Abstract: Objective To determine the expression ofmicroRNA-125b (miR-125b) and microRNA132 (miR-132) in hippocampus of FMR1 gene knockout mice,and to investigate whether fragile X mental retardation protein (FMRP) deletion interferes with expression of miR-125b and miR-132,and consequently with immature dendritic spine development.Methods The expression of miR-125b and miR-132 was detected in hippocampus harvested from 1-week-old FMR1 knockout male FVB inbred mice and age-matched wild-type mice (n=3 for each group) using microRNAs array detection and fluorescence quantitative real-time PCR.Results MicroRNAs array detection did not show any significant difference in fluorescence level between the two groups (miR-125b: 4 919.295±431.981 vs 4 997.578±141.402; miR-132:244.289±31.125 vs 238.517±62.275,both P>0.05).By fluorescence quantitative real-time PC R,the relative levels of miR-125b and miR-132 expression were statistically comparable between FMRl knockout mice and wild-type mice (miR-125b: 11.45±0.32 vs 11.55±0.43; miR -132:18.28 ± 0.34 vs 18.50±0.40,both P>0.05).Conclusion The immature dendritic spine development in fragile X syndrome is not associated with changes in post transcriptional expression levels of miR125b and miR-132.