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

Related in: MedlinePlus

Mineralized bone area in vertebrate spine and tibia and age-dependent differences in bone mineral density in Per2Brdm1 mutant mice.(A) Representative examples of photomicrographs of the mineralized bone area in lumbar vertebrae of 3, 12, 24 and 48 week old Per2Brdm1 mutant mice and their wild type littermates. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (B) Quantitative analysis of BV/TV (bone volume as a ratio of tissue volume) values of lumbar vertebrae for the different age groups. Shown are the means (in percent) ±SD (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test). Note that the significant differences at 3, 12 and 48 weeks of age is absent in the 24 week age group. (C) Representative examples of photomicrographs of the mineralized bone area in tibiae of 3, 12, 24 and 48 week old female wild type and Per2Brdm1 mutant mice. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (D) Quantitative analysis of BV/TV values of tibiae for the different age groups. Shown are the means±SD (* = 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-g001: Mineralized bone area in vertebrate spine and tibia and age-dependent differences in bone mineral density in Per2Brdm1 mutant mice.(A) Representative examples of photomicrographs of the mineralized bone area in lumbar vertebrae of 3, 12, 24 and 48 week old Per2Brdm1 mutant mice and their wild type littermates. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (B) Quantitative analysis of BV/TV (bone volume as a ratio of tissue volume) values of lumbar vertebrae for the different age groups. Shown are the means (in percent) ±SD (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test). Note that the significant differences at 3, 12 and 48 weeks of age is absent in the 24 week age group. (C) Representative examples of photomicrographs of the mineralized bone area in tibiae of 3, 12, 24 and 48 week old female wild type and Per2Brdm1 mutant mice. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (D) Quantitative analysis of BV/TV values of tibiae for the different age groups. Shown are the means±SD (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).

Mentions: To determine the optimal age to investigate clock gene mediated bone phenotypes we tested bone volume at various ages in Per2Brdm1 mice and compared them with wild type littermates. We found that Per2Brdm1 animals show an age-dependent bone volume phenotype in both lumbar vertebrae and tibiae (Figure 1). At 3, 12 and 48 weeks of age bone density was increased in vertebral spine, but was, as shown before, statistically indistinguishable from wild type at 24 weeks of age ([12]; Figure 1B). Only the 12 week old females had significantly higher tibial bone volume (Figure 1D).


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)

Mineralized bone area in vertebrate spine and tibia and age-dependent differences in bone mineral density in Per2Brdm1 mutant mice.(A) Representative examples of photomicrographs of the mineralized bone area in lumbar vertebrae of 3, 12, 24 and 48 week old Per2Brdm1 mutant mice and their wild type littermates. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (B) Quantitative analysis of BV/TV (bone volume as a ratio of tissue volume) values of lumbar vertebrae for the different age groups. Shown are the means (in percent) ±SD (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test). Note that the significant differences at 3, 12 and 48 weeks of age is absent in the 24 week age group. (C) Representative examples of photomicrographs of the mineralized bone area in tibiae of 3, 12, 24 and 48 week old female wild type and Per2Brdm1 mutant mice. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (D) Quantitative analysis of BV/TV values of tibiae for the different age groups. Shown are the means±SD (* = 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-g001: Mineralized bone area in vertebrate spine and tibia and age-dependent differences in bone mineral density in Per2Brdm1 mutant mice.(A) Representative examples of photomicrographs of the mineralized bone area in lumbar vertebrae of 3, 12, 24 and 48 week old Per2Brdm1 mutant mice and their wild type littermates. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (B) Quantitative analysis of BV/TV (bone volume as a ratio of tissue volume) values of lumbar vertebrae for the different age groups. Shown are the means (in percent) ±SD (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test). Note that the significant differences at 3, 12 and 48 weeks of age is absent in the 24 week age group. (C) Representative examples of photomicrographs of the mineralized bone area in tibiae of 3, 12, 24 and 48 week old female wild type and Per2Brdm1 mutant mice. Black areas represent calcified extracellular matrix, as visualized by Von Kossa staining. (D) Quantitative analysis of BV/TV values of tibiae for the different age groups. Shown are the means±SD (* = p<0.05, ** = p<0.01, *** = p<0.001, ANOVA with Bonferroni post-test).
Mentions: To determine the optimal age to investigate clock gene mediated bone phenotypes we tested bone volume at various ages in Per2Brdm1 mice and compared them with wild type littermates. We found that Per2Brdm1 animals show an age-dependent bone volume phenotype in both lumbar vertebrae and tibiae (Figure 1). At 3, 12 and 48 weeks of age bone density was increased in vertebral spine, but was, as shown before, statistically indistinguishable from wild type at 24 weeks of age ([12]; Figure 1B). Only the 12 week old females had significantly higher tibial bone volume (Figure 1D).

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
Related in: MedlinePlus