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Dominant negative Bmp5 mutation reveals key role of BMPs in skeletal response to mechanical stimulation.

Ho AM, Marker PC, Peng H, Quintero AJ, Kingsley DM, Huard J - BMC Dev. Biol. (2008)

Bottom Line: Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse.Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5.Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Biology and Howard Hughes Medical Institute, Beckman Center B300, Stanford University School of Medicine, Stanford, California 94305, USA. andrewho@pitt.edu

ABSTRACT

Background: Over a hundred years ago, Wolff originally observed that bone growth and remodeling are exquisitely sensitive to mechanical forces acting on the skeleton. Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse. Although the processes of mechanotransduction and functional response of bone to mechanical strain have been extensively studied, the molecular signaling mechanisms that mediate the response of bone cells to mechanical stimulation remain unclear.

Results: Here, we identify a novel germline mutation at the mouse Bone morphogenetic protein 5 (Bmp5) locus. Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5. Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo. Biomechanical studies of osteoblasts from these anatomic sites show that the mutation inhibits the proper response of bone cells to mechanical stimulation.

Conclusion: The results from these genetic, biochemical, and biomechanical studies suggest that BMPs are required not only for skeletal patterning during embryonic development, but also for bone response and remodeling to mechanical stimulation at specific anatomic sites in the skeleton.

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Related in: MedlinePlus

Bmp5clv mutation causes more severe skeletal defects than a Bmp5  (Bmp5) mutation. Alizarin red-stained bones of 12-week +/+, Bmp5/Bmp5, and Bmp5clv/Bmp5clv mice show the following: (a) shortening of the greater horn (gh) and lesser horn (lh) of the hyoid bone and decreased calcification of the thyroid cartilage (tc), (b) absence of anterior tubercles (at) and thinning of the neural arch (na) of the 6th cervical vertebra, (c) reduction of the sesamoid (s) and nearly complete loss of the deltoid tuberosity (dt) of the humerus, (d) absence of the spinous process (sp) of the 2nd thoracic vertebra, (e) absence of the transverse process (tp) and anapophysis (a) of the 3rd lumbar vertebra, and (f) abnormal fusion of posterior sternal segments and loss of the xiphoid process (x) at the end of the sternum in Bmp5clv/Bmp5clv mice.
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Figure 2: Bmp5clv mutation causes more severe skeletal defects than a Bmp5 (Bmp5) mutation. Alizarin red-stained bones of 12-week +/+, Bmp5/Bmp5, and Bmp5clv/Bmp5clv mice show the following: (a) shortening of the greater horn (gh) and lesser horn (lh) of the hyoid bone and decreased calcification of the thyroid cartilage (tc), (b) absence of anterior tubercles (at) and thinning of the neural arch (na) of the 6th cervical vertebra, (c) reduction of the sesamoid (s) and nearly complete loss of the deltoid tuberosity (dt) of the humerus, (d) absence of the spinous process (sp) of the 2nd thoracic vertebra, (e) absence of the transverse process (tp) and anapophysis (a) of the 3rd lumbar vertebra, and (f) abnormal fusion of posterior sternal segments and loss of the xiphoid process (x) at the end of the sternum in Bmp5clv/Bmp5clv mice.

Mentions: We expect homozygosity for the mutation to further decrease the activity of BMP5 and increase the production of the non-processed BMP5 molecules that may inactivate other coexpressed BMPs. To determine the effect of this mutation on homozygotes carrying this allele, we crossed heterozygous carriers of the Bmp5clv mutation and generated viable Bmp5clv/Bmp5clv homozygotes, but at rates ~10-times lower than Mendelian predictions (4/156 progeny, P < 0.001). Despite the increased prenatal lethality, some Bmp5clv homozygotes survived with normal life spans and fertility. Among these surviving homozygous Bmp5clv mice, we noted more severe defects than those seen with age-controlled Bmp5 homozygotes, including shorter external ears (wild-type: 6.4 ± 0.4 mm, : 4.8 ± 0.2 mm, Bmp5clv: 2.9 ± 0.2 mm; P < 0.01), loss of lesser horns of the hyoid (Fig. 2a), more misshapen xiphisternum and missing ribs (Fig. 2f), less calcification of thyroid cartilage (Fig. 2a), abnormal bony fusion (fused posterior sternum; Fig. 2f), and reduced or absent processes on the sixth cervical (Fig. 2b), second thoracic (Fig. 2d), and lumbar vertebrae (Fig. 2e). The spectrum of phenotypes, and the consistent reduction rather than overgrowth of skeletal tissue, both suggest that the Bmp5clvmutation leads to loss rather than gain of BMP5 activity.


