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The ank gene story
1Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA. lryan@mcw.edu
Abstract:
The underlying molecular defect resulting in the abnormal calcification observed in ank/ank mice has been identified. The responsible nonsense mutation affects the protein product of ank, resulting in diminished production of extracellular inorganic pyrophosphate, an important inhibitor of nucleation and of the growth of apatite crystals. The ank gene product is one of several cell membrane proteins, including ectonucleoside triphosphate pyrophosphohydrolase enzymes and alkaline phosphatase, that regulate extracellular inorganic pyrophosphate levels and thereby regulate mineralization.
Insights
A mutation in the ank gene causes abnormal calcification in mice by reducing extracellular inorganic pyrophosphate, a key inhibitor of crystal growth. This finding clarifies the molecular basis of mineralization defects.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Ankylosis (ank/ank) mice exhibit abnormal calcification.
- The molecular basis for this defect was previously unknown.
Purpose of the Study:
- To identify the molecular defect causing abnormal calcification in ank/ank mice.
- To elucidate the role of the ank gene product in regulating mineralization.
Main Methods:
- Genetic analysis to identify the mutation in the ank gene.
- Biochemical assays to measure extracellular inorganic pyrophosphate levels.
- Analysis of the ank gene product's function in mineralization.
Main Results:
- A nonsense mutation in the ank gene was identified as the cause of abnormal calcification.
- This mutation leads to diminished production of extracellular inorganic pyrophosphate.
- The ank gene product regulates mineralization by controlling extracellular inorganic pyrophosphate levels.
Conclusions:
- The ank gene product is crucial for regulating mineralization.
- Defects in the ank gene and subsequent pyrophosphate reduction cause pathological calcification.