pitkin(D), a novel gain-of-function enhancer of position-effect variegation, affects chromatin regulation during oogenesis and early embryogenesis in Drosophila

• Published in: Genetics (Austin) Vol. 157; no. 3; pp. 1227 - 1244
• Main Authors: Kuhfittig, S, Szabad, J, Schotta, G, Hoffmann, J, Máthé, E, Reuter, G
• Format: Journal Article
• Language: English
• Published: United States 01.03.2001
• Subjects: Animals; Cell Nucleus - metabolism; Chromatin - metabolism; Chromosome Mapping; Chromosomes - ultrastructure; Crosses, Genetic; Drosophila - genetics; Embryo, Nonmammalian - physiology; Enhancer Elements, Genetic; Female; Genes, Dominant; Heterochromatin - metabolism; Infertility, Female - genetics; Insect Proteins - genetics; Insect Proteins - physiology; Male; Microscopy, Fluorescence; Models, Genetic; Mosaicism; Mothers; Mutagenesis; Mutation; Oogenesis - genetics; Ovarian Follicle - metabolism; Ovary - metabolism; Phenotype; Photoreceptor Cells, Invertebrate - metabolism; Reproduction - genetics
• ISSN: 0016-6731

The vast majority of the >100 modifier genes of position-effect variegation (PEV) in Drosophila have been identified genetically as haplo-insufficient loci. Here, we describe pitkin(Dominant) (ptn(D)), a gain-of-function enhancer mutation of PEV. Its exceptionally strong enhancer effect is evident as elevated spreading of heterochromatin-induced gene silencing along euchromatic regions in variegating rearrangements. The ptn(D) mutation causes ectopic binding of the SU(VAR)3-9 heterochromatin protein at many euchromatic sites and, unlike other modifiers of PEV, it also affects stable position effects. Specifically, it induces silencing of white+ transgenes inserted at a wide variety of euchromatic sites. ptn(D) is associated with dominant female sterility. +/+ embryos produced by ptn(D)/+ females mated with wild-type males die at the end of embryogenesis, whereas the ptn(D)/+ sibling embryos arrest development at cleavage cycle 1-3, due to a combined effect of maternally provided mutant product and an early zygotic lethal effect of ptn(D). This is the earliest zygotic effect of a mutation so far reported in Drosophila. Germ-line mosaics show that ptn+ function is required for normal development in the female germ line. These results, together with effects on PEV and white+ transgenes, are consistent with the hypothesis that the ptn gene plays an important role in chromatin regulation during development of the female germ line and in early embryogenesis.