Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice

Catherine N. Withers, Drew M. Brown, Innocent Byiringiro, Matthew Allen, Keith W. Condon, Jonathan Satin, Douglas A. Andres

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The small GTP-binding protein Rad (RRAD, Ras associated with diabetes) is the founding member of the RGK (Rad, Rem, Rem2, and Gem/Kir) family that regulates cardiac voltage-gated Ca2 + channel function. However, its cellular and physiological functions outside of the heart remain to be elucidated. Here we report that Rad GTPase function is required for normal bone homeostasis in mice, as Rad deletion results in significantly lower bone mass and higher bone marrow adipose tissue (BMAT) levels. Dynamic histomorphometry in vivo and primary calvarial osteoblast assays in vitro demonstrate that bone formation and osteoblast mineralization rates are depressed, while in vitro osteoclast differentiation is increased, in the absence of Rad. Microarray analysis revealed that canonical osteogenic gene expression (Runx2, osterix, etc.) is not altered in Rad−/− calvarial osteoblasts; instead robust up-regulation of matrix Gla protein (MGP, + 11-fold), an inhibitor of extracellular matrix mineralization and a protein secreted during adipocyte differentiation, was observed. Strikingly, Rad deficiency also resulted in significantly higher marrow adipose tissue levels in vivo and promoted spontaneous in vitro adipogenesis of primary calvarial osteoblasts. Adipogenic differentiation of wildtype calvarial osteoblasts resulted in the loss of endogenous Rad protein, further supporting a role for Rad in the control of BMAT levels. These findings reveal a novel in vivo function for Rad and establish a role for Rad signaling in the complex physiological control of skeletal homeostasis and bone marrow adiposity.

Original languageEnglish (US)
Pages (from-to)270-280
Number of pages11
JournalBone
Volume103
DOIs
StatePublished - Oct 1 2017

Fingerprint

GTP Phosphohydrolases
Osteoblasts
Bone Density
Adipose Tissue
Bone Marrow
Bone and Bones
Homeostasis
Adipogenesis
Adiposity
Osteoclasts
Microarray Analysis
GTP-Binding Proteins
Adipocytes
Osteogenesis
Extracellular Matrix
Proteins
Up-Regulation
Gene Expression
In Vitro Techniques

Keywords

  • Adipogenesis
  • Bone marrow adipose tissue
  • Matrix Gla protein
  • Osteoblasts
  • Osteogenesis
  • Ras GTPase

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Histology
  • Physiology

Cite this

Withers, C. N., Brown, D. M., Byiringiro, I., Allen, M., Condon, K. W., Satin, J., & Andres, D. A. (2017). Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice. Bone, 103, 270-280. https://doi.org/10.1016/j.bone.2017.07.018

Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice. / Withers, Catherine N.; Brown, Drew M.; Byiringiro, Innocent; Allen, Matthew; Condon, Keith W.; Satin, Jonathan; Andres, Douglas A.

In: Bone, Vol. 103, 01.10.2017, p. 270-280.

Research output: Contribution to journalArticle

Withers, CN, Brown, DM, Byiringiro, I, Allen, M, Condon, KW, Satin, J & Andres, DA 2017, 'Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice', Bone, vol. 103, pp. 270-280. https://doi.org/10.1016/j.bone.2017.07.018
Withers, Catherine N. ; Brown, Drew M. ; Byiringiro, Innocent ; Allen, Matthew ; Condon, Keith W. ; Satin, Jonathan ; Andres, Douglas A. / Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice. In: Bone. 2017 ; Vol. 103. pp. 270-280.
@article{d5f7ba70ac274818bf3c126e81895d15,
title = "Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice",
abstract = "The small GTP-binding protein Rad (RRAD, Ras associated with diabetes) is the founding member of the RGK (Rad, Rem, Rem2, and Gem/Kir) family that regulates cardiac voltage-gated Ca2 + channel function. However, its cellular and physiological functions outside of the heart remain to be elucidated. Here we report that Rad GTPase function is required for normal bone homeostasis in mice, as Rad deletion results in significantly lower bone mass and higher bone marrow adipose tissue (BMAT) levels. Dynamic histomorphometry in vivo and primary calvarial osteoblast assays in vitro demonstrate that bone formation and osteoblast mineralization rates are depressed, while in vitro osteoclast differentiation is increased, in the absence of Rad. Microarray analysis revealed that canonical osteogenic gene expression (Runx2, osterix, etc.) is not altered in Rad−/− calvarial osteoblasts; instead robust up-regulation of matrix Gla protein (MGP, + 11-fold), an inhibitor of extracellular matrix mineralization and a protein secreted during adipocyte differentiation, was observed. Strikingly, Rad deficiency also resulted in significantly higher marrow adipose tissue levels in vivo and promoted spontaneous in vitro adipogenesis of primary calvarial osteoblasts. Adipogenic differentiation of wildtype calvarial osteoblasts resulted in the loss of endogenous Rad protein, further supporting a role for Rad in the control of BMAT levels. These findings reveal a novel in vivo function for Rad and establish a role for Rad signaling in the complex physiological control of skeletal homeostasis and bone marrow adiposity.",
keywords = "Adipogenesis, Bone marrow adipose tissue, Matrix Gla protein, Osteoblasts, Osteogenesis, Ras GTPase",
author = "Withers, {Catherine N.} and Brown, {Drew M.} and Innocent Byiringiro and Matthew Allen and Condon, {Keith W.} and Jonathan Satin and Andres, {Douglas A.}",
year = "2017",
month = "10",
day = "1",
doi = "10.1016/j.bone.2017.07.018",
language = "English (US)",
volume = "103",
pages = "270--280",
journal = "Bone",
issn = "8756-3282",
publisher = "Elsevier Inc.",

