In both mouse and chick embryos, Sprouty genes are expressed in intimate association with FGF signaling centers.
Today, two teams of researchers report having solved one part of this mystery, pinpointing how the organ gets its start in snake, lizard, mouse, and chick embryos.
bmp4 is expressed in the developing cristae of zebrafish, mouse and chick [1] [4], while in mouse and chick, Bmp2 is expressed in the canal genesis zone, adjacent to the cristae, and in the epithelium of the developing canals [5].
Although the forebrain regions of the mouse and chick are not directly comparable, the cerebellar structure and hindbrain are highly conserved between species.
In addition, phosphorylation of c-Jun was shown to be required for embryonic programmed cell death in motoneurons in mouse and chick [46].
These distinct results may reflect the difference between mouse and chick models, or differences between the in vitro and in vivo approaches.
In mouse and chick embryos, Gli3 expression is excluded from the posterior part of the limb buds, when Hand2 expression appears in the posterior region.
Based on multiple sequence alignment analysis, this Thr residue is not highly evolutionarily conserved, with alternative amino acids being found in dog, mouse and chick.
However, cyclic PSM expression of lunatic fringe (Lfng), which encodes a glycosyl-transferase that modulates activity of the Notch receptor, is detected in mouse and chick [10] [12], but not in fish [13], [14].
Hoxd9-Hoxd13 arexpresseded in overlapping domains centred on the posterior-distal region in early mouse and chick wing buds with Hoxd13 expression being most posteriorly and distally restricted [9], [10].
(1) Shh expression appears as soon as there is a morphological bud in mouse and chick embryos (concomitant with Hoxd10), whereas Shh is transcribed very late (concomitant with Hoxd13) in pectoral fin buds of dogfish (S. canicula).
