The zebrafish dyrk1b gene is important for endoderm formation

Abstract Nodal‐signaling is required for specification of mesoderm, endoderm, establishing left–right asymmetry, and craniofacial development. Wdr68 is a WD40‐repeat domain‐containing protein recently shown to be required for endothelin‐1 (edn1 ) expression and subsequent lower jaw development. Previous reports detected the Wdr68 protein in multiprotein complexes containing mammalian members of the dual‐specificity tyrosine‐regulated kinase (dyrk ) family. Here we describe the characterization of the zebrafish dyrk1b homolog. We report the detection of a physical interaction between Dyrk1b and Wdr68. We also found perturbations of nodal signaling in dyrk1b antisense morpholino knockdown ( dyrk1b‐ MO) animals. Specifically, we found reduced expression of lft1 and lft2 ( lft1/2 ) during gastrulation and a near complete loss of the later asymmetric lft1 / 2 expression domains. Although wdr68 ‐MO animals did not display lft1/2 expression defects during gastrulation, they displayed a near complete loss of the later asymmetric lft1 / 2 expression domains. While expression of ndr1 was not substantially effected during gastrulation, ndr2 expression was moderately reduced in dyrk1b‐ MO animals. Analysis of additional downstream components of the nodal signaling pathway in dyrk1b‐ MO animals revealed modestly expanded expression of the dorsal axial mesoderm marker gsc while the pan‐mesodermal marker bik was largely unaffected. The endodermal markers cas and sox17 were also moderately reduced in dyrk1b‐ MO animals. Notably, and similar to defects previously reported for wdr68 mutant animals, we also found reduced expression of the pharyngeal pouch marker edn1 in dyrk1b‐ MO animals. Taken together, these data reveal a role for dyrk1b in endoderm formation and craniofacial patterning in the zebrafish. genesis 48:20–30, 2010. © 2009 Wiley‐Liss, Inc.