Dataset Information

Competition between Jagged-Notch and Endothelin1 Signaling Selectively Restricts Cartilage Formation in the Zebrafish Upper Face.

ABSTRACT: The intricate shaping of the facial skeleton is essential for function of the vertebrate jaw and middle ear. While much has been learned about the signaling pathways and transcription factors that control facial patterning, the downstream cellular mechanisms dictating skeletal shapes have remained unclear. Here we present genetic evidence in zebrafish that three major signaling pathways - Jagged-Notch, Endothelin1 (Edn1), and Bmp - regulate the pattern of facial cartilage and bone formation by controlling the timing of cartilage differentiation along the dorsoventral axis of the pharyngeal arches. A genomic analysis of purified facial skeletal precursors in mutant and overexpression embryos revealed a core set of differentiation genes that were commonly repressed by Jagged-Notch and induced by Edn1. Further analysis of the pre-cartilage condensation gene barx1, as well as in vivo imaging of cartilage differentiation, revealed that cartilage forms first in regions of high Edn1 and low Jagged-Notch activity. Consistent with a role of Jagged-Notch signaling in restricting cartilage differentiation, loss of Notch pathway components resulted in expanded barx1 expression in the dorsal arches, with mutation of barx1 rescuing some aspects of dorsal skeletal patterning in jag1b mutants. We also identified prrx1a and prrx1b as negative Edn1 and positive Bmp targets that function in parallel to Jagged-Notch signaling to restrict the formation of dorsal barx1+ pre-cartilage condensations. Simultaneous loss of jag1b and prrx1a/b better rescued lower facial defects of edn1 mutants than loss of either pathway alone, showing that combined overactivation of Jagged-Notch and Bmp/Prrx1 pathways contribute to the absence of cartilage differentiation in the edn1 mutant lower face. These findings support a model in which Notch-mediated restriction of cartilage differentiation, particularly in the second pharyngeal arch, helps to establish a distinct skeletal pattern in the upper face.

SUBMITTER: Barske L

PROVIDER: S-EPMC4825933 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Competition between Jagged-Notch and Endothelin1 Signaling Selectively Restricts Cartilage Formation in the Zebrafish Upper Face.

Barske Lindsey L Askary Amjad A Zuniga Elizabeth E Balczerski Bartosz B Bump Paul P Nichols James T JT Crump J Gage JG

PLoS genetics 20160408 4

The intricate shaping of the facial skeleton is essential for function of the vertebrate jaw and middle ear. While much has been learned about the signaling pathways and transcription factors that control facial patterning, the downstream cellular mechanisms dictating skeletal shapes have remained unclear. Here we present genetic evidence in zebrafish that three major signaling pathways - Jagged-Notch, Endothelin1 (Edn1), and Bmp - regulate the pattern of facial cartilage and bone formation by c ...[more]

PMID: 27058748

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Project description:Distinct shaping of the upper versus lower facial skeleton is essential for function of the vertebrate jaw and middle ear, yet the cellular mechanisms by which this occurs have remained unclear. Here, we show that Endothelin1 (Edn1) signaling accelerates mesenchymal condensation and subsequent cartilage formation in the lower face through antagonism of Jagged-Notch signaling and Prrx1 transcription factors. A genomic analysis of facial skeletal precursors in mutants and overexpression embryos reveals that Jagged-Notch signaling represses genes that are strongly induced as pharyngeal arch neural crest-derived cells begin skeletal differentiation. In wild types, initial Jagged-Notch repression dorsally ensures that barx1+ condensations and cartilage differentiation occur first in ventral-intermediate zones of the pharyngeal arches. Reduced Jagged-Notch signaling results in an expansion of pre-cartilage condensations in the upper face, with loss of barx1 partially restoring dorsal cartilage shapes in jag1b mutants. Further, by studying new mutants for zebrafish prrx1a and prrx1b, we find that Prrx1 genes function in parallel to Jagged-Notch signaling to restrict the formation of dorsal barx1+ pre-cartilage condensations. Consistently, combined losses of jag1b and prrx1a/b robustly rescue ventral barx1+ condensations and lower facial cartilage development in edn1 mutants. Together, our work suggests that Edn1 works through parallel inhibition of Jagged-Notch and Prrx1 pathways to promote an earlier and more extensive establishment of cartilage condensations in the lower face. We performed RNAseq on FACS-sorted neural crest-derived pharyngeal arch cells (fli1a:GFP; sox10:DsRed double positive) from wild-type embryos at 3 different stages (20, 28, and 36 hours post fertilization) and embryos with altered levels of Edn1 and Notch signaling (edn1 mutants and hsp70I:Gal4; UAS:Edn1 transgenics; jag1b mutants, dibenzazepine-treated embryos, and hsp70I:Gal4; UAS:NICD transgenics. We also sequenced RNA from heat-shocked UAS:Edn1+ and hsp70I:Gal4+ transgenics and jag1b+/+ controls.

Project description:Teleosts live in aquatic habitats, where they encounter ionic and acid-base fluctuations as well as infectious pathogens. To protect from these external challenges, the teleost epidermis is composed of living cells, including keratinocytes and ionocytes that maintain body fluid ionic homeostasis, and mucous cells that secret mucus. While ionocyte progenitors are known to be specified by Delta-Notch-mediated lateral inhibition during late gastrulation and early segmentation, it remains unclear how epidermal mucous cells (EMCs) are differentiated and maintained. Here, we show that Delta/Jagged-mediated activation of Notch signaling induces the differentiation of agr2-positive (agr2+) EMCs in zebrafish embryos during segmentation. We demonstrated that agr2+ EMCs contain cytoplasmic secretory granules and express muc5.1 and muc5.2. Reductions in agr2+ EMC number were observed in mib mutants and notch3 MOs-injected notch1a mutants, while increases in agr2+ cell number were detected in notch1a- and X-Su(H)/ANK-overexpressing embryos. Treatment with γ-secretase inhibitors further revealed that Notch signaling is required during bud to 15 hpf for the differentiation of agr2+ EMCs. Increased agr2+ EMC numbers were also observed in jag1a-, jag1b-, jag2a- and dlc-overexpressing, but not jag2b-overexpressing embryos. Meanwhile, reductions in agr2+ EMC numbers were detected in jag1a morphants, jag1b mutants, jag2a mutants and dlc morphants, but not jag2b mutants. Reduced numbers of pvalb8-positive epidermal cells were also observed in mib or jag2a mutants and jag1a or jag1b morphants, while increased pvalb8-positive epidermal cell numbers were detected in notch1a-overexpressing, but not dlc-overexpressing embryos. BrdU labeling further revealed that the agr2+ EMC population is maintained by proliferation. Cell lineage experiments showed that agr2+ EMCs are derived from the same ectodermal precursors as keratinocytes or ionocytes. Together, our results indicate that specification of agr2+ EMCs in zebrafish embryos is induced by DeltaC/Jagged-dependent activation of Notch1a/3 signaling, and the cell population is maintained by proliferation.

Dataset Information

Competition between Jagged-Notch and Endothelin1 Signaling Selectively Restricts Cartilage Formation in the Zebrafish Upper Face.

Publications

Competition between Jagged-Notch and Endothelin1 Signaling Selectively Restricts Cartilage Formation in the Zebrafish Upper Face.

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