High impact information on actin

• In hair cells of the inner ear, evidence suggests that an extracellular tip link pulls on a channel, which attached intracellularly to actin via a tension-regulating myosin 1beta [1].
• Molecular genetic approaches to understanding the actin cytoskeleton [2].
• Instead, these spermatocytes arrest with missegregated chromosomes and mislocalized actin filaments, endoplasmic reticulum and ribosomes [3].
• Recent insights from this system have determined the involvement in morphogenesis of key proteins, including the actin-regulating WASP and Ena proteins, potential guidance molecules such as the Eph and Robo receptors, and the cell-cell signaling proteins of the Wnt pathway [4].
• In Caenorhabditis elegans, UNC-60A and UNC-60B, nonmuscle and muscle isoforms of actin depolymerizing factor (ADF)/cofilin, are expressed by alternative splicing of unc-60 and regulate distinct actin-dependent developmental processes [5].

Biological context of actin

• RNA interference of Ce-kettin caused weak disorganization of the actin filaments in body wall muscle [6].
• Although the model refers primarily to the locomotion of nematode sperm, it has important implications for the mechanics of actin-based cell motility [7].
• It is hypothesized that actin plays a role in the shaping of the cell and in the arrangement of its organelles during nematode spermiogenesis, when MSP is present, in an inactive state, in the fibrous bodies [8].
• In Caenorhabditis elegans and Ascaris suum, previous studies have reported that sperm motility does not involve actin, but, instead, requires a specific cytoskeletal protein, namely major-sperm-protein (MSP) [8].
• SCAR-cells have reduced levels of F-actin staining during vegetative growth, and abnormal cell morphology and actin distribution during chemotaxis [9].

Anatomical context of actin

• Given these advantages, it has been possible to use C. elegans to investigate the different ways in which the actin cytoskeleton drives the cellular rearrangements underlying morphogenesis, through regulated polymerization or actomyosin contraction [4].
• TM4SF10 colocalized with ZO1 and p120ctn in undifferentiated confluent podocytes and also colocalized with the tips of actin filaments at cell contacts [10].
• Tropomyosin shows a distinct pattern in spermatids, but is located in the MSP and actin-containing cap in spermatozoa [8].
• We have studied the localization of actin and MSP in spermatids and spermatozoa of Graphidium strigosum (Dujardin, 1845), a species which has elongate male germ cells in which organelles are easily identified [11].
• Immunocytochemical observations reveal that actin and MSP have an identical localization in precise areas of the male germ cells [11].

Associations of actin with chemical compounds

• Our analysis of vab-10 reveals novel insights into the role of this plakin subfamily. vab-10 generates isoforms related either to plectin (termed VAB-10A) or to microtubule actin cross-linking factor plakins (termed VAB-10B) [12].
• Integrin receptors for extracellular matrix transmit mechanical and biochemical information through molecular connections to the actin cytoskeleton and to several intracellular signaling pathways [13].

Other interactions of actin

• The fourth actin gene, act-4 mapped to 20-35% from the left end of X [14].
• The myo-3 gene mapped to the middle of linkage group V near the cluster of three actin genes (act-1,2,3) [14].
• Moreover, nematode sperm lack detectable molecular motors or the battery of actin-binding proteins that characterize actin-based motility [7].
• Sperm of the nematode, Ascaris suum, are amoeboid cells that do not require actin or myosin to crawl over solid substrata [15].
• The increased synthesis of forms of myosin, actin and troponin in the nematode living in the rapid-responder SWR host may relate to the attempted reorganisation or repair of the cytoskeleton and/or muscle layer in the host immune initiated, increased mucus production and smooth muscle activity within intestinal environment [16].

Analytical, diagnostic and therapeutic context of actin

• New tools in molecular genetics, such as genetic interaction screens and conditional gene targeting, have advanced the study of actin dynamics in a number of model systems [2].
• To help illuminate this role, we used actin filament affinity chromatography to isolate actin binding proteins from large quantities of Caenorhabditis elegans oocytes [17].
• Here, we performed a detailed characterization of the pha-2 phenotype using cell-type-specific reporters, physical manipulation of the nuclei in pharyngeal muscle cells using "optical tweezers", electron microscopy, staining of the actin cytoskeleton as well as phenotypic rescue and ectopic expression experiments [18].
• The FBs contain actin as shown by immunofluorescence using a monoclonal anti-actin antibody and by affinity cytochemistry using fluorescent phalloidin [19].

References