Assembly of the Drosophila germ plasm

Mahowald, Anthony P.

doi:10.1016/s0074-7696(01)03007-8

Cited by 230 publications

(236 citation statements)

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“…During oogenesis, the germ plasm is assembled at the posterior pole of the oocyte. Germ plasm is composed of RNAs and proteins, which are specifically required for the formation of germ cells in the early embryo and specification of germ cell fate (3). Germ plasm is also the source of the Nanos protein gradient required for embryonic polarity.…”

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confidence: 99%

Structure of Drosophila Oskar reveals a novel RNA binding protein

Yang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Oskar (Osk) protein plays critical roles during Drosophila germ cell development, yet its functions in germ-line formation and body patterning remain poorly understood. This situation contrasts sharply with the vast knowledge about the function and mechanism of osk mRNA localization. Osk is predicted to have an N-terminal LOTUS domain (Osk-N), which has been suggested to bind RNA, and a C-terminal hydrolase-like domain (Osk-C) of unknown function. Here, we report the crystal structures of Osk-N and Osk-C. Osk-N shows a homodimer of winged-helix–fold modules, but without detectable RNA-binding activity. Osk-C has a lipase-fold structure but lacks critical catalytic residues at the putative active site. Surprisingly, we found that Osk-C binds the 3′UTRs of osk and nanos mRNA in vitro. Mutational studies identified a region of Osk-C important for mRNA binding. These results suggest possible functions of Osk in the regulation of stability, regulation of translation, and localization of relevant mRNAs through direct interaction with their 3′UTRs, and provide structural insights into a novel protein–RNA interaction motif involving a hydrolase-related domain.

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confidence: 99%

Structure of Drosophila Oskar reveals a novel RNA binding protein

Yang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…During Drosophila oogenesis, Vasa localizes to two functionally distinct compartments in the egg chamber: the germ plasm in oocytes and the nuage in nurse cells (Mahowald 2001;Gao and Arkov 2013). Nurse cells are transcriptionally active and provide the growing oocyte with RNAs and proteins required for oocyte development and patterning of the future embryo (Johnstone and Lasko 2001).…”

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confidence: 99%

“…In the nuage, Vasa plays an essential role in the piRNA pathway (Malone et al 2009;Xiol et al 2014;Nishida et al 2015), a retrotransposon defense mechanism that helps maintain genome integrity (Luteijn and Ketting 2013;Sato and Siomi 2013;Czech and Hannon 2016). The Drosophila germ plasm (or pole plasm) is assembled at the posterior tip of the oocyte and specifies the Drosophila germ cell precursors called pole cells, which form at the posterior pole during early embryogenesis (for review, see Mahowald 2001). In Drosophila, germ cell specification is coupled to abdominal patterning: Embryos that fail to assemble a functional pole plasm are devoid of pole cells, and the resulting larvae lack abdominal segments such that the mispatterned larvae arrest in early development and die.…”

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confidence: 99%

The LOTUS domain is a conserved DEAD-box RNA helicase regulator essential for the recruitment of Vasa to the germ plasm and nuage

2017

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DEAD-box RNA helicases play important roles in a wide range of metabolic processes. Regulatory proteins can stimulate or block the activity of DEAD-box helicases. Here, we show that LOTUS (Limkain, Oskar, and Tudor containing proteins 5 and 7) domains present in the germline proteins Oskar, TDRD5 (Tudor domain-containing 5), and TDRD7 bind and stimulate the germline-specific DEAD-box RNA helicase Vasa. Our crystal structure of the LOTUS domain of Oskar in complex with the C-terminal RecA-like domain of Vasa reveals that the LOTUS domain occupies a surface on a DEAD-box helicase not implicated previously in the regulation of the enzyme's activity. We show that, in vivo, the localization of Drosophila Vasa to the nuage and germ plasm depends on its interaction with LOTUS domain proteins. The binding and stimulation of Vasa DEAD-box helicases by LOTUS domains are widely conserved.

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“…In the case of germ plasm, the data to date suggest that this convergent phenotype results from distinct genetic pathways in different lineages. For example, the oskar gene has been shown to be sufficient for germ-plasm assembly in D. melanogaster (79)(80)(81). This gene has been identified in a number of insect lineages (66,82), but lacks known orthologs in noninsect metazoan lineages, including those with germ plasm (e.g., birds, fish, and frogs) (82).…”

Section: Is the Transition To Inheritance Mode Irreversible And Convementioning

confidence: 99%

Causes and evolutionary consequences of primordial germ-cell specification mode in metazoans

Whittle

Extavour

2017

Proc. Natl. Acad. Sci. U.S.A.

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In animals, primordial germ cells (PGCs) give rise to the germ lines, the cell lineages that produce sperm and eggs. PGCs form in embryogenesis, typically by one of two modes: a likely ancestral mode wherein germ cells are induced during embryogenesis by cell-cell signaling (induction) or a derived mechanism whereby germ cells are specified by using germ plasm-that is, maternally specified germ-line determinants (inheritance). The causes of the shift to germ plasm for PGC specification in some animal clades remain largely unknown, but its repeated convergent evolution raises the question of whether it may result from or confer an innate selective advantage. It has been hypothesized that the acquisition of germ plasm confers enhanced evolvability, resulting from the release of selective constraint on somatic gene networks in embryogenesis, thus leading to acceleration of an organism's protein-sequence evolution, particularly for genes expressed at early developmental stages, and resulting in high speciation rates in germ plasm-containing lineages (denoted herein as the "PGCspecification hypothesis"). Although that hypothesis, if supported, could have major implications for animal evolution, our recent large-scale coding-sequence analyses from vertebrates and invertebrates provided important examples of genera that do not support the hypothesis of liberated constraint under germ plasm. Here, we consider reasons why germ plasm might be neither a direct target of selection nor causally linked to accelerated animal evolution. We explore alternate scenarios that could explain the repeated evolution of germ plasm and propose potential consequences of the inheritance and induction modes to animal evolutionary biology.germ line | preformation | epigenesis | primordial germ cell | spandrel P rimordial germ cells (PGCs) are specialized cells located in sexual organs of animals. These cells are central to reproduction because they give rise to the germ lines and, ultimately, the sperm and eggs. The PGCs typically arise during early embryogenesis by one of two distinct modes: (i) induction, wherein germ cells are induced by cell-cell signaling pathways (also known as epigenesis); or (ii) inheritance, wherein germ cells are formed by using germ plasm (a specialized cytoplasm containing proteins and RNAs needed for PGC formation), that is, maternally generated germ-line determinants that are "preformed" before embryogenesis begins (also known as preformation) (1-3). The induction mode appears to be the more prevalent mode in animals and occurs in basally branching lineages, and thus is the hypothesized ancestral mechanism of PGC specification, whereas inheritance comprises the likely derived state (1) (Fig. 1) (see SI Appendix, section 1 on the less parsimonious scenario that induction is the derived mode). Induction has been inferred based on microscopic data from most animal clades studied to date and has been experimentally shown to occur in a diverse range of organisms, including mammals (Mus musculus) (4-8), salamanders (...

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Assembly of the Drosophila germ plasm

Cited by 230 publications

References 91 publications

Structure of Drosophila Oskar reveals a novel RNA binding protein

Structure of Drosophila Oskar reveals a novel RNA binding protein

The LOTUS domain is a conserved DEAD-box RNA helicase regulator essential for the recruitment of Vasa to the germ plasm and nuage

Causes and evolutionary consequences of primordial germ-cell specification mode in metazoans

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