COL1A1 and miR-29b expression in normal, OI1 and OI3 samples during osteoblast differentiation. Total RNA from samples of control subjects and patients was extracted and levels of miR-29b and COL1A1 messenger RNA (mRNA) were measured quantitatively with real-time polymerase chain reaction. miR-29b and COL1A1 expression were severely reduced in both type I and type III OI patients. The results are presented as the fold increase of expression of the individual mRNAs, with normalization with the target internal control RNU6B using the cycle threshold method. Data are shown as mean ± SD.