Enhanced p53 Levels Are Involved in the Reduced Mineralization Capacity of Osteoblasts Derived from Shwachman-Diamond
Annalisa Frattini1,2, Simona Bolamperti3, Roberto Valli2
1Institute for Genetic and Biomedical Research (IRGB), UOS Milano CNR, Via Fantoli, 15/16, 20138 Milano, Italy.
Abstract:
Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, caused by loss-of-function mutations in the SBDS gene, a factor involved in ribosome biogenesis. By analyzing osteoblasts from SDS patients (SDS-OBs), we show that SDS-OBs displayed reduced SBDS gene expression and reduced/undetectable SBDS protein compared to osteoblasts from healthy subjects (H-OBs). SDS-OBs cultured in an osteogenic medium displayed a lower mineralization capacity compared to H-OBs. Whole transcriptome analysis showed significant differences in the gene expression of SDS-OBs vs. H-OBs, particularly in the ossification pathway. SDS-OBs expressed lower levels of the main genes responsible for osteoblastogenesis. Of all downregulated genes, Western blot analyses confirmed lower levels of alkaline phosphatase and collagen type I in SDS-OBs than in H-OBs. Interestingly, SDS-OBs showed higher protein levels of p53, an inhibitor of osteogenesis, compared to H-OBs. Silencing of Tp53 was associated with higher collagen type I and alkaline phosphatase protein levels and an increase in SDS-OB mineralization capacity. In conclusion, our results show that the reduced capacity of SDS-OBs to mineralize is mediated, at least in part, by the high levels of p53 and highlight an important role of SBDS in osteoblast functions.
Insights
Shwachman-Diamond syndrome (SDS) impairs osteoblast function, reducing bone mineralization. This is linked to high p53 levels, an osteogenesis inhibitor, and reduced SBDS protein, crucial for ribosome biogenesis and bone cell activity.
Area of Science:
- Genetics and Molecular Biology
- Cell Biology
- Orthopedics
Background:
- Shwachman-Diamond syndrome (SDS) is a rare genetic disorder.
- SDS is caused by mutations in the SBDS gene, affecting ribosome biogenesis.
- SDS patients exhibit bone marrow failure, pancreatic insufficiency, and skeletal abnormalities.
Purpose of the Study:
- To investigate the role of SBDS in osteoblast function and bone mineralization.
- To explore the molecular mechanisms underlying skeletal abnormalities in SDS patients.
- To identify potential therapeutic targets for SDS-related bone complications.
Main Methods:
- Analysis of osteoblasts from SDS patients (SDS-OBs) and healthy subjects (H-OBs).
- Assessment of SBDS gene and protein expression.
- Evaluation of osteoblast mineralization capacity in vitro.
- Whole transcriptome analysis to identify differentially expressed genes.
- Western blot analysis to confirm protein expression levels.
- TP53 gene silencing in SDS-OBs.
Main Results:
- SDS-OBs showed reduced SBDS expression and lower mineralization capacity compared to H-OBs.
- Transcriptome analysis revealed significant downregulation of osteoblastogenesis genes in SDS-OBs.
- SDS-OBs exhibited lower levels of alkaline phosphatase and collagen type I.
- Elevated p53 protein levels were observed in SDS-OBs, inhibiting osteogenesis.
- TP53 silencing in SDS-OBs restored collagen type I and alkaline phosphatase levels and increased mineralization.
Conclusions:
- Reduced bone mineralization in SDS is partly mediated by elevated p53 levels.
- SBDS plays a critical role in osteoblast function and bone formation.
- Targeting p53 may offer a therapeutic strategy for skeletal abnormalities in SDS.
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