PUBLICATION

Knockdown and overexpression of Unc-45b result in defective myofibril organization in skeletal muscles of zebrafish embryos

Authors

Bernick, E., Zhang, P., and Du, S.

ID

ZDB-PUB-101004-12

Date

2010

Source

BMC Cell Biology 11: 70 (Journal)

Registered Authors

Du, Shao Jun (Jim)

Keywords

none

MeSH Terms

Embryo Research
Zebrafish*
Transgenes/genetics
RNA, Small Interfering/genetics
Structural Homology, Protein
Molecular Chaperones/genetics
Molecular Chaperones/metabolism*
Caenorhabditis elegans
Myosins/biosynthesis*
Myosins/genetics
Sarcomeres/genetics
Sarcomeres/metabolism
Muscle, Skeletal/cytology
Muscle, Skeletal/embryology
Muscle, Skeletal/metabolism*
Zebrafish Proteins/genetics
Zebrafish Proteins/metabolism
Gene Knockdown Techniques
Myofibrils/genetics
Myofibrils/metabolism*
Caenorhabditis elegans Proteins/genetics
Caenorhabditis elegans Proteins/metabolism
Animals
Muscle Development/genetics

PubMed

20849610 Full text @ BMC Cell Biol.

Abstract

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.

Genes / Markers

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