Shared molecular signature in Alzheimer's disease and schizophrenia: A systematic review of the reelin signaling pathway.

The Reelin signaling pathway, particularly the RELN-APOER2-DAB1 complex, has emerged as a key contributor to the neuropathology of Alzheimer's disease (AD) and Schizophrenia (SZ). Despite being distinct clinical conditions, these disorders exhibit similar patterns of cognitive decline, including early disruptions in synaptic function and memory impairments. Notably, individuals with SZ have a 2-4 fold increased risk of developing AD or other dementias, highlighting potential shared molecular mechanisms, and positioning Reelin as a pivotal link between them. This systematic review explores the role of Reelin and its signaling components across these disorders. In AD, Reelin disruption correlates with hallmark features such as Tau hyperphosphorylation, amyloid-beta accumulation, and cognitive deficits. In SZ, alterations in Reelin signaling, including epigenetic modifications affecting RELN expression, are linked to disruptions in neuronal development and synaptic plasticity, particularly in the parietal and prefrontal cortices. Additionally, genomic studies reveal specific RELN variants and allelic imbalances that may influence disease severity and treatment response in SZ, suggesting RELN's role as a potential biomarker for therapeutic outcomes. Region-specific Reelin alterations in both AD and SZ suggest differing impacts yet underscore a potential common molecular origin. Our findings highlight the Reelin pathway as a molecular convergence point, warranting further investigation as a therapeutic and diagnostic target for AD, SZ, and potentially other neuropsychiatric disorders. The interplay between genetic and epigenetic regulation of RELN may provide novel insights into neurodegeneration, with implications for personalized intervention strategies in AD and SZ.