Multiscale causal networks identify VGF as a key regulator of Alzheimer's disease

Though discovered over 100 years ago, the molecular foundation of sporadic Alzheimer's disease (AD) remains elusive. To better characterize the complex nature of AD, we constructed multiscale causal networks on a large human AD multi-omics dataset, integrating clinical features of AD, DNA variation, and gene- and protein-expression. These probabilistic causal models enabled detection, prioritization and replication of high-confidence master regulators of AD-associated networks, including the top predicted regulator, VGF. Overexpression of neuropeptide precursor VGF in 5xFAD mice partially rescued beta-amyloid-mediated memory impairment and neuropathology. Molecular validation of network predictions downstream of VGF was also achieved in this AD model, with significant enrichment for homologous genes identified as differentially expressed in 5xFAD brains overexpressing VGF. Our findings support a causal role for VGF in protecting against AD pathogenesis and progression.

MuSK expressed in the brain mediates cholinergic responses, synaptic plasticity, and memory formation

Muscle-specific tyrosine kinase receptor (MuSK) has been believed to be mainly expressed and functional in muscle, in which it mediates the formation of neuromuscular junctions. Here we show that MuSK is expressed in the brain, particularly in neurons, as well as in non-neuronal tissues. We also provide evidence that MuSK expression in the hippocampus is required for memory consolidation, because temporally restricted knockdown after training impairs memory retention. Hippocampal disruption of MuSK also prevents the learning-dependent induction of both cAMP response element binding protein (CREB) phosphorylation and CCAAT enhancer binding protein beta (C/EBPbeta) expression, suggesting that the role of MuSK during memory consolidation critically involves the CREB-C/EBP pathway. Furthermore, we found that MuSK also plays an important role in mediating hippocampal oscillatory activity in the theta frequency as well as in the induction and maintenance of long-term potentiation, two synaptic responses that correlate with memory formation. We conclude that MuSK plays an important role in brain functions, including memory formation. Therefore, its expression and role are broader than what was believed previously.