Molecular Regulation of Nuclear Events in Mitosis and Meiosis

375 Pages·1987·9.44 MB·English

by  Robert A. Schlegel, Margaret S. Halleck and Potu N. Rao (Eds.)

CELL BIOLOGY: A Series of Monographs
EDITORS
D. E. BUETOW I. L. CAMERON
Department of Physiology Department of Cellular and
and Biophysics Structural Biology
University of Illinois The University of Texas
Urbana, Illinois Health Science Center at San Antonio
San Antonio, Texas
G. M. PADILLA A. M. ZIMMERMAN
Department of Physiology Department of Zoology
Duke University Medical Center University of Toronto
Durham, North Carolina Toronto, Ontario, Canada
Recently published volumes
Gary L. Whitson (editor). NUCLEAR-CYTOPLASMIC INTERACTIONS IN THE CELL CYCLE, 1980
Danton H. O'Day and Paul A. Horgen (editors). SEXUAL INTERACTIONS IN EUKARYOTIC MICROBES,
1981
Ivan L. Cameron and Thomas B. Pool (editors). THE TRANSFORMED CELL, 1981
Arthur M. Zimmerman and Arthur Forer (editors). MITOSIS/CYTOKINESIS, 198J
Ian R. Brown (editor). MOLECULAR APPROACHES TO NEUROBIOLOGY, 1982
Henry C. Aldrich and John W. Daniel (editors). CELL BIOLOGY OF PHYSARUM AND DIDYMIUM. Volume
I: Organisms, Nucleus, and Cell Cycle, 1982; Volume II: Differentiation, Metabolism, and Methodology, 1982
John A. Heddle (editor). MUTAGENICITY: New Horizons in Genetic Toxicology, 1982
Potu N. Rao, Robert T. Johnson, and Karl Sperling (editors). PREMATURE CHROMOSOME CONDENSA
TION: Application in Basic, Clinical, and Mutation Research, 1982
George M. Padilla and Kenneth S. McCarty, Sr. (editors). GENETIC EXPRESSION IN THE CELL CYCLE,
1982
David S. McDevitt (editor). CELL BIOLOGY OF THE EYE, 1982
P. Michael Conn (editor). CELLULAR REGULATION OF SECRETION AND RELEASE, 1982
Govindjee (editor). PHOTOSYNTHESIS, Volume I: Energy Conversion by Plants and Bacteria, 1982; Volume II:
Development, Carbon Metabolism, and Plant Productivity, 1982
John Morrow. EUKARYOTIC CELL GENETICS, 1983
John F. Hartmann (editor). MECHANISM AND CONTROL OF ANIMAL FERTILIZATION, 1983
Gary S. Stein and Janet L. Stein (editors). RECOMBINANT DNA AND CELL PROLIFERATION, 1984
Prasad S. Sunkara (editor). NOVEL APPROACHES TO CANCER CHEMOTHERAPY, 1984
Burr G. Atkinson and David B. Walden (editors). CHANGES IN EUKARYOTIC GENE EXPRESSION IN
RESPONSE TO ENVIRONMENTAL STRESS, 1985
Reginald M. Gorczynski (editor). RECEPTORS IN CELLULAR RECOGNITION AND DEVELOPMENTAL
PROCESSES, 1986
Govindjee, Jan Amesz, and David Charles Fork (editors). LIGHT EMISSION BY PLANTS AND BACTERIA,
1986
Peter B. Moens (editor). MEIOSIS, 1987
Robert A. Schlegel, Margaret S. Halleck, and Potu N. Rao (editors). MOLECULAR REGULATION OF
NUCLEAR EVENTS IN MITOSIS AND MEIOSIS, 1987
In preparation
Monique C. Braude and Arthur M. Zimmerman (editors). GENETIC AND PERINATAL EFFECTS OF
ABUSED SUBSTANCES, 1987
E. J. Rauckman and George M. Padilla (editors). THE ISOLATED HEPATOCYTE: USE IN TOXICOLOGY
AND XENOBIOTIC BIOTRANSFORMATIONS, 1987
Molecular Regulation
of Nuclear Events
in Mitosis and Meiosis
Edited by
Robert A. Schlegel
Department of Molecular and Cell Biology
The Pennsylvania State University
University Park, Pennsylvania
Margaret S. Halleck
Department of Molecular and Cell Biology
The Pennsylvania State University
University Park, Pennsylvania
Potu N. Rao
Department of Medical Oncology
The University of Texas System Cancer Center
M. D. Anderson Hospital and Tumor Institute
Houston, Texas
mi
ACADEMIC PRESS, INC.
