Comparison of extraembryonic expression of Eomes and Cdx2 in pregastrulation chick and mouse embryo unveils regulatory changes along evolution.
In the mouse blastocyst, Eomes and Cdx2 are critical for establishing the trophoectoderm, the precursor of the placenta. To better understand how the trophoectoderm lineage arose in mammals during evolution, we examined the expression of their orthologues in the pregastrulation chick embryo and found that, while both genes are expressed in extraembryonic tissues, their temporal pattern of expression differs from what occurs in mouse. Moreover, we failed to detect expression of other genes specific from the mouse trophoectoderm in extraembryonic regions of the chick. Also unlike the mouse, chick Eomes is expressed in primordial germ cells. Finally, conserved noncoding elements in the Eomes genomic region are unable to drive trophoectoderm restricted expression in the mouse blastocyst, but do so in conserved sites of expression such as the forebrain. These results suggest that critical changes in the gene regulatory networks controlling extraembryonic development accompanied the appearance of the trophoectoderm in mammals.
Pernaute
Bárbara
B
Department of Cardiovascular Developmental Biology, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain.
Cañon
Susana
S
Crespo
Miguel
M
Fernandez-Tresguerres
Beatriz
B
Rayon
Teresa
T
Manzanares
Miguel
M
D000818:Animals; D005075:Biological Evolution; D001755:Blastocyst / Q000378:metabolism; D000071616:CDX2 Transcription Factor; D019070:Cell Lineage; D002642:Chick Embryo / Q000378:metabolism*; D017124:Conserved Sequence; D004742:Enhancer Elements, Genetic; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D010920:Placenta / Q000196:embryology; D011247:Pregnancy; D020825:T-Box Domain Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
D000071616:CDX2 Transcription Factor; C487514:Cdx2 protein, mouse; C491198:Eomes protein, mouse; D018398:Homeodomain Proteins; D020825:T-Box Domain Proteins; D014157:Transcription Factors