Limits...
The clock genes Period 2 and Cryptochrome 2 differentially balance bone formation.

Maronde E, Schilling AF, Seitz S, Schinke T, Schmutz I, van der Horst G, Amling M, Albrecht U - PLoS ONE (2010)

Bottom Line: Interestingly, inactivation of both Per2 and Cry2 genes leads to normal bone volume as observed in wild type animals.Importantly, osteoclast parameters affected due to the lack of Cry2, remained at the level seen in the Cry2(-/-) mutants despite the simultaneous inactivation of Per2.This indicates that Cry2 and Per2 affect distinct pathways in the regulation of bone volume with Cry2 influencing mostly the osteoclastic cellular component of bone and Per2 acting on osteoblast parameters.

View Article: PubMed Central - PubMed

Affiliation: Dr. Senckenbergische Anatomie, Institute for Anatomy III, Goethe University, Frankfurt, Germany. E.Maronde@em.uni-frankfurt.de

ABSTRACT

Background: Clock genes and their protein products regulate circadian rhythms in mammals but have also been implicated in various physiological processes, including bone formation. Osteoblasts build new mineralized bone whereas osteoclasts degrade it thereby balancing bone formation. To evaluate the contribution of clock components in this process, we investigated mice mutant in clock genes for a bone volume phenotype.

Methodology/principal findings: We found that Per2(Brdm1) mutant mice as well as mice lacking Cry2(-/-) displayed significantly increased bone volume at 12 weeks of age, when bone turnover is high. Per2(Brdm1) mutant mice showed alterations in parameters specific for osteoblasts whereas mice lacking Cry2(-/-) displayed changes in osteoclast specific parameters. Interestingly, inactivation of both Per2 and Cry2 genes leads to normal bone volume as observed in wild type animals. Importantly, osteoclast parameters affected due to the lack of Cry2, remained at the level seen in the Cry2(-/-) mutants despite the simultaneous inactivation of Per2.

Conclusions/significance: This indicates that Cry2 and Per2 affect distinct pathways in the regulation of bone volume with Cry2 influencing mostly the osteoclastic cellular component of bone and Per2 acting on osteoblast parameters.

Show MeSH
Osteoblast, osteoclast and serum parameters in Per2Brdm1 mutant mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoblasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoclasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (C) Serum levels of the circulating osteoclast marker TRAP5b in female wild type and Per2Brdm1 mice. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type and Per2Brdm1 mice. (E) Bone formation rate (BFR) (µm3/µm2/day)) in female wild type and Per2Brdm1 mice. Shown are the means±SD (panel A, B, E) or SEM (panel C and D) (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2902506&req=5

pone-0011527-g002: Osteoblast, osteoclast and serum parameters in Per2Brdm1 mutant mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoblasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoclasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (C) Serum levels of the circulating osteoclast marker TRAP5b in female wild type and Per2Brdm1 mice. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type and Per2Brdm1 mice. (E) Bone formation rate (BFR) (µm3/µm2/day)) in female wild type and Per2Brdm1 mice. Shown are the means±SD (panel A, B, E) or SEM (panel C and D) (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).

Mentions: To determine the origin of the increased bone mineralization in Per2Brdm1 mice, we next investigated various indicators for osteoblastic or osteoclastic involvement in the constitution of the observed bone phenotypes. We found that the number of osteoblasts and osteoclasts per bone perimeter was not different between wild type and Per2Brdm1 mutant animals (Figure 2A and B, respectively). In line with this finding was the observation that the serum concentrations of the circulating osteoclast activity marker TRAP5b [21], [22] as well as the osteoblast activity marker osteocalcin did not differ between wild type and Per2Brdm1 animals (Figure 2C and D, respectively). Neither conventional curve nor cosinor analysis showed any statistically significant difference in the mesor, acrophase or amplitude of the serum osteocalcin profiles (Figure S1). However, the bone formation rate (BFR), which is mainly influenced by osteoblasts, was significantly higher in Per2Brdm1 mice as compared to wild type littermates (p≤0.01; Figure 2E). These findings suggest that other factors regulating osteoblast activity may be altered in Per2Brdm1 mutant mice. In this context we observed that osteoblasts from Per2Brdm1 mutant mice exerted a significantly higher ability to form bone nodules after 14 days in culture (Figure S5).


The clock genes Period 2 and Cryptochrome 2 differentially balance bone formation.

