Behavioral, Neurotransmitter and Transcriptomic Analyses in male and female Fmr1 Knockout Mice

Fragile X Syndrome is an inherited X-linked disorder associated with intellectual disabilities that begin in childhood and last a lifetime. The symptoms overlap with autism spectrum disorder, and the syndrome predominantly affects males. Consequently, FXS research tends to favor analysis of social behaviors in males, leaving a gap in our understanding of other behavioral traits, especially in females. Here we used a mouse model of FXS to analyze developmental, behavioral, neurochemical, and transcriptomic profiles in males and females. Our behavioral assays demonstrated locomotor hyperactivity, motor impulsivity, increased approach behavior in an approach-avoidance assay, and deficits in nest building behavior. Analysis of brain neurotransmitter content revealed deficits in striatal GABA, glutamate, and serotonin content. RNA sequencing of the ventral striatum unveiled expression changes associated with neurotransmission as well as motivation and substance use pathways. Sex differences were identified in nest building behavior, striatal neurotransmitter content, and ventral striatal gene expression. In summary, our study identified sex differences in specific behavioral, neurotransmitter, and gene expression phenotypes and gene set enrichment analysis identified significant enrichment of pathways associated with motivation and drug reward. Ventral striatum mRNA from adult C57BL6 (https://www.jax.org/strain/000664) and Fmr1 KO (https://www.jax.org/strain/003025) male and female mice were analyzed by RNA sequencing using an Illumina NovaSeq 6000脆性X综合征（Fragile X Syndrome，FXS）是一种X连锁遗传性疾病，伴随始于童年且持续终生的智力障碍。其临床症状与自闭症谱系障碍存在重叠，且该综合征的受累群体以男性为主。因此，现有FXS研究多聚焦于男性群体的社会行为分析，导致我们对该疾病其他行为特征的认知存在显著空白，尤其是在女性群体中。 本研究采用FXS小鼠模型，对雌雄小鼠的发育特征、行为表型、神经化学指标及转录组图谱展开系统性分析。行为学实验结果显示，模型小鼠表现出运动过度活跃、运动冲动性增强、趋避冲突实验中趋近行为增加，以及筑巢行为缺陷等异常表型。 对小鼠脑组织神经递质含量的检测发现，纹状体中γ-氨基丁酸（GABA）、谷氨酸及5-羟色胺的水平存在显著异常。对腹侧纹状体进行RNA测序分析后，本研究揭示了与神经传递、动机调控及物质使用通路相关的基因表达变化。 研究同时鉴定出筑巢行为、纹状体神经递质含量以及腹侧纹状体基因表达均存在性别差异。综上，本研究明确了FXS模型小鼠在特定行为、神经递质及基因表达表型中的性别差异；基因集富集分析进一步发现，与动机及药物奖赏通路相关的基因集存在显著富集现象。 本研究通过Illumina NovaSeq 6000测序平台，对成年C57BL/6（https://www.jax.org/strain/000664）与Fmr1敲除（Fmr1 KO，https://www.jax.org/strain/003025）雌雄小鼠的腹侧纹状体mRNA开展了RNA测序分析。