ZFIN ID: ZDB-PUB-101004-12
Knockdown and overexpression of Unc-45b result in defective myofibril organization in skeletal muscles of zebrafish embryos
Bernick, E., Zhang, P., and Du, S.
Date: 2010
Source: BMC Cell Biology   11: 70 (Journal)
Registered Authors: Du, Shao Jun (Jim)
Keywords: none
MeSH Terms:
  • Animals
  • Caenorhabditis elegans
  • Caenorhabditis elegans Proteins/genetics
  • Caenorhabditis elegans Proteins/metabolism
  • Embryo Research
  • Gene Knockdown Techniques
  • Molecular Chaperones/genetics
  • Molecular Chaperones/metabolism*
  • Muscle Development/genetics
  • Muscle, Skeletal/cytology
  • Muscle, Skeletal/embryology
  • Muscle, Skeletal/metabolism*
  • Myofibrils/genetics
  • Myofibrils/metabolism*
  • Myosins/biosynthesis*
  • Myosins/genetics
  • RNA, Small Interfering/genetics
  • Sarcomeres/genetics
  • Sarcomeres/metabolism
  • Structural Homology, Protein
  • Transgenes/genetics
  • Zebrafish*
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
PubMed: 20849610 Full text @ BMC Cell Biol.
BACKGROUND: Unc-45 is a myosin chaperone and a Hsp90 co-chaperone that plays a key role in muscle development. Genetic and biochemical studies in C. elegans have demonstrated that Unc-45 facilitates the process of myosin folding and assembly in body wall muscles. Loss or overexpression of Unc-45 in C. elegans results in defective myofibril organization. In the zebrafish Danio rerio, unc-45b, a homolog of C. elegans unc-45, is expressed in both skeletal and cardiac muscles. Earlier studies indicate that mutation or knockdown of unc-45b expression in zebrafish results in a phenotype characterized by a loss of both thick and thin filament organization in skeletal and cardiac muscle. The effects of unc-45b knockdown on other sarcomeric structures and the phenotype of Unc-45b overexpression, however, is poorly understood in vertebrates. RESULTS: Both knockdown and overexpression provide useful tools to study gene function during animal development. Using such methods, we characterized the role of Unc-45b in myofibril assembly of skeletal muscle in Danio rerio. We showed that, in addition to thick and thin filament defects, knockdown of unc-45b expression disrupted sarcomere organization in M-lines and Z-lines of skeletal muscles in zebrafish embryos. Western blotting analysis showed that myosin protein levels were significantly decreased in unc-45b knockdown embryos. Similarly, embryos overexpressing Unc-45b also exhibited severely disorganized myosin thick filaments. Disruption of thick filament organization by Unc-45b overexpression depends on the C-terminal UCS domain in Unc-45b required for interaction with myosin. Deletion of the C-terminal UCS domain abolished the disruptive activity of Unc-45b in myosin thick filament organization. In contrast, deletion of the N-terminal TPR domain required for binding with Hsp90 had no effect. CONCLUSION: Collectively, these studies indicate that the expression levels of Unc-45b must be precisely regulated to ensure normal myofibril organization. Loss or overexpression of Unc-45b leads to defective myofibril organization.