PER2 and sarcopenia: BMAL1 KO, premature aging: reduced lifespan, sarcopenia, cataracts, organ atrophy; aged ↓Bmal1 in hippocampus linked to impaired neurogenesis and memory-related declineAltered PER1/2 linked to impaired memory and circadian rhythmicity; SCN PER2 fragility, reduced robustness of central clock outputs (behavioral and physiological rhythm dampening)REV-ERBα deletion, increased microglial phagocytosis and synaptic loss (hippocampus) and altered complement expression, links to synaptic loss/neuroinflammation relevant to neurodegeneration/aging