Future investigations of branchial tracts should focus on embryologic molecular genetics, especially with respect to the Hox genes
Regulation of Hox gene
expression during mammalian development is complex and involves regulatory RNAs and proteins whose activities orchestrate the establishment and subsequent maintenance of the AP Hox expression patterns (for review, see Chopra 2010).
Under the direction of Duboule and Daniel Noordermeer, the team analyzed thousands of Hox gene
But what was surprising to us in this study was that a single Hox gene
acts as a global organizer of motor neurons and their connections.
This particular Hox gene
may regulate the amount of grooming performed by an animal," Capecchi says.
On the other hand, the specific nerve cells are actually produced in the head region, but the Hox genes
turn them into another, unknown, type of cell.
The myriad developmental roles of the Hox genes
have obscured the fact that some of them also operate within the adult animal.
Holland's preliminary studies of lampreys suggest that they have fewer clusters of hox genes
than other vertebrates do.
While at the University of Oxford in England, Jordi Garcia-Fernandez and Peter Holland joined in by tracking down this animal's hox genes
are arranged in particular clusters on an animal genome and only a subset of Hox genes
are active in a given cell.
However, when inserted into transgenic mouse embryos, the fish Hox genes
were only active in the mouse arm but not in the digits, showing that the fish DNA lacks essential genetic elements for digit formation.
Snakes have a nearly complete set of Hox genes
, which lay out the body plans of a variety of animals.