TABLE 1.
Altered synaptic function in Rett syndrome and Fragile X syndrome.
| Source | Cell type (Age) | Finding | References |
| Mecp2Null/y, Mecp2Tg1 | Hippocampal neurons (7–14 DIV) | MeCP2 regulates glutamatergic synapse number and synapse strength | Chao et al., 2007 |
| Mecp2–/Y | L5 neurons in S1 (P28–P35) | Reduced Cortical Activity: ↓mEPSC | Dani et al., 2005 |
| Mecp2–/Y | L2/3 neurons of M1 (P21–28) | ↓Local Excitatory input; No Change to Local Inhibitory input | Wood and Shepherd, 2010 |
| Mecp2–/Y | L2/3 neurons of V1 (P∼45) | ↓ Excitatory and ↓ inhibitory conductance; Altered GABA reversal potential | Banerjee et al., 2016 |
| Mecp2–/Y | Pyramidal Neurons of the Hippocampus (P1, DIV 11–14) | ↓ mEPSC; No change in mIPSC | Nelson et al., 2006 |
| Mecp2–/Y | Layer 2/3 pyramidal neurons of S1 (P25–35). Primary culture of striatal neurons (P1, newborn) | ↓ mIPSC | Chao et al., 2010 |
| Mecp2 tm1.1Jae | Pyramidal CA3 Hippocampal Neurons (P40–60) | ↑ mEPSC ↓mIPSC | Calfa et al., 2015 |
| Mecp2–/Y | Layer 4 pyramidal and paravalbumin neurons of V1 (P28–30 and P50) | Selective ↓ excitatory input; No change in inhibitory or thalamo-cortical input | He et al., 2014 |
| Mecp2–/Y | PV + and SOM + neurons | Specific RTT-like symptoms: ↓ Motor coordination and learning/memory (PV + Mecp2–/Y), seizures and ↑ Stereotypes (SOM + Mecp2–/Y) | Ito-Ishida et al., 2015 |
| Mecp2 tm1.1Jae | Layer 5 pyramidal neurons of mPFC (p32–42) | ↓ E/I Ratio and sEPSC; No change sIPSC, mEPSC, mIPSC | Sceniak et al., 2016 |
| Mecp2–/Y | Layer 2/3 and layers 5/6 of V1 (P60–240) | ↓ E/I Ratio; ↓ Excitatory input | Durand et al., 2012 |
| Mecp230I heterozygous iPSCs | IPSCs differentiated into glutamatergic neurons | ↓ Sodium and potassium currents ↓ sEPSC frequency | Farra et al., 2012 |
| Fmr1 –/Y | Layer 2/3 neurons of S1 (P19–31) | ↓ Inhibitory control on pyramidal output | Paluszkiewicz et al., 2011 |
| Fmr1–/Y | Principal excitatory neurons of Basolateral amygdala (P21–30) | ↓ Tonic GABAergic capacity; No change in E/I ratio | Martin et al., 2014 |
| Fmr1–/y, Fmr1–/HET | Pyramidal neurons of CA1 (P18–23) | ↑ E/I ratio; ↓GABA release (TA inhibitory synapses) | Wahlstrom-Helgren and Klyachko, 2015 |
| Fmr1–/Y | Layer 2/3 and layer 4 fast-spiking inhibitory and excitatory (mostly spiny stellate), Neurons of somatosensory cortex | ↓ Excitatory input onto fast spiking Inhibitory neurons and onto excitatory neurons | Gibson et al., 2008 |
| Fmr1 –/Y | CA1 pyramidal layer of dorsal hippocampus | ↑ Theta oscillation power; ↑ Slow gamma band coherence; ↓ Spike count of specific interneurons | Arbab et al., 2018 |
| Fmr1–/Y | Layer 4 fast-spiking neurons, layer 5 fast-spiking and layer 4 excitatory neurons in the somatosensory cortex | ↓ Excitatory input on fast-spiking inhibitory neurons | Patel et al., 2013 |
Main findings of studies reporting on synaptic function in Rett syndrome and Fragile X syndrome. Mecp2, methyl-CpG binding protein 2 gene; S1, primary somatosensory cortex; M1, primary motor cortex; V1, primary visual cortex; mEPSC, miniature excitatory postsynaptic currents; mIPSC, miniature inhibitory postsynaptic currents; DIV, days in vitro; PV+, parvalbumin-positive neurons; SOM+, somatostatin-positive neurons; mPFC, medial prefrontal cortex; sEPSC, spontaneous excitatory postsynaptic currents; sIPSC, spontaneous excitatory postsynaptic currents; iPSC, induced pluripotent stem cells; Fmr1, fragile X mental retardation 1 gene; TA, temporoammonic.