Dataset Information

Pax37 gene function in Oikopleura dioica supports a neuroepithelial-like origin for its house-making Fol territory

ABSTRACT: Larvacean tunicates feature a spectacular innovation not seen in other animals - the trunk oikoplastic epithelium (OE). This epithelium produces a house, a large and complex extracellular structure used for filtering and concentrating food particles. Previously we identified several homeobox transcription factors expressed during early OE patterning. Among these are two Pax3/7 duplicates that we named Pax37A and Pax37B. The vertebrate homologs, PAX3 and PAX7 are involved in developmental processes related to neural crest and muscles. In the ascidian tunicate Ciona intestinalis, Pax3/7 is playing a role in the development of cells deriving from the neural plate border, including trunk epidermal sensory neurons and tail nerve cord neurons, as well as in the neural tube closure. Here we have investigated the roles of Oikopleura dioica Pax37A and Pax37B in the development of the OE, using CRISPR-Cas9 mutant lines and analyzing scRNA-seq data from wild-type animals that we compared with scRNA-seq data from C. intestinalis. We revealed that Pax37B but not Pax37A is essential for the differentiation of cell fields that produce the food concentrating filter of the house: the anterior Fol, giant Fol and Nasse cells. Trajectory analysis supports that these cells have a neuroepithelial-like transcriptional signature. We propose that the highly specialized secretory epithelial cells of the Fol region either maintained or evolved neuroepithelial features such as “glue” secreting collocytes of ascidians. Their development seems to be controlled by a fragmented GRN that also operates in ascidian epidermal neurons.

ORGANISM(S): Oikopleura dioica

PROVIDER: GSE255790 | GEO | 2024/03/21

REPOSITORIES: GEO

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Project description:Neural crest development is orchestrated by a complex and still poorly understood gene regulatory network. Premigratory neural crest is induced at the lateral border of the neural plate by the combined action of signaling molecules and transcription factors such as AP2, Gbx2, Pax3 and Zic1. Among them, Pax3 and Zic1 are both necessary and sufficient to trigger a complete neural crest developmental program. However, their gene targets in the neural crest regulatory network remain unknown. Here, through a transcriptome analysis of frog microdissected neural border, we identified an extended gene signature for the premigratory neural crest, and we defined novel potential members of the regulatory network. This signature includes 34 novel genes, as well as 44 known genes expressed at the neural border. Using another microarray analysis which combined Pax3 and Zic1 gain-of-function and protein translation blockade, we uncovered 25 Pax3 and Zic1 direct targets within this signature. We demonstrated that the neural border specifiers Pax3 and Zic1 are direct upstream regulators of neural crest specifiers Snail1/2, Foxd3, Twist1, and Tfap2b. In addition, they may modulate the transcriptional output of multiple signaling pathways involved in neural crest development (Wnt, Retinoic Acid) through the induction of key pathway regulators (Axin2 and Cyp26c1). We also found that Pax3 could maintain its own expression through a positive autoregulatory feedback loop. These hierarchical inductions, feedback loops, and pathway modulation provide novel tools to understand the neural crest induction network. Transcriptomes of animal caps overexpressing Pax3+/-Zic1 in the presence/absence of cycloheximide, a translation inhibitor, were compared to control animal caps to identify direct Pax3 and Zic1 targets 2-4 cells stage embryos were injected with inducible Pax3-GR+/-Zic1-GR constructs. Animal caps were cut at stage 9. Cycloheximide (Chx, 0.1mg/ml) was then applied to the healed animal caps, from stage 10 to 10.5 (i.e. for 30 min at 23*C), then dexamethasone (Dex) was added at stage 10.5 to the cycloheximide-containing medium. Explants were rinced and lysed after two additional hours at 23*C, i.e. when sibling embryos reached stage 11.5-12. Total RNA was then extracted and hybridized on Affymetrix microarrays. Transcriptomes were compared to determine Pax3 and Zic1 targets.

Project description:Neural crest development is orchestrated by a complex and still poorly understood gene regulatory network. Premigratory neural crest is induced at the lateral border of the neural plate by the combined action of signaling molecules and transcription factors such as AP2, Gbx2, Pax3 and Zic1. Among them, Pax3 and Zic1 are both necessary and sufficient to trigger a complete neural crest developmental program. However, their gene targets in the neural crest regulatory network remain unknown. Here, through a transcriptome analysis of frog microdissected neural border, we identified an extended gene signature for the premigratory neural crest, and we defined novel potential members of the regulatory network. This signature includes 34 novel genes, as well as 44 known genes expressed at the neural border. Using another microarray analysis which combined Pax3 and Zic1 gain-of-function and protein translation blockade, we uncovered 25 Pax3 and Zic1 direct targets within this signature. We demonstrated that the neural border specifiers Pax3 and Zic1 are direct upstream regulators of neural crest specifiers Snail1/2, Foxd3, Twist1, and Tfap2b. In addition, they may modulate the transcriptional output of multiple signaling pathways involved in neural crest development (Wnt, Retinoic Acid) through the induction of key pathway regulators (Axin2 and Cyp26c1). We also found that Pax3 could maintain its own expression through a positive autoregulatory feedback loop. These hierarchical inductions, feedback loops, and pathway modulation provide novel tools to understand the neural crest induction network. The transcriptomes of neural border samples (stage 14 and 18) were compared to the transcriptome of anterior neural fold (stage 18), early neural plate (stage 12), and animal cap explants (stage14) to identify genes expressed specifically in neural border samples. Tissue samples from Xenopus laevis embryos were dissected, then total RNA was extracted and hybridized on Affymetrix microarrays. Selected tissue samples encompass the neural crest at different stages of its induction (early neural plate at stage 12, neural border at stage 14, neural border at stage 18), as well as reference tissues (anterior neural fold at stage 18, a tissue that belongs to the neural border but does not produce neural crest, and animal cap grown until stage 14 that differentiates into epidermis).

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Pax37 gene function in Oikopleura dioica supports a neuroepithelial-like origin for its house-making Fol territory

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