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Critical role of dorsomedial hypothalamic nucleus in a wide range of behavioral circadian rhythms.

ABSTRACT: The suprachiasmatic nucleus (SCN) contains the brain's circadian pacemaker, but mechanisms by which it controls circadian rhythms of sleep and related behaviors are poorly understood. Previous anatomic evidence has implicated the dorsomedial hypothalamic nucleus (DMH) in circadian control of sleep, but this hypothesis remains untested. We now show that excitotoxic lesions of the DMH reduce circadian rhythms of wakefulness, feeding, locomotor activity, and serum corticosteroid levels by 78-89% while also reducing their overall daily levels. We also show that the DMH receives both direct and indirect SCN inputs and sends a mainly GABAergic projection to the sleep-promoting ventrolateral preoptic nucleus, and a mainly glutamate-thyrotropin-releasing hormone projection to the wake-promoting lateral hypothalamic area, including orexin (hypocretin) neurons. Through these pathways, the DMH may influence a wide range of behavioral circadian rhythms.

SUBMITTER: Chou TC

PROVIDER: S-EPMC6740926 | biostudies-literature | 2003 Nov

REPOSITORIES: biostudies-literature

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Critical role of dorsomedial hypothalamic nucleus in a wide range of behavioral circadian rhythms.

Chou Thomas C TC Scammell Thomas E TE Gooley Joshua J JJ Gaus Stephanie E SE Saper Clifford B CB Lu Jun J

The Journal of neuroscience : the official journal of the Society for Neuroscience 20031101 33

The suprachiasmatic nucleus (SCN) contains the brain's circadian pacemaker, but mechanisms by which it controls circadian rhythms of sleep and related behaviors are poorly understood. Previous anatomic evidence has implicated the dorsomedial hypothalamic nucleus (DMH) in circadian control of sleep, but this hypothesis remains untested. We now show that excitotoxic lesions of the DMH reduce circadian rhythms of wakefulness, feeding, locomotor activity, and serum corticosteroid levels by 78-89% wh ...[more]

PMID: 14627654

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Project description:In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus coordinates daily rhythms including sleep-wake, hormone release, and gene expression. The cells of the SCN must synchronize to each other to drive these circadian rhythms in the rest of the body. The ontogeny of circadian cycling and intercellular coupling in the SCN remains poorly understood. Recent in vitro studies have recorded circadian rhythms from the whole embryonic SCN. Here, we tracked the onset and precision of rhythms in PERIOD2 (PER2), a clock protein, within the SCN isolated from embryonic and postnatal mice of undetermined sex. We found that a few SCN cells developed circadian periodicity in PER2 by 14.5 d after mating (E14.5) with no evidence for daily cycling on E13.5. On E15.5, the fraction of competent oscillators increased dramatically corresponding with stabilization of their circadian periods. The cells of the SCN harvested at E15.5 expressed sustained, synchronous daily rhythms. By postnatal day 2 (P2), SCN oscillators displayed the daily, dorsal-ventral phase wave in clock gene expression typical of the adult SCN. Strikingly, vasoactive intestinal polypeptide (VIP), a neuropeptide critical for synchrony in the adult SCN, and its receptor, VPAC2R, reached detectable levels after birth and after the onset of circadian synchrony. Antagonists of GABA or VIP signaling or action potentials did not disrupt circadian synchrony in the E15.5 SCN. We conclude that endogenous daily rhythms in the fetal SCN begin with few noisy oscillators on E14.5, followed by widespread oscillations that rapidly synchronize on E15.5 by an unknown mechanism.SIGNIFICANCE STATEMENT We recorded the onset of PER2 circadian oscillations during embryonic development in the mouse SCN. When isolated at E13.5, the anlagen of the SCN expresses high, arrhythmic PER2. In contrast, a few cells show noisy circadian rhythms in the isolated E14.5 SCN and most show reliable, self-sustained, synchronized rhythms in the E15.5 SCN. Strikingly, this synchrony at E15.5 appears before expression of VIP or its receptor and persists in the presence of blockers of VIP, GABA or neuronal firing. Finally, the dorsal-ventral phase wave of PER2 typical of the adult SCN appears ?P2, indicating that multiple signals may mediate circadian synchrony during the ontogeny of the SCN.

