Investigations Into The Functions Of MeCP2 And Magneto2.0 In Cerebellum And Their Mechanisms

Cerebellum plays an important role in motor memory.Purkinje cells are major inhibitory neurons in the cerebellar cortex,which regulate the output of cerebellum.Purkinje cells are regulated by parallel fibers,climbing fibers and interneurons.Increasing evidences support a role for the cerebellum in cognition and emotion as a part of cortical-limbic system.Methyl-CpG-binding protein 2(Me CP2)is an important transcription regulator,and its deletion or mutation is closely related to Rett syndrome(RTT).RTT patients have motor and cognitive loss,social disorder,repetitive behavior,epilepsy,and other symptoms.Clinical investigations show the reduced volume of the cerebellum and the loss of Purkinje cells in RTT patients.However,it is not clear how Me CP2 regulates cerebellar function.In order to answer this question,we constructed a mouse model with specific deletion of Mecp2 in Purkinje cell.Behavioral tests showed that the knockout mice had RTT-like behaviors,such as motor learning disability,social ability impairment,and repetitive behaviors.Meanwhile,Me CP2 deficiency did not interrupt the development and morphology of the cerebellum and Purkinje cells.By detecting the electrophysiological characteristics of Purkinje cells,it was found that Me CP2 deficiency caused the reduced intrinsic excitability of Purkinje cells and the impaired intrinsic excitability plasticity,but did not affect the synaptic transmissions of Purkinje cells.Preliminary study showed that Me CP2 affected the membrane expression of SK2 through PTP1B-Trk B/BDNF signaling pathway.These results elucidate the mechanism of Me CP2 in Purkinje cells and provide a molecular basis for exploring the role of cerebellum in RTT pathology.Optogenetics and chemogenetics are currently popular research techniques,and are widely used to regulate neurons such as Purkinje cells.While both techniques have shortcomings,the magnetogenetics provides a new choice instead.Some studies have fused paramagnetic protein and TRPV4 into Magneto2.0,and then used static magnetic field to stimulate Magneto2.0 to regulate animal behaviors.In order to verify these studies,we use SFV to express Magneto2.0 into Purkinje cells and record the electrical activity with magnetic stimulation.Through a comprehensive analysis of membrane potential and action potential in Magneto2.0-expressing Purkinje cells under magnetic stimulation,we found that Magneto2.0 did not response to magnetic stimulation with no change in the electrical activity of Purkinje cells.In fact,Magento2.0 is barely expressed on the cell membrane.These results suggest that Magneto2.0 cannot be used as an effective magnetic induction protein,and magnetogenetical technology needs to be further explored.