Characterizing a role for α-parvin in Xenopus laevis Development
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In metazoans dynamic regulation of cell adhesion is critical for the cell movements that characterize gastrulation. It is clear that the adhesive property of cells is modulated in a highly coordinated spatial and temporal fashion. In Xenopus, gastrulation has been extensively characterized at the cell and tissue level. The directed intercalation of cells generates the forces that drive tissue shape changes and rearrangements. In Xenopus, the adhesive properties of cells are mediated through the integrin and cadherin families of cell adhesion receptors. The integrins mediate bidirectional signaling across cell membranes. Integrin ligation recruits multi-protein complexes such as the ILK-PINCH-Parvin (IPP) complex to the cytoplasmic tail at sites of focal adhesion. α-parvin is a member of the IPP complex and has two functional calponin-homology (CH) domains. In the IPP complex, α-parvin primarily functions as a scaffolding molecule. However, the mechanistic role of α-parvin has yet to be described in Xenopus. I asked if α-parvin acts as an active modulator of integrin-mediated adhesion during Xenopus laevis gastrulation. I successfully isolated Xenopus α-parvin and performed a phylogenetic analysis on the sequence. α-parvin shares high sequence identity with α-parvin orthologs from other model organisms. The CH domains are also highly conserved. Xenopus α-parvin displays peak expression levels during gastrulation suggesting a role in the rearrangement of cells and tissues during gastrulation. To analyze function, I created GFP tagged α-parvin deletion constructs that isolate each domain. In Xenopus A6 cells, the full length α-parvin construct localizes to focal adhesions. The isolated CH1 domain is not recruited to focal adhesions, while the isolated CH2 domain is found in focal adhesions. This suggests that the CH2 domain of Xenopus α-parvin is responsible for recruitment to sites of integrin adhesion. In embryos, over-expression of full length α-parvin has no effect on development. When the CH1 domain is over expressed, blastopore closure is delayed and anterior–posterior axis extension is inhibited. These embryos develop axial protrusions that resemble a second axis. This would suggest that the CH1 domain is somehow influencing the β-catenin pathway that influences axial development. When the CH2 domain is over expressed, embryos show a dramatic delay and failure of blastopore closure. The anterior-posterior axis is truncated, and the blastocoel is retained. The embryos over-expressing the CH2 domain resemble those in which integrin-FN interactions are disrupted and it is likely that the CH2 domain is acting as a dominant negative to inhibit integrin adhesion. This thesis provides a preliminary analysis of α-parvin function in Xenopus laevis development.
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Richard Do (2021). Characterizing a role for α-parvin in Xenopus laevis Development. UWSpace. http://hdl.handle.net/10012/17417