Nejvíce citovaný článek - PubMed ID 32939088
Evolution of the endothelin pathway drove neural crest cell diversification
The endostyle is an endodermal organ unique to nonvertebrate chordates except for lamprey larvae, where it serves as forerunner to the adult thyroid. Here, we examine whether the acquisition of neural crest in the vertebrate lineage played a role in the elaboration of the endostyle. CM-DiI lineage tracing reveals a neural crest contribution to the endostyle, and CRISPR-Cas9 mutagenesis of key neural crest genes causes endostyle defects including formation of a single rather than bilobed structure. RNA sequencing reveals gene profiles characteristic of embryonic neural crest cells and Schwann cell precursors in the developing endostyle. Contrasting with the prevailing view that the endostyle is an endoderm-derived organ, we propose that the acquisition of the neural crest played a critical step in promoting thyroid evolution from chordate endostyle.
In electroreceptive jawed fishes and amphibians, individual lateral line placodes form lines of neuromasts on the head containing mechanosensory hair cells, flanked by fields of ampullary organs containing electroreceptors-modified hair cells that respond to weak electric fields. Extensively shared gene expression between neuromasts and ampullary organs suggests that conserved molecular mechanisms are involved in their development, but a few transcription factor genes are restricted either to the developing electrosensory or mechanosensory lateral line. Here, we used CRISPR/Cas9-mediated mutagenesis in G0-injected sterlet embryos (Acipenser ruthenus, a sturgeon) to test the function of three such genes. We found that the 'hair cell' transcription factor gene Atoh1 is required for both hair cell and electroreceptor differentiation in sterlet, and for Pou4f3 and Gfi1 expression in both neuromasts and ampullary organs. These data support the conservation of developmental mechanisms between hair cells and electroreceptors. Targeting ampullary organ-restricted Neurod4 did not yield any phenotype, potentially owing to redundancy with other Neurod genes that we found to be expressed in sterlet ampullary organs. After targeting mechanosensory-restricted Foxg1, ampullary organs formed within neuromast lines, suggesting that FoxG1 normally represses their development, whether directly or indirectly. We speculate that electrosensory organs may be the 'default' developmental fate of lateral line primordia in electroreceptive vertebrates.
- Klíčová slova
- Acipenser ruthenus, Atoh1, Foxg1, ampullary organs, developmental biology, lateral line, neuromasts, sterlet sturgeon,
- MeSH
- buněčná diferenciace MeSH
- forkhead transkripční faktory * metabolismus genetika MeSH
- proudový orgán * embryologie metabolismus MeSH
- rybí proteiny * metabolismus genetika MeSH
- ryby * embryologie genetika MeSH
- transkripční faktory bHLH * metabolismus genetika MeSH
- vláskové buňky * fyziologie MeSH
- vývojová regulace genové exprese MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- forkhead transkripční faktory * MeSH
- rybí proteiny * MeSH
- transkripční faktory bHLH * MeSH
In the last decade, the CRISPR/Cas9 bacterial virus defense system has been adapted as a user-friendly, efficient, and precise method for targeted mutagenesis in eukaryotes. Though CRISPR/Cas9 has proven effective in a diverse range of organisms, it is still most often used to create mutant lines in lab-reared genetic model systems. However, one major advantage of CRISPR/Cas9 mutagenesis over previous gene targeting approaches is that its high efficiency allows the immediate generation of near-null mosaic mutants. This feature could potentially allow genotype to be linked to phenotype in organisms with life histories that preclude the establishment of purebred genetic lines; a group that includes the vast majority of vertebrate species. Of particular interest to scholars of early vertebrate evolution are several long-lived and slow-maturing fishes that diverged from two dominant modern lineages, teleosts and tetrapods, in the Ordovician, or before. These early-diverging or "basal" vertebrates include the jawless cyclostomes, cartilaginous fishes, and various non-teleost ray-finned fishes. In addition to occupying critical phylogenetic positions, these groups possess combinations of derived and ancestral features not seen in conventional model vertebrates, and thus provide an opportunity for understanding the genetic bases of such traits. Here we report successful use of CRISPR/Cas9 mutagenesis in one such non-teleost fish, sterlet Acipenser ruthenus, a small species of sturgeon. We introduced mutations into the genes Tyrosinase, which is needed for melanin production, and Sonic hedgehog, a pleiotropic developmental regulator with diverse roles in early embryonic patterning and organogenesis. We observed disruption of both loci and the production of consistent phenotypes, including both near-null mutants' various hypomorphs. Based on these results, and previous work in lamprey and amphibians, we discuss how CRISPR/Cas9 F0 mutagenesis may be successfully adapted to other long-lived, slow-maturing aquatic vertebrates and identify the ease of obtaining and injecting eggs and/or zygotes as the main challenges.
- Klíčová slova
- CRISPR/Cas9, development, evo-devo, evolution, non-teleost fish, sturgeon, targeted mutagenesis, vertebrates,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
