Limits...
Thyrostimulin Regulates Osteoblastic Bone Formation During Early Skeletal Development.

Bassett JH, van der Spek A, Logan JG, Gogakos A, Bagchi-Chakraborty J, Murphy E, van Zeijl C, Down J, Croucher PI, Boyde A, Boelen A, Williams GR - Endocrinology (2015)

Bottom Line: However, thyrostimulin failed to induce a canonical cAMP response or activate the noncanonical Akt, ERK, or mitogen-activated protein kinase (P38) signaling pathways in primary calvarial or bone marrow stromal cell-derived osteoblasts.Furthermore, thyrostimulin did not directly inhibit osteoblast proliferation, differentiation or mineralization in vitro.These studies identify thyrostimulin as a negative but indirect regulator of osteoblastic bone formation during skeletal development.

View Article: PubMed Central - PubMed

Affiliation: Molecular Endocrinology Laboratory (J.H.D.B., J.G.L., A.G., J.B.C., E.M., G.R.W.), Department of Medicine, Imperial College London, London, W12 0NN United Kingdom; Department of Endocrinology (A.v.d.S., C.v.Z., A.Boe.), Academic Medical Centre, University of Amsterdam, 1100 DD Amsterdam, The Netherlands; Bone Biology Program (J.D., P.I.C.), Garvan Institute of Medical Research, Sydney, NSW 2010 Australia; and Centre for Oral Growth and Development (A.Boy.), Queen Mary, University of London, London, E1 4NS United Kingdom.

ABSTRACT
The ancestral glycoprotein hormone thyrostimulin is a heterodimer of unique glycoprotein hormone subunit alpha (GPA)2 and glycoprotein hormone subunit beta (GPB)5 subunits with high affinity for the TSH receptor. Transgenic overexpression of GPB5 in mice results in cranial abnormalities, but the role of thyrostimulin in bone remains unknown. We hypothesized that thyrostimulin exerts paracrine actions in bone and determined: 1) GPA2 and GPB5 expression in osteoblasts and osteoclasts, 2) the skeletal consequences of thyrostimulin deficiency in GPB5 knockout (KO) mice, and 3) osteoblast and osteoclast responses to thyrostimulin treatment. Gpa2 and Gpb5 expression was identified in the newborn skeleton but declined rapidly thereafter. GPA2 and GPB5 mRNAs were also expressed in primary osteoblasts and osteoclasts at varying concentrations. Juvenile thyrostimulin-deficient mice had increased bone volume and mineralization as a result of increased osteoblastic bone formation. However, thyrostimulin failed to induce a canonical cAMP response or activate the noncanonical Akt, ERK, or mitogen-activated protein kinase (P38) signaling pathways in primary calvarial or bone marrow stromal cell-derived osteoblasts. Furthermore, thyrostimulin did not directly inhibit osteoblast proliferation, differentiation or mineralization in vitro. These studies identify thyrostimulin as a negative but indirect regulator of osteoblastic bone formation during skeletal development.

Show MeSH

Related in: MedlinePlus

Serum thyroid hormone and TSH levels. A and B, Serum T4, T3, and TSH levels in female and male juvenile (P42) and adult (P112) WT and GPB5KO mice (mean ± SEM for T4 and T3; individual values, median, and interquartile range for TSH). Mann-Whitney U test; #, P < .05: ##, P < .01 GPB5KO vs WT (n = 4–9 per genotype per age). nd, not determined because insufficient sample. C, Serum TSH response to TRH (100 ng ip) in female and male juvenile (P42) WT and GPB5KO mice. Mann-Whitney U test; #, P < .05 response to TRH; GPB5KO+TRH vs WT+TRH not significant (n = 6–8 per genotype).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4541616&req=5

Figure 2: Serum thyroid hormone and TSH levels. A and B, Serum T4, T3, and TSH levels in female and male juvenile (P42) and adult (P112) WT and GPB5KO mice (mean ± SEM for T4 and T3; individual values, median, and interquartile range for TSH). Mann-Whitney U test; #, P < .05: ##, P < .01 GPB5KO vs WT (n = 4–9 per genotype per age). nd, not determined because insufficient sample. C, Serum TSH response to TRH (100 ng ip) in female and male juvenile (P42) WT and GPB5KO mice. Mann-Whitney U test; #, P < .05 response to TRH; GPB5KO+TRH vs WT+TRH not significant (n = 6–8 per genotype).

Mentions: An alternative spice variant of Tshb (Tshb-sv) that includes a 27 nucleotide portion of intron 4 adjoining the coding region of exon 5 has been previously identified in mouse (Figure 2B) but not human bone marrow and has also been shown to stimulate a cAMP response in TSHR-expressing cells in vitro (38–41). The Tshb-sv isoform was present at low levels in primary mouse osteoblasts but not in osteoclasts (Figure 1B). Notably, this 27bp sequence has only limited conservation between species (Supplemental Figure 1, C and D).


