The precise function of specialized GABAergic interneuron subtypes is required to provide appropriate synaptic inhibition for regulating principal neuron excitability and synchronization within brain circuits. Of these, parvalbumin-type (PV neuron) dysfunction is a feature of several sex-biased psychiatric and brain disorders, although, the underlying developmental mechanisms are unclear. While the transcriptional action of sex hormones generates sexual dimorphism during brain development, whether kinase signaling contributes to sex differences in PV neuron function remains unexplored. In the hippocampus, we report that gephyrin, the main inhibitory post-synaptic scaffolding protein, is phosphorylated at serine S268 and S270 in a developmentally-dependent manner in both males and females. When examining Gphn^S268A/S270A mice in which site-specific phosphorylation is constitutively blocked, we found that sex differences in PV neuron density in the hippocampal CA1 present in WT mice were abolished, coincident with a female-specific increase in PV neuron-derived terminals and increased inhibitory input onto principal cells. Electrophysiological analysis of CA1 PV neurons indicated that gephyrin phosphorylation is required for sexually dimorphic function. Moreover, while male and female WT mice showed no difference in hippocampus-dependent memory tasks, Gphn^S268A/S270A mice exhibited sex- and task-specific deficits, indicating that gephyrin phosphorylation is differentially required by males and females for convergent cognitive function. In fate mapping experiments, we uncovered that gephyrin phosphorylation at S268 and S270 establishes sex differences in putative PV neuron density during early postnatal development. Furthermore, patch-sequencing of putative PV neurons at postnatal day 4 revealed that gephyrin phosphorylation contributes to sex differences in the transcriptomic profile of developing interneurons. Therefore, these early shifts in male-female interneuron development may drive adult sex differences in PV neuron function and connectivity. Our results identify gephyrin phosphorylation as a new substrate organizing PV neuron development at the anatomical, functional, and transcriptional levels in a sex-dependent manner, thus implicating kinase signaling disruption as a new mechanism contributing to the sex-dependent etiology of brain disorders.

需要专门的 GABA 能中间神经元亚型的精确功能来提供适当的突触抑制，以调节脑回路内主要神经元的兴奋性和同步性。其中，小白蛋白型（PV 神经元）功能障碍是几种性别偏向的精神和脑部疾病的一个特征，尽管其潜在的发育机制尚不清楚。虽然性激素的转录作用在大脑发育过程中产生性别二态性，但激酶信号传导是否会导致PV神经元功能的性别差异仍有待探索。在海马体中，我们报道了 gephyrin（主要的抑制性突触后支架蛋白）在雄性和雌性中以发育依赖性方式在丝氨酸 S268 和 S270 处被磷酸化。当检查位点特异性磷酸化被组成性阻断的Gphn ^S268A/S270A小鼠时，我们发现 WT 小鼠海马 CA1 中 PV 神经元密度的性别差异被消除，这与女性特异性 PV 神经元衍生末梢的增加相一致并增加对主细胞的抑制输入。CA1 PV 神经元的电生理分析表明，gephyrin 磷酸化是性二态性功能所必需的。此外，虽然雄性和雌性 WT 小鼠在海马依赖性记忆任务方面没有表现出差异，但Gphn ^S268A/S270A小鼠表现出性别和任务特异性缺陷，表明雄性和雌性对于趋同认知功能所需的 gephyrin 磷酸化存在差异。在命运图谱实验中，我们发现 S268 和 S270 处的 gephyrin 磷酸化在出生后早期发育过程中建立了假定的 PV 神经元密度的性别差异。此外，出生后第 4 天对假定的 PV 神经元进行贴片测序表明，gephyrin 磷酸化导致发育中的中间神经元转录组谱中的性别差异。因此，男性和女性中间神经元发育的这些早期转变可能会导致成年PV神经元功能和连接性的性别差异。我们的结果将 gephyrin 磷酸化确定为以性别依赖性方式在解剖、功能和转录水平上组织 PV 神经元发育的新底物，从而暗示激酶信号传导破坏是导致脑部疾病的性别依赖性病因学的新机制。