Um golpe na hipótese de ancestralidade comum???

terça-feira, fevereiro 15, 2011

Trophectoderm Lineage Determination in Cattle

Developmental Cell, Volume 20, Issue 2, 244-255, 15 February 2011
Copyright © 2011 Elsevier Inc. All rights reserved.


Debra K. Berg, Craig S. Smith, David J. Pearton, David N. Wells, Ric Broadhurst, Martyn Donnison, Peter L. Pfeffer


Late blastocyst cattle trophectoderm (TE) expresses Oct4 and is not yet committed 

Cdx2 is required for cattle TE maintenance but not for Oct4 repression 

The mouse Oct4 locus is also repressed via 

AP2 binding sites that are not conserved

TE regulatory circuitry correlates with the timing of TE commitment and implantation


The trophectoderm (TE) and inner cell mass (ICM) are committed and marked by reciprocal expression of Cdx2 and Oct4 in mouse late blastocysts. We find that the TE is not committed at equivalent stages in cattle, and that bovine Cdx2 is required later, for TE maintenance, but does not repress Oct4 expression. A mouse Oct4 (mOct4) reporter, repressed in mouse TE, remained active in the cattle TE; bovine Oct4 constructs were not repressed in the mouse TE. mOct4 has acquired Tcfap2 binding sites mediating Cdx2-independent repression—cattle, humans, and rabbits do not contain these sites and maintain highOct4 levels in the TE. Our data suggest that the regulatory circuitry determining ICM/TE identity has been rewired in mice, to allow rapid TE differentiation and early blastocyst implantation. These findings thus emphasize ways in which mice may not be representative of the earliest stages of mammalian development and stem cell biology.




A embriogênese é um estágio que não tolera muito as mutações. Uma vez que se trata de uma mesma classe -- mamíferos, isso aqui deve significar um golpe na hipótese da ancestralidade comum??? Eu acho que sim...