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Knocking out FAM20C in pre-osteoblasts leads to up-regulation of osteoclast differentiation to affect long bone
Lili Jiang1, Xinpeng Liu2, Lixue Liu1
1Heilongjiang Provincial Key Laboratory of Hard Tissue Development and Regeneration, The Second Affiliated Hospital of Harbin Medical University, Harbin, China.
Abstract:
Family with sequence similarity 20 member C (FAM20C) is a Golgi casein kinase that phosphorylates extracellularly-secreted regulatory proteins involved in bone development and mineralization, but its specific role in bone development is still largely unknown. In this study, to examine the specific mechanisms that FAM20C influences bone development, we cross-bred Osx-Cre with FAM20Cflox/flox mice to establish a Osx-Cre; FAM20Cflox/flox knockout (oKO) mouse model; FAM20C was KO in pre-osteoblasts. oKO development was examined at 1-10 weeks, in which compared to control FAM20Cflox/flox, they had lower body weights and bone tissue mineralization. Furthermore, oKO had lower bone volume fractions, thickness, and trabecular numbers, along with higher degrees of trabecular separation. These mice also had decreased femoral metaphyseal cartilage proliferation layer, along with thickened hypertrophic layer and increased apoptotic cell counts. Transcriptomic analysis found that differentially-expressed genes in oKO were concentrated in the osteoclast differentiation pathway, in line with increased osteoclast presence. Additionally, up-regulation of osteoclast-related, and down-regulation of osteogenesis-related genes, were identified, in which the most up-regulated genes were signal regulatory protein β-1 family (Sirpb1a-c) and mitogen-activated protein kinase 13. Overall, FAM20C KO in pre-osteoblasts leads to abnormal long bone development, likely due to subsequent up-regulation of osteoclast differentiation-associated genes.
Insights
Family with sequence similarity 20 member C (FAM20C) knockout in pre-osteoblasts impairs bone development and mineralization. This leads to abnormal long bone growth, likely by increasing osteoclast differentiation genes.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Family with sequence similarity 20 member C (FAM20C) is a Golgi casein kinase crucial for bone development and mineralization.
- Its precise role in bone development remains largely unelucidated.
Purpose of the Study:
- To investigate the specific mechanisms by which FAM20C influences bone development.
- To establish and analyze a pre-osteoblast-specific FAM20C knockout mouse model.
Main Methods:
- Generation of Osx-Cre; FAM20Cflox/flox (oKO) mice for targeted FAM20C deletion in pre-osteoblasts.
- Phenotypic analysis of oKO mice from 1-10 weeks, including body weight, bone mineralization, and microarchitecture.
- Transcriptomic analysis to identify differentially expressed genes and pathways in oKO mice.
Main Results:
- oKO mice exhibited reduced body weight, bone mineralization, bone volume, thickness, and trabecular number, with increased trabecular separation.
- Histological analysis revealed decreased cartilage proliferation, thickened hypertrophic zones, and increased apoptosis in the femoral metaphysis.
- Transcriptomic data indicated enrichment of the osteoclast differentiation pathway, with increased osteoclast presence and altered expression of osteogenesis/osteoclastogenesis-related genes (e.g., Sirpb1a-c, MAPK13).
Conclusions:
- FAM20C knockout in pre-osteoblasts severely disrupts normal long bone development and mineralization.
- The observed bone abnormalities are associated with dysregulation of osteoclast differentiation and osteogenesis pathways.
- FAM20C plays a critical role in regulating bone homeostasis by modulating osteoblast-osteoclast balance.
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