Impact of human disease-causing mutation on striatal synaptic and behavioral plasticity

G2019 S突变是富含亮氨酸重复序列激酶2中几种突变中最常见的 在某些人群中，LRRK 2导致高达40%的家族性帕金森病。这个致病点 突变是常染色体显性的，并使激酶活性增加2-3倍。在运动和 突变型LRRK 2携带者的非运动症状与特发性病例相似，提示了共同的机制， 但由于对LRRK 2生物学知之甚少， G2019 S-LRRK 2的细胞或突触作用。 LRRK 2在背侧和腹侧纹状体的棘状投射神经元（spiny projection neurons，SPNs）中表达高，并且在背侧和腹侧纹状体的棘状投射神经元（spiny projection neurons，SPNs）中表达升高。 在轴突向内生长和兴奋性突触发生过程中迅速地。表达的时间和位置表明 突变LRRK 2可能不适应地影响影响纹状体兴奋回路的发育， 功能为了开始测试这一想法，我们探测了G2019 S-LRRK 2中SPNs中的突触能突触功能。 敲入老鼠我们发现，在出生后的早期，背侧纹状体中的G2019 S-SPNs表现出显著的 与WT小鼠或小鼠相比，自发兴奋性突触电流（sEPSC）异常增加 表达LRRK 2激酶-死亡敲入突变（D2017 A）。观察到这种异常兴奋活动 在直接和间接途径的SPN中，LRRK 2激酶抑制剂使其正常化， 具有较大的SPN树突棘头和sEPSC振幅。 背侧纹状体SPNs接受来自大脑皮层的会聚输入，并控制多种类型的目标- 定向行为，后者被认为反映了对双向变化的平衡控制， 皮质纹状体突触强度SPN突触功能和结构的早期异常表明， 突触可塑性将被G2019 S-LRRK 2改变，其结果是基于纹状体的行为。 初步数据支持这两种观点。总之，我们假设， 在表达G2019 S-LRRK 2的SPN中，增强或减弱突触传递的机制发生改变 以一种既揭示突变LRRK 2靶向的分子信号传导途径， 行为的后果。拟议的实验将评估突变LRRK 2对突触的影响， 加强和削弱亚型鉴定的SPN;他们将确定分子途径， 他们将确定突变的LRRK 2是否改变了与SPN突触相关的行为， 他们将测试生命早期的体内LRRK 2抑制是否会改善对大脑的适应不良影响。 突触和行为的可塑性。

The G2019S mutation is the most common of several mutations in leucine-rich repeat kinase 2 (LRRK2) causing up to 40% of familial Parkinson's disease in certain populations. This pathogenic point mutation is autosomal dominant and increases kinase activity 2-3 fold. Disease progression in both motor and non-motor symptoms of mutant LRRK2 carriers is similar to idiopathic cases suggesting common mechanisms, but progress has been limited because LRRK2 biology is poorly understood and little is known of pathogenic cellular or synaptic actions of G2019S-LRRK2. LRRK2 expression is high in spiny projection neurons (SPNs) of dorsal and ventral striatum, and rises rapidly during axon ingrowth and excitatory synaptogenesis. The timing and location of expression suggests that mutant LRRK2 may be maladaptively influencing development of excitatory circuits that impact striatal function. To begin to test this idea, we probed glutamatergic synaptic function in SPNs in G2019S-LRRK2 knockin mice. We showed that early in postnatal life, G2019S-SPNs in dorsal striatum exhibit a significantly abnormal increase in spontaneous excitatory synaptic currents (sEPSCs) compared to WT mice or mice expressing a LRRK2 kinase-dead knockin mutation (D2017A). Such abnormal excitatory activity was observed in both direct- and indirect-pathway SPNs, was normalized by LRRK2 kinase inhibitors, and was associated with larger SPN dendritic spine-heads and sEPSC amplitudes. Dorsal striatal SPNs receive convergent input from cerebral cortex and control many types of goal- directed behaviors, and the latter are thought to reflect balanced control of bidirectional changes in corticostriatal synaptic strength. The early abnormalities in SPN synaptic function and structure suggest that synaptic plasticity will be altered by G2019S-LRRK2 with consequences for striatally-based behaviors. Preliminary data support both of these ideas. Together, we hypothesize that the normal balance between mechanisms that strengthen or weaken synaptic transmission is altered in SPNs expressing G2019S-LRRK2 in a way that both reveals molecular signaling pathways targeted by mutant LRRK2 and that has predictable consequences for behaviors. The proposed experiments will assess the impact of mutant LRRK2 on synapse strengthening and weakening in subtype-identified SPNs; they will identify the molecular pathways and mechanisms involved; they will determine if mutant LRRK2 alters behaviors associated with SPN synapse plasticity; and they will test whether in vivo LRRK2 inhibition early in life ameliorates maladaptive effects on synaptic and behavioral plasticity documented later in life.