Dominant negative Bmp5 mutation reveals key role of BMPs in skeletal response to mechanical stimulation.

Ho AM, Marker PC, Peng H, Quintero AJ, Kingsley DM, Huard J - BMC Dev. Biol. (2008)

Bmp5clv mutation causes more severe skeletal defects than a Bmp5  (Bmp5) mutation. Alizarin red-stained bones of 12-week +/+, Bmp5/Bmp5, and Bmp5clv/Bmp5clv mice show the following: (a) shortening of the greater horn (gh) and lesser horn (lh) of the hyoid bone and decreased calcification of the thyroid cartilage (tc), (b) absence of anterior tubercles (at) and thinning of the neural arch (na) of the 6th cervical vertebra, (c) reduction of the sesamoid (s) and nearly complete loss of the deltoid tuberosity (dt) of the humerus, (d) absence of the spinous process (sp) of the 2nd thoracic vertebra, (e) absence of the transverse process (tp) and anapophysis (a) of the 3rd lumbar vertebra, and (f) abnormal fusion of posterior sternal segments and loss of the xiphoid process (x) at the end of the sternum in Bmp5clv/Bmp5clv mice.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 2: Bmp5clv mutation causes more severe skeletal defects than a Bmp5 (Bmp5) mutation. Alizarin red-stained bones of 12-week +/+, Bmp5/Bmp5, and Bmp5clv/Bmp5clv mice show the following: (a) shortening of the greater horn (gh) and lesser horn (lh) of the hyoid bone and decreased calcification of the thyroid cartilage (tc), (b) absence of anterior tubercles (at) and thinning of the neural arch (na) of the 6th cervical vertebra, (c) reduction of the sesamoid (s) and nearly complete loss of the deltoid tuberosity (dt) of the humerus, (d) absence of the spinous process (sp) of the 2nd thoracic vertebra, (e) absence of the transverse process (tp) and anapophysis (a) of the 3rd lumbar vertebra, and (f) abnormal fusion of posterior sternal segments and loss of the xiphoid process (x) at the end of the sternum in Bmp5clv/Bmp5clv mice.
Mentions: We expect homozygosity for the mutation to further decrease the activity of BMP5 and increase the production of the non-processed BMP5 molecules that may inactivate other coexpressed BMPs. To determine the effect of this mutation on homozygotes carrying this allele, we crossed heterozygous carriers of the Bmp5clv mutation and generated viable Bmp5clv/Bmp5clv homozygotes, but at rates ~10-times lower than Mendelian predictions (4/156 progeny, P < 0.001). Despite the increased prenatal lethality, some Bmp5clv homozygotes survived with normal life spans and fertility. Among these surviving homozygous Bmp5clv mice, we noted more severe defects than those seen with age-controlled Bmp5 homozygotes, including shorter external ears (wild-type: 6.4 ± 0.4 mm, : 4.8 ± 0.2 mm, Bmp5clv: 2.9 ± 0.2 mm; P < 0.01), loss of lesser horns of the hyoid (Fig. 2a), more misshapen xiphisternum and missing ribs (Fig. 2f), less calcification of thyroid cartilage (Fig. 2a), abnormal bony fusion (fused posterior sternum; Fig. 2f), and reduced or absent processes on the sixth cervical (Fig. 2b), second thoracic (Fig. 2d), and lumbar vertebrae (Fig. 2e). The spectrum of phenotypes, and the consistent reduction rather than overgrowth of skeletal tissue, both suggest that the Bmp5clvmutation leads to loss rather than gain of BMP5 activity.

Bottom Line: Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse.Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5.Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Biology and Howard Hughes Medical Institute, Beckman Center B300, Stanford University School of Medicine, Stanford, California 94305, USA. andrewho@pitt.edu

ABSTRACT

Background: Over a hundred years ago, Wolff originally observed that bone growth and remodeling are exquisitely sensitive to mechanical forces acting on the skeleton. Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse. Although the processes of mechanotransduction and functional response of bone to mechanical strain have been extensively studied, the molecular signaling mechanisms that mediate the response of bone cells to mechanical stimulation remain unclear.

Results: Here, we identify a novel germline mutation at the mouse Bone morphogenetic protein 5 (Bmp5) locus. Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5. Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo. Biomechanical studies of osteoblasts from these anatomic sites show that the mutation inhibits the proper response of bone cells to mechanical stimulation.

Conclusion: The results from these genetic, biochemical, and biomechanical studies suggest that BMPs are required not only for skeletal patterning during embryonic development, but also for bone response and remodeling to mechanical stimulation at specific anatomic sites in the skeleton.

Show MeSH
Related in: MedlinePlus