Finley Kenneth R, Tennessen Jason, Shawlot William
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.
Gene Expr Patterns. 2003 Oct;3(5):681-4. doi: 10.1016/s1567-133x(03)00091-7.
The anterior visceral endoderm (AVE) plays an important role in anterior-posterior axis formation in the mouse. The AVE functions in part by expressing secreted factors that antagonize growth factor signaling in the proximal epiblast. Here we report that the Secreted frizzled-related protein 5 (Sfrp5) gene, which encodes a secreted factor that can antagonize Wnt signaling, is expressed in the AVE and foregut endoderm during early mouse development. At embryonic day (E) 5.5, Sfrp5 is expressed in the visceral endoderm at the distal tip region of the embryo and at E6.5 in the AVE opposite the primitive streak. In Lim1 embryos, which lack anterior neural tissue and sometimes form a secondary body axis, Sfrp5-expressing cells fail to move towards the anterior and remain at the distal tip of E6.5 embryos. When compared with Dkk1, which encodes another secreted Wnt antagonist molecule present in the visceral endoderm, Sfrp5 and Dkk1 expression overlap but Sfrp5 is expressed more broadly in the AVE. Between E7.5 and 8, Sfrp5 is expressed in the foregut endoderm underlying the cardiac mesoderm. At E8.5, Sfrp5 is expressed in the ventral foregut endoderm that gives rise to the liver. Additional domains of Sfrp5 expression occur in the dorsal neural tube and in the forebrain anterior to the optic placode. These findings identify a gene encoding a secreted Wnt antagonist that is expressed in the extraembryonic visceral endoderm and anterior definitive endoderm during axis formation and organogenesis in the mouse.
前肠内胚层（AVE）在小鼠前后轴形成过程中发挥着重要作用。AVE部分通过表达分泌因子来发挥功能，这些分泌因子可拮抗近端上胚层中的生长因子信号传导。在此，我们报告分泌型卷曲相关蛋白5（Sfrp5）基因，该基因编码一种可拮抗Wnt信号传导的分泌因子，在小鼠早期发育过程中在AVE和前肠内胚层中表达。在胚胎第（E）5.5天，Sfrp5在胚胎远端尖端区域的内胚层中表达，在E6.5时在与原条相对的AVE中表达。在缺乏前神经组织且有时会形成次生体轴的Lim1胚胎中，表达Sfrp5的细胞无法向前移动，而是留在E6.5胚胎的远端尖端。与Dkk1相比，Dkk1编码在内胚层中存在的另一种分泌型Wnt拮抗剂分子，Sfrp5和Dkk1的表达有重叠，但Sfrp5在AVE中的表达更广泛。在E7.5至E8之间，Sfrp5在心脏中胚层下方的前肠内胚层中表达。在E8.5时，Sfrp5在产生肝脏的腹侧前肠内胚层中表达。Sfrp5表达的其他区域出现在背神经管和视板前方的前脑中。这些发现确定了一个编码分泌型Wnt拮抗剂的基因，该基因在小鼠轴形成和器官发生过程中在胚外内胚层和前确定内胚层中表达。
