Potential R-spondin1 involvement in mammary stem cell function.
Résumé
The R-spondin (Rspo) family genes were recently isolated in mouse (Kamata et al., 2004) and human (Kim et al., 2005). The Rspo physiological functions were reported in various developmental processes, including mouse apical ectodermal ridge (Nam et al., 2007), placental (Aoki et al., 2007) and ovarian (Tomizuka et al., 2008; Chassot et al., 2008) developments. All members of the Rspo family directly activate the canonical Wnt signaling pathway by binding to the Wnt co-receptor LRP6 (Nam et al., 2006; Wei et al., 2007; Kim et al., 2008). Their gene expression analyses in mouse embryogenesis revealed a different expression pattern for each transcript (Nam et al., 2007). Rspo1 knock-out XX mice were shown to be sex-reversed and some that remain sub-fertile (Tomizuka et al., 2008; Chassot et al., 2008) were unable to feed their pups for some unknown reason. This observation let us to investigate a potential role of this gene in the mammary gland biology.