Maronde E, Schilling AF, Seitz S, Schinke T, Schmutz I, van der Horst G, Amling M, Albrecht U - PLoS ONE (2010)

Osteoblast, osteoclast and serum parameters in Per2Brdm1 mutant mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoblasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoclasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (C) Serum levels of the circulating osteoclast marker TRAP5b in female wild type and Per2Brdm1 mice. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type and Per2Brdm1 mice. (E) Bone formation rate (BFR) (µm3/µm2/day)) in female wild type and Per2Brdm1 mice. Shown are the means±SD (panel A, B, E) or SEM (panel C and D) (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2902506&req=5

pone-0011527-g002: Osteoblast, osteoclast and serum parameters in Per2Brdm1 mutant mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoblasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old wild type and Per2Brdm1 mutant female mice. The number of osteoclasts per bone perimeter is not significantly different between wild type and Per2Brdm1 mice. (C) Serum levels of the circulating osteoclast marker TRAP5b in female wild type and Per2Brdm1 mice. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type and Per2Brdm1 mice. (E) Bone formation rate (BFR) (µm3/µm2/day)) in female wild type and Per2Brdm1 mice. Shown are the means±SD (panel A, B, E) or SEM (panel C and D) (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).
Mentions: To determine the origin of the increased bone mineralization in Per2Brdm1 mice, we next investigated various indicators for osteoblastic or osteoclastic involvement in the constitution of the observed bone phenotypes. We found that the number of osteoblasts and osteoclasts per bone perimeter was not different between wild type and Per2Brdm1 mutant animals (Figure 2A and B, respectively). In line with this finding was the observation that the serum concentrations of the circulating osteoclast activity marker TRAP5b [21], [22] as well as the osteoblast activity marker osteocalcin did not differ between wild type and Per2Brdm1 animals (Figure 2C and D, respectively). Neither conventional curve nor cosinor analysis showed any statistically significant difference in the mesor, acrophase or amplitude of the serum osteocalcin profiles (Figure S1). However, the bone formation rate (BFR), which is mainly influenced by osteoblasts, was significantly higher in Per2Brdm1 mice as compared to wild type littermates (p≤0.01; Figure 2E). These findings suggest that other factors regulating osteoblast activity may be altered in Per2Brdm1 mutant mice. In this context we observed that osteoblasts from Per2Brdm1 mutant mice exerted a significantly higher ability to form bone nodules after 14 days in culture (Figure S5).

Bottom Line: Interestingly, inactivation of both Per2 and Cry2 genes leads to normal bone volume as observed in wild type animals.Importantly, osteoclast parameters affected due to the lack of Cry2, remained at the level seen in the Cry2(-/-) mutants despite the simultaneous inactivation of Per2.This indicates that Cry2 and Per2 affect distinct pathways in the regulation of bone volume with Cry2 influencing mostly the osteoclastic cellular component of bone and Per2 acting on osteoblast parameters.

View Article: PubMed Central - PubMed

Affiliation: Dr. Senckenbergische Anatomie, Institute for Anatomy III, Goethe University, Frankfurt, Germany. E.Maronde@em.uni-frankfurt.de

ABSTRACT

Background: Clock genes and their protein products regulate circadian rhythms in mammals but have also been implicated in various physiological processes, including bone formation. Osteoblasts build new mineralized bone whereas osteoclasts degrade it thereby balancing bone formation. To evaluate the contribution of clock components in this process, we investigated mice mutant in clock genes for a bone volume phenotype.

Methodology/principal findings: We found that Per2(Brdm1) mutant mice as well as mice lacking Cry2(-/-) displayed significantly increased bone volume at 12 weeks of age, when bone turnover is high. Per2(Brdm1) mutant mice showed alterations in parameters specific for osteoblasts whereas mice lacking Cry2(-/-) displayed changes in osteoclast specific parameters. Interestingly, inactivation of both Per2 and Cry2 genes leads to normal bone volume as observed in wild type animals. Importantly, osteoclast parameters affected due to the lack of Cry2, remained at the level seen in the Cry2(-/-) mutants despite the simultaneous inactivation of Per2.

Conclusions/significance: This indicates that Cry2 and Per2 affect distinct pathways in the regulation of bone volume with Cry2 influencing mostly the osteoclastic cellular component of bone and Per2 acting on osteoblast parameters.

Show MeSH