From the early part of the twentieth century, embryologists recognized that the cytoplasmic asymmetry established in the egg
during oogenesis directs the proper spatial development of the embryo. Development of this polarity in the Drosophila oocyte
depends also on the correct sorting of maternal RNAs. Bicaudal-D is a Drosophila protein that is involved in establishing the
asymmetric cytoplasm in the developing oocyte. The gene encodes a cytoskeleton-like coiled-coil polypeptide, with a leucine
zipper and 5 alpha-helix domains or heptad repeats showing sequence similarity to the tail domains of myosin heavy chains
(OMIM 160730), the microtubule motor kinesin , and intermediate filament proteins.
General function
RNA binding
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Cellular localization
Cytoplasmic, Cytoskeleton
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Ovarian function
Oogenesis
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The intracellular localization of mRNA, a common mechanism for targeting
proteins to specific regions of the cell, probably occurs in most if not all
polarized cell types. Many of the best characterized localized mRNAs are found
in oocytes and early embryos, where they function as localized determinants
that control axis formation and the development of the germline.
Bullock SL, et al 2001 reported conserved signals and machinery for RNA transport in Drosophila
oogenesis and embryogenesis.
Localization of cytoplasmic messenger RNA transcripts is widely used to target
proteins within cells. For many transcripts, localization depends on
cis-acting elements within the transcripts and on microtubule-based motors;
however, little is known about other components of the transport machinery or
how these components recognize specific RNA cargoes. The authors show that in
Drosophila the same machinery and RNA signals drive specific accumulation of
maternal RNAs in the early oocyte and apical transcript localization in
blastoderm embryos. They demonstrate in vivo that Egalitarian (Egl) and Bicaudal D (BicD), maternal proteins required for oocyte determination, are selectively
recruited by, and co-transported with, localizing transcripts in blastoderm
embryos, and that interfering with the activities of Egl and BicD blocks
apical localization. It was proposed that Egl and BicD are core components of a
selective dynein motor complex that drives transcript localization in a
variety of tissues.
Expression regulated by
Comment
Ovarian localization
Oocyte
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Herrera L et al reported mouse ovary developmental RNA and protein markers from gene expression profiling.
To identify genes involved in morphogenetic events during mouse ovary development, we started with microarray analyses of whole organ RNA. Transcripts for 60% of the 15,000 gene NIA panel were detected, and about 2000 were differentially expressed in nascent newborn compared to adult ovary. Highly differentially expressed transcripts included noncoding RNAs and newly detected genes involved in transcription regulation and signal transduction. The phased pattern of newborn mouse ovary differentiation allowed us to (1) extend information on activity and stage specificity of cell type-specific genes; and (2) generate a list of candidate genes involved in primordial follicle formation, including podocalyxin (Podxl), PDGFR-beta, and a follistatin-domain-encoding gene Flst1. Oocyte-specific transcripts included many (e.g., Deltex2, Bicd2, and Zfp37) enriched in growing oocytes, as well as a novel family of untranslated RNA's (RLTR10) that is selectively expressed in early stage follicles. The results indicate that global expression profiling of whole organ RNA provides sensitive first-line information about ovarian histogenesis for which no in vitro cell models are currently available.
BicD-dependent localization processes: from Drosophilia development to human cell biology
Claussen M, .
Many eukaryotic cells depend on proper cell polarization for their development and physiological function. The establishment of these polarities often involve the subcellular localization of a specific subset of proteins, RNAs and organelles. In Drosophila, the microtubule-dependent BicD (BicaudalD) localization machinery is involved in the proper localization of mRNA during oogenesis and embryogenesis and the proper positioning of the oocyte and photoreceptor nuclei. BicD acts together with the minus-end directed motor dynein as well as Egl and Lis-1. The finding that the mammalian homologs of BicD function in retrograde Golgi-to-ER transport has supported the view that BicD may be part of a repeatedly used and evolutionary conserved localization machinery. In this review we focus on the various processes in which BicD is involved during Drosophilian development and in mammals. In addition, we evaluate the interactions between BicD, the dynein localization machinery and associated factors.