Publisher Summary This chapter reviews the current state of the knowledge of transcription and translation in Caenorhabditis elegans. Transcription in eukaryotes is accomplished by three RNA polymerases, each transcribing a particular type of RNA; RNA polymerase I transcribes ribosomal RNA, RNA polymerase II transcribes mRNAs and snRNAs, and RNA polymerase III transcribes tRNAs and other low-molecular-weight RNAs. The chapter focuses on RNA polymerase II transcription. The C. elegans gene for the large subunit of RNA polymerase II has been cloned, and has shown to encode a protein that resembles its vertebrate counterparts. For most polymerase II transcribed genes in C. elegans, a sequence fitting the consensus TATA element about 30 bp upstream of the transcriptional start site is found. Recently, a cDNA encoding the TATA box binding protein, or TATA binding protein (TBP) subunit of transcription factor II D (TFIID), has been identified in the nematode. This protein shows extended regions of sequence similarity to vertebrate TBP, binds to a TATA box sequence and can substitute for vertebrate TFIID basal activity in in vitro extracts. These results illustrate a high degree of evolutionary conservation in the basic transcription machinery.

Transcription and translation.

Interaction between endothelial cells and mural cells (pericytes and vascular smooth muscle) is essential for vascular development and maintenance Endothelial cells arise from Flk1-expressing (Flk1+) mesoderm cells, whereas mural cells are believed to derive from mesoderm, neural crest or epicardial cells and migrate to form the vessel wall Difficulty in preparing pure populations of these lineages has hampered dissection of the mechanisms underlying vascular formation Here we show that Flk1+ cells derived from embryonic stem cells can differentiate into both endothelial and mural cells and can reproduce the vascular organization process Vascular endothelial growth factor promotes endothelial cell differentiation, whereas mural cells are induced by platelet-derived growth factor-BB Vascular cells derived from Flk1+ cells can organize into vessel-like structures consisting of endothelial tubes supported by mural cells in three-dimensional culture Injection of Flk1+ cells into chick embryos showed that they can incorporate as endothelial and mural cells and contribute to the developing vasculature in vivo Our findings indicate that Flk1+ cells can act as 'vascular progenitor cells' to form mature vessels and thus offer potential for tissue engineering of the vascular system

Flk1-positive cells derived from embryonic stem cells serve as vascular progenitors

Analysis of Development Edited by Prof Benjamin H Willier, Prof Paul A Weiss and Prof Viktor Hamburger Pp xii + 735 (Philadelphia and London: W B Saunders Company, 1955) 105s

Mechanisms of Development

Cl− channels reside both in the plasma membrane and in intracellular organelles Their functions range from ion homeostasis to cell volume regulation, transepithelial transport, and regulation of e

https://www.leibniz-fmp.de/fileadmin/user_upload/Physiology_and_Pathology_of_Ion_Transport/documents/PhysRev2002.pdf

Molecular Structure and Physiological Function of Chloride Channels

The nematode Caenorhabditis elegans is an important model for studying the genetics of ageing, with over 50 life-extension mutations known so far. However, little is known about the pathobiology of ageing in this species, limiting attempts to connect genotype with senescent phenotype. Using ultrastructural analysis and visualization of specific cell types with green fluorescent protein, we examined cell integrity in different tissues as the animal ages. We report remarkable preservation of the nervous system, even in advanced old age, in contrast to a gradual, progressive deterioration of muscle, resembling human sarcopenia. The age-1(hx546) mutation, which extends lifespan by 60-100%, delayed some, but not all, cellular biomarkers of ageing. Strikingly, we found strong evidence that stochastic as well as genetic factors are significant in C. elegans ageing, with extensive variability both among same-age animals and between cells of the same type within individuals.

Stochastic and genetic factors influence tissue-specific decline in ageing C. elegans.

