The Neuron-specific IIS/FOXO Transcriptome in Aged Animals Reveals Regulatory Mechanisms of Cognitive Aging

Abstract

Cognitive decline is a significant public health concern in our aging society. In this study, we used the model organism C. elegans to investigate the impact of the IIS/FOXO pathway on age-related cognitive decline. The daf-2 Insulin/IGF-1 receptor mutant exhibits a significant extension of learning and memory span with age compared to wild-type worms, an effect that is dependent on the DAF-16 transcription factor. To determine the mechanisms by which aging daf-2 mutants can maintain learning and memory with age while wild-type worms lose neuronal function, we carried out neuron-specific transcriptomic analysis in aged animals. We observed downregulation of neuronal genes and upregulation of transcriptional regulation genes in aging wild-type neurons. By contrast, IIS/FOXO pathway mutants exhibit distinct neuronal transcriptomic alterations in response to cognitive aging, including upregulation of stress response genes and downregulation of specific insulin signaling genes. We tested the roles of significantly transcriptionally-changed genes in regulating cognitive functions, identifying several novel regulators of learning and memory. These findings suggest a potential mechanism for regulating cognitive function with age and offer insights into novel therapeutic targets for age-related cognitive decline.

Adult Single-nucleus Neuronal Transcriptomes of Insulin Signaling Mutants Reveal Regulators of Behavior and Learning

“…We previously found that the insulin/IGF receptor mutant, daf-2, has extended short-term associative memory 1 , and its long-term memory is extended as well, through increased CREB expression 1,2 . daf-2 mutants also better maintain motor functions and axon regeneration ability with age [13][14][15] , and maintain their memory ability with age for twice as long as wild-type worms 16 . We are interested in how the daf-2 mutation changes the AWC transcriptome, as well as the transcriptomes of other neurons, to change learning ability and allow extended memory function.…”

“…In addition to their greatly extended lifespan, daf-2 mutants have improved and extended cognitive and neuronal behaviors 1,6,15,36 , some of which may depend on gene expression changes in individual neurons. We previously used pan-neuronal transcriptional profiling to identify genes whose expression is high in young wild-type neurons and declines with age 16 . These genes are enriched in neuronal and synaptic function 16,54 , and their downregulation with age correlates with behavioral deficits that rise with age.…”

“…We previously used pan-neuronal transcriptional profiling to identify genes whose expression is high in young wild-type neurons and declines with age 16 . These genes are enriched in neuronal and synaptic function 16,54 , and their downregulation with age correlates with behavioral deficits that rise with age. With the exception of the ubiquitously-downregulated lysozyme ilys-5 (Extended Data Fig.…”

“…The genes that decline with age in wild-type neurons 16 are enriched in all of daf-2's neurons (Fig. 4b), although some sensory neurons show lower GSEA (gene set enrichment) scores; this may be due to the relatively low representation of sensory neurons in the bulk sequencing results due to dissociation and sorting difficulties, or because of their unique transcriptomes, while inter, pharyngeal, and motor neurons are more homogenous.…”

“…Neuronal clusters and genes are hierarchically clustered. The annotation row denotes whether the gene was previously identified as a neuronal IIS target in previous studies 2, 3,16 . (B) GSEA Enrichment score comparing the daf-2 vs N2 differentially expressed genes in each neuron to previous bulk-sequencing results.…”