A Mouse Model for Dominant Collagen VI Disorders: HETEROZYGOUS DELETION OF Col6a3 EXON 16

Raimund Wagener,Machiko Arita,Sheila M Adams,David E Birk,Sasha Bogdanovich,Sudheer Kumar Gara,Mon-Li Chu,Rui-Zhu Zhang,Te-Cheng Pan,Tejvior S Khurana

doi:10.1074/jbc.m114.549311

Abstract

Dominant and recessive mutations in collagen VI genes, COL6A1, COL6A2, and COL6A3, cause a continuous spectrum of disorders characterized by muscle weakness and connective tissue abnormalities ranging from the severe Ullrich congenital muscular dystrophy to the mild Bethlem myopathy. Herein, we report the development of a mouse model for dominant collagen VI disorders by deleting exon 16 in the Col6a3 gene. The resulting heterozygous mouse, Col6a3(+/d16), produced comparable amounts of normal Col6a3 mRNA and a mutant transcript with an in-frame deletion of 54 bp of triple-helical coding sequences, thus mimicking the most common molecular defect found in dominant Ullrich congenital muscular dystrophy patients. Biosynthetic studies of mutant fibroblasts indicated that the mutant α3(VI) collagen protein was produced and exerted a dominant-negative effect on collagen VI microfibrillar assembly. The distribution of the α3(VI)-like chains of collagen VI was not altered in mutant mice during development. The Col6a3(+/d16) mice developed histopathologic signs of myopathy and showed ultrastructural alterations of mitochondria and sarcoplasmic reticulum in muscle and abnormal collagen fibrils in tendons. The Col6a3(+/d16) mice displayed compromised muscle contractile functions and thereby provide an essential preclinical platform for developing treatment strategies for dominant collagen VI disorders.

Highlights

Dominant collagen VI gene mutations cause the severe Ullrich congenital muscular dystrophy (UCMD) and mild Bethlem myopathy
Dominant and recessive mutations in collagen VI genes, COL6A1, COL6A2, and COL6A3, cause a continuous spectrum of disorders characterized by muscle weakness and connective tissue abnormalities ranging from the severe Ullrich congenital muscular dystrophy to the mild Bethlem myopathy
The observation that the anti-␣1(VI) antibody could immunoprecipitate all three collagen VI chains in the Col6a3d16/d16 fibroblasts indicated that the mutant ␣3(VI) chain with an inframe deletion of six Gly-X-Y repeats was synthesized, formed triple-helical collagen VI molecules with the other two chains, and was secreted extracellularly

Summary

A Mouse Model for Dominant Collagen VI Disorders

Te-Cheng Pan‡, Rui-Zhu Zhang‡, Machiko Arita‡, Sasha Bogdanovich§, Sheila M. Adams¶, Sudheer Kumar Garaʈ, Raimund Wagenerʈ**, Tejvior S. Birk¶, and Mon-Li Chu‡1 From the ‡Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, §Department of Physiology and Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, ¶Department of Molecular Pharmacology and Physiology, University of South Florida, Morsani College of Medicine, Tampa, Florida 33612, and ʈCenter for Biochemistry and **Center for Molecular Medicine, Medical Faculty Cologne, University of Cologne, Cologne D-50931, Germany

Background

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION