The cells of the inner cell mass constitute the pluripotent cell population of the early embryo. They have the potential to form all of the tissues of the embryo proper and some extra-embryonic tissues. They can be considered a transient stem cell population for the whole of the embryo, and stem cells maintaining the same capacity can be isolated from these cells. We have isolated, characterised and mutated a novel gene, taube nuss (Tbn), that is essential for the survival of this important cell population. The taube nuss protein sequence (TBN) was highly conserved between human, mouse, Xenopus laevis, Drosophila melanogaster, Caenorhabditis elegans and Arabidopsis thaliana, particularly in a domain that is not present in any published proteins, showing that TBN is the founding member of a completely new class of proteins with an important function in development. The Tbn gene was expressed ubiquitously as early as E2. 5 and throughout embryonic development. It was also expressed in adult brain with slightly higher levels in the hippocampus. The Tbn mutant embryos developed normally to the blastocyst stage and contained inner cell masses. They hatched from the zonae pellucidae, implanted and induced decidual reactions, but failed to develop beyond E4.0. At this time the trophoblast cells were viable, but inner cell masses were not detectable. At E3.75, massive TUNEL-positive DNA degradation and chromatin condensation were visible within the inner cell masses, whereas the cell membranes where intact. Caspase 3 was expressed in these cells. In vitro, the inner cell mass of mutant embryos failed to proliferate and died after a short period in culture. These results indicate that the novel protein, taube nuss, is necessary for the survival of the inner cell mass cells and that inner cell mass cells died of apoptosis in the absence of the taube nuss protein. As cell pruning by apoptosis is a recognised developmental process at this stage of development, the taube nuss protein may be one of the factors regulating the extent of programmed cell death at this time point.

Brison
D. R.
,
Schultz
R. M.
(
1997
)
Apoptosis during mouse blastocyst formation: evidence for a role for survival factors including transforming growth factor alpha.
Biol. Reprod
56
,
1088
1096
Chautan
M.
,
Chazal
G.
,
Cecconi
F.
,
Gruss
P.
,
Goldstein
P.
(
1999
)
Interdigital cell death can occur through a necrotic and caspase-independent pathway.
Curr. Biol
9
,
967
970
Copp
A. J.
(
1978
)
Interaction between inner cell mass and trophectoderm of the mouse blastocyst. I. A study of cellular proliferation.
J. Embryol. Exp. Morphol
48
,
109
125
Coucouvanis
E.
,
Martin
G. R.
(
1995
)
Signals for death and survival: a two-step mechanism for cavitation in the vertebrate embryo.
Cell
83
,
279
287
Duckett
C. S.
,
Nava
V. E.
,
Gedrich
R. W.
,
Clem
R. J.
,
Van Dongen
J. L.
,
Gilfillan
M. C.
,
Shiels
H.
,
Hardwick
J. M.
,
Thompson
C. B.
(
1996
)
A conserved family of cellular genes related to the baculovirus iap gene and encoding apoptosis inhibitors.
EMBO J
15
,
2685
2694
Enari
M.
,
Sakahira
H.
,
Yokoyama
H.
,
Okawa
K.
,
Iwamatsu
A.
,
Nagata
S.
(
1998
)
A caspase-activated DNase that degrades DNA during apoptosis, and its inhibitor ICAD.
Nature
391
,
43
50
Exley
G. E.
,
Tang
C.
,
McElhinny
A. S.
,
Warner
C. M.
(
1999
)
Expression of caspase and BCL-2 apoptotic family members in mouse preimplantation embryos.
Biol. Reprod
61
,
231
239
Feldman
B.
,
Poueymirou
W.
,
Papaioannou
V. E.
,
DeChiara
T. M.
,
Goldfarb
M.
(
1995
)
Requirement of FGF-4 for postimplantation mouse development.
Science
267
,
246
249
Guillemot
F.
,
Nagy
A.
,
Auerbach
A.
,
Rossant
J.
,
Joyner
A. L.
(
1994
)
Essential role of Mash-2 in extraembryonic development.
Nature
371
,
333
336
Jurisicova
A.
,
Latham
K. E.
,
Casper
R. F.
,
Varmuza
S. L.
(
1998
)
Expression and regulation of genes associated with cell death during murine preimplantation embryo development.
Mol. Reprod. Dev
51
,
243
253
King
R. D.
,
Sternberg
M. J.
(
1996
)
Identification and application of the concepts important for accurate and reliable protein secondary structure prediction.
Protein Sci
5
,
2298
2310
Kozak
M.
(
1989
)
The scanning model for translation: an update.
J. Cell Biol
108
,
229
241
Motoyama
N.
,
Wang
F.
,
Roth
K. A.
,
Sawa
H.
,
Nakayama
K.
,
Negishi
I.
,
Senju
S.
,
Zhang
Q.
,
Fujii
S.
, et al. 
(
1995
)
Massive cell death of immature hematopoietic cells and neurons in Bcl-x-deficient mice.
Science
267
,
1506
1510
Nichols
J.
,
Zevnik
B.
,
Anastassiadis
K.
,
Niwa
H.
,
Klewe-Nebenius
D.
,
Chambers
I.
,
Scholer
H.
,
Smith
A.
(
1998
)
Formation of pluripotent stem cells in the mammalian embryo depends on the POU transcription factor Oct4.
Cell
95
,
379
91
Palmieri
S.
,
Peter
W.
,
Hess
H.
,
Schöler
H.
(
1994
)
Oct-4 transcription factor is differentially expressed in the mouse embryo during establishment of the first two extraembryonic cell lineages involved in implantation.
Dev. Biol
166
,
259
267
Pampfer
S.
,
Vanderheyden
I.
,
McCracken
J. E.
,
Vesela
J.
,
De Hertogh
R.
(
1997
)
Increased cell death in rat blastocysts exposed to maternal diabetes in utero and to high glucose or tumor necrosis factor-alpha in vitro.
Development
124
,
4827
4836
Pierce
G. B.
,
Lewellyn
A. L.
,
Parchment
R. E.
(
1989
)
Mechanism of programmed cell death in the blastocyst.
Proc. Natl. Acad. Sci. USA
86
,
3654
3658
Print
C. G.
,
Loveland
K. L.
,
Gibson
L.
,
Meehan
T.
,
Stylianou
A.
,
Wreford
N.
,
de Kretser
D.
,
Metcalf
D.
,
Kontgen
F.
,
Adams
J. M.
,
Cory
S.
(
1998
)
Apoptosis regulator bcl-w is essential for spermatogenesis but appears otherwise redundant.
Proc. Natl. Acad. Sci. USA
95
,
12424
31
Ross
A. J.
,
Waymire
K. G.
,
Moss
J. E.
,
Parlow
A. F.
,
Skinner
M. K.
,
Russell
L. D.
,
MacGregor
G. R.
(
1998
)
Testicular degeneration in Bclw-deficient mice.
Nat. Genet
18
,
251
256
Roth
M. B.
,
Zahler
A. M.
,
Stolk
J. A.
(
1991
)
A conserved family of nuclear phosphoproteins localized to sites of polymerase II transcription.
J. Cell Biol
115
,
587
96
Sahara
S.
,
Aoto
M.
,
Eguchi
Y.
,
Imamoto
N.
,
Yoneda
Y.
,
Tsujimoto
Y.
(
1999
)
Acinus is a caspase-3-activated protein required for apoptotic chromatin condensation.
Nature
401
,
168
173
Sanders
E. J.
,
Wride
M. A.
(
1995
)
Programmed cell death in development.
Int. Rev. Cytol
163
,
105
173
Skarnes
W. C.
,
Moss
J. E.
,
Hurtley
S. M.
,
Beddington
R. S.
(
1995
)
Capturing genes encoding membrane and secreted proteins important for development.
Proc. Natl. Acad. Sci. USA
92
,
6592
6596
Smith
M. S.
,
Wilson
I. B.
(
1971
)
Histochemical observations on early implantation in the mouse.
J. Embryol. Exp. Morphol
25
,
165
174
Susin
S. A.
,
Lorenzo
H. K.
,
Zamzami
N.
,
Marzo
I.
,
Snow
B. E.
,
Brothers
G. M.
,
Mangion
J.
,
Jacotot
E.
,
Costantini
P.
,
Loeffler
M.
, et al. 
(
1999
)
Molecular characterization of mitochondrial apoptosis-inducing factor.
Nature
397
,
441
446
Thompson
J. D.
,
Higgins
D. G.
,
Gibson
T. J.
(
1994
)
CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice.
Nucleic Acids Res
22
,
4673
4680
Vaux
D. L.
,
Korsmeyer
S. J.
(
1999
)
Cell death in development.
Cell
96
,
245
254
Veis
D. J.
,
Sorenson
C. M.
,
Shutter
J. R.
,
Korsmeyer
S. J.
(
1993
)
Bcl-2-deficient mice demonstrate fulminant lymphoid apoptosis, polycystic kidneys, and hypopigmented hair.
Cell
75
,
229
240
Voss
A. K.
,
Thomas
T.
,
Gruss
P.
(
1997
)
Germ line chimeras from female ES cells.
Exp. Cell Res
230
,
45
49
Voss
A. K.
,
Thomas
T.
,
Gruss
P.
(
1998
)
Compensation for a gene trap mutation in the microtubule associated protein 4 locus by alternative polyadenylation and alternative splicing.
Dev. Dyn
212
,
258
266
Voss
A. K.
,
Thomas
T.
,
Gruss
P.
(
1998
)
Efficieny assessment of the gene trap aproach.
Dev. Dyn
212
,
171
180
Voss
A. K.
,
Thomas
T.
,
Gruss
P.
(
2000
)
Mice lacking HSP90beta fail to develop a placental labyrinth.
Development
127
,
1
11
Weil
M.
,
Jacobson
M. D.
,
Coles
H. S.
,
Davies
T. J.
,
Gardner
R. L.
,
Raff
K. D.
,
Raff
M. C.
(
1996
)
Constitutive expression of the machinery for programmed cell death.
J. Cell Biol
133
,
1053
1059
This content is only available via PDF.