generating Muvs from Muvs


I have mutagenized C. briggsae AF-16 strain using EMS and got Muv worms. Next I picked the Muvs onto separate plates to expand. However there was no Muv worms in F1. Neither were any in F2. I would really appreciate if anyone could tell me the ways by which I could get Muvs from Muvs. Thanks

Also, out of the 8 Muv wells I picked onto, 4 of them are sterile. The rest that did give rise to progeny give normal worms. One possible cause of Muv not appearing in F1 might be that in the original population, there was high incidence of males phenotype (EMSing worms always resulted in Him). So the Muvs might have undergone crossing with abundant males so that F1 are all hets. This would mean that Muv might reappear on F2? But so far, there is no Muv in F2.

You didn’t mention if the non-transmitting Muvs were seen in the F1. Brenner described this phenomenon in C. elegans in his classic 1974 paper (downloadable here: This is what he said on p.75:

In most of the experiments, mutants have come from the clones produced by mutagenized adults. Although the F1 progeny are heterozygous for induced mutations, a detectable fraction are abnormal in appearance or movement. Such variants have been picked with the intention of isolating dominant or semidominant mutants, but in all cases these have produced wild-type progeny or segregated a coincidental recessive mutant with an unrelated phenotype. These animals are likely to be mosaics in which the EMS-induced mutations become fixed after fertilization and then only in cells that produce somatic structures.

This seems a likely explanation for why some of the Muvs didn’t breed true, if you saw them in the F1 generation after mutagenesis.

The sterile Muvs, on the other hand, might be heritable mutants that are also sterile. Another approach might be to do a conditional screen, that is propagate plates containing F2s at 15°C then test at 25°C.

Just some thoughts…

  • MM