Tuberous sclerosis complex is associated with a novel human tauopathy.

Tuberous sclerosis complex (TSC) is a neurogenetic disorder leading to epilepsy, developmental delay, and neurobehavioral dysfunction. The syndrome is caused by pathogenic variants in TSC1 (coding for hamartin) or TSC2 (coding for tuberin). Recently, we reported a progressive frontotemporal dementia-like clinical syndrome in a patient with a mutation in TSC1, but the neuropathological changes seen in adults with TSC with or without dementia have yet to be systematically explored. Here, we examined neuropathological findings in adults with TSC (n = 11) aged 30-58 years and compared them to age-matched patients with epilepsy unrelated to TSC (n = 9) and non-neurological controls (n = 10). In 3 of 11 subjects with TSC, we observed a neurofibrillary tangle-predominant "TSC tauopathy" not seen in epilepsy or non-neurological controls. This tauopathy was observed in the absence of pathological amyloid beta, TDP-43, or alpha-synuclein deposition. The neurofibrillary tangles in TSC tauopathy showed a unique pattern of post-translational modifications, with apparent differences between TSC1 and TSC2 mutation carriers. Tau acetylation (K274, K343) was prominent in both TSC1 and TSC2, whereas tau phosphorylation at a common phospho-epitope (S202) was observed only in TSC2. TSC tauopathy was observed in selected neocortical, limbic, subcortical, and brainstem sites and showed a 3-repeat greater than 4-repeat tau isoform pattern in both TSC1 and TSC2 mutation carriers, but no tangles were immunolabeled with MC1 or p62 antibodies. The findings suggest that individuals with TSC are at risk for a unique tauopathy in mid-life and that tauopathy pathogenesis may involve TSC1, TSC2, and related molecular pathways.

Selective activation of the extended ventrolateral preoptic nucleus during rapid eye movement sleep.

We found previously that damage to a cluster of sleep-active neurons (Fos-positive during sleep) in the ventrolateral preoptic nucleus (VLPO) decreases non-rapid eye movement (NREM) sleep in rats, whereas injury to the sleep-active cells extending dorsally and medially from the VLPO cluster (the extended VLPO) diminishes REM sleep. These results led us to examine whether neurons in the extended VLPO are activated during REM sleep and the connectivity of these neurons with pontine sites implicated in producing REM sleep: the laterodorsal tegmental nucleus (LDT), dorsal raphe nucleus (DRN), and locus ceruleus (LC). After periods of dark exposure that triggered enrichment of REM sleep, the number of Fos-positive cells in the extended VLPO was highly correlated with REM but not NREM sleep. In contrast, the number of Fos-positive cells in the VLPO cluster was correlated with NREM but not REM sleep. Sixty percent of sleep-active cells in the extended VLPO and 90% of sleep-active cells in the VLPO cluster in dark-treated animals contained galanin mRNA. Retrograde tracing from the LDT, DRN, and LC demonstrated more labeled cells in the extended VLPO than the VLPO cluster, and 50% of these in the extended VLPO were sleep-active. Anterograde tracing showed that projections from the extended VLPO and VLPO cluster targeted the cell bodies and dendrites of DRN serotoninergic neurons and LC noradrenergic neurons but were not apposed to cholinergic neurons in the LDT. The connections and physiological activity of the extended VLPO suggest a specialized role in the regulation of REM sleep.