A Missense Mutation in Kcnc3 Causes Hippocampal Learning Deficits in Mice. A Missense Mutation in Kcnc3 Causes Hippocampal Learning Deficits in Mice

Although a wide variety of genetic tools have been developed to study learning and memory, the molecular basis of memory encoding remains incompletely understood. Here, we undertook an unbiased approach to identify novel genes critical for memory encoding. From a large-scale in vivo mutagenesis screen using contextual fear conditioning, we isolated a mutant, named Clueless, with spatial learning deficits. A causative missense mutation (G434V) was found in the voltage gated potassium channel, subfamily C member 3 (Kcnc3) gene in a region that encodes a transmembrane voltage sensor. Generation of a Kcnc3G434V CRISPR mutant mouse confirmed this mutation as the cause of the learning defects. While G434V had no effect on transcription, translation, or trafficking of the channel, electrophysiological analysis of the G434V Kcnc3 mutant channel revealed a complete loss of voltage-gated conductance, a broadening of the action potential, and decreased neuronal firing. Together, our findings have revealed a previously unrecognized role for Kcnc3 in learning and memory. Overall design: Comparative gene expression profiling analysis of RNA-seq data (4 replicates) in the dorsal and ventral parts of DG and CA in mice hippocampus after contextual fear conditioning training

尽管已开发出种类繁多的遗传学工具用于学习与记忆研究，但记忆编码的分子基础仍未完全阐明。本研究采用无偏倚筛选策略，以鉴定记忆编码过程中至关重要的新基因。我们依托情境恐惧条件反射开展大规模体内诱变筛选，成功分离得到一株命名为Clueless的突变小鼠，其表现出空间学习障碍。在编码跨膜电压感应结构域的区域内，电压门控钾离子通道C亚家族成员3（Kcnc3）基因中存在一处致病错义突变（G434V）。通过构建Kcnc3G434V CRISPR编辑突变小鼠，证实该突变即为学习障碍的致病原因。尽管G434V突变对该通道的转录、翻译或膜转运均无影响，但对G434V突变型Kcnc3通道的电生理分析显示，其电压门控电导完全丧失，动作电位时程显著延长，且神经元放电频率降低。综上，本研究揭示了Kcnc3在学习与记忆过程中此前未被认知的重要作用。实验设计：对情境恐惧条件反射训练后小鼠海马齿状回（DG）与CA区背侧及腹侧部位的RNA-seq数据（4次生物学重复）开展比较基因表达谱分析。