}

TY - JOUR

T1 - Rad GTPase is essential for the regulation of bone density and bone marrow adipose tissue in mice

AU - Withers, Catherine N.

AU - Brown, Drew M.

AU - Byiringiro, Innocent

AU - Allen, Matthew

AU - Condon, Keith W.

AU - Satin, Jonathan

AU - Andres, Douglas A.

PY - 2017/10/1

Y1 - 2017/10/1

N2 - The small GTP-binding protein Rad (RRAD, Ras associated with diabetes) is the founding member of the RGK (Rad, Rem, Rem2, and Gem/Kir) family that regulates cardiac voltage-gated Ca2 + channel function. However, its cellular and physiological functions outside of the heart remain to be elucidated. Here we report that Rad GTPase function is required for normal bone homeostasis in mice, as Rad deletion results in significantly lower bone mass and higher bone marrow adipose tissue (BMAT) levels. Dynamic histomorphometry in vivo and primary calvarial osteoblast assays in vitro demonstrate that bone formation and osteoblast mineralization rates are depressed, while in vitro osteoclast differentiation is increased, in the absence of Rad. Microarray analysis revealed that canonical osteogenic gene expression (Runx2, osterix, etc.) is not altered in Rad−/− calvarial osteoblasts; instead robust up-regulation of matrix Gla protein (MGP, + 11-fold), an inhibitor of extracellular matrix mineralization and a protein secreted during adipocyte differentiation, was observed. Strikingly, Rad deficiency also resulted in significantly higher marrow adipose tissue levels in vivo and promoted spontaneous in vitro adipogenesis of primary calvarial osteoblasts. Adipogenic differentiation of wildtype calvarial osteoblasts resulted in the loss of endogenous Rad protein, further supporting a role for Rad in the control of BMAT levels. These findings reveal a novel in vivo function for Rad and establish a role for Rad signaling in the complex physiological control of skeletal homeostasis and bone marrow adiposity.

AB - The small GTP-binding protein Rad (RRAD, Ras associated with diabetes) is the founding member of the RGK (Rad, Rem, Rem2, and Gem/Kir) family that regulates cardiac voltage-gated Ca2 + channel function. However, its cellular and physiological functions outside of the heart remain to be elucidated. Here we report that Rad GTPase function is required for normal bone homeostasis in mice, as Rad deletion results in significantly lower bone mass and higher bone marrow adipose tissue (BMAT) levels. Dynamic histomorphometry in vivo and primary calvarial osteoblast assays in vitro demonstrate that bone formation and osteoblast mineralization rates are depressed, while in vitro osteoclast differentiation is increased, in the absence of Rad. Microarray analysis revealed that canonical osteogenic gene expression (Runx2, osterix, etc.) is not altered in Rad−/− calvarial osteoblasts; instead robust up-regulation of matrix Gla protein (MGP, + 11-fold), an inhibitor of extracellular matrix mineralization and a protein secreted during adipocyte differentiation, was observed. Strikingly, Rad deficiency also resulted in significantly higher marrow adipose tissue levels in vivo and promoted spontaneous in vitro adipogenesis of primary calvarial osteoblasts. Adipogenic differentiation of wildtype calvarial osteoblasts resulted in the loss of endogenous Rad protein, further supporting a role for Rad in the control of BMAT levels. These findings reveal a novel in vivo function for Rad and establish a role for Rad signaling in the complex physiological control of skeletal homeostasis and bone marrow adiposity.

KW - Adipogenesis

KW - Bone marrow adipose tissue

KW - Matrix Gla protein

KW - Osteoblasts

KW - Osteogenesis

KW - Ras GTPase

UR - http://www.scopus.com/inward/record.url?scp=85026218413&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85026218413&partnerID=8YFLogxK

U2 - 10.1016/j.bone.2017.07.018

DO - 10.1016/j.bone.2017.07.018

M3 - Article

VL - 103

SP - 270

EP - 280

JO - Bone

JF - Bone

SN - 8756-3282

ER -