Nuclear Factor of Activated T Cells-5 Regulates Notochord Lumenogenesis in Chordate Larval Development

Abstract

Osmoregulation is essential for organisms to adapt to the exterior environment and plays an important role in embryonic organogenesis. Tubular organ formation usually involves a hyperosmotic lumen environment. The mechanisms of how the cells respond and regulate lumen formation remain largely unknown. Here, we reported that the nuclear factor of activated T cells-5 (NFAT5), the only transcription factor in the NFAT family involved in the cellular responses to hypertonic stress, regulated notochord lumen formation in chordate Ciona. Ciona NFAT5 (Ci-NFAT5) was expressed in notochord, and its expression level increased during notochord lumen formation and expansion. Knockout and expression of the dominant negative of NFAT5 in Ciona embryos resulted in the failure of notochord lumen expansion. We further demonstrated that the Ci-NFAT5 transferred from the cytoplasm into nuclei in HeLa cells under the hyperosmotic medium, indicating Ci-NFAT5 can respond the hypertonicity. To reveal the underly mechanisms, we predicted potential downstream genes of Ci-NFAT5 and further validated Ci-NFAT5-interacted genes by the luciferase assay. The results showed that Ci-NFAT5 promoted SLC26A6 expression. Furthermore, expression of a transport inactivity mutant of SLC26A6 (L421P) in notochord led to the failure of lumen expansion, phenocopying that of Ci-NFAT5 knockout. These results suggest that Ci-NFAT5 regulates notochord lumen expansion via the SLC26A6 axis. Taken together, our results reveal that the chordate NFAT5 responds to hypertonic stress and regulates lumen osmotic pressure via an ion channel pathway on luminal organ formation.

Matrix metalloproteinase Nas15 regulates the lumen formation and expansion in Ciona notochord

“…But there is no basement membrane ECM can be found but only short fiber ECM instead in the extracellular lumen (Wei et al, 2017), which suggesting a degradation mechanism may exist on the initial apical domain. During the expansion of the Ciona notochord lumen, a hydrostatic pressure is generated within the lumen space, driving its expansion (He et al, 2022). In this mechanism, the apical ECM need to be soluble.…”

Dynamics of Chromatin Opening across Larval Development in the Urochordate Ascidian Ciona savignyi

“…These methods are described in detail in [ 80 ]. RNAiso plus (TAKARA, Kusatsu, Shiga Japan) was used to isolate total RNA from frozen embryos at different stages.…”

Recent Developments in Ion Channel and Ion-Related Signaling

“…He et al [4] investigated the involvement of the chordate NFAT5 in the regulation of lumen osmotic pressure via an ion channel-mediated pathway on luminal organ formation. Changes in the apical delivery of ions by ion pumps and channels create an osmotic pressure within the lumen of acini.…”