36.2 Wednesday, Jan. 5 Wnt signaling in the cnidarian Nematostella vectensis: Insights into the evolution of gastrulation WIJESENA, N.*; KUMBUREGAMA, S.; XU, R.; WIKRAMANAYAKE, A.; Univ. Miami, Coral Gables, FL 33146 ; Univ. Miami, Coral Gables, FL 33146 ; Univ. Hawaii at Manoa, Honolulu, HI 96822; Univ. Miami, Coral Gables, FL 33146 firstname.lastname@example.org
Evolution of gastrulation was arguably the key step that enabled the remarkable metazoan diversification. The developmental mechanisms that induced archenteron formation in the “urmetazoan” are unknown, but insights into this process will come from an increased understanding of development in basal metazoan taxa. Here, we show that in Nematostella vectensis initial archenteron invagination requires NvStrabismus (NvStbm), a maternally-expressed core component of the Wnt/Planar Cell Polarity (PCP) pathway. NvStbm protein is localized to the animal pole from the zygote through the cleavage stages, and becomes restricted to the apical side of invaginating bottle cells at the blastopore. Antisense morpholino-mediated NvStbm-knockdown blocked archenteron invagination, but had no effect on Wnt/ß-catenin signaling-mediated endoderm cell fate specification. Conversely, blocking ß-catenin nuclearization blocked endoderm specification, but had no effect on primary archenteron invagination. Our results demonstrate that initial archenteron invagination can be uncoupled from endoderm cell fate specification in Nematostella, and provides evidence that these two processes could have evolved independently during metazoan evolution. We propose a model for the evolution of gastrulation, where asymmetric accumulation and activation of Wnt pathway components at the animal pole of a blastula-like urmetazoan induced endoderm cell fate specification and the cell shape changes that led to the initial formation of an archenteron. We will also present experimental results showing that two other localized Wnt pathway components, NvFlamingo and NvFrizzled10, mediate both Wnt/β-catenin signaling and Wnt/PCP signaling in Nematostella.