Novel role for carbamoyl phosphate synthetase 2 in cranial sensory circuit formation

Cox, J.A., Lamora, A., Johnson, S.L., and Voigt, M.M.
International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience   33C: 41-48 (Journal)
Registered Authors
Cox, Jane, Johnson, Stephen L., Voigt, Mark
Axon guidance, Epibranchial, Ganglia, Glycosylation, Tg(p2xr3.2:gfp)(sl23), UPR, Zebrafish, bmn, branchiomotor neurons, cad, carbamoyl-phosphate synthetase 2-aspartate transcarbamylase-dihydroorotase, perplexed mutant, plx(a52), sl23, unfolded protein response
MeSH Terms
  • Animals
  • Animals, Genetically Modified
  • Aspartate Carbamoyltransferase/genetics
  • Aspartate Carbamoyltransferase/metabolism*
  • Cranial Nerves*/embryology
  • Cranial Nerves*/enzymology
  • Cranial Nerves*/growth & development
  • Embryo, Nonmammalian
  • Gene Expression Regulation, Developmental/drug effects
  • Gene Expression Regulation, Developmental/genetics
  • Gene Expression Regulation, Developmental/physiology*
  • Glycosylation
  • Green Fluorescent Proteins/genetics
  • Green Fluorescent Proteins/metabolism
  • Larva
  • Morpholinos/pharmacology
  • Tunicamycin/pharmacology
  • Zebrafish
24280100 Full text @ Int. J. Dev. Neurosci.

In zebrafish, cranial sensory circuits form by 4 days post-fertilization. We used a forward genetic screen to identify genes involved in the formation of these circuits. In one mutant allele, sl23, axons arising from the epibranchial sensory ganglia do not form their stereotypical terminal fields in the hindbrain. These embryos also had small eyes and deformed jaws, suggesting a pleiotropic effect. Using positional cloning, a 20-nucleotide deletion in the carbamoyl-phosphate-synthetase2-aspartate-transcarbamylase-dihydroorotase (cad) gene was found. Injection of a CAD morpholino phenocopied the mutant and mutants were rescued by injection of cad RNA. Cad activity is required for pyrimidine biosynthesis, and thus is a prerequisite for nucleic acid production and UDP-dependent protein glycosylation. Perturbation of nucleic acid biosynthesis can result in cell death. sl23 mutants did not exhibit elevated cell death, or gross morphological changes, in their hindbrains. To determine if defective protein glycosylation was involved in the aberrant targeting of sensory axons, we treated wild type embryos with tunicamycin, which blocks N-linked protein glycosylation. Interference with glycosylation via tunicamycin treatment mimicked the sl23 phenotype. Loss of cad reveals a critical role for protein glycosylation in cranial sensory circuit formation.

Genes / Markers
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Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes