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Dact1/2 modifies noncanonical Wnt signaling and calpain 8 expression to regulate convergent extension and craniofacial development

ABSTRACT: 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.

ORGANISM(S): Danio rerio

PROVIDER: GSE240264 | GEO | 2024/09/04

REPOSITORIES: GEO

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Project description:The process that partitions the nascent vertebrate central nervous system into forebrain, midbrain, hindbrain, and spinal cord after neural induction is of fundamental interest in developmental biology, and is known to be dependent on Wnt/beta-catenin signaling at multiple steps. Neural induction specifies neural ectoderm with forebrain character that is subsequently posteriorized by graded Wnt signaling: embryological and mutant analyses have shown that progressively higher levels of Wnt signaling induce progressively more posterior fates. However, the mechanistic link between Wnt signaling and the molecular subdivision of the neural ectoderm into distinct domains in the anteroposterior (AP) axis is still not clear. To better understand how Wnt mediates neural AP patterning, we performed a temporal dissection of neural patterning in response to manipulations of Wnt signaling in zebrafish. We show that Wnt-mediated neural patterning in zebrafish can be divided into three phases: (I) a primary AP patterning phase, which occurs during gastrulation, (II) a mes/r1 (mesencephalon-rhombomere 1) specification and refinement phase, which occurs immediately after gastrulation, and (III) a midbrain-hindbrain boundary (MHB) morphogenesis phase, which occurs during segmentation stages. A major outcome of these Wnt signaling phases is the specification of the major compartment divisions of the developing brain: first the MHB, then the diencephalic-mesencephalic boundary (DMB). The specification of these lineage divisions depends upon the dynamic changes of gene transcription in response to Wnt signaling, which we show primarily involves transcriptional repression or indirect activation. We show that otx2b is directly repressed by Wnt signaling during primary AP patterning, but becomes resistant to Wnt-mediated repression during late gastrulation. Also during late gastrulation, Wnt signaling becomes both necessary and sufficient for expression of wnt8b, en2a, and her5 in mes/r1. We suggest that the change in otx2b response to Wnt regulation enables a transition to the mes/r1 phase of Wnt-mediated patterning, as it ensures that Wnts expressed in the midbrain and MHB do not suppress midbrain identity, and consequently reinforce formation of the DMB. These findings integrate important temporal elements into our spatial understanding of Wnt-mediated neural patterning and may serve as an important basis of a better understanding of neural patterning defects that have implications in human health.

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Dact1/2 modifies noncanonical Wnt signaling and calpain 8 expression to regulate convergent extension and craniofacial development

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