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Analysis of Nkx3.1:Cre-driven Erk5 deletion reveals a profound spinal deformity which is linked to increased
Carolyn J Loveridge1,2, Rob J van 't Hof3, Gemma Charlesworth4
1Institute of Cancer Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Bearsden, Glasgow, G61 1BD, UK.
Abstract:
Extracellular signal-regulated protein kinase 5 (ERK5) has been implicated during development and carcinogenesis. Nkx3.1-mediated Cre expression is a useful strategy to genetically manipulate the mouse prostate. While grossly normal at birth, we observed an unexpected phenotype of spinal protrusion in Nkx3.1:Cre;Erk5 fl/fl (Erk5 fl/fl) mice by ~6-8 weeks of age. X-ray, histological and micro CT (µCT) analyses showed that 100% of male and female Erk5 fl/fl mice had a severely deformed curved thoracic spine, with an associated loss of trabecular bone volume. Although sex-specific differences were observed, histomorphometry measurements revealed that both bone resorption and bone formation parameters were increased in male Erk5 fl/fl mice compared to wild type (WT) littermates. Osteopenia occurs where the rate of bone resorption exceeds that of bone formation, so we investigated the role of the osteoclast compartment. We found that treatment of RANKL-stimulated primary bone marrow-derived macrophage (BMDM) cultures with small molecule ERK5 pathway inhibitors increased osteoclast numbers. Furthermore, osteoclast numbers and expression of osteoclast marker genes were increased in parallel with reduced Erk5 expression in cultures generated from Erk5 fl/fl mice compared to WT mice. Collectively, these results reveal a novel role for Erk5 during bone maturation and homeostasis in vivo.
Insights
Extracellular signal-regulated protein kinase 5 (ERK5) deficiency in mice leads to severe spinal deformities and bone loss. This study reveals ERK5
Area of Science:
- Skeletal biology
- Molecular biology
- Genetics
Background:
- Extracellular signal-regulated protein kinase 5 (ERK5) is involved in development and cancer.
- Nkx3.1-driven Cre expression enables genetic manipulation in the mouse prostate.
- ERK5 plays a role in cellular signaling pathways.
Purpose of the Study:
- To investigate the role of ERK5 in bone maturation and homeostasis.
- To characterize the skeletal phenotype of mice with conditional knockout of Erk5 in the prostate.
- To explore the impact of ERK5 deficiency on bone resorption and formation.
Main Methods:
- Generation of Nkx3.1:Cre;Erk5 fl/fl mice to study ERK5 function.
- Skeletal analysis using X-ray, histology, and micro CT (µCT).
- Analysis of osteoclast differentiation and function in vitro using bone marrow-derived macrophages (BMDM).
Main Results:
- Erk5 fl/fl mice exhibited severe thoracic spinal curvature and reduced trabecular bone volume.
- Both bone resorption and formation markers were elevated in male Erk5 fl/fl mice.
- ERK5 inhibition or deficiency increased osteoclast numbers and osteoclast marker gene expression.
Conclusions:
- ERK5 plays a critical role in maintaining bone homeostasis and maturation.
- Loss of ERK5 function leads to osteopenia and skeletal deformities.
- ERK5 signaling pathway regulates osteoclast differentiation and activity.