WA488 3831 P1825-T43-Nr4 AP.Pdf

Acta Protozool. (2004) 43: 291 - 301 Syndrome of the Failure to Turn off Mitotic Activity in Tetrahymena thermophila: in cdaA1 Phenotypes Ewa JOACHIMIAK, Janina KACZANOWSKA, Mauryla KIERSNOWSKA and Andrzej KACZANOWSKI Department of Cytophysiology, Institute of Zoology, Warsaw University, Warsaw, Poland Summary. During early micronuclear mitosis of a wild type Tetrahymena thermophila, basal body proliferation and cortical growth are localized in the equatorial region of the pre-dividing cell. These processes are arrested prior to cytokinesis when the fission line gaps appear in ciliary rows. Then a putative marker of cellular polarity, the fenestrin antigen, appears in the apical zone of the dividing cell and around the old oral apparatus (OA1) and in the cortex localized posterior to the fission line gaps and around the new oral apparatus (OA2) i.e. in the apical cortex of the prospective posterior daughter cell. Prior to cytokinesis, the membranelles within OA1 and OA2 oral apparatuses are strongly labeled with the MPM2 antibody against mitotic phosphoproteins. The transition to cytokinesis is correlated with disappearance of both the polar fenestrin staining and of the phosphoprotein antigens in OA1 and OA2. cdaA1 (cell division arrest) mutant cells grown at the restrictive temperature do not produce a fission line and they do not undergo cytokinesis thereby generating irregular chains. The cdaA1 phenotypes continue elongation of their ciliary rows in equatorial regions, mostly without formation of the fission line gaps, accompanied with repetitive micronuclear mitoses and repetitive formation of the defective oral structures. In cdaA1 cells at restrictive temperature, the fenestrin antigen was recruited and then permanently found in the apical regions and around all oral apparatuses, and was always absent in equatorial regions, in spite of variability of immunostaining patterns, sizes and advancement of organization of OAs in different specimens of the same sample. The MPM2- tagged phosphoproteins were retained in all oral apparatuses in different cdaA 1 phenotypes. We suggest that the cdaA1 phenotypes produced at restrictive temperature behave as cells trapped in a metastable phase with a syndrome of an arrest of the mechanism required to regain the morphostatic stage of a non-dividing cell. Key words: cdaA1 mutation, cell cycle, fenestrin, MPM2 phosphoproteins, Tetrahymena thermophila. INTRODUCTION (Casamayor and Snyder 2002, Niccoli and Nurse 2002). The cell cycle is ended with an activation of the mitotic In yeasts many regulators define the spatial pattern exit network (MEN) of events stimulated by an activa- of cell growth, positioning of the fission line, cytokinesis tion of the specific phosphatase (Cdc 14) and then (Ayscough et al. 1997, Finger et al. 1998) and pattern turned off by an activation of the specific inhibitor of the of acquisition of cell polarity during the cell cycle G protein signaling involved in acquisition of cell polarity to reset the whole cell cycle (Visintin et al. 1998, Wang et al. 2003). Address for correspondence: Janina Kaczanowska, Department The regulators corresponding to yeast’s regulators of of Cytophysiology, Institute of Zoology, Warsaw University, Miecznikowa str. 1, 02-096 Warszawa, Poland; Fax: (0-48) 22 554 the patterned growth, mitotic exit and resetting of the cell 1203; E-mail: [email protected] cycle remain unknown in the ciliate cells. Biometrical 292 E. Joachimiak et al. analysis showed that localization of the oral primordium T. thermophila (Frankel et al. 1976, 1977) shows for the prospective posterior cell division product in complete arrest in cytokinesis, general increase of cell T. thermophila (OA2), is specified by two gradients of size, consecutive rounds of incomplete oral morphogen- ciliary basal body proliferation within ciliary rows: an esis, repetitive micronuclear divisions, repetitive macro- antero-posterior gradient and a dorso-ventral gradient nuclear DNA synthesis leading to a 2-4 fold increase of (Kaczanowski 1978). In the later stages of divisional DNA content in the macronucleus (Frankel et al. 1976, morphogenesis, the proliferation of the basal bodies is 1980; Cleffmann and Frankel 1978). This resulted in arrested, resulting in fission zone gaps within ciliary formation of an array of cdaA1 phenotypes with: dis- meridians that localizes the equatorial position of a turbed cortical polarity of ciliary rows (Ng and Frankel fission line (Kaczanowska et al. 1992, 1993). The fission 1977), which are folded in irregular cortical protrusions line separates nascent posterior and anterior poles of within the cortex of the prospective fission zone prospective daughter cells (Frankel et al. 1981, (Buzanska et al. 1989), and with repetitive but curtailed Kaczanowska et al. 1999). The metamery of divisional and defective stomatogenesis (Frankel et al. 1977, 1980; morphogenesis and the asymmetry of the fission zone Kaczanowska 1990). correlates with a transient appearance of the fenestrin The aim of this report is to characterize the cdaA1 antigen in the apical region of the parental dividing cell phenotypes (Frankel et al. 1976) by an analysis of the and in a belt localized posterior to its fission line (Nelsen patterns of immunofluorescence with the anti-fenestrin et al. 1994). Thus the fenestrin antigen is a transient marker (Nelsen et al. 1994) and with the MPM-2 cortical marker of an anterior pole character antibody against the phosphorylated epitopes of (Kaczanowska et al. 2003), and this patterned cortical cytoskeletal mitotic phosphoproteins (Davies et al. 1983) growth during divisional morphogenesis is also associ- in the cdaA1 cells. Therefore the following questions ated with stage-dependent patterns of phosphorylation were asked in this study: (1) whether in cytokinesis - of proteins in oral membranelles (Kaczanowska et al. arrested cdaA1, the fenestrin antigen will appear in the 1999). Subdivision of the anterior-posterior axis of the putative fission line zones and in the anterior apical mother cell into two axes of prospective daughter cells region, (2) whether the variability of phenotypes corre- is correlated with a transient appearance of the anterior lates with the defined anti-fenestrin immunostained in- marker of the submembrane protein - fenestrin (Nelsen ternal oral patterns, or with the advancement of devel- et al. 1994) and with a transient decrease of the opment achieved by particular oral structures in the B antigen against the submembrane cytoskeletal epiplasm specimen, and (3) whether parallel correlations affect (Williams et al.1987,1995; Kaczanowska et al. 1993, MPM2 immunostaining of oral patterns in particular 1999; Honts and Williams 2003). The apical staining with specimens in the array of phenotypes. the anti-fenestrin antibody (Nelsen et al. 1994) appears at specific stages of oral development both in dividing and in reorganizing cells (Kaczanowska et al. 2003). MATERIALS AND METHODS The MPM2 antibody. directed against some mitotic phosphoproteins (Davies et al. 1983, Westendorf et al. Material. Tetrahymena thermophila cdaA1 (previously 1994, Ding et al. 1997) permanently labeled basal bodies mola/mola, Frankel et al. 1976) strain IA104 was kindly provided by of ciliary rows and other cortical organelles (like the Dr J. Frankel, Iowa University, U.S.A. For inducing expression of the contractile vacuole pores and cytoproct), but during cdaA1 mutation 300 ml Erhlenmeyer flasks containing 50 ml of the morphogenesis this label only transiently appears in the growth medium (1% PPY supplemented with iron and antibiotics, oral membranelles of the developing or reorganizing oral Nelsen et al. 1981) were inoculated with the mutant strain and incubated overnight at the 28°C to yield densities about 1000 cells/ apparatus and increases in surrounding cortical regions, ml. Then some flasks were shifted to the 36°C restrictive temperature then disappears during the transition to a morphostatic and other (controls) were left at the 28°C. The cell samples were state (Kiersnowska and Golinska1996, Kaczanowska et immunostained at different times after shifting the cells to the restric- al. 1999). Thus both the fenestrin and MPM2 antibodies tive temp (2, 2.5, 4 and 7 h). In one control experiment, the wild type may be used as markers of the exit of a cell from a conjugants of two complementary strains of T. thermophila CU427 ° metastable phase to the morphostatic condition of the (mt VI) and CU428 (mt VII) mixed for 4.5 h at 28 C were used. These strains were derived from Cornell University Athens, U.S.A and quiescent cell. obtained from Dr J. Gaertig. To address this problem, we used the cdaA1 mutant. Antibodies. The monoclonal antibodies: FXIX-9A7 (against At the restrictive temperature, the cdaA1 mutant of 64 kDa polypeptide - fenestrin) and MPM-2 (against phosphopro- Fenestrin and phosphoproteins in cdaA1 Tetrahymena 293 teins) were generously supplied by Drs: N. Williams, J. Frankel, and the middle segments of ciliary rows (Fig. 1). In dividing M. Nelsen, and by Dr P. Rao, Houston, U.S.A respectively. The cells, a weak apical fluorescence intensified (Fig. 2, secondary antibody was FITC - conjugated goat anti-mouse IgG arrowhead) and the newly developing oral primordium (SIGMA). Indirect immunofluorescence. The fenestrin epitopes were (OA2) gradually differentiates a “negative pattern of labeled according to Williams et al. (1990). The cells were collected by oral membranelles” in which the three membranelles are the low speed

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