Project description:Single-cell RNA-seq data from the mouse Dorsomedial Hypothalamic Nucleus (DMH) was generated following a modified protocol from https://www.nature.com/articles/s41586-020-2821-8. Briefly, six 7.5 week old C57B6 mice (3 male, 3 female) were anaesthetized with isoflurane. Brains were rapidly extracted and dropped into ice-cold carbogenated NMDG-HEPES-ACSF. Brain sections (2 mm) containing DMH were cut with a razor blade on a stainless steel brain matrix (51392, Stoelting) and transferred to a dissection dish on ice containing NMDG-HEPES-ACSF. DMH was bilaterally microdissected in ~700·700·350 micron tissue block. Microdissected tissue was aggregated in a collection tube on ice containing NMDG-HEPES-ACSF and 30 μM actinomycin D. For enzymatic tissue digestion, NMDG-HEPES-ACSF was replaced by trehalose-HEPES-ACSF containing papain (50 U/ml; P3125, Sigma Aldrich, pre-activated with 2.5 mM cysteine and a 30-min incubation at 34 °C and supplemented with 0.5 mM EDTA) and 15 μM actinomycin D. Extracted DMH tissue was incubated at room temperature with gentle carbogenation for 55 min. During enzymatic digestion the tissue was pipetted periodically every 10 min. At the end of enzymatic digestion, the medium was replaced with 200μl of room temperature trehalose-HEPES-ACSF containing 3 mg/ml ovomucoid inhibitor (OI-BSA,Worthington)25 U/ml DNase I (90083, Thermo Scientific) and 15 μM actinomycin D and tissue was gently triturated into a uniform single-cell suspension with fire-polished glass Pasteur pipettes. The resulting cell suspension volume was brought up to 1 ml with trehalose-HEPES-ACSF with 3 mg/ml ovomucoid inhibitor and pipetted through a 40μm cell strainer. Single-cell suspension was centrifuged down at 300g for 5 min at 4 °C and the supernatant was replaced with 1 ml fresh ice-cold trehalose-HEPES-ACSF and the cell pellet was resuspended. Cells were pelleted again and resuspended in 100 μl of ice-cold resuspension-ACSF. Cell suspensions were kept on ice while cell densities were quantified with a haemocytometer and the final cell densities were verified to be in the range of 300–1,000 cells/μl. Cell suspension volumes estimated to retrieve ~10,000 single-cell transcriptomes were added to the 10x Genomics RT reaction mix and loaded to the 10X Next GEM Chip G (2000177, 10x Genomics) per the manufacturer’s protocol. We used the Chromium Next GEM Single Cell 3’ Reagents Kit v3.1 (1000128, 10x Genomics) and the Single Index Kit Set A (100213) to prepare Illumina sequencing libraries downstream of reverse transcription following the manufacturer’s protocol. Resulting scRNA-seq sequencing library was sequenced on an Illumina NovaSeq 6000 sequencers (paired-end 150). Sequencing data were aligned to optimized pre-mRNA reference transcriptome52 and digital gene-cell matrices were generated with the 10x Genomics Cell Ranger v.6.0.0 count pipeline. The resulting scRNA-seq data were analyzed in R (4.1.2) using Seurat (v.4.1.0.9007) as previously described51. Briefly, expression data were filtered to exclude cells with fewer than 1,000 unique transcripts as well as cells exhibiting more than 15% of mitochondrial transcripts. We followed the standard Seurat workflow to identify transcriptomic cell-types and assigned cel class identities based on canonical cell-type markers: Ndrg4 for neurons, Ntsr2 for astrocytes, Slco1c1 for endothelial cells, Fcer1g for microglia and Mag for oligodendrocytes. We digitally extracted neuronal clusters from our dataset resulting in expression data for 4587 DMH neurons that we used to establish an unbiased neuronal nomenclature for DMH.

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Critical role of dorsomedial hypothalamic nucleus in a wide range of behavioral circadian rhythms.

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Critical role of dorsomedial hypothalamic nucleus in a wide range of behavioral circadian rhythms.

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