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Mutation in type II collagen gene disturbs spinal development and gene expression patterns in transgenic Del1 mice
M Savontaus1, M Metsäranta, E Vuorio
1Department of Medical Biochemistry, University of Turku, Finland.
Abstract:
Transgenic Del1 mice harboring a deletion mutation in the cartilage-specific type II collagen gene were used for a systematic study on the dose-dependent effects of this dominant mutation on the embryonic development and growth of the vertebral column. Skeletal staining of homozygous and heterozygous Del1 mice and their nontransgenic littermates with Alcian blue/Alizarin red revealed not only a dose-dependent retardation in the appearance of ossification centers in transgene-positive offspring but also abnormal shapes and proportions of their vertebral columns. Histologic analysis confirmed these findings and demonstrated also retarded removal of the notochord, abnormal shapes and sizes of vertebral bodies and intervertebral discs, and the presence of an occult spina bifida in homozygous Del1 mice. In situ hybridization revealed abnormalities in the expression patterns of type I, II, IX, and X collagens and aggrecan, corresponding to the disorganization of the columnar chondrocyte architecture of the growth zones, increased appositional growth activity along the periphery of the vertebrae, increased numbers of hypertrophic chondrocytes, and development of necrotic areas in the central cartilaginous areas of vertebral bodies of homozygous Del1 embryos. Many of these findings parallel those seen in human chondrodysplasias and help us to understand the pathogenetic mechanisms involved in these developmental abnormalities.
Insights
This study investigated dominant collagen II gene mutations in Del1 mice, revealing dose-dependent effects on vertebral development. Findings show skeletal abnormalities mirroring human chondrodysplasias, aiding understanding of developmental defects.
Area of Science:
- Developmental biology
- Genetics
- Skeletal biology
Background:
- Cartilage-specific type II collagen is crucial for skeletal development.
- Dominant mutations can significantly impact embryonic growth and morphology.
- Understanding collagen gene mutations aids in studying skeletal dysplasias.
Purpose of the Study:
- To investigate the dose-dependent effects of a dominant type II collagen gene deletion mutation (Del1) on vertebral column development in mice.
- To characterize the skeletal and histological abnormalities resulting from this mutation.
- To correlate molecular changes with observed developmental defects.
Main Methods:
- Generation and analysis of transgenic Del1 mice (homozygous, heterozygous, and wild-type littermates).
- Skeletal staining using Alcian blue/Alizarin red.
- Histological examination of vertebral column structures.
- In situ hybridization to analyze gene expression patterns (collagens I, II, IX, X, and aggrecan).
Main Results:
- A dose-dependent retardation in ossification center appearance was observed.
- Abnormal vertebral column shapes, proportions, and delayed notochord removal were noted.
- Homozygous Del1 mice exhibited occult spina bifida, disorganized chondrocytes, and altered collagen/aggrecan expression.
Conclusions:
- The Del1 mutation causes significant dose-dependent defects in vertebral development.
- Observed abnormalities in gene expression and chondrocyte architecture contribute to skeletal malformations.
- These findings provide insights into the pathogenesis of human chondrodysplasias.