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Calcitonin receptor isoforms in mouse and rat osteoclasts
M Ikegame1, M Rakopoulos, H Zhou
1St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
Summary
Researchers identified two calcitonin receptor (CTR) isoforms, C1a and C1b, in rat osteoclasts. Both isoforms are expressed early in mouse osteoclast cultures, with C1a predominating.
Area of Science:
- Molecular biology
- Cell biology
- Endocrinology
Background:
- Calcitonin receptors (CTRs) are 7 transmembrane domain receptors.
- Two rat CTR isoforms, C1a and C1b, have been identified, differing by a 37-amino-acid insert in C1b.
Purpose of the Study:
- To investigate the expression of CTR isoforms in rat and mouse osteoclasts.
- To determine the temporal expression of CTR isoforms during osteoclast differentiation in culture.
Main Methods:
- Autoradiography for 125I-salmon CT binding to detect CTR-bearing cells.
- Tartrate-resistant acid phosphatase (TRAP) staining to identify osteoclasts.
- Northern blot analysis for CTR mRNA detection.
- Reverse transcription-polymerase chain reaction (RT-PCR) to characterize CTR isoform mRNA.
Main Results:
- TRAP-positive mononucleated cells appeared by day 2 in mouse marrow cultures, with multinucleated osteoclasts (TRAP and CTR positive) appearing from day 4.
- A 4 kb CTR mRNA band was detected by Northern blot in cultures from day 4 onwards.
- RT-PCR confirmed the expression of both C1a and C1b mRNA homologs in mouse osteoclast cultures, with C1a being the predominant isoform.
Conclusions:
- Both C1a and C1b CTR isoforms are expressed in mouse osteoclasts.
- C1a isoform expression appears to predominate over C1b in developing osteoclasts.