dact1/2 modifies noncanonical Wnt signaling and calpain 8 expression to regulate convergent extension and craniofacial development

Wnt signaling plays a fundamental role in the initial patterning and development of the embryo, including in the regulation of convergent extension during gastrulation and the establishment of the dorsal axis. Further, Wnt signaling is a crucial regulator of craniofacial morphogenesis. The relationship between early embryo patterning and craniofacial outcomes warrants further study. The adapter proteins Dact1 and Dact2 modulate the Wnt signaling pathway through binding to Disheveled, however, the distinct roles of Dact1 and Dact2 during embryogenesis remain to be fully elucidated. In this study, we investigated the spatiotemporal gene expression patterns of dact1 and dact2 during zebrafish embryogenesis, revealing both shared and unique domains of expression. We found that both dact1 and dact2 contribute to axis extension, with compound mutants exhibiting a similar convergent extension defect and craniofacial phenotype to the wnt11f2/slb mutant. Utilizing single-cell RNAseq and gpc4-/- zebrafish, a convergent extension mutant with an opposite craniofacial phenotype, we identified dact1/2 specific roles during early development. Using this subtractive approach, we discovered a novel role for dact1/2 in regulating the mRNA expression of the classical calpain, capn8, suggesting a previously unappreciated role of calcium-dependent proteolysis during embryogenesis. Taken together, our findings highlight the distinct and overlapping roles of dact1 and dact2 in embryonic craniofacial development, providing new insights into the multifaceted regulation of Wnt signaling. Overall design: Single-cell RNA sequencing (scRNA-seq) analyses were performed on 10 zebrafish embryos (4 WT, 3 dact1-/-;dact2-/- compound mutant, and 3 gpc4-/- mutant embryos) harvested at the 3 somite stage, to assess transcriptomic perturbations during development induced by deletion of dact1/2.