Bardwell, Vivian J.

Krentz, Anthony D.

Matson, Clinton K.

Murphy, Mark W.

Yoshida, Shosei

Zarkower, David

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The mammalian Doublesex homolog DMRT1 controls the mitosis versus meiosis decision in males 

reductions by PP2 and U7 may have been generated via different
mechanisms, given that the two drugs had varying effects on sperm
incorporations and pronuclear differentiations. Moreover, confocal
imaging revealed Ca2+ oscillations were blocked by U7 but not by
PP2. Collectively, such data fail to support the view that SFK signaling is
required for either GVBD or for initiating fertilization-induced Ca2+
oscillations in Cerebratulus and instead suggest that PP2-mediated
inhibitions of polar body formation and cleavage involve undeter-
mined drug effects on processes other than oscillation generation.
doi:10.1016/j.ydbio.2010.05.352
Program/Abstract # 342
The mammalian Doublesex homolog DMRT1 controls the mitosis
versus meiosis decision in males
David Zarkowera, Clinton K. Matsona, Mark W. Murphya,
Anthony D. Krentza, Shosei Yoshidab, Vivian J. Bardwella
aDepartment of Genetics, Cell Biology, and Development,
University of Minnesota, Minneapolis, MN 55455, USA
bNational Institute of Basic Biology, Okazaki, Aichi 444-8787 Japan
Germ cells are uniquely capable of undergoing either mitotic
divisions, like other cells, or meiotic divisions that permit gameto-
genesis. In mammals meiosis is triggered by retinoic acid (RA), which
activates genes including the meiotic inducer Stra8. Fetal males avoid
meiosis by degrading RA in the fetal testis. When meiosis begins in
males at puberty it requires RA and Stra8, but how these are
controlled in spermatogonia has been unknown. We have found that
the Doublesex-related transcription factor DMRT1 determines
whether spermatogonia undergo mitosis or initiate meiosis. Sperma-
togonia lacking DMRT1 have abnormally active RA signaling and
prematurely enter meiosis, independent of the normal spermatogenic
cycle. Chromatin immunoprecipitation and other approaches show
that control of meiotic initiation by DMRT1 involves direct transcrip-
tional regulation of key RA metabolic enzymes and Stra8. Analysis of
vitamin A depleted animals that lack RA reveals that DMRT1 also
controls at least one retinoid-independent meiotic inducer. These
results establish DMRT1 as an essential and direct regulator of the
mitosis versus meiosis switch. The DM domain gene family to which
DMRT1 belongs is deeply conserved in metazoan sexual regulation,
and thus our findings also may have implications for meiotic control
outside of mammals.
doi:10.1016/j.ydbio.2010.05.353
Program/Abstract # 343
The RNA-binding protein Nanos2 is required to maintain
spermatogonial stem cells
Aiko Sadaa, Atsushi Suzukib, Hitomi Suzukic, Yumiko Sagaa,d
aDept. of Genetics, SOKENDAI, Mishima, Shizuoka, Japan
bIRC, Yokohama National Univ., Hodogaya-ku, Yokohama, Japan
cDept. of Biological Sciences, Tokyo Univ., Bunkyo-ku, Tokyo, Japan
dDivision of Mammalian Development, NIG, Mishima, Shizuoka, Japan
In mice, spermatogenesis is initiated from a small number of stem
cells belonging to undifferentiated spermatogonia. However, it
remains unclear 1) which types of spermatogonia actually act as the
stemcells and 2) how is the stemcell function regulated. Nanos, a zinc-
finger RNA-binding protein, has been proposed as a conserved factor
for germline stem cell function. In adult testes, Nanos2 is predomi-
nantly expressed in a subset of undifferentiated spermatogonia.
However, the majority of Nanos2-null germ cells die by apoptosis
before birth, hindering functional studies of Nanos2 during sperma-
togenesis.With the use of transgenicmouse strategies, I found that the
RNA-binding protein Nanos2 is a key regulator for the maintenance of
spermatogonial stem cells. Lineage-tracing analyses revealed that
Nanos2-expressing spermatogonia self-renew and generate the entire
spermatogenic cell lineage. Conditional disruption of postnatalNanos2
depleted spermatogonial stem cell reserves, whereas mouse testes in
which Nanos2 had been overexpressed accumulated spermatogonia
with undifferentiated, stem cell-like properties. Thus, Nanos2 is
expressed in self-renewing spermatogonial stem cells and maintains
the stem cell state during murine spermatogenesis.
doi:10.1016/j.ydbio.2010.05.354
Program/Abstract # 344
Stage-specific expression of the homeodomain protein Cux1 in
Sertoli cells and spermatids during spermatogenesis
Tony N. Jelsmaa, Melissa R. Krolla,b, Engela S. Vissa,b, Jonathan Lambb,
Joy Horstmana,b, Alexander Powella,b, Andrea VanWykb,
Kaarlo Hinkkalaa,b, Aaron Taylorb, Gregory VandenHeuvelb
aDept. of Biology, Dordt College, Sioux Center, IA, USA
bDept. of Anatomy and Cell Biology, Univ. Kansas Med. Center,
Kansas City KS, USA
The homeodomain protein Cux1 exists as multiple isoforms. The
200 kDa Cux1 protein is highly expressed in the developing kidney,
where it functions to regulate cell proliferation. A 55 kDa Cux1 isoform
is expressed exclusively in the testes. Transgenic mice ectopically
expressing the 200 kDa Cux1 protein develop transient multiorgan
hyperplasia, including the testes. We determined the pattern and
timing of Cux1 protein expression in the developing testes. Cux1
expression was continuous in Sertoli cells of prepubertal testes, but
became cyclic when spermatids appeared. In mature mice, Cux1 was
highly expressed only in round spermatids at stages IV–V of
spermatogenesis, in both spermatids and Sertoli cells at stages VI–X,
and only in Sertoli cells at Stage XI. In Cux1 transgenic mice therewere
significantly fewer tubules expressing Cux1 in both Sertoli cells and
spermatids and significantly more tubules expressing Cux1 in either
spermatids or Sertoli cells. Moreover, Cux1 was not expressed in
proliferating cells in testes from either wild type or transgenic mice.
Thus, unlike the role of the somatic form of Cux1 in cell proliferation,
the testis-specific form of Cux1 is not involved in cell division and
appears to play a role in signaling between spermatids and Sertoli cells.
doi:10.1016/j.ydbio.2010.05.355
Program/Abstract # 345
Inhibitory action of Xenopus dicalcin on sperm–egg interaction
during fertilization
Naofumi Miwaa, Motoyuki Ogawab, Yoshiki Hiraokac, Ken Takamatsua,
Satoru Kawamurad
aDept. of Physiol., Toho Univ., Tokyo, Japan
bDept. of Med. Educ., Kitasato Univ., Kanagawa, Japan
cDept. of Anat., Keio Univ., Tokyo, Japan
dGrad. Sch. Frontier Biosci., Osaka Univ., Osaka, Japan
To contribute to the study of sperm–egg interaction in the course of
fertilization, we have isolated and characterized Xenopus dicalcin in
Xenopus eggs. Xenopus dicalcin is localized markedly in the egg-coating
envelope (called vitelline envelope; VE), and exhibits a Ca2+-dependent
binding to two glycoproteins that constitute polymeric filaments of VE.
Since these VE glycoproteins are considered to function as sperm-
receptors, we examined the effect of dicalcin on sperm–VE binding,
sperm–VEpenetration, and fertilization in vitro. Preincubation ofXenopus
511Abstracts


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The mammalian Doublesex homolog DMRT1 controls the mitosis versus meiosis decision in males

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