Biology subjects

Kurogi, Y.

Publications and source records attributed to Kurogi, Y..

4 recordsLinked to original sources

bioRxiv2024

Chemogenetic activation of astrocytes modulates sleep/wakefulness states in a brain region-dependent manner

Study objectivesAstrocytes change their intracellular calcium (Ca2+) concentration during sleep/wakefulness states in mice. Furthermore, the Ca2+ dynamics in astrocytes vary depending on the brain region. However, whether alterations in intracellular Ca2+ concentration in astrocytes can affect sleep/wakefulness states and cortical oscillations in a brain region-dependent manner remain unclear. MethodsThe Ca2+ concentration in astrocytes was artificially increased using chemogenetics in mice. Astrocytes in the hippocampus and pons, which are 2 brain regions previously classified into different clusters based on their Ca2+ dynamics during sleep/wakefulness, were focused on to compare whether there are differences in the effects of astrocytes from different brain regions. ResultsThe activation of astrocytes in the hippocampus significantly decreased the total time of wakefulness and increased the total time of sleep. This had minimal effects on cortical oscillations in all sleep/wakefulness states. On the other hand, the activation of astrocytes in the pons substantially suppressed rapid eye movement (REM) sleep in association with a decreased number of REM episodes, indicating strong inhibition of REM onset. Regarding cortical oscillations, the delta wave component during non-REM sleep was significantly enhanced. ConclusionsThese results suggest that astrocytes modulate sleep/wakefulness states and cortical oscillations. Furthermore, the role of astrocytes in sleep/wakefulness states appears to vary among brain regions. Statement of SignificanceSleep is an instinctive behavior for many organisms. Recently, it has been reported that not only neurons, but also astrocytes, a type of glial cell, contribute to sleep/wakefulness states. Intracellular Ca2+ concentration, an indicator of astrocyte activity, fluctuates during sleep/wakefulness states. However, it is still unclear whether changes in Ca2+ concentration in astrocytes can affect sleep/wakefulness states. In this study, we utilized chemogenetics to activate astrocytes in mice. Our results showed that activation of astrocytes in the hippocampus causes decreased wakefulness, and that in the pons causes decreased REM sleep. Therefore, our findings demonstrate that the activation of astrocytes modulates sleep/wakefulness states in a brain region-dependent manner. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/597103v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@100a766org.highwire.dtl.DTLVardef@1ee1d21org.highwire.dtl.DTLVardef@1ba8044org.highwire.dtl.DTLVardef@13af766_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

The seminal vesicle is a juvenile hormone-responsive tissue in adult male Drosophila melanogaster

Juvenile hormone (JH) is one of the most essential hormones controlling insect metamorphosis and physiology. While it is well known that JH affects many tissues throughout the insects life cycle, the difference in JH responsiveness and the repertoire of JH-inducible genes among different tissues has not been fully investigated. In this study, we monitored JH responsiveness in vivo using transgenic Drosophila melanogaster flies carrying a JH response element-GFP (JHRE-GFP) construct. Our data highlight the high responsiveness of the epithelial cells within the seminal vesicle, a component of the male reproductive tract, to JH. Specifically, we observe an elevation in the JHRE-GFP signal within the seminal vesicle epithelium upon JH analog administration, while suppression occurs upon knockdown of genes encoding the intracellular JH receptors, Methoprene-tolerant and germ cell-expressed. Starting from published transcriptomic and proteomics datasets, we next identified Lactate dehydrogenase as a JH-response gene expressed in the seminal vesicle epithelium, suggesting insect seminal vesicles undergo metabolic regulation by JH. Together, this study sheds new light on biology of the insect reproductive regulatory system.

physiology↗

bioRxiv2022

Female reproductive dormancy in Drosophila melanogaster is regulated by DH31-producing neurons projecting into the corpus allatum

Female reproductive dormancy in insects is a process that drastically suppresses oogenesis to conserve energy under adverse environments. In many insects, including the fruit fly, Drosophila melanogaster, reproductive dormancy is induced under low-temperature and short-day conditions by the downregulation of juvenile hormone (JH) biosynthesis by the corpus allatum (CA). Previous studies have suggested that brain neurons that project directly to the CA are important for the regulation of reproductive dormancy. However, the role of CA-projecting neurons in JH-mediated reproductive dormancy has not yet been confirmed by molecular genetic studies. In this study, we report that, in adult D. melanogaster, the neuropeptide diuretic hormone 31 (DH31) is produced by brain neurons that project into the CA. DH31-producing-CA-projecting neurons are connected downstream with a subset of circadian clock neurons, such as s-LNvs, which are known to be involved in reproductive dormancy regulation. The CA expresses the gene encoding the DH31 receptor, which is required for DH31-triggered elevation of intracellular cAMP in the CA. Knocking down Dh31 in these CA-projecting neurons or DH31 receptor in the CA leads to a failure in the decrease of the JH titer, normally observed under dormancy-inducing conditions, leading to abnormal yolk accumulation in the ovaries. Our findings provide the first molecular genetic evidence demonstrating that CA-projecting peptidergic neurons play an essential role in regulating reproductive dormancy by suppressing JH biosynthesis. Significance StatementDormancy is an adaptive physiological response to environmental changes that are unsuitable for survival. Adult females of many insect species undergo reproductive dormancy in which oogenesis is drastically arrested; it is induced by a decrease in juvenile hormone (JH) titers. However, we are yet to fully understand the molecular mechanisms underlying the control of JH biosynthesis under dormancy-inducing conditions. In this study using the fruit fly, we demonstrated that brain neurons projecting directly to the JH-producing organ, corpus allatum, play an essential role in regulating reproductive dormancy via the neuropeptide DH31. As the morphologically-similar neurons have previously been suggested to be involved in reproductive dormancy regulation, this study provides a fundamental molecular and neuronal basis for reproductive dormancy in insects.

physiology↗

bioRxiv2021

A population of neurons that produce hugin and express the diuretic hormone 44 receptor gene projects to the corpora allata in Drosophila melanogaster

The corpora allata (CA) are essential endocrine organs that biosynthesize and secrete the sesquiterpenoid hormone, namely juvenile hormone (JH), to regulate a wide variety of developmental and physiological events in insects. Previous studies had demonstrated that the CA are directly innervated with neurons in many insect species, implying the innervations to be important for regulating JH biosynthesis in response to internal physiology and external environments. While this is also true for the model organism, Drosophila melanogaster, which neurotransmitters are produced in the CA-projecting neurons are yet to be clarified. In this study on D. melanogaster, we aimed to demonstrate that a subset of neurons producing the neuropeptide hugin, the invertebrate counterpart of the vertebrate neuromedin U, directly projects to the adult CA. A synaptic vesicle marker in the hugin neurons was observed at their axon termini located on the CA, which were immunolabeled with a newly-generated antibody to the JH biosynthesis enzyme JH acid O-methyltransferase (JHAMT). We also found the CA-projecting hugin neurons to likely express a gene encoding the specific receptor for diuretic hormone 44 (Dh44). Moreover, our data suggested that the CA-projecting hugin neurons have synaptic connections with the upstream neurons producing Dh44. To the best of our knowledge, this is the first study to identify a specific neurotransmitter of the CA-projecting neurons in D. melanogaster, and to anatomically characterize a neuronal pathway of the CA-projecting neurons and their upstream neurons.

zoology↗