Project description:Astrocytes in the retrotrapezoid nucleus (RTN) stimulate breathing in response to CO2/H+, however, it is not clear how these cells detect changes in CO2/H+. Considering Kir4.1/5.1 channels are CO2/H+-sensitive and important for several astrocyte-dependent processes, we consider Kir4.1/5.1 a leading candidate CO2/H+ sensor in RTN astrocytes. To address this, we show that RTN astrocytes express Kir4.1 and Kir5.1 transcripts. We also characterized respiratory function in astrocyte-specific inducible Kir4.1 knockout mice (Kir4.1 cKO); these mice breathe normally under room air conditions but show a blunted ventilatory response to CO2, which could be partly rescued by viral mediated re-expression of Kir4.1 in RTN astrocytes. At the cellular level, astrocytes in slices from astrocyte-specific inducible Kir4.1 knockout mice are less responsive to CO2/H+ and show a diminished capacity for paracrine modulation of respiratory neurons. These results suggest Kir4.1/5.1 channels in RTN astrocytes contribute to respiratory behavior.
Project description:Diversified neurons are essential for sensorimotor function, but whether astrocytes become specialized to optimize circuit performance remains unclear. Large fast α-motor neurons (FαMNs) of spinal cord innervate fast-twitch muscles that generate peak strength. We report that ventral horn astrocytes express the inward rectifying K+ channel Kir4.1 (aka, Kcnj10) around MNs in a VGLUT1-dependent manner. Loss-of astrocyte-encoded Kir4.1 selectively altered FαMN size, function and led to reduced peak strength. Overexpression of Kir4.1 in astrocytes was sufficient to increase MN size through activation of the PI3K/mTOR/pS6 pathway. Kir4.1 was downregulated cell-autonomously in astrocytes derived from amyotrophic lateral sclerosis (ALS) patients with SOD1 mutation. However, astrocyte Kir4.1 was dispensable for FαMN survival even in the mutant SOD1 background. These findings show that astrocyte Kir4.1 is essential for maintenance of peak strength and suggest that Kir4.1 downregulation uncouples symptoms of muscle weakness from MN cell death in ALS.
Project description:Previous studies have suggested that astrocyte activation in the spinal dorsal horn may play an important role in the development of chronic neuropathic pain; but the mechanisms involved in astrocyte activation and their modulatory effects remain unknown. The inward rectifying potassium channel protein 4.1 (Kir4.1) is the most important background K+ channel in astrocytes. However, how Kir4.1 is regulated and contributes to behavioral hyperalgesia in chronic pain is unknown. In this study, single-cell RNA sequencing analysis indicated that the expression of Kir4.1 and Methyl-CpG-binding protein 2 (MeCP2) were both decreased in spinal astrocytes after chronic constriction injury (CCI) in a mouse model. