Maps, myelin, and you: Genetic analyses of vertebrate development

Genetic screens in zebrafish have identified thousands of mutations in hundreds of essential genes. Here we present an extensive genetic map for the zebrafish, which has facilitated the molecular identification of mutations. We employ our map in comparative genomic analyses to study aspects of vertebrate genome evolution, including identification of conserved syntenic regions, analyses of gene and genome duplication, delineation of the ancestral vertebrate karyotype, and illumination of gene content within ancestral chromosomes.; Screens in zebrafish have facilitated analysis of conserved signaling pathways essential for development. Hedgehog signaling controls specification of many cell types and can lead to cancer when misregulated. In zebrafish, disruptions in Hedgehog signaling cause a U-shaped somite phenotype; consequently, these mutants have been designated as "you-class". We show that the extracellular EGF-CUB gene scube2 is disrupted in the eponymous you-class mutant, you, and is required downstream of Hedgehog transcription and upstream of Hedgehog reception. Analysis of genetic chimeras indicates that you is required neither in cells sending nor in cells receiving Hedgehog signals. Our data instead support a role for you in stabilization or transport of Hedgehog.; Screens for disruptions in myelin gene expression have identified mutations in several genes essential for myelination. We show that two of these mutations disrupt nsf, an ATPase with critical roles in membrane fusion and synaptic transmission. Zebrafish nsf mutants are paralyzed and visually impaired, reflecting the requirement of nsf in synaptic transmission and neural activity. Strikingly, sodium channels fail to cluster along myelinated axons at the nodes of Ranvier in mutants. Pharmacological inhibition of neural activity and chemical synaptic transmission indicate that these roles of nsf are not required for sodium channel clustering. Instead, we have uncovered a novel function of nsf, independent of its synaptic role, in organizing nodes of Ranvier.; Reverse genetic techniques are less advanced than forward genetic approaches in zebrafish. We employ a sequencing based approach to identify heterozygous carriers of mutations in specific genes. Using these methods, we generated zebrafish with disrupted function of the deltac gene, and have thereby uncovered an essential role for deltac in somitogenesis.