1063-0740/02/2806- $27.00 © 2002
Russian Journal of Marine Biology, Vol. 28, No. 6, 2002, pp. 355–364.
Original Russian Text Copyright © 2002 by Biologiya Morya, Lamash.
Development of oocytes is blocked in many inverte-
brates at the end of prophase of the ﬁrst meiotic divi-
sion. At this stage of cellular cycle, oocytes have a large
nucleus termed the germinal vesicle. The resumption of
meiotic divisions in most instances occurs under the
effect of a species-speciﬁc mitogen (usually a hor-
mone). At present, two such hormones, serotonin in
bivalves  and 1-methyladenine (1-MeA) in star-
ﬁshes , have been identiﬁed.
The hormonal signal (primary messenger) should be
perceived (recognized) through binding with a speciﬁc
plasma membrane receptor and then be apprehended
(decoded) by subsequent transmembrane messengers
bound with the receptor. In some instances, the messen-
gers are GTP-binding regulatory proteins (G-proteins).
They activate or inhibit such membrane enzyme sys-
tems as lipid-speciﬁc phosphodiesterases (PL-S, PL-
A2) and adenylate cyclase (AC). Catabolic products of
these enzymes (secondary messengers) speciﬁcally
modulate various protein kinases and/or phosphatases,
which, in turn, vary the activity of corresponding endo-
cellular effectors. Meiosis-inducing factor, the so-
called M-phase promoting factor (MPF) is the cellular
effector of maturation. It consists of a catalytic subunit,
serine–threonine protein kinase p34
(cdc2) and a
regulatory subunit, cyclin B . MPF is present in
cytoplasm in form of an inactive complex, which is
sometimes referred to as MPF precursor (pre-MPF).
Activation of MPF is associated with a complex pro-
cess of phosphorylation and dephosphorylation of its
subunits and occurs concurrently with breakdown of
the nuclear membrane (germinal vesicle breakdown)
. Germinal vesicle breakdown is the ﬁrst visualized
response of the oocyte to the hormonal signal and a
morphological marker signifying MPF activation.
It has been shown that MPF is formed in process of
meiotic and mitotic divisions in virtually all studied
species, from yeasts to humans. Thus, formation of
active MPF is considered to be part of a universal
mechanism of regulation of cell division.
Oocytes of starﬁshes are a convenient experimental
model for studies of signal pathways leading to MPF
formation, due to the relative ease of reproduction of
meiotic maturation in vitro. The achievements of recent
decades in study of mechanisms of oocyte maturation
in these animals have been presented in a series of
papers [14, 27, 34]. In this review, we analyze the infor-
mation available today on the role of the membrane
enzyme complexes participating in transduction of the
hormonal signal from the receptor to the cell, as well as
the processes occurring in the oocyte up to germinal
vesicle breakdown and MPF formation.
1-Methyladenine: The Hormone of Oocyte Maturation
The hormone of starﬁsh oocyte maturation, 1-MeA,
was the ﬁrst hormone identiﬁed as a meiosis-inducing
substance in invertebrates . It was determined that
synthesis of 1-MeA occurred in follicular cells sur-
rounding oocytes, under the effect of gonad-stimulat-
ing substance (GSS), a peptide hormone produced by
cells of the radial nerve . Within several minutes
after processing of a slice of gonad with GSS, the quan-
tity of 1-MeA in follicular cells reached a level sufﬁ-
cient to induce maturation and release of oocytes .
The rate of synthesis of 1-MeA depends on the concen-
tration of the neurohormone and the duration of its
action on the gonad, as well as on the number of follic-
ular cells surrounding the oocyte . The effect of
Hormonal Control of Meiosis in Starfishes
N. E. Lamash
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received July 10, 2002
—Development of starﬁsh oocytes is blocked at the prophase stage of the ﬁrst meiotic division. The
resumption of meiotic divisions occurs under the effect of the maturation hormone 1-methyladenine (1-MeA),
which binds to a speciﬁc receptor of the oocyte cell surface. New data in the literature on endocellular signal
mechanisms taking part in conduction of the regulatory signal modulated by 1-MeA are adduced in the review.
Data on the properties of the 1-MeA receptor are presented and mechanisms of biosynthesis of 1-MeA are con-
sidered. The main focus is on processes occurring in the oocyte during the ﬁrst minutes after the impact of the
hormone, before the destruction of the germinal vesicle. A hypothetical pattern of transduction of the hormonal
signal is proposed.
maturation of oocytes, starﬁshes, 1-methyladenine