Related Experiment Videos
EXT genes are differentially expressed in bone and cartilage during mouse embryogenesis
D Stickens1, D Brown, G A Evans
1McDermott Center for Human Growth and Development, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235-8591, USA. stickens@utsw.swmed.edu
Summary
Hereditary multiple exostoses (HME) is caused by mutations in EXT genes. This study identifies mouse EXTL1 and reveals distinct expression patterns for EXT1, EXT2, and EXTL1 during embryonic development, suggesting a role in exostoses formation.
Area of Science:
- Genetics
- Developmental Biology
- Molecular Biology
Background:
- Hereditary multiple exostoses (HME) is a genetic disorder causing bone growths.
- HME is linked to mutations in EXT1 and EXT2 genes, which are involved in heparan sulfate synthesis.
- Additional EXT-like genes (EXTL1-3) exist but are not associated with HME.
Purpose of the Study:
- To identify the mouse EXTL1 gene and analyze its homology to human EXTL1.
- To investigate the expression patterns of mouse EXT1, EXT2, and EXTL1 during embryonic development.
- To propose a model for exostoses formation involving EXT1, EXT2, and signaling pathways.
Main Methods:
- Gene identification and sequence analysis (homology to human EXTL1).
- Expression studies using whole-mount and section in situ hybridization in mouse embryos.
- Analysis of gene expression in developing limb buds and other embryonic tissues.
Main Results:
- Mouse EXTL1 gene identified, showing 74% identity to human EXTL1.
- All three mouse EXT genes (EXT1, EXT2, EXTL1) are highly expressed in developing limb buds.
- Distinct expression profiles observed for EXT1, EXT2, and EXTL1 in sectioned embryos.
- Identical expression patterns for EXT1 and EXT2 suggest they form a complex.
Conclusions:
- Mouse EXTL1 is a homolog of human EXTL1, with conserved functions.
- Differential expression of EXT genes during development is crucial.
- EXT1 and EXT2 likely function together in the Indian hedgehog/PTHrP pathway to regulate chondrocyte maturation and potentially cause HME.