Harcourt Brace Jovanovich, Publishers
Orlando San Diego New York Austin
Boston London Sydney Tokyo Toronto
COPYRIGHT © 1987 BY ACADEMIC PRESS, INC
ALL RIGHTS RESERVED.
NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR
TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECTRONIC
OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR
ANY INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT
PERMISSION IN WRITING FROM THE PUBLISHER.
ACADEMIC PRESS, INC.
Orlando, Florida 32887
United Kingdom Edition published by
ACADEMIC PRESS INC. (LONDON) LTD.
24-28 Oval Road, London NW1 7DX
Library of Congress Cataloging in Publication Data
Molecular regulation of nuclear events in mitosis and
meiosis.
(Cell biology)
Includes index.
1. Mitosis. 2. Meiosis. 3. Molecular biology.
1. Schlegel, Robert A. II. Halleck, Margaret S.
III. Rao, PotuN. IV. Series. [DNLM: 1. Meiosis.
2. Mitogens. 3. Mitosis. 4. Molecular Biology.
QH 605.2 M718]
QH605.M69 1987 574.87'623 86-17216
ISBN 0-12-625115-0 (alk. paper)
PRINTED IN THE UNITED STATES OF AMERICA
87 88 89 90 9 8 7 6 5 4 3 2 1
Preface
In the past several years the molecular mechanisms involved in the
control of the early events of amphibian oocyte maturation have been
elaborated in some detail. The later events which culminate in germinal
vesicle breakdown and chromosome condensation, the cytological events
distinctive of meiotic maturation, are much less well understood. One
point is, however, perfectly clear: transplantation of cytoplasm from a
mature oocyte into an immature recipient can bypass normally requisite
early events and initiate the processes which immediately precede final
nuclear transformation. Studies of the regulation of the meiotic cell cycle
dramatically converged with similar studies of the mitotic cell cycle upon
demonstration that the signal which induced these nuclear events in oo-
cytes could also be furnished by cytoplasmic extracts prepared from de-
veloping blastomeres and that this activity cycled in relation to the mitotic
cell cycle. Only some five years ago this message was brought home most
forcefully when cytoplasmic extracts prepared from culture cells arrested
in mitosis were shown capable of inducing maturation when injected into
immature oocytes. Such activity has now been revealed to be universal in
oocytes undergoing maturation or in somatic cells in mitosis; extracts
from maturing amphibian oocytes can induce maturation in immature
starfish oocytes, and extracts from synchronized yeast can induce matu-
ration in amphibian oocytes. Furthermore, in reciprocal experiments, cy-
toplasmic extracts from mature oocytes were shown to induce mitotic
events in somatic nuclei, and, soon thereafter, extracts from somatic
culture cells were shown capable of inducing condensation of interphase
chromatin of somatic nuclei.
This convergence of meiotic and mitotic cell cycles has lent new impe-
tus to identifying and comparing the molecular species responsible for the
biological activity in each type of extract. Partial purification and charac-
terization of the active factors from both meiotic and mitotic sources have
been accomplished, and these pursuits continue. Concomitantly, efforts
are under way to purify and characterize factors which are inhibitory to
xi
xii Preface
meiotic and mitotic processes. In the case of meiotic maturation, factors
are present in follicular fluids which maintain arrest of oocytes prior to
initiation of maturation, and other factors, cytoplasmic in nature, are
required to maintain matured oocytes in metaphase arrest until fertiliza-
tion. Reversal of this arrest upon fertilization and its dominance over
sperm pronuclei are also of relevance in this context. In the case of cells
traversing mitosis, factors inhibitory to nuclear membrane breakdown
and chromosome condensation can be found in cells in the early portion
of the Gj phase of the cell cycle.
