Biology subjects

Waskiewicz, A. J.

Publications and source records attributed to Waskiewicz, A. J..

4 recordsLinked to original sources

bioRxiv2025

The BMP ligand Gdf6a Regulates Development of the Zebrafish Craniofacial Skeleton in a Pharyngeal Arch-Specific Manner

Craniofacial development involves the concerted action of several different tissue types and cellular processes that must be intricately regulated. Here, we describe the role of the BMP ligand Growth and Differentiation Factor 6a (gdf6a) in the development of the zebrafish craniofacial skeleton. Larval gdf6a mutant zebrafish have malformations in the midline of the craniofacial skeleton that correlate with the expression of gdf6a in the embryonic pharyngeal arches. We show that Gdf6a has arch-specific roles in craniofacial morphogenesis; Gdf6a promotes chondrogenesis and alignment of midline craniofacial elements in the posterior pharyngeal arches (arches 2 and 3) and regulates morphogenesis within the mandibular symphysis of pharyngeal arch 1. We demonstrate that Gdf6a regulates craniofacial development through activation of canonical BMP signaling, likely acting cooperatively with additional BMP ligands. Taken together, this work elucidates how Gdf6a/BMP signaling directs development of the craniofacial skeleton, specifically along the ventral midline. Summary StatementGdf6a regulates the development of the midline structures in the zebrafish craniofacial skeleton in an arch-specific manner via canonical BMP signaling.

developmental biology↗

bioRxiv2020

Pleiotropy in FOXC1-attributable phenotypes involves altered ciliation and cilia-dependent signaling

Alterations to cilia are responsible for a wide range of severe disease; however, understanding of the transcriptional control of ciliogenesis remains incomplete. We evaluated whether ciliary dysfunction contributed to the pleiotropic phenotypes caused by the Forkhead transcription factor FOXC1. Here, we show that patients with FOXC1-attributable Axenfeld-Rieger Syndrome (ARS) have a prevalence of ciliopathy-associated phenotypes comparable to syndromic ciliopathies. We demonstrate that altering the level of Foxc1, via shRNA mediated inhibition and mRNA overexpression, modifies cilia length in vitro. These structural changes were associated with substantially perturbed cilia-dependent signaling [Hedgehog (Hh) and PDGFR] and the altered ciliary compartmentalization of a major Hh pathway transcription factor, Gli2. Analyses of two Foxc1 murine mutant strains demonstrated altered axonemal length in the choroid plexus with the increased expression of an essential regulator of multi-ciliation, Foxj1. The novel complexity revealed in ciliation of the choroid plexus indicates a partitioning of function between these Forkhead transcription factors. Collectively, these results support a contribution from ciliary dysfunction to some FOXC1-induced phenotypes.

genetics↗

bioRxiv2020

The Axenfeld-Rieger syndrome gene FOXC1 contributes to left-right patterning

Normal body situs requires precise spatiotemporal expression of the Nodal-Lefty-Pitx2 cascade in the lateral plate mesoderm. The ultimate output of this patterning is establishment of the left-right axis, which provides vital cues for correct organ formation and function. Mutations, deletions and duplications in PITX2 and FOXC1 lead to the rare genetic disease Axenfeld-Rieger syndrome (ARS). While situs defects are not a recognised feature of ARS, partial penetrance of cardiac septal defects and valve incompetence is observed; both of these congenital heart defects (CHDs) also occur following disruption of left-right patterning. Here we investigated whether foxc1 genes have a critical role in specifying organ situs. We demonstrate that CRISPR/Cas9 generated mutants for the zebrafish paralogs foxc1a and foxc1b recapitulate ARS phenotypes including craniofacial dysmorphism, hydrocephalus and intracranial haemorrhage. Furthermore, foxc1a-/-; foxc1b-/- mutant animals display cardiac and gut situs defects. Modelling FOXC1 duplication by transient mRNA overexpression revealed that increased foxc1 dosage also results in organ situs defects. Analysis of known left-right patterning genes revealed a loss in expression of the NODAL antagonist lefty2 in the lateral plate mesoderm. Consistently, LEFTY2 mutations are known to cause human cardiac situs defects. Our data reveal a novel role for the forkhead-box transcription factor foxc1 in patterning of the left-right axis, and provide a plausible mechanism for the incidence of congenital heart defects in Axenfeld-Rieger syndrome patients. Author SummaryThis manuscript investigates the functional consequences of abrogating the activity of Foxc1 (Forkhead Box C1). We demonstrate that loss of zebrafish foxc1a and foxc1b results in phenotypes that resemble human patients with deletions in the FOXC1 locus. Notably, such phenotypes include alterations to the morphology of the heart. Investigations into the mechanisms underlying this phenotype led to the discovery that Foxc1 functions as a regulator of left-right patterning. Most components of left-right specification function normally in foxc1a/b mutants, but there is a pronounced loss of lefty2, a known inhibitor of Nodal signaling. This supports a model in which Foxc1 regulates situs of the heart via the regulation of Lefty2.

genetics↗

bioRxiv2018

Genetically regulated human NODAL splice variants are differentially post-transcriptionally processed and functionally distinct

NODAL is a morphogen essential for early embryonic development in vertebrates. Since much of our understanding of NODAL comes from model organisms, we aimed to directly assess post-transcriptional regulation of human NODAL with specific attention to a newly discovered human-specific NODAL splice variant. Selective depletion of the NODAL variant in human embryonic stem cells resulted in increased LIFR levels, while total NODAL knockdown resulted in a decrease of several markers of pluripotency. The NODAL variant did not transmit a canonical NODAL signal in zebrafish embryos, but may share some functional capability with canonical NODAL in cancer cells. At the protein level, disruption of disulfide bond formation dramatically enhanced proteolytic processing of NODAL. Disruption of NODAL N-glycosylation decreased its secretion but not extracellular stability, and a novel N-glycosylation in the NODAL variant contributed to enhanced secretion. Collectively, this work offers a direct and precise account of post-transcriptional regulation of human NODAL.

developmental biology↗