The Microglial TREM2 Receptor Programs Hippocampal Development in a Mouse Model of Childhood Deprivation.

Childhood neglect and deprivation are the most common forms of adversity, yet their biological impact on cognitive development-and how enrichment mitigates these effects-remains unclear. Using limited bedding (LB) as a mouse model of deprivation, we previously showed that abnormal microglial-mediated synaptic pruning during the second and third postnatal weeks leads to impaired synaptic connectivity and hippocampal dysfunction, particularly in males. Here, we demonstrate that LB reduces expression of Triggering Receptor Expressed on Myeloid cells 2 (TREM2) in different mouse strains and that TREM2 deficiency contributes to, but does not fully explain, impaired microglial pruning. Overexpressing TREM2 restored microglial phagocytic function and rescued deficits in hippocampal connectivity and fear learning. Brief postnatal enrichment (P14-P17) also normalized synaptic pruning in a TREM2-dependent manner. Together, our findings identify TREM2 as a key molecular mediator of experience-dependent plasticity, revealing its central role in linking early-life deprivation and enrichment to cognitive outcomes later in life.