Identification of Genes that InfluencegurkenExpression

Abstract

We thank Will Kruesi and Monica Sullivian for assistance with the screen. We thank the Bloomington, Szeged and Harvard Medical School stock centers for flies, and Trudi Schupbach, David Stein and Daniel St. Johnson for fly stocks, cDNAs and antibodies. The 1D12, 40-1a antibody was from the Developmental Studies Hybridoma Bank, which was developed under the auspices of the NICHD and maintained by The Universities of Iowa, Department of Biological Sciences, Iowa City, IA 52242. This work was supported by grants GM42612 and GM54409 from the NIH. AbstrACtAxial patterning in Drosophila relies on the deployment of patterning proteins at specific regions within the developing oocyte. This process involves transport of mRNAs from the nurse cells to the oocyte, localization of mRNAs within the oocyte, and translational regulation of these mRNAs to restrict the final distribution of the proteins. Despite extensive analysis, the events of deployment are not fully understood and it seems certain that many contributing factors remain to be identified. We describe the development and application of a sensitized genetic screen to reveal such additional factors. Overexpression of Imp, a factor implicated in regulation of gurken mRNA, causes a weak dorsalization that can be enhanced by reducing the level of other factors acting in the same pathway. A collection of deficiency mutants was screened using this assay, leading to the identification of 5 genes that are candidates to contribute to axial patterning. Three of the genes were characterized in greater detail. The mushroom body expressed gene was implicated in axial patterning, with overexpression leading to a range of patterning abnormalities that can be explained by a more primary defect in organization of the cytoskeleton. Two mitotic cell cycle control factors, cyclin E and E2f1, were also implicated, raising the possibility that a mitotic cell cycle checkpoint may impinge on grk expression, much as meiotic checkpoints can alter expression of this gene.

Rasputin Functions as a Positive Regulator of Orb in Drosophila Oogenesis

“…Lig is expressed at high levels in the nervous system and gonads and was initially identified because of defects in mating behavior evident in hypomorphic lig mutant males [17]. More recent studies indicate that lig functions in the ovary as a negative regulator of gurken mRNA translation [36]. The remaining 16 proteins (Table 2) include many known translational factors, namely five 60S and three 40S ribosomal proteins, one elongation factor, and two RNA-binding proteins (Ataxin-2 (Atx-2) and Poly(A) Binding Protein (PABP)).…”

Bazooka regulates microtubule organization and spatial restriction of germ plasm assembly in the Drosophila oocyte

“…Ectopic localization of osk mRNA has been reported in numerous mutants documented to affect localization of Kin-βgal and therefore the organization of microtubule plus ends. These mutants include genes of no known function, such as mushroom-body expressed ( mub ) (Geng and Macdonald, 2007), factors involved in vesicle trafficking including several Rabs, (Coutelis and Ephrussi, 2007; Dollar et al, 2002; Jankovics et al, 2001; Tanaka and Nakamura, 2008), as well as genes predicted to affect the signaling cascade that triggers the reorganization of the microtubule cytoskeleton including lamininA ( lanA ) and grk (Deng and Ruohola-Baker, 2000; Roth et al, 1995). Although the distribution of Osk protein has not been established in many of these mutants, Osk is ectopically translated in six out of nine mutants where it has been examined, and the ectopic Osk localization frequently mirrors that of ectopic osk mRNA and Kin-βgal (Table 1).…”

Complex basis of hybrid female sterility and Haldane’s rule inHeliconiusbutterflies: Z-linkage and epistasis

“…On chromosome 8, HMEL037834g1.t2, with ortholog Neurexin 1 ( Nrx-1 ), stood out as having the third highest log 2 fold change (5.51) in the dataset. While not known to be involved in oogenesis, Neurexin 1 is known to influence expression of gurken ( grk ) (Geng & Macdonald, 2007). The asymmetrical localization of gurken mRNA is key for its function during oogenesis, to establish anterior-posterior and dorso-ventral axes in the egg and embryo, and gurken encodes a TGF α family signaling ligand that activates the intracellular MAP kinase pathway via the the product of Egfr .…”