotic stages were observed in the one-cell arrested emb-30(tn377ts) embryos. The last stage that appeared normal was meiotic metaphase I.
Chromatin morphology was scored as condensed if the DAPI-staining bivalents appeared compacted, as in the wild type. Other morphologies were scored as less condensed. The less condensed morphology included both subtle deviations from the wild type and gross alterations in which the chromatin had a stringy appearance and was spread out in the center of the cell.
The spindle morphology was scored as meiotic if the acentriolar meiotic spindle had a barrel shape that was within the range of structures visualized in the wild type.
Disorganized spindles included those in which a bipolar structure was still evident and those in which the spindle was a cloud of tubulin surrounding the chromatin.
The multipolar designation was given to spindles in which the tubulin-staining structures were centrosomes with asters. Multipolar spindles were seen irrespective of the genotype of the sperm. The multipolar spindles are inferred to arise from duplication of the sperm centrosome and not polyspermy, because we did not observe more than one major focus of condensed sperm chromatin.
No tubulin staining included cases in which the spindle was likely to have been disassembled or the embryo was not properly permeabilized. In either case, this was a small fraction of the total sample and was unlikely to affect the conclusions drawn.