Objective: To investigate the effects of CACNA1H gene knockout (KO) on autistic-like behaviors and the morphology of hippocampal neurons in mice.
Methods: In the study, 25 CACNA1H KO mice of 3-4 weeks old and C57BL/6 background were recruited as the experimental group, and 26 wild type (WT) mice of the same age and background were recruited as the control group. Three-chamber test and open field test were used to observe the social interaction, anxiety, and repetitive behaviors in mice. After that, their brain weight and size were measured, and the number of hippocampal neurons were observed by Nissl staining. Furthermore, the CACNA1H heterozygote mice were interbred with Thy1-GFP-O mice to generate CACNA1H-/--Thy1+(KO-GFP) and CACNA1H+/+-Thy1+ (WT-GFP) mice. The density and maturity of dendritic spines of hippocampal neurons were observed.
Results: In the sociability test session of the three-chamber test, the KO mice spent more time in the chamber of the stranger mice than in the object one (F1, 14=95.086, P < 0.05; Post-Hoc: P < 0.05), without any significant difference for the explored preference index between the two groups (t=1.044, P>0.05). However, in the social novelty recognition test session, no difference was observed between the time of the KO mice spend in the chamber of new stranger mice and the stranger one (F1, 14=18.062, P < 0.05; Post-Hoc: P>0.05), and the explored preference index of the KO mice was less than that of the control group (t=2.390, P < 0.05). In the open field test, the KO mice spent less time in the center of the open field apparatus than the control group (t=2.503, P < 0.05), but the self-grooming time was significantly increased compared with the control group (t=-2.299, P < 0.05). Morphological results showed that the brain weight/body weight ratio (t=0.356, P>0.05) and brain size (t=-0.660, P>0.05) of the KO mice were not significantly different from those of the control group, but the number of neurons were significantly reduced in hippocampal dentate gyrus compared with the control group (t=2.323, P < 0.05). Moreover, the density of dendritic spine of dentate gyrus neurons in the KO-GFP mice was significantly increased compared with the control group (t=-2.374, P < 0.05), without any significant difference in spine maturity (t=-1.935, P>0.05).
Conclusion: CACNA1H KO mice represent autistic-like behavior, which may be related to the decrease in the number of neurons and the increase in the density of dendritic spine in the dentate gyrus.
目的: 研究CACNA1H基因敲除(knockout, KO)对小鼠孤独症样行为及海马神经元形态学的影响。
方法: 25只3~4周龄C57BL/6背景的CACNA1H KO小鼠作为实验组, 26只同年龄同背景的野生型(wild type, WT)小鼠作为对照组。通过三箱实验和旷场实验观察小鼠社交、焦虑和重复刻板行为后测量其脑质量与脑体积, 用尼氏染色法(Nissl staining)观察海马神经元数目。将CACNA1H杂合子小鼠与Thy1-GFP-O小鼠杂交, 构建CACNA1H-/--Thy1+(KO-GFP)及CACNA1H+/+-Thy1+(WT-GFP)小鼠, 观察海马神经元树突棘密度及成熟度。
结果: 三箱实验中, 社交测试阶段, KO小鼠在陌生鼠箱中的时间比空箱更长(F1, 14=95.086, P < 0.05;Post-Hoc: P < 0.05), 探索的偏好指数与对照组相比差异无统计学意义(t=1.044, P>0.05);新社交对象识别测试阶段, KO小鼠在新陌生鼠箱与陌生鼠箱中的时间差异无统计学意义(F1, 14=18.062, P < 0.05;Post-Hoc: P>0.05), 探索的偏好指数低于对照组(t=2.390, P < 0.05)。旷场实验中, KO小鼠在旷场中心活动时间明显少于对照组(t=2.503, P < 0.05), 自梳理时间明显多于对照组(t=-2.299, P < 0.05)。形态学结果显示, KO小鼠脑质量/体质量和脑体积与对照组相比差异均无统计学意义(t=0.356, P>0.05;t=-0.660, P>0.05), 但其海马齿状回区神经元数目较对照组减少(t=2.323, P < 0.05), 且KO-GFP小鼠海马齿状回区树突棘密度较对照组增加(t=-2.374, P < 0.05), 而成熟度差异无统计学意义(t=-1.935, P>0.05)。
结论: CACNA1H KO小鼠具有孤独症样行为, 可能与海马齿状回区神经元数目减少及树突棘密度增高有关。
Keywords: Autism spectrum disorder; Behavior test; CACNA1H; Mice, knockout.