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 Cry2−/− mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Cry2−/− mutant mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old female wild type and Cry2−/− mutant mice (C) Bone formation rate (BFR) (µm3/µm2/day) in female Cry2−/− mutant mice and wild type controls. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type or Cry2−/− mutant mice. (E) Serum levels of the circulating osteoclast marker TRAP5b in 12 week old wild type and Cry2−/− mutant mice. Shown are the means±SD (panel A–C) or SEM (panel D,E) (* = 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-g003: Osteoblast, osteoclast and serum parameters in Cry2−/− mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Cry2−/− mutant mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old female wild type and Cry2−/− mutant mice (C) Bone formation rate (BFR) (µm3/µm2/day) in female Cry2−/− mutant mice and wild type controls. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type or Cry2−/− mutant mice. (E) Serum levels of the circulating osteoclast marker TRAP5b in 12 week old wild type and Cry2−/− mutant mice. Shown are the means±SD (panel A–C) or SEM (panel D,E) (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).

Mentions: Similar to Per2Brdm1, also Cry2−/− mice displayed a mean vertebral spine density (BV/TV) of 21.6±1.5% (mean±SD) in comparison to wild type (10.9±1.9%; Figure 3A). The tibiae of Cry2−/− mice displayed also a significantly higher bone volume (Figure S4). In order to find a cellular basis of the Cry2 defect, we investigated the same parameters as described above for the Per2-deficient animals. We found that both the number of osteoblasts and the number of osteoclasts per bone perimeter was not different between wild type and Cry2−/− mutant animals (Figure 3A and B, respectively). Also, bone formation rate and the levels of the osteoblast activity marker osteocalcin in serum did not differ between wild type and Cry2−/− (ANOVA with Bonferroni post-test; Figure 3C, D, respectively). However, in contrast to Per2Brdm1 mutant mice, the serum levels of the circulating osteoclast activity marker TRAP5b [21], [22] were significantly lowered at any time point in Cry2−/− animals as compared to wild type mice (p≤0.001; ANOVA with Bonferroni post-test; Figure 3E). This indicates reduced osteoclast activity and hence lower bone resorption in Cry2−/− mice and correlates with our observation that these animals show higher bone volume. These findings strongly suggest that the bone phenotype of the Cry2-deficient female animals is based on lowered osteoclast activity and hence is mechanistically different from the bone phenotype observed in Per2Brdm1 mutant animals.


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 Cry2−/− mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Cry2−/− mutant mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old female wild type and Cry2−/− mutant mice (C) Bone formation rate (BFR) (µm3/µm2/day) in female Cry2−/− mutant mice and wild type controls. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type or Cry2−/− mutant mice. (E) Serum levels of the circulating osteoclast marker TRAP5b in 12 week old wild type and Cry2−/− mutant mice. Shown are the means±SD (panel A–C) or SEM (panel D,E) (* = 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-g003: Osteoblast, osteoclast and serum parameters in Cry2−/− mice.(A) Osteoblast number per bone perimeter (Ob.N./B.pm) in 12 week old wild type and Cry2−/− mutant mice. (B) Osteoclast number per bone perimeter (Oc.N./B.pm) in 12 week old female wild type and Cry2−/− mutant mice (C) Bone formation rate (BFR) (µm3/µm2/day) in female Cry2−/− mutant mice and wild type controls. (D) Serum levels of the osteoblast activity marker osteocalcin in female wild type or Cry2−/− mutant mice. (E) Serum levels of the circulating osteoclast marker TRAP5b in 12 week old wild type and Cry2−/− mutant mice. Shown are the means±SD (panel A–C) or SEM (panel D,E) (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).
Mentions: Similar to Per2Brdm1, also Cry2−/− mice displayed a mean vertebral spine density (BV/TV) of 21.6±1.5% (mean±SD) in comparison to wild type (10.9±1.9%; Figure 3A). The tibiae of Cry2−/− mice displayed also a significantly higher bone volume (Figure S4). In order to find a cellular basis of the Cry2 defect, we investigated the same parameters as described above for the Per2-deficient animals. We found that both the number of osteoblasts and the number of osteoclasts per bone perimeter was not different between wild type and Cry2−/− mutant animals (Figure 3A and B, respectively). Also, bone formation rate and the levels of the osteoblast activity marker osteocalcin in serum did not differ between wild type and Cry2−/− (ANOVA with Bonferroni post-test; Figure 3C, D, respectively). However, in contrast to Per2Brdm1 mutant mice, the serum levels of the circulating osteoclast activity marker TRAP5b [21], [22] were significantly lowered at any time point in Cry2−/− animals as compared to wild type mice (p≤0.001; ANOVA with Bonferroni post-test; Figure 3E). This indicates reduced osteoclast activity and hence lower bone resorption in Cry2−/− mice and correlates with our observation that these animals show higher bone volume. These findings strongly suggest that the bone phenotype of the Cry2-deficient female animals is based on lowered osteoclast activity and hence is mechanistically different from the bone phenotype observed in Per2Brdm1 mutant animals.

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