Caenorhabditis elegans oocytes, like those of most animals, arrest during meiotic prophase. Sperm promote the resumption of meiosis (maturation) and contraction of smooth muscle-like gonadal sheath cells, which are required for ovulation. We show that the major sperm cytoskeletal protein (MSP) is a bipartite signal for oocyte maturation and sheath contraction. MSP also functions in sperm locomotion, playing a role analogous to actin. Thus, during evolution, MSP has acquired extracellular signaling and intracellular cytoskeletal functions for reproduction. Proteins with MSP-like domains are found in plants, fungi, and other animals, suggesting that related signaling functions may exist in other phyla.

http://science.sciencemag.org/content/sci/291/5511/2144.full.pdf

A Sperm Cytoskeletal Protein That Signals Oocyte Meiotic Maturation and Ovulation

Ultrastructural features of the adult hermaphrodite gonad of Caenorhabditis elegans: relations between the germ line and soma.

Sexual reproduction of multicellular organisms depends critically on the coordinate development of the germ line and somatic gonad, a process known as gonadogenesis. Together these tissues ensure the formation of functional gametes and, in the female of many species, create a context for production and further development of the zygote. Since the future of the species hangs in the balance, it is not surprising that gonadogenesis is a complex process involving conserved and multi-faceted developmental mechanisms. Genetic, anatomical, cell biological, and molecular experiments have established the nematode Caenorhabditis elegans as a paradigm for studying gonadogenesis. Furthermore, these studies demonstrate the utility of C. elegans gonadogenesis for exploring broad issues in cell and developmental biology, such as cell fate specification, morphogenesis, cell signaling, cell cycle control, and programmed cell death. The synergy of molecular genetics and cell biology conducted at single-cell resolution in real time permits an extraordinary depth of analysis in this organism. In this review, we first describe the embryonic and post-embryonic development and morphology of the C. elegans gonad. Next we recount seminal experiments that established the field, highlight recent results that provide insight into conserved developmental mechanisms, and present future prospects for the field.

https://anatomypubs.onlinelibrary.wiley.com/doi/pdf/10.1002/%28SICI%291097-0177%28200005%29218%3A1%3C2%3A%3AAID-DVDY2%3E3.0.CO%3B2-W

The Caenorhabditis elegans gonad: a test tube for cell and developmental biology.

During sexual reproduction in most animals, oocytes arrest in meiotic prophase and resume meiosis (meiotic maturation) in response to sperm or somatic cell signals. Despite progress in delineating mitogen-activated protein kinase (MAPK) and CDK/cyclin activation pathways involved in meiotic maturation, it is less clear how these pathways are regulated at the cell surface. The Caenorhabditis elegans major sperm protein (MSP) signals oocytes, which are arrested in meiotic prophase, to resume meiosis and ovulate. We used DNA microarray data and an in situ binding assay to identify the VAB-1 Eph receptor protein-tyrosine kinase as an MSP receptor. We show that VAB-1 and a somatic gonadal sheath cell-dependent pathway, defined by the CEH-18 POU-class homeoprotein, negatively regulate meiotic maturation and MAPK activation. MSP antagonizes these inhibitory signaling circuits, in part by binding VAB-1 on oocytes and sheath cells. Our results define a sperm-sensing control mechanism that inhibits oocyte maturation, MAPK activation, and ovulation when sperm are unavailable for fertilization. MSP-domain proteins are found in diverse animal taxa, where they may regulate contact-dependent Eph receptor signaling pathways.

/pdf/an-eph-receptor-sperm-sensing-control-mechanism-for-oocyte-4yk0mja97e.pdf

An Eph receptor sperm-sensing control mechanism for oocyte meiotic maturation in Caenorhabditis elegans.

Copyright: © 2005 E Jane Albert Hubbard and David Greenstein This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited To whom correspondence should be addressed E-mail: janehubbard@nyuedu Introduction to the germ line* E Jane Albert Hubbard, Department of Biology, New York University, New York, NY 10003 USA

http://wormbook.org/chapters/www_introgermline/introgermline.pdf

David Greenstein

Papers

A Sperm Cytoskeletal Protein That Signals Oocyte Meiotic Maturation and Ovulation

Ultrastructural features of the adult hermaphrodite gonad of Caenorhabditis elegans: relations between the germ line and soma.

The Caenorhabditis elegans gonad: a test tube for cell and developmental biology.

An Eph receptor sperm-sensing control mechanism for oocyte meiotic maturation in Caenorhabditis elegans.

Introduction to the germ line.