Thyrostimulin Regulates Osteoblastic Bone Formation During Early Skeletal Development.

Bassett JH, van der Spek A, Logan JG, Gogakos A, Bagchi-Chakraborty J, Murphy E, van Zeijl C, Down J, Croucher PI, Boyde A, Boelen A, Williams GR - Endocrinology (2015)

Serum thyroid hormone and TSH levels. A and B, Serum T4, T3, and TSH levels in female and male juvenile (P42) and adult (P112) WT and GPB5KO mice (mean ± SEM for T4 and T3; individual values, median, and interquartile range for TSH). Mann-Whitney U test; #, P < .05: ##, P < .01 GPB5KO vs WT (n = 4–9 per genotype per age). nd, not determined because insufficient sample. C, Serum TSH response to TRH (100 ng ip) in female and male juvenile (P42) WT and GPB5KO mice. Mann-Whitney U test; #, P < .05 response to TRH; GPB5KO+TRH vs WT+TRH not significant (n = 6–8 per genotype).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541616&req=5

Figure 2: Serum thyroid hormone and TSH levels. A and B, Serum T4, T3, and TSH levels in female and male juvenile (P42) and adult (P112) WT and GPB5KO mice (mean ± SEM for T4 and T3; individual values, median, and interquartile range for TSH). Mann-Whitney U test; #, P < .05: ##, P < .01 GPB5KO vs WT (n = 4–9 per genotype per age). nd, not determined because insufficient sample. C, Serum TSH response to TRH (100 ng ip) in female and male juvenile (P42) WT and GPB5KO mice. Mann-Whitney U test; #, P < .05 response to TRH; GPB5KO+TRH vs WT+TRH not significant (n = 6–8 per genotype).
Mentions: An alternative spice variant of Tshb (Tshb-sv) that includes a 27 nucleotide portion of intron 4 adjoining the coding region of exon 5 has been previously identified in mouse (Figure 2B) but not human bone marrow and has also been shown to stimulate a cAMP response in TSHR-expressing cells in vitro (38–41). The Tshb-sv isoform was present at low levels in primary mouse osteoblasts but not in osteoclasts (Figure 1B). Notably, this 27bp sequence has only limited conservation between species (Supplemental Figure 1, C and D).

Bottom Line: However, thyrostimulin failed to induce a canonical cAMP response or activate the noncanonical Akt, ERK, or mitogen-activated protein kinase (P38) signaling pathways in primary calvarial or bone marrow stromal cell-derived osteoblasts.Furthermore, thyrostimulin did not directly inhibit osteoblast proliferation, differentiation or mineralization in vitro.These studies identify thyrostimulin as a negative but indirect regulator of osteoblastic bone formation during skeletal development.

View Article: PubMed Central - PubMed

Affiliation: Molecular Endocrinology Laboratory (J.H.D.B., J.G.L., A.G., J.B.C., E.M., G.R.W.), Department of Medicine, Imperial College London, London, W12 0NN United Kingdom; Department of Endocrinology (A.v.d.S., C.v.Z., A.Boe.), Academic Medical Centre, University of Amsterdam, 1100 DD Amsterdam, The Netherlands; Bone Biology Program (J.D., P.I.C.), Garvan Institute of Medical Research, Sydney, NSW 2010 Australia; and Centre for Oral Growth and Development (A.Boy.), Queen Mary, University of London, London, E1 4NS United Kingdom.

ABSTRACT
The ancestral glycoprotein hormone thyrostimulin is a heterodimer of unique glycoprotein hormone subunit alpha (GPA)2 and glycoprotein hormone subunit beta (GPB)5 subunits with high affinity for the TSH receptor. Transgenic overexpression of GPB5 in mice results in cranial abnormalities, but the role of thyrostimulin in bone remains unknown. We hypothesized that thyrostimulin exerts paracrine actions in bone and determined: 1) GPA2 and GPB5 expression in osteoblasts and osteoclasts, 2) the skeletal consequences of thyrostimulin deficiency in GPB5 knockout (KO) mice, and 3) osteoblast and osteoclast responses to thyrostimulin treatment. Gpa2 and Gpb5 expression was identified in the newborn skeleton but declined rapidly thereafter. GPA2 and GPB5 mRNAs were also expressed in primary osteoblasts and osteoclasts at varying concentrations. Juvenile thyrostimulin-deficient mice had increased bone volume and mineralization as a result of increased osteoblastic bone formation. However, thyrostimulin failed to induce a canonical cAMP response or activate the noncanonical Akt, ERK, or mitogen-activated protein kinase (P38) signaling pathways in primary calvarial or bone marrow stromal cell-derived osteoblasts. Furthermore, thyrostimulin did not directly inhibit osteoblast proliferation, differentiation or mineralization in vitro. These studies identify thyrostimulin as a negative but indirect regulator of osteoblastic bone formation during skeletal development.

Show MeSH
Related in: MedlinePlus