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Dev Biol December 15, 2006; 300 (2): 554-69.

Neurotrophin receptor homolog (NRH1) proteins regulate mesoderm formation and apoptosis during early Xenopus development.

Knapp D , Messenger N , Ahmed Rana A , Smith JC .

Recent experiments suggest that Xenopus Neurotrophin Receptor Homolog 1 (NRH1) proteins act through the planar cell polarity pathway to regulate convergent extension movements during gastrulation and neurulation. We show in this paper that NRH1 proteins are also required for the proper expression of mesodermally expressed genes such as Xbra and Chordin, and to a lesser extent, of Xwnt11. Loss of NRH1 function is followed, during gastrula and neurula stages, by a dramatic increase in apoptosis. Apoptosis is delayed by injection of Xbra RNA, suggesting that cell death is a consequence, at least in part, of the down-regulation of this gene, and it is also delayed by expression of activated forms of Rho, Rac and Cdc42. These small GTPases have previously been implicated in the planar cell polarity pathway in Xenopus and, in other systems, in the regulation of apoptosis. We conclude that the effects of NRH1 proteins include the regulation of mesodermal gene expression and that the disruption of gastrulation that is caused by their loss of function is a consequence of the down-regulation of Xbra and other genes, in addition to direct interference with the planar cell polarity pathway. The apoptosis observed in embryos lacking NRH1 function is not an indirect consequence of the disruption of gastrulation, and indeed it may contribute to the observed morphological defects.

PubMed ID: 17055478
Article link: Dev Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: akt1 cdc42 chrd.1 dvl1 dvl2 fn1 gnao1 gsc itgam mob1a nradd odc1 rac1 rho rho.2 tbx2 tbxt wnt11b
Morpholinos: nradd MO1 nradd MO2 nradd MO3 nradd MO4 nradd MO5 nradd MO6 nradd MO7 tbxt.2 MO1

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