Global change and premature hatching of aquatic embryos.

Anthropogenically induced changes to the natural world are increasingly exposing organisms to stimuli and stress beyond that to which they are adapted. In aquatic systems, it is thought that certain life stages are more vulnerable than others, with embryos being flagged as highly susceptible to environmental stressors. Interestingly, evidence from across a wide range of taxa suggests that aquatic embryos can hatch prematurely, potentially as an adaptive response to external stressors, despite the potential for individual costs linked with underdeveloped behavioural and/or physiological functions.

Complete persistence of the primary somatosensory system in zebrafish.

The somatosensory system detects peripheral stimuli that are translated into behaviors necessary for survival. Fishes and amphibians possess two somatosensory systems in the trunk: the primary somatosensory system, formed by the Rohon-Beard neurons, and the secondary somatosensory system, formed by the neural crest cell-derived neurons of the Dorsal Root Ganglia. Rohon-Beard neurons have been characterized as a transient population that mostly disappears during the first days of life and is functionally replaced by the Dorsal Root Ganglia.

Single-cell transcriptome analysis reveals three sequential phases of gene expression during zebrafish sensory hair cell regeneration.

Loss of sensory hair cells (HCs) in the mammalian inner ear leads to permanent hearing and vestibular defects, whereas loss of HCs in zebrafish results in their regeneration. We used single-cell RNA sequencing (scRNA-seq) to characterize the transcriptional dynamics of HC regeneration in zebrafish at unprecedented spatiotemporal resolution. We uncovered three sequentially activated modules: first, an injury/inflammatory response and downregulation of progenitor cell maintenance genes within minutes after HC loss; second, the transient activation of regeneration-specific genes; and third, a robust re-activation of developmental gene programs, including HC specification, cell-cycle activation, ribosome biogenesis, and a metabolic switch to oxidative phosphorylation.

The zebrafish issue: 25 years on.

In the 1990s, labs on both sides of the Atlantic performed the largest genetic mutagenesis screen at that time using an emerging model organism: the zebrafish. Led by Christiane Nüsslein-Volhard in Tübingen, Germany, and Wolfgang Driever in Boston, USA, these colossal screens culminated in 1996 with the publication of 37 articles in a special issue of Development, which remains the journal's largest issue to this day. To celebrate the anniversary of the zebrafish issue and reflect on the 25 years since its publication, five zebrafish researchers share what the issue means to them, how it has contributed to their career and its impact on the zebrafish community.

Emergence of Neuronal Diversity during Vertebrate Brain Development.

Neurogenesis comprises many highly regulated processes including proliferation, differentiation, and maturation. However, the transcriptional landscapes underlying brain development are poorly characterized. We describe a developmental single-cell catalog of ∼220,000 zebrafish brain cells encompassing 12 stages from embryo to larva.

PCP and Wnt pathway components act in parallel during zebrafish mechanosensory hair cell orientation.

Planar cell polarity (PCP) plays crucial roles in developmental processes such as gastrulation, neural tube closure and hearing. Wnt pathway mutants are often classified as PCP mutants due to similarities between their phenotypes. Here, we show that in the zebrafish lateral line, disruptions of the PCP and Wnt pathways have differential effects on hair cell orientations.

Evolutionary Origin and Nomenclature of Vertebrate -Family Genes.

To adequately connect zebrafish medical models to human biology, it is essential that gene nomenclature reflects gene orthology. Analysis of gene phylogenies and conserved syntenies shows that the zebrafish gene currently called (ENSDARG00000004256, ZFIN ID: ZDB-GENE-990603-12) is not the ortholog of the human gene called (ENSG00000085741); instead, the gene currently called (ENSDARG00000014796, ZFIN ID: ZDB-GENE-980526-249) is the zebrafish ortholog of human Genomic analysis of family genes suggests a model for the birth of family gene ohnologs in genome duplication events, provides a mechanism for the death of a family ohnolog in mammals after they diverged from birds, and suggests revised nomenclature to better connect teleost disease models to human biology.

Retinoic acid is required and Fgf, Wnt, and Bmp signaling inhibit posterior lateral line placode induction in zebrafish.

The lateral line system is a mechanosensory systems present in aquatic animals. The anterior and posterior lateral lines develop from anterior and posterior lateral line placodes (aLLp and pLLp), respectively. Although signaling molecules required for the induction of other cranial placodes have been well studied, the molecular mechanisms underlying formation of the lateral line placodes are unknown.

Regeneration of Sensory Hair Cells Requires Localized Interactions between the Notch and Wnt Pathways.

In vertebrates, mechano-electrical transduction of sound is accomplished by sensory hair cells. Whereas mammalian hair cells are not replaced when lost, in fish they constantly renew and regenerate after injury. In vivo tracking and cell fate analyses of all dividing cells during lateral line hair cell regeneration revealed that support and hair cell progenitors localize to distinct tissue compartments.

Acrofacial Dysostosis, Cincinnati Type, a Mandibulofacial Dysostosis Syndrome with Limb Anomalies, Is Caused by POLR1A Dysfunction.

We report three individuals with a cranioskeletal malformation syndrome that we define as acrofacial dysostosis, Cincinnati type. Each individual has a heterozygous mutation in POLR1A, which encodes a core component of RNA polymerase 1. All three individuals exhibit varying degrees of mandibulofacial dysostosis, and two additionally have limb anomalies.