Proteomic profile of hippocampal growth cones through early postnatal development

1.The early postnatal period represents a critical window for neural circuit assembly in the developing hippocampus. Growth cones (GCs) play essential roles in establishing connectivity patterns, yet their proteomic composition during this dynamic developmental phase remains poorly characterized. Here, we performed comprehensive proteomic profiling of GCs isolated from the whole hippocampus (HP-GCs) and dentate gyrus (DG-GCs) across the first five postnatal days (P1, P3, P5) in mice. Mass spectrometry and proteomic analysis revealed that GCs from both regions are highly similar at P1, subsequently diverging. This earliest timepoint seems to be characterized by a high metabolic demand. Developmental trajectories of the GCs from the two subregions then start to differ, with P3 being a very dynamic period for HP-GCs, with GO terms related to RNA splicing, and a transition towards synapse formation by P5. On the contrary, DG-GCs seem to still be in an exploratory phase by P5, suggesting a delayed maturation and reflecting the later time course of the invasion of EC layer 2 Reelin-positive axons into this region. We identified over 5,000 proteins, with each timepoint characterized by distinct protein subsets. Temporal trajectory analysis revealed key GC markers including DCC, DPSYL2, and FABP7, which showed dynamic regulation across development. Notably, we identified multiple proteins containing nuclear localization sequences, suggesting bidirectional communication between GCs and the nucleus during critical developmental periods. Furthermore, our dataset contains over 400 proteins associated with neurological and neurodegenerative diseases, with twenty showing temporal regulation, highlighting the potential relevance of early developmental disruptions to disease pathogenesis. These findings provide a comprehensive proteomic resource for understanding GC function during hippocampal circuit formation and offer insights into the molecular mechanisms underlying region-specific developmental timelines in the brain.