Genetics, Vol 122, 417-428, Copyright © 1989

INVESTIGATIONS

Phenotypic and Molecular Analysis of the facets, a Group of Intronic Mutations at the Notch Locus of Drosophila melanogaster Which Affect Postembryonic Development

K. Markopoulou, W. J. Welshons and S. Artavanis-Tsakonas
Department of Biology, Yale University, New Haven, Connecticut 06511 Present address: Department of Molecular Biology, University of California, Berkeley, California 94720.

The function of the Notch locus of Drosophila melanogaster is essential for normal development both during embryogenesis and during postembryonic stages. In the embryo its function is necessary for the correct segregation of neural from epidermal lineages. During postembryonic stages Notch exhibits pleiotropic effects that are both tissue- and stage-specific. Here, we examine a group of six recessive mutations, the facets (fa, fa(3), fa(g), fa(g-2), fa(fx) and fa(sw)), which affect eye morphology and have been previously shown to be associated with the insertion of transposable elements in an intronic region of Notch. The analysis of revertants has shown that the mutant phenotype depends on the presence of the transposable element and that the disruption of the wild-type sequence organization per se is not its cause. Four of these alleles, even though they are associated with the insertion of the same transposable element, display considerably different phenotypes. Therefore, no simple correlation exists between the mutant phenotype and the type of inserted element. A comparison of the tissue localization of the Notch and the transposable element transcripts revealed that in the third larval instar the elements are transcribed in both orientations in tissues in which Notch is also transcriptionally active. The complexity of the defects associated with the facet alleles, as well as the findings of the transcriptional analysis, indicate that a mutational mechanism based solely on transcriptional interference is not sufficient to explain the nature of the mutational event. It is likely that in these mutations alterations, in the temporal and/or spatial context caused by transcriptional and perhaps post-transcriptional interference mechanisms by the inserted elements, may be responsible for the mutant phenotype.

This article has been cited by other articles:

				X Sun and S Artavanis-Tsakonas Secreted forms of DELTA and SERRATE define antagonists of Notch signaling in Drosophila Development, January 9, 1997; 124(17): 3439 - 3448. [Abstract] [PDF]

				G. Weinmaster, V. J. Roberts, and G. Lemke Notch2: a second mammalian Notch gene Development, December 1, 1992; 116(4): 931 - 941. [Abstract] [PDF]

				T Xu, I Rebay, R J Fleming, T N Scottgale, and S Artavanis-Tsakonas The Notch locus and the genetic circuitry involved in early Drosophila neurogenesis. Genes & Dev., March 1, 1990; 4(3): 464 - 475. [Abstract] [PDF]