Conserved properties ofDrosophilaInsomniac link sleep regulation and synaptic function

Abstract

Sleep is an ancient animal behavior that is regulated similarly in species ranging from flies to mammals. Various genes that regulate sleep have been identified in invertebrates, but whether the functions of these genes are conserved in mammals remains poorly explored. Drosophila insomniac (inc) mutants exhibit severely shortened and fragmented sleep. Inc protein physically associates with the Cullin-3 (Cul3) ubiquitin ligase, and neuronal depletion of Inc or Cul3 strongly curtails sleep, suggesting that Inc is a Cul3 adaptor that directs the ubiquitination of neuronal substrates that regulate sleep. Three proteins similar to Inc exist in vertebrates—KCTD2, KCTD5, and KCTD17—but are uncharacterized within the nervous system and their functional conservation with Inc has not been addressed. Here we show that Inc and its mouse orthologs exhibit striking biochemical and functional interchangeability within Cul3 complexes. Remarkably, KCTD2 and KCTD5 restore sleep to inc mutants, indicating that they can substitute for Inc in vivo and engage its neuronal targets that impact sleep. Inc and its orthologs traffic similarly within fly and mammalian neurons and are present at synapses, suggesting that their substrates include synaptic proteins. Consistent with such a mechanism, inc mutants exhibit defects in synaptic structure and physiology, indicating that Inc is vital for both synaptic function and sleep. Our findings reveal that molecular functions of Inc are conserved through ~600 million years of evolution and support the hypothesis that Inc and its orthologs participate in an evolutionarily conserved ubiquitination pathway that links synaptic function and sleep regulation.Author summarySleep is ubiquitous among animals and is regulated in a similar manner across phylogeny, but whether conserved molecular mechanisms govern sleep is poorly defined. The Insomniac protein is vital for sleep in Drosophila and is a putative adaptor for the Cul3 ubiquitin ligase. We show that two mammalian orthologs of Insomniac can restore sleep to flies lacking Insomniac, indicating that the molecular functions of these proteins are conserved through evolution. Our comparative analysis reveals that Insomniac and its mammalian orthologs localize to neuronal synapses and that Insomniac impacts synaptic structure and physiology. Our findings suggest that Insomniac and its mammalian orthologs are components of an evolutionarily conserved ubiquitination pathway that links synaptic function and the regulation of sleep.

Epigenome-wide association analysis of daytime sleepiness in the Multi-Ethnic Study of Atherosclerosis reveals African-American specific associations

“…One of the associations, that of cg26130090 (intergenic), replicated in CHS AAs (p-value =0.0004), and there was an overall directional agreement in the significant associations in MESA AA and CHS AA (Binomial p-value=0.005). Additional top DNAm associations were observed in the RAI1 and KCTD5 genes, which have strong biological relevance and were previously reported as associated with several sleep traits 58-60,62-64 .…”

“…In race/ethnicity stratified analyses, significant associations were only observed in the AA group, where 61 DNAm probes were significantly associated with ESS at q-value ≤ 0.1 (Table 3). The top probe was in KCTD5 (p=3.96 × 10 -7 ), a gene with known sleep-wake effects 58 . Two significant probes were within RAI1 , a gene associated with several sleep and circadian phenotypes 59,60 , and 5 probes were within KIF3 , involved in cytokinesis with effects on photoreceptors 61 .…”

“…KCTD5 is a mammalian ortholog of the Drosophila gene Inc , a gene expressed in multiple sleep associated regions in the central nervous system and shown to play a fundamental role in sleep in Drosophila by interacting with Cullin-3 ubiquitin ligase ( Cul3 ). When mutated, both genes ( KCTD5 and Cul3 ) produce similar phenotypes characterized by markedly shortened and fragmented sleep together with altered synaptic structure and impaired synaptic transmission in relevant neuronal circuits 58 . This suggests that alterations in protein dynamics (e.g.…”