The methyl-CpG-binding domain (MBD) is crucial for MeCP2’s dysfunction-induced defects in adult newborn neurons

Abstract

Mutations in the human X-linked gene MECP2 are responsible for most Rett syndrome (RTT) cases, predominantly within its methyl-CpG-binding domain (MBD). To examine the role of MBD in the pathogenesis of RTT, we generated two MeCP2 mutant constructs, one with a deletion of MBD (MeCP2-ΔMBD), another mimicking a mutation of threonine 158 within the MBD (MeCP2-T158M) found in RTT patients. MeCP2 knockdown resulted in a decrease in total dendrite length, branching, synapse number, as well as altered spontaneous Ca2+ oscillations in vitro, which could be reversed by expression of full length human MeCP2 (hMeCP2-FL). However, the expression of hMeCP2-ΔMBD in MeCP2-silenced neurons did not rescue the changes in neuronal morphology and spontaneous Ca2+ oscillations, while expression of hMeCP2-T158M in these neurons could only rescue the decrease in dendrite length and branch number. In vivo over expression of hMeCP2-FL but not hMeCP2-ΔMBD in adult newborn neurons of the dentate gyrus also rescued the cell autonomous effect caused by MeCP2 deficiency in dendrites length and branching. Our results demonstrate that an intact and functional MBD is crucial for MeCP2 functions in cultured hippocampal neurons and adult newborn neurons.

Autism spectrum disorders: emerging mechanisms and mechanism-based treatment

“…The methyl-CpG-binding domain (MBD) of MeCP2 is crucial for its function as a transcriptional repressor. Zhao et al provide further evidence from cultured hippocampal neurons and in vivo newborn neurons that mutations of MBD affect the roles of MeCP2 in neuronal development (Zhao et al, 2015 ).…”

Neuropilin 2 Signaling Is Involved in Cell Positioning of Adult-born Neurons through Glycogen Synthase Kinase-3β (GSK3β)

“…Adult (5-6-week-old) female C57Bl/6 mice were purchased from the SingHealth Experimental Medicine Centre, Singapore, and housed in the Specific Pathogen Free animal facility at Duke-NUS Graduate Medical School, Singapore. The surgical and postsurgical procedures were performed as described previously (13,37).…”

“…To prevent biased quantification, all counting and analysis were done blindly. The dendritic structure of newborn neurons was analyzed according to previously published methods (13,37). A total of 25-30 neurons from 4 -6 animals per experimental group were analyzed.…”

Epigenetic mechanisms: A possible link between autism spectrum disorders and fetal alcohol spectrum disorders

“…They have also reported that newly matured neurons in MeCP2 KO mice have reduced dendritic spine density. Further, their results showed that mutations of MBD affected the roles of MeCP2 in neuronal development in cultured hippocampal neurons and in vivo newborn neurons [73]. Moreover, it has been shown that loss of MBD1 leads to autism like behavioral and learning deficits in mice, anxiety, depression, abnormal brain serotonin activity and HPA axis regulation [72,74].…”