Data from: Altered development of synapse structure and function in striatum caused by Parkinson's disease-linked LRRK2-G2019S mutation

Mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) can
cause Parkinson's disease (PD), and the most common
disease-associated mutation, G2019S, increases kinase activity. Because
LRRK2 expression levels rise during synaptogenesis and are highest in
dorsal striatal spiny projection neurons (SPNs), we tested the hypothesis
that the LRRK2–G2019S mutation would alter development of excitatory
synaptic networks in dorsal striatum. To circumvent experimental confounds
associated with LRRK2 overexpression, we used mice expressing LRRK2–G2019S
or D2017A (kinase-dead) knockin mutations. In whole-cell recordings,
G2019S SPNs exhibited a fourfold increase in sEPSC frequency compared with
wild-type SPNs in postnatal day 21 mice. Such heightened neural activity
was increased similarly in direct- and indirect-pathway SPNs, and action
potential-dependent activity was particularly elevated. Excitatory
synaptic activity in D2017A SPNs was similar to wild type, indicating a
selective effect of G2019S. Acute exposure to LRRK2 kinase inhibitors
normalized activity, supporting that excessive neural activity in G2019S
SPNs is mediated directly and is kinase dependent. Although dendritic
arborization and densities of excitatory presynaptic terminals and
postsynaptic dendritic spines in G2019S SPNs were similar to wild type,
G2019S SPNs displayed larger spines that were matched functionally by a
shift toward larger postsynaptic response amplitudes. Acutely isolating
striatum from overlying neocortex normalized sEPSC frequency in G2019S
mutants, supporting that abnormal corticostriatal activity is involved.
These findings indicate that the G2019S mutation imparts a
gain-of-abnormal function to SPN activity and morphology during a stage of
development when activity can permanently modify circuit structure and
function.

编码富亮氨酸重复激酶2（leucine-rich repeat kinase 2, LRRK2）的基因发生突变可引发帕金森病（Parkinson's disease, PD），其中最常见的致病突变G2019S可增强其激酶活性。由于LRRK2的表达水平在突触发生过程中上调，且在背侧纹状体棘投射神经元（dorsal striatal spiny projection neurons, SPNs）中表达量最高，我们验证了如下假说：LRRK2-G2019S突变会改变背侧纹状体兴奋性突触网络的发育进程。为规避与LRRK2过表达相关的实验混杂因素，我们采用了携带LRRK2-G2019S或D2017A（激酶失活型）敲入突变的小鼠模型。全细胞记录结果显示，在出生后第21天的小鼠中，与野生型SPNs相比，G2019S突变SPNs的微小兴奋性突触后电流（small excitatory postsynaptic current, sEPSC）频率升高了四倍。这种增强的神经活动在直接通路与间接通路SPNs中均出现相似程度的提升，且动作电位依赖的神经活动升高尤为显著。D2017A突变SPNs的兴奋性突触活动水平与野生型组无显著差异，表明G2019S的效应具有选择性。急性给予LRRK2激酶抑制剂可使神经活动恢复至正常水平，证实G2019S突变SPNs中过度的神经活动由激酶活性直接介导，且依赖于激酶功能。尽管G2019S突变SPNs的树突分支、兴奋性突触前末梢密度以及突触后树突棘密度与野生型组相近，但其树突棘体积更大，且功能上对应更大的突触后反应振幅。将纹状体与上方覆盖的新皮层急性分离后，G2019S突变体的sEPSC频率恢复至正常水平，提示异常的皮层-纹状体环路活动参与了该表型的形成。上述研究结果表明，G2019S突变在活动可永久修饰神经环路结构与功能的发育阶段，赋予了SPNs异常的功能增益及形态学改变。