Int. J. Dev. Biol. 57: 407 - 414 (2013)

https://doi.org/10.1387/ijdb.130010st

Vol 57, Issue 5

Hippo signaling components, Mst1 and Mst2, act as a switch between self-renewal and differentiation in Xenopus hematopoietic and endothelial progenitors

Open Access | Original Article | Published: 15 April 2013

Susumu Nejigane¹, Shuji Takahashi*^,2, Yoshikazu Haramoto³, Tatsuo Michiue¹ and Makoto Asashima³

¹Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Japan, ²Komaba Organization for Educational Excellence, College of Arts and Sciences, The University of Tokyo, Japan and ³Research Center for Stem Cell Engineering (SCRC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan

Abstract

Hippo signaling is a conserved pathway that regulates cell proliferation and organ size control. Mst1 and Mst2 were identified as homologs of hippo and as core kinases of the Hippo pathway in mammals. Here, we have characterized the role of Mst1 and Mst2 during Xenopus primitive hematopoiesis. We showed that Mst1 and Mst2 were strongly expressed in the Xenopus ventral blood island, where primitive hematopoiesis is initiated. Loss-of-function analysis of Mst1/2 revealed morphogenetic defects, including short axis, smaller eyes and abnormal epidermis, and decreased phosphorylation of Yap. Mst1/2 morphants did not exhibit any change in the expression of hematopoietic and endothelial progenitor markers in early hematopoietic development. In addition, we have shown that such progenitor markers were continuously expressed through to the late hematopoietic development stage. As a result, the expression of erythroid, myeloid and endothelial differentiation markers were decreased in Mst1/2 morphants. Our results indicate that Mst1/2 act as a differentiation switch in Xenopus hematopoietc and endothelial progenitors.

Keywords

Hippo signaling, Mst, Yap, primitive hematopoiesis, Xenopus tropicalis