COL1A1 and miR-29b show lower expression levels during osteoblast differentiation of bone marrow stromal cells from Osteogenesis Imperfecta patients

BACKGROUND: The majority of Osteogenesis Imperfecta (OI) cases are caused by mutations in one of the two genes, COL1A1 and COL1A2 encoding for the two chains that trimerize to form the procollagen 1 molecule. However, alterations in gene expression and microRNAs (miRNAs) are responsible for the regulation of cell fate determination and may be evolved in OI phenotype. METHODS: In this work, we analyzed the coding region and intron/exon boundaries of COL1A1 and COL1A2 genes by sequence analysis using an ABI PRISM 3130 automated sequencer and Big Dye Terminator Sequencing protocol. COL1A1 and miR-29b expression were also evaluated during the osteoblastic differentiation of mesenchymal stem cell (MSC) by qRT-PCR using an ABI7500 Sequence Detection System. RESULTS: We have identified eight novel mutations, where of four may be responsible for OI phenotype. COL1A1 and miR-29b showed lower expression values in OI type I and type III samples. Interestingly, one type III OI sample from a patient with Bruck Syndrome showed COL1A1 and miR-29b expressions alike those from normal samples. CONCLUSIONS: Results suggest that the miR-29b mechanism directed to regulate collagen protein accumulation during mineralization is dependent upon the amount of COL1A1 mRNA. Taken together, results indicate that the lower levels observed in OI samples were not sufficient for the induction of miR-29b.