Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Neuron. 2011 Apr 14;70(1):35-42. doi: 10.1016/j.neuron.2011.03.001.
Mutations in MECP2 underlie the neurodevelopmental disorder Rett syndrome (RTT). One hallmark of RTT is relatively normal development followed by a later onset of symptoms. Growing evidence suggests an etiology of disrupted synaptic function, yet it is unclear how these abnormalities explain the clinical presentation of RTT. Here we investigate synapse maturation in Mecp2-deficient mice at a circuit with distinct developmental phases: the retinogeniculate synapse. We find that synapse development in mutants is comparable to that of wild-type littermates between postnatal days 9 and 21, indicating that initial phases of synapse formation, elimination, and strengthening are not significantly affected by MeCP2 absence. However, during the subsequent experience-dependent phase of synapse remodeling, the circuit becomes abnormal in mutants as retinal innervation of relay neurons increases and retinal inputs fail to strengthen further. Moreover, synaptic plasticity in response to visual deprivation is disrupted in mutants. These results suggest a crucial role for Mecp2 in experience-dependent refinement of synaptic circuits.
MECP2 基因突变是导致神经发育障碍雷特综合征（RTT）的原因。RTT 的一个显著特征是相对正常的发育，然后是症状的后期发作。越来越多的证据表明突触功能障碍是其病因，但这些异常如何解释 RTT 的临床表现尚不清楚。在这里，我们研究了具有不同发育阶段的电路中的 Mecp2 缺陷型小鼠中的突触成熟：视网膜-视放射突触。我们发现，在出生后第 9 天至 21 天之间，突变体中的突触发育与野生型同窝仔相似，这表明突触形成、消除和强化的初始阶段不受 MeCP2 缺失的显著影响。然而，在随后的突触重塑的经验依赖性阶段，由于中继神经元的视网膜神经支配增加，而视网膜输入未能进一步增强，因此突变体中的电路变得异常。此外，视觉剥夺后的突触可塑性在突变体中被破坏。这些结果表明 Mecp2 在突触回路的经验依赖性细化中起着关键作用。
