Worm Breeder's Gazette 12(1): 31 (September 1, 1991)

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.

Molecular analysis of the dosage compensation gene dpy-27

Pao-Tien Chuang, David Hsu, Barbara Meyer

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Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720

C. elegans compensates for the difference in X chromosome dose between males and hermaphrodites by equalizing X-linked transcript levels between the sexes. The genes dpy-26 , dpy-27 and dpy-28 are essential components of this dosage compensation process in XX animals. Mutations in any of these genes cause elevated X-linked transcript levels in XX animals and an incompletely penetrant maternal-effect XX-specific lethality. While XO dpy animals are fully viable, wild-type males, XX dpy animals that escape the lethality are Dpy and Egl. Genetic analysis of these genes suggests that they act together to regulate X chromosome expression. However, the mechanism by which they achieve this regulation is unknown.

In order to understand the mechanism of dosage compensation, we have undertaken a molecular approach to study the function of dpy-27 . dpy-27 maps within the 3.5 map unit interval between the two cloned genes unc-93 and ced-4 .These two endpoints define a region of approximately 800 kb on the contig that should contain the dpy-27 locus. Using RFLP's between N2 and AB2 (Adelaide, Australia), we mapped dpy-27 between the cosmids C14B1 and C36E8 .Further localization of dpy-27 came from the finding that pat-3 ,recently shown to reside on cosmid ZK1058 ,maps very close to, or to the right of dpy-27 (S. Gettner, J. Plenefisch, personal communications). With this combined information, we attempted to rescue the dpy-27 maternal-effect lethal phenotype by germline transformation using cosmids from the region. Pools of cosmids were coinjected with the dominant rol-6 ( pRF4 )marker into dpy-27 ( y57 )animals. The F1 roller progeny were scored for rescue of the Dpy, Egl, PvuI phenotypes characteristic of survivors of the dpy-27 maternal-effect lethality. Once rescue was obtained, we localized the rescuing activity to cosmid C17A5 .Rescued animals range in phenotype from wild-type length to slightly Dpy, Egl and PvuI. This range of phenotypes occurs in both F1 rescued animals and in transmitting lines carrying the extrachromosomal array. Preliminary results indicate that a 14 kb subclone of C17A5 also contains rescuing activity.

We are currently in the process of defining the minimal region required for rescue, searching for allele-specific polymorphisms, and determining the transcripts located in the rescuing region.

[See Figure 1]

Figure 1