Chunk #18 — 3. Overview of Monogenic Mouse Models of ASDs — 3.2 Post-Transcriptional Protein Modifiers or Regulators: Fmr1, Tsc1/2, Ube3a, and Pten — 3.2.1 Fmr1 (Fragile X syndrome)
Many studies have reported differences in dendritic spines in Fmr1 knockouts. The first study reported that the cortical neurons have increased numbers of spines in adult mice, most of which morphologically resemble immature spines (Comery et al., 1997). Since then, there have been conflicting reports regarding spine density in various brain regions and periods of development, but the immature morphology of spines is a relatively consistent finding (reviewed in He and Portera-Cailliau, 2013). Using in vivo two-photon imaging, researchers recently have found increased turnover in dendritic spines from Fmr1 knockout mice in layer 2/3 neurons in the barrel cortex at P10–P12 (Cruz-Martin et al., 2010) and in layer 5 neurons in primary somatosensory cortex at P20–P30 (Pan et al., 2010). Together, these findings suggest that FMRP is required for the development of mature, stable dendritic spines.
