Tuesday, November 25, 2008

Trichoplax adhaerens: Hex and Dbx genes

More preadaptations from Trichoplax:
Its function?
Critical element in the development of the liver:
The role of Hex in hemangioblast and hematopoietic development.
The homeoprotein Hex is required for hemangioblast differentiation.
The homeobox gene HEX regulates proliferation and differentiation of hemangioblasts and endothelial cells during ES cell differentiation.

Detoxification of free radicals and damaging molecules play a crucial part in cellular homeostasis as well as systems homeostasis. The liver is mainly responsible for system homeostasis as it contains the highest concentration cells (hepatocytes do the heavy lifting) capable of detoxification, modification and excretion of hazardous molecules. It would be interesting to see what a gene that is associated with the development of the liver is doing in this simple organism at the base of the eumetazoan tree.

The trend of neurologically associated homeobox genes continues.
Regulation and function of Dbx genes in the zebrafish spinal cord.
Dbx homeodomain proteins are important for spinal cord dorsal/ventral patterning and the production of multiple spinal cord cell types. We have examined the regulation and function of Dbx genes in the zebrafish. We report that Hedgehog signaling is not required for the induction or maintenance of these genes; in the absence of Hedgehog signaling, dbx1a/1b/2 are expanded ventrally with concomitant increases in postmitotic neurons that differentiate from this domain. Also, we find that retinoic acid signaling is not required for the induction of Dbx expression. Furthermore, we are the first to report that knockdown of Dbx1 function causes a dorsal expansion of nkx6.2, which is thought to be the cross-repressive partner of Dbx1 in mouse. Our data confirm that the dbx1a/1b/2 domain in zebrafish spinal cord development behaves similarly to amniotes, while extending knowledge of Dbx1 function in spinal cord patterning. 2007 Wiley-Liss, Inc

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