title: Treatment with Myf5-morpholino results in somite patterning and brain formation defects in zebrafish.
abstract: Myf-5 is a stage-dependent transcription factor associated with somitogenesis. To study its biological functions in zebrafish, we injected the Myf5-morpholinos ZMF-MO (antisense nucleotides 28 to 52) and ZMF-OTHER (antisense nucleotides 3 to 27) into zebrafish embryos to establish a myf-5 gene knockdown. No phenotypic abnormalities were observed following injection with 0.2 ng of ZMF-MO, but defects were displayed in 2 of 118 (1.7%) surviving embryos injected with 1 ng ZMF-MO. Morphological defects became more severe with increased dosages: 105 of 270 (38.9%) surviving embryos injected with 4.5 ng of ZMF-MO displayed such abnormalities as the absence of eyes or brains in addition to the following low-dosage defects in 24 hpf embryos: longitudinal yolk sacs, incomplete epiboly coverage, abnormal and suspended tail buds, diffused somite boundaries, and head shrinkage. Similar results were observed in the 4.5 ng ZMF-OTHER injection group. However, when fish were co-injected with 4.5 ng ZMF-MO and 4.5 ng myf-5 mRNA, abnormality rates decreased from 49.6% to 5.5%. Our results show that the brain krox20 gene was down-regulated at rhombomere 3; the pax2.1 gene was completely down-regulated; myoD was expressed normally; myogenin was substantially down-regulated in whole somites; and desmin was partly inhibited in newly forming somites. Our conclusion is that zebrafish Myf-5 may play important roles in brain formation and in the convergence and extension of shield epiblasts and tail buds during early embryogenesis, in addition to its well-understood role as a muscle regulatory factor in somites.
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D051767:Early Growth Response Protein 2; D005819:Genetic Markers; D017403:In Situ Hybridization; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D051762:PAX2 Transcription Factor; D019170:Somites / Q000378:metabolism*; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism; D029961:Zebrafish Proteins
chemical_list: D004268:DNA-Binding Proteins; D051767:Early Growth Response Protein 2; D005819:Genetic Markers; D009124:Muscle Proteins; D051787:Myogenic Regulatory Factor 5; D016376:Oligonucleotides, Antisense; D051762:PAX2 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D029961:Zebrafish Proteins; C497320:pax2a protein, zebrafish