The mouse embryo autonomously acquires anterior-posterior polarity at implantation.
The earliest recognizable sign of patterning of the mouse embryo along the anteroposterior (A-P) axis is the migration of the distal visceral endoderm (DVE) toward the future anterior side. Here we report an asymmetry in the mouse embryo at an unexpectedly early stage. The gene for Lefty1, a Nodal antagonist that influences the direction of DVE migration, was found to be asymmetrically expressed in the primitive endoderm of the implanting blastocyst. Lefty1 expression begins randomly in the inner cell mass (ICM) of the blastocyst but is regionalized to one side of the tilted ICM shortly after implantation. Asymmetric expression of Lefty1 can be established by in vitro culture, indicating that it does not require interaction with the uterus. The asymmetric Lefty1 expression is induced by Nodal signaling, although Nodal and genes for its effectors are expressed symmetrically. This asymmetry in molecular patterning of the mouse embryo pushes back the origin of the A-P body axis to the peri-implantation stage.
Developmental Genetics Group, Graduate School of Frontier Biosciences, Osaka University and Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan.
Katsuyoshi
K
Takaoka
Masamichi
M
Yamamoto
Hidetaka
H
Shiratori
Chikara
C
Meno
Janet
J
Rossant
Yukio
Y
Saijoh
Hiroshi
H
Hamada
D000818:Animals; D001483:Base Sequence; D001757:Blastomeres / Q000502:physiology; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D010064:Embryo Implantation / Q000235:genetics / Q000502:physiology*; D004707:Endoderm / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D066298:In Vitro Techniques; D055458:Left-Right Determination Factors; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D055457:Nodal Protein; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*
D055458:Left-Right Determination Factors; C111386:Lefty1 protein, mouse; D008565:Membrane Proteins; D055457:Nodal Protein; C526008:Nodal protein, mouse; D016212:Transforming Growth Factor beta