Targeted deletion of the zebrafish obscurin A RhoGEF domain affects heart, skeletal muscle and brain development

Raeker, M.O., Bieniek, A.N., Ryan, A.S., Tsai, H.J., Zahn, K.M., and Russell, M.W.
Developmental Biology   337(2): 432-443 (Journal)
Registered Authors
Tsai, Huai-Jen
Obscurin, RhoGEF, Cellular differentiation, Cardiac development, Retina
MeSH Terms
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Brain/embryology*
  • Brain/pathology
  • Brain/ultrastructure
  • Catalytic Domain
  • Embryo, Nonmammalian/abnormalities
  • Embryo, Nonmammalian/ultrastructure
  • Exons/genetics
  • Eye/pathology
  • Eye/ultrastructure
  • Gene Targeting*
  • Guanine Nucleotide Exchange Factors/chemistry
  • Guanine Nucleotide Exchange Factors/genetics*
  • Guanine Nucleotide Exchange Factors/metabolism
  • Heart/embryology*
  • Heart Defects, Congenital/embryology
  • Molecular Sequence Data
  • Muscle, Skeletal/abnormalities
  • Muscle, Skeletal/embryology*
  • Muscle, Skeletal/ultrastructure
  • Myocytes, Cardiac/ultrastructure
  • Phenotype
  • Protein Structure, Tertiary
  • Rho Guanine Nucleotide Exchange Factors
  • Sequence Deletion/genetics*
  • Zebrafish/genetics*
  • Zebrafish Proteins/chemistry
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/metabolism
19931525 Full text @ Dev. Biol.
Obscurin is a giant structural and signaling protein that participates in the assembly and structural integrity of striated myofibrils. Previous work has examined the physical interactions between obscurin and other cytoskeletal elements but its in vivo role in cell signaling, including the functions of its RhoGTPase Exchange Factor (RhoGEF) domain have not been characterized. In this study, morpholino antisense oligonucleotides were used to create an in-frame deletion of the active site of the obscurin A RhoGEF domain in order to examine its functions in zebrafish development. Cardiac myocytes in the morphant embryos lacked the intercalated disks that were present in controls by 72 and, in the more severely affected embryos, the contractile filaments were not organized into mature sarcomeres. Neural abnormalities included delay or loss of retinal lamination. Rescue of the phenotype with co-injection of mini-obscurin A expression constructs demonstrated that the observed effects were due to the loss of small GTPase activation by obscurin A. The immature phenotype of the cardiac myocytes and the retinal neuroblasts observed in the morphant embryos suggests that obscurin A-mediated small GTPase signaling promotes tissue-specific cellular differentiation. This is the first demonstration of the importance of the obscurin A-mediated RhoGEF signaling in vertebrate organogenesis and highlights the central role of obscurin A in striated muscle and neural development.
Genes / Markers
Figure Gallery
Mutation and Transgenics
Human Disease / Model Data
Sequence Targeting Reagents
Engineered Foreign Genes
Errata and Notes