The molecular mechanism underlying brain regeneration in vertebrates remains elusive. We performed spatial enhanced resolution omics sequencing (Stereo-seq) to capture spatially resolved single-cell transcriptomes of axolotl telencephalon sections during development and regeneration. Annotated cell types exhibited distinct spatial distribution, molecular features, and functions. We identified an injury-induced ependymoglial cell cluster at the wound site as a progenitor cell population for the potential replenishment of lost neurons, through a cell state transition process resembling neurogenesis during development. Transcriptome comparisons indicated that these induced cells may originate from local resident ependymoglial cells. We further uncovered spatially defined neurons at the lesion site that may regress to an immature neuron–like state. Our work establishes spatial transcriptome profiles of an anamniote tetrapod brain and decodes potential neurogenesis from ependymoglial cells for development and regeneration, thus providing mechanistic insights into vertebrate brain regeneration.

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Repressible knockdown approaches were investigated to manipulate for transgenic sterilization in channel catfish, Ictalurus punctatus. Two primordial germ cell (PGC) marker genes, nanos and dead end, were targeted for knockdown and an off-target gene, vasa, was monitored. Two potentially copper-sensitive repressible promoters, yeast ctr3 (M) and ctr3-reduced (Mctr), were coupled with four knockdown strategies separately including: ds-sh RNA targeting the 5' end (N1) or 3' end (N2) of channel catfish nanos, full-length cDNA sequence of channel catfish nanos for overexpression (cDNA), and ds-sh RNA-targeting channel catfish dead end (DND). Each construct had an untreated group and treated group with copper sulfate as the repressor compound. Spawning rates of full-sibling P fish exposed or not exposed to the constructs as treated and untreated embryos were 85 and 54%, respectively, indicating potential sterilization of fish and repression of the constructs. In F fish, mRNA expressions of PGC marker genes for most constructs were downregulated in the untreated group and the knockdown was repressed in the treated group. Gonad development in transgenic, untreated F channel catfish was reduced compared to non-transgenic fish for MctrN2, MN1, MN2, and MDND. For 3-year-old adults, gonad size in the transgenic untreated group was 93.4% smaller than the non-transgenic group for females and 92.3% for males. However, mean body weight of transgenic females (781.8 g) and males (883.8 g) was smaller than of non-transgenic counterparts (984.2 and 1254.3 g) at 3 years of age, a 25.8 and 41.9% difference for females and males, respectively. The results indicate that repressible transgenic sterilization is feasible for reproductive control of fish, but negative pleiotropic effects can result.

Repressible knockdown approaches were investigated for transgenic sterilization in channel catfish, Ictalurus punctatus. Two primordial germ cell (PGC) marker genes, nanos and dead end, were targeted for knockdown, and an off-target gene, vasa, was monitored. Two potentially salt sensitive repressible promoters, zebrafish adenylosuccinate synthase 2 (ADSS) and zebrafish racemase (Rm), were each coupled with four knockdown strategies: ds-sh RNA targeting the 5 end (N1) or 3 end (N2) of channel catfish nanos, full-length cDNA sequence of channel catfish nanos for overexpression (cDNA) and ds-sh RNA targeting channel catfish dead end (DND). Each construct had an untreated group and treated group with sodium chloride as the repressor compound. Spawning rates of full-sibling P 1 fish exposed or not exposed to the constructs as treated and untreated embryos were 93% and 59%, respectively, indicating potential sterilization of fish and repression of the constructs. Although the mRNA expression data of PGC marker genes were inconsistent in P 1 fish, most F 1 individuals were able to downregulate the target genes in untreated groups and repress the knockdown process in treated groups. The results indicate that repressible transgenic sterilization is feasible for reproductive control of fish, but more data from F 2 or F 3 are needed for evaluation.

Teleosts, the most species-rich group of jawed vertebrates, have evolved a remarkable diversity of primitive and specialized features that provide a valuable resource for understanding vertebrate evolution. Here, we collected a comprehensive genome dataset of fish, including 115 newly sequenced species, to fill genome gaps for seven orders. By combining the phylogenetic and fossil records of teleosts, we observed that they were relatively scarce from the early to middle Triassic but quickly flourished following the massive extinction event at the end of the Triassic. This rapid radiation coincided with global temperature increases and the fragmentation of Gondwana, implying a positive correlation between temperature rise, tectonic plate movements, and teleost radiations. Our data also revealed that the end-Triassic extinction event had a greater impact on teleost radiation than the Permian-Triassic extinction. We identified a core set of regulatory elements related to aquatic adaptation traits such as swim bladder functional shift and structural specialization of pectoral fin, which were crucial for the adaptation of teleosts to their broad ecological niches. Functional experiments validated the regulatory roles of these conserved elements on the formation of specialized homologous organs in teleosts. Overall, our findings shed light on the links between teleost speciation bursts with geological events, and genetic innovations that have shaped extant teleost biodiversity.