Evolutionarily conserved requirement of Cdx for post-occipital tissue emergence.
Mouse Cdx genes are involved in axial patterning and partial Cdx mutants exhibit posterior embryonic defects. We found that mouse embryos in which all three Cdx genes are inactivated fail to generate any axial tissue beyond the cephalic and occipital primordia. Anterior axial tissues are laid down and well patterned in Cdx null embryos, and a 3' Hox gene is initially transcribed and expressed in the hindbrain normally. Axial elongation stops abruptly at the post-occipital level in the absence of Cdx, as the posterior growth zone loses its progenitor activity. Exogenous Fgf8 rescues the posterior truncation of Cdx mutants, and the spectrum of defects of Cdx null embryos matches that resulting from loss of posterior Fgfr1 signaling. Our data argue for a main function of Cdx in enforcing trunk emergence beyond the Cdx-independent cephalo-occipital region, and for a downstream role of Fgfr1 signaling in this function. Cdx requirement for the post-head section of the axis is ancestral as it takes place in arthropods as well.
Hubrecht Institute, Developmental Biology and Stem Cell Research, Uppsalalaan 8, 3584 CT Utrecht, and University Medical Center Utrecht, 3584 CX Utrecht,  The Netherlands.
Carina
C
van Rooijen
Salvatore
S
Simmini
Monika
M
Bialecka
Roel
R
Neijts
Cesca
C
van de Ven
Felix
F
Beck
Jacqueline
J
Deschamps
D000818:Animals; D000071616:CDX2 Transcription Factor; D004622:Embryo, Mammalian / Q000378:metabolism; D047108:Embryonic Development / Q000235:genetics / Q000502:physiology*; D019143:Evolution, Molecular; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D019170:Somites / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D000071616:CDX2 Transcription Factor; C491272:Cdx1 protein, mouse; C487514:Cdx2 protein, mouse; C084563:Cdx4 protein, mouse; D018398:Homeodomain Proteins; D014157:Transcription Factors