With the development of these various assays for biological activities
and with the partial purification of the substances responsible, the time is
ripe for investigating the possible modes of action of the molecular spe-
cies involved. Reversible modifications of the proteins which compose
the nuclear lamina and chromatin have been known for some time to
occur concomitantly with breakdown of the nuclear membrane and con-
densation of chromatin into discrete chromosomes. Whether these modifi-
cations are causal has been a question of some controversy. Perhaps the
modification most closely linked with mitotic nuclear events is phospho-
rylation. Thus, the possible role of protein phosphorylation/dephosphory-
lation in the regulation of these events is currently being actively pursued
by identifying the protein kinases present at mitosis as well as their phos-
phoprotein substrates.
This book seeks to bring together in one volume the related studies of
investigators in the various fields which this area of research encom-
passes. Authors describe their relevant background work and present
their most up-to-date findings. Beyond this, however, they provide their
views on how the various systems and factors described relate to one
another and formulate the direction and priorities they anticipate for their
continuing research. In this way, the goals achievable in the not-too-
distant future may begin to take shape.
Robert A. Schlegel
Margaret S. Halleck*
Potu N. Rao
*Present address: Department of Pharmacology, The University of Texas Medical School,
P.O. Box 20708, Houston, Texas 77225.
1
Development of Cytoplasmic
Activities That Control
Chromosome Cycles during
Maturation of
Amphibian Oocytes
YOSHIO MASUI AND ELLEN K. SHIBUYA
Department of Zoology
University of Toronto
Toronto, Ontario
Canada M5S 1A1
I. INTRODUCTION
A. Maturation and Activation
The characteristic feature of female meiosis in animals, which distin-
guishes it from male meiosis and mitosis, is that female meiosis is arrested
at a certain phase of the chromosome cycle, and an external stimulus is
required to release it from the arrest. In most species, primary oocytes are
arrested at prophase of the first meiosis (prophase I) while enclosed in the
ovarian follicles, but in some marine animals, meiosis resumes when
spawned eggs are fertilized. Chromosomes arrested at prophase I are
partially condensed and contained in a large nucleus called the germinal
vesicle (GV). Each chromosome is composed of two chromatids and is
l
MOLECULAR REGULATION OF NUCLEAR EVENTS Copyright © 1987 by Academic Press, Inc.
IN MITOSIS AND MEIOSIS All rights of reproduction in any form reserved.
2 Yoshio Masui and Ellen K. Shibuya
associated with its homologue. Normally, the resumption of prophase-
arrested meiosis is brought about by gonadotropin stimulation of the folli-
cles enclosing the oocytes, or by penetration of the sperm if the oocytes
have already been spawned. The resumption of prophase-arrested meio-
sis and its subsequent processes have been called (meiotic) maturation.
During maturation the oocyte undergoes a sequence of morphological
changes including germinal vesicle breakdown (GVBD), followed by
chromosome condensation to a metaphase state, and segregation of one
of the haploid sets of chromosomes into the first polar body.
However, in many species, meiosis is arrested again before its comple-
tion, either at metaphase I, as seen in many invertebrates including in-
sects, or at metaphase II, as seen in cephalochordates and vertebrates
(see Masui, 1985, for review). Only in the echinoderms and coelenterates
(Cnidaria) is the chromosome cycle arrested after meiosis is completed,
and a pronucleus is formed. In all these cases, oocytes are induced to
resume chromosome cycles by fertilization, completing meiosis and/or
initiating mitosis. The process induced by fertilization is called (egg) acti-
vation and can be induced by other stimuli as well.
B. Early Studies of Oocyte Maturation
Our classic notion of maturation was derived exclusively from studies
of the oocytes of marine invertebrates. Until the methods of inducing
maturation of vertebrate oocytes in vitro were developed, oocytes of
marine animals were the only source of information about the mechanism
of maturation, since their maturation processes are easily observed and
controlled in vitro. Thus, Wilson (1903) and Yatsu (1905), using oocytes of
Cerebraturus, and Delage (1901), using starfish oocytes, discovered that
maturation was a prerequisite for the oocyte to undergo cell division and
that the contribution of nucleoplasm from the GV was essential for this
process. Since then, numerous studies have been done concerning condi-
tions for initiating maturation of marine eggs (Tyler, 1941; Brachet, 1951;
see Heilbrunn, 1952, for review). At that time, it was generally accepted
that the reaction that induces maturation first occurs in the cortex and that
the most important factor in this process is calcium ions. Indeed,
Heilbrunn (1952) stated that 4'thus in the marine egg cell response to
stimulation involves a liquefaction of the cortex with liberation of cal-
cium."
Pincus and Enzman (1935) were the first to observe maturation of verte-
brate oocytes in vitro, i.e., spontaneous maturation of mammalian oo-
3
1. Development of Cytoplasmic Activities
cytes isolated from follicles. Rugh (1934) found that intraperitoneal injec-
tions of macerated pituitary glands caused not only oocyte maturation,
but ovulation as well in the amphibian Rana pipiens. A year or so later,
Shapiro (1936) and Zwarenstein (1937) found that ovarian follicles of
Xenopus laevis could be induced to ovulate in vitro by culturing in
Ringer's solution containing progesterone. On the other hand, Heilbrunn
et al. (1939) succeeded in inducing oocyte maturation and ovulation in
vitro by incubating dissected ovaries of R. pipiens in Ringer's solution
containing homogenized frog pituitaries. This technique was widely used
by Wright (1945), Nadamitsu (1953), and Tchou-Su and Wang Yu-Lan
(1958) for further investigation of conditions for ovulation in amphibians.
Wright (1961) also reported a synergistic effect of pituitary hormone and
progesterone on ovulation in R. pipiens. Although in this early research
less attention had been devoted to oocyte maturation than ovulation, the
importance of oocyte maturation had been well recognized. Brachet
(1951), commenting on the physiological significance of maturation,
stated that "this field, so interesting both from the point of view of embry-
ology and cellular physiology, remains to be explored." Tchou-Su and
Wang Yu-Lan (1958) were the first researchers to place an emphasis on
studying the cytological aspects of maturation as well as ovulation of
amphibian oocytes in vitro. However, it was not until Dettlaff et al. (1964)
performed a series of microsurgical experiments including nuclear trans-
plantation on toad oocytes that nucleocytoplasmic relations during matu-
ration were analyzed in vertebrate oocytes.
Over the years, animal oocytes have become a unique cell system
particularly well suited to studies of nucleocytoplasmic interactions. Oo-
cytes have provided us with several advantages over other cells in manip-
ulating chromosome cycle events. First, because of their large cell size
and capacity to survive mechanical injuries, oocytes are suitable for vari-
ous microsurgical operations such as enucleation and nuclear transplanta-
tion. Second, by releasing oocytes from their meiotic arrest using artificial
stimulation, we can obtain a fairly large quantity of cells with highly
synchronous chromosome cycles. Third, mainly because of a large store
of nutrients, fully grown oocytes can be handled and cultured with rela-
tive ease.
This chapter describes the progress in research of oocyte maturation
during the past 20 years, with major emphasis on the problems of amphib-
ian oocyte maturation. We discuss amphibian oocytes as a model system
for the study of cytoplasmic control of chromosome behavior, and some
relevant aspects of oocyte maturation in other animals are discussed in
comparison with those in amphibians.
4 Yoshio Masui and Ellen K. Shibuya
II. OOCYTE MATURATION
A. Hormonal Control of Oocyte Maturation
/. Dettlaffs Study
The paper published by Dettlaff et al. (1964) renewed interest in the
study of oocyte maturation among embryologists and endocrinologists
using amphibians. These authors, using the toad species Bufo bufo and B.
viridis, reported that maturation could be induced by pituitary hormone in
oocytes from which follicular investments had been removed, and oo-
cytes induced to mature in this manner could respond to an activation
stimulus, such as pricking with a glass needle, by undergoing surface
contractions. Moreover, when used as recipients for nuclear transplanta-
tion, these oocytes were able to cleave, but failed to acquire this capabil-
ity for cell division if the GV had been removed. Surgical breakage of the
GV and mixing its contents with cytoplasm in oocytes without hormone
treatment did not cause maturation, but "a small amount of karyoplasm
with some cytoplasm taken at the onset of GV dissolution" from hor-
mone-stimulated oocytes could cause maturation when injected into un-
treated oocytes. From these observations the authors speculated that
"unknown changes in nuclear properties precede changes in the cyto-
plasm" and that "substances inducing cytoplasmic maturation are formed
in the karyoplasm only just prior to dissolution of the GV membrane."
Further, since the cytoplasm lacking the GV does not respond to the
action of the hormone, the gonadotropic hormones must affect oocyte
maturation through the oocyte nucleus. However, these authors were
also cautious about implicating cytoplasmic factors, stating that "karyo-
plasm (with cytoplasm) taken from the oocyte at the onset of GV dissolu-
tion can stimulate maturation of oocytes at the initial stage, i.e., it substi-
tutes for the action of gonadotropic hormone."
Two years later, using R. temporaria oocytes, Dettlaff (1966) showed
that actinomycin D and puromycin could prevent hormone-induced matu-
ration, and concluded that "gonadotropins induce DNA-dependent syn-
thesis of specific mRNAs" and "after some time protein synthesis starts,
including the synthesis of enzymes participating somehow in the rupture
of the germinal vesicle membrane." Independently, Smith et al. (1966)
studied protein synthesis by microinjecting [3H]leucine into R. pipiens
oocytes and demonstrated considerable increase in labeled amino acid
incorporation into oocyte proteins during maturation. These studies taken
1. Development of Cytoplasmic Activities 5
together suggested that the induction of oocyte genomic activities by
gonadotropin leads to oocyte maturation.
2. Relative Roles of Pituitary, Follicles, and Progesterone
The implication of the findings by Dettlaff and associates was so impor-
tant that it was necessary to repeat their experiments. Thus, Brachet
(1967) confirmed that both RNA and protein synthesis inhibitors could
inhibit oocyte maturation induced by gonadotropins in several amphibian
species including X. laevis. However, Gurdon (1967) found that human
chorionic gonadotropin (hCG) did not induce maturation of Xenopus oo-
cytes if it was directly injected into the oocytes, while the same hormone
externally applied to the isolated follicles was effective, thus casting a
doubt on the theory of direct hormonal action on the oocyte genome.
Schuetz (1967a), on the other hand, tested in the effects of various go-
nadal steroids on R. pipiens follicles cultured in vitro, and found that
progesterone was the most potent steroid for inducing maturation.
Schuetz (1967b) also found that manual removal of follicle cells reduced
pituitary-induced GVBD by 50% but that it did not affect progesterone-
induced GVBD and that the former could be inhibited by both actinomy-
cin D and puromycin, but the latter only by puromycin. Based on these
results, Schuetz suggested the presence of "a common mechanism con-
cerned with protein synthesis" that mediated pituitary and steroid-in-
duced GVBD and also "the presence of a pituitary-stimulated intermedi-
ary process prior to the initiation of protein synthesis." However, Masui
(1967) pointed out that after manual removal of follicular investments, R.
pipiens oocytes were not totally devoid of adhering follicle cells unless
ovarian pieces were treated with Ca2+-free medium prior to divestment of
the follicular envelopes. He also showed that once all follicle cells were
removed, oocytes were unable to respond to pituitary hormone, but still
responded to progesterone. The oocytes induced to mature by progester-
one were capable of cleavage upon nuclear transplantation. Similar
results were obtained independently by Smith et al. (1968) with oocytes
from which follicle cells were completely removed by pronase treatment.
Masui (1967) also observed that pituitary hormone could induce matura-
tion in follicle-free oocytes if oocytes were packed with follicle cells pre-
viously removed from the oocytes, suggesting that "pituitary hormone
first affects follicle cells that in turn secrete some diffusible factor that
acts on oocytes to cause maturation." The hypothesis that "the follicle
cells secrete a progesterone-like substance" in response to pituitary hor-