Miozzo Federico, Murru Luca, Maiellano Greta, di Iasio Ilaria, Zippo Antonio G, Zambrano Avendano Annalaura, Metodieva Verjinia D, Riccardi Sara, D'Aliberti Deborah, Spinelli Silvia, Canu Tamara, Chaabane Linda, Hirano Shinji, Kas Martien J H, Francolini Maura, Piazza Rocco, Moretto Edoardo, Passafaro Maria
Institute of Neuroscience, CNR, Vedano al Lambro, Italy.
Present address: Instituto de Neurociencias, Consejo Superior de Investigaciones Científicas, Universidad Miguel Hernández, Alicante, Spain.
J Neurosci. 2024 Nov 18;44(50). doi: 10.1523/JNEUROSCI.0491-24.2024.
Protocadherins, a family of adhesion molecules with crucial role in cell-cell interactions, have emerged as key players in neurodevelopmental and psychiatric disorders. In particular, growing evidence links genetic alterations in Protocadherin 9 () gene with Autism Spectrum Disorder (ASD) and Major Depressive Disorder (MDD). Furthermore, deletion induces neuronal defects in the mouse somatosensory cortex, accompanied by sensorimotor and memory impairment. However, the synaptic and molecular mechanisms of in the brain remain largely unknown, particularly concerning its impact on brain pathology. To address this question, we conducted a comprehensive investigation of PCDH9 role in the male mouse hippocampus at the ultrastructural, biochemical, transcriptomic, electrophysiological and network level. We show that PCDH9 mainly localizes at glutamatergic synapses and its expression peaks in the first week after birth, a crucial time window for synaptogenesis. Strikingly, KO neurons exhibit oversized presynaptic terminal and postsynaptic density (PSD) in the CA1. Synapse overgrowth is sustained by the widespread up-regulation of synaptic genes, as revealed by single-nucleus RNA-seq (snRNA-seq), and the dysregulation of key drivers of synapse morphogenesis, including the SHANK2/CORTACTIN pathway. At the functional level, these structural and transcriptional abnormalities result into increased excitatory postsynaptic currents (mEPSC) and reduced network activity in the CA1 of KO mice. In conclusion, our work uncovers pivotal role in shaping the morphology and function of CA1 excitatory synapses, thereby modulating glutamatergic transmission within hippocampal circuits. Converging evidence indicates that genetic alterations in Protocadherin 9 () gene are associated with Autism Spectrum Disorder (ASD) and Major Depressive Disorder (MDD). However, our understanding of physiological role and molecular mechanisms in the brain, as well as its connection to synaptic dysfunction and brain pathology, remains limited. Here we demonstrate that regulates the transcriptional profile, morphology and function of glutamatergic synapses in the CA1, thereby tuning hippocampal network activity. Our results elucidate the molecular and synaptic mechanisms of a gene implicated in neurodevelopmental and psychiatric disorders, and suggest potential hippocampal alterations contributing to the cognitive deficits associated with these conditions.
原钙黏蛋白是一类在细胞间相互作用中起关键作用的黏附分子，已成为神经发育和精神疾病的关键因素。特别是，越来越多的证据将原钙黏蛋白9（PCDH9）基因的遗传改变与自闭症谱系障碍（ASD）和重度抑郁症（MDD）联系起来。此外，PCDH9缺失会在小鼠体感皮层诱导神经元缺陷，并伴有感觉运动和记忆障碍。然而，PCDH9在大脑中的突触和分子机制在很大程度上仍然未知，尤其是其对脑病理学的影响。为了解决这个问题，我们在超微结构、生化、转录组学、电生理和网络水平上对雄性小鼠海马体中PCDH9的作用进行了全面研究。我们发现PCDH9主要定位于谷氨酸能突触，其表达在出生后的第一周达到峰值，这是突触发生的关键时间窗口。令人惊讶的是，PCDH9基因敲除（KO）神经元在CA1区表现出超大的突触前终末和突触后致密物（PSD）。单细胞核RNA测序（snRNA-seq）显示，突触基因的广泛上调以及包括SHANK2/CORTACTIN途径在内的突触形态发生关键驱动因子的失调维持了突触过度生长。在功能水平上，这些结构和转录异常导致PCDH9基因敲除小鼠CA1区的兴奋性突触后电流（mEPSC）增加和网络活动减少。总之，我们的工作揭示了PCDH9在塑造CA1兴奋性突触的形态和功能方面的关键作用，从而调节海马回路内的谷氨酸能传递。越来越多的证据表明，原钙黏蛋白9（PCDH9）基因的遗传改变与自闭症谱系障碍（ASD）和重度抑郁症（MDD）有关。然而，我们对PCDH9在大脑中的生理作用和分子机制及其与突触功能障碍和脑病理学的联系的理解仍然有限。在这里，我们证明PCDH9调节CA1区谷氨酸能突触的转录谱、形态和功能，从而调节海马网络活动。我们的结果阐明了一个与神经发育和精神疾病相关基因的分子和突触机制，并提出了可能导致与这些疾病相关认知缺陷的海马改变。
