Dendritic spines, the actin-rich protrusions emerging from dendrites, are the subcellular locations of excitatory synapses in the mammalian brain. Many actin-regulating molecules modulate dendritic spine morphology. Since dendritic spines are neuron-specific structures, it is reasonable to speculate that neuron-specific or -predominant factors are involved in dendritic spine formation. KLHL17 (Kelch-like 17, also known as Actinfilin), an actin-binding protein, is predominantly expressed in brain. Human genetic study has indicated an association of KLHL17/Actinfilin with infantile spasms, a rare form of childhood epilepsy also resulting in autism and mental retardation, indicating that KLHL17/Actinfilin plays a role in neuronal function. However, it remains elusive if and how KLHL17/Actinfilin regulates neuronal development and brain function. Fluorescent immunostaining and electrophysiological recording were performed to evaluate dendritic spine formation and activity in cultured hippocampal neurons. Knockdown and knockout of KLHL17/Actinfilin and expression of truncated fragments of KLHL17/Actinfilin were conducted to investigate the function of KLHL17/Actinfilin in neurons. Mouse behavioral assays were used to evaluate the role of KLHL17/Actinfilin in brain function. We found that KLHL17/Actinfilin tends to form circular puncta in dendritic spines and are surrounded by or adjacent to F-actin. Klhl17 deficiency impairs F-actin enrichment at dendritic spines. Knockdown and knockout of KLHL17/Actinfilin specifically impair dendritic spine enlargement, but not the density or length of dendritic spines. Both N-terminal Broad-Complex, Tramtrack and Bric-a-brac (BTB) domain and C-terminal Kelch domains of KLHL17/Actinfilin are required for F-actin remodeling and enrichment at dendritic spines, as well as dendritic spine enlargement. A reduction of postsynaptic and presynsptic markers at dendritic spines and altered mEPSC profiles due to Klhl17 deficiency evidence impaired synaptic activity in Klhl17-deficient neurons. Our behavioral assays further indicate that Klhl17 deficiency results in hyperactivity and reduced social interaction, strengthening evidence for the physiological role of KLHL17/Actinfilin. Our findings provide evidence that KLHL17/Actinfilin modulates F-actin remodeling and contributes to regulation of neuronal morphogenesis, maturation and activity, which is likely relevant to behavioral impairment in Klhl17-deficient mice. Trial registration Non-applicable.

中文翻译：

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KLHL17 / Actinfilin是与婴儿痉挛和自闭症相关的大脑特异性基因，可调节树突状脊柱增大

树突棘是从树突中出现的富含肌动蛋白的突起，是哺乳动物脑中兴奋性突触的亚细胞位置。许多肌动蛋白调节分子可调节树突棘的形态。由于树突棘是神经元特异性结构，因此有理由推测神经元特异性或优势因子参与树突棘形成。KLHL17（类似于Kelch的17，也称为肌动蛋白）是一种肌动蛋白结合蛋白，主要在大脑中表达。人类基因研究表明，KLHL17 / Actinfilin与婴儿痉挛有关，这是一种罕见的儿童癫痫病，也导致自闭症和智力低下，表明KLHL17 / Actinfilin在神经元功能中起作用。但是，KLHL17 / Actinfilin是否以及如何调节神经元发育和大脑功能仍然难以捉摸。进行荧光免疫染色和电生理记录，以评估培养的海马神经元中树突棘的形成和活性。进行了KLHL17 / Actinfilin的敲除和敲除以及KLHL17 / Actinfilin的片段的表达，以研究KLHL17 / Actinfilin在神经元中的功能。小鼠行为分析用于评估KLHL17 / Actinfilin在脑功能中的作用。我们发现KLHL17 / Actinfilin倾向于在树突棘中形成圆形点，并被F-肌动蛋白包围或与其相邻。Khl17缺乏症损害了树突棘中F-肌动蛋白的富集。敲除和敲除KLHL17 / Actinfilin会特别损害树突棘的扩张，但不会损害树突棘的密度或长度。都是N端的Broad-Complex，KLHL17 / Actinfilin的Tramtrack和Bric-a-brac（BTB）结构域和C末端Kelch结构域是F-肌动蛋白重塑和在树突棘富集以及树突棘增大所必需的。树突棘的突触后和突触前标志物减少，以及由于Khl1717缺乏引起的mEPSC谱改变，证明Klhl17缺乏神经元的突触活性受损。我们的行为分析进一步表明，Khl1717缺乏症会导致过度活跃并减少社交互动，从而增强了KLHL17 / Actinfilin的生理作用的证据。我们的发现提供了KLHL17 / Actinfilin调节F-肌动蛋白重塑并有助于调节神经元形态发生，成熟和活性的证据，这可能与Khl1717缺陷小鼠的行为障碍有关。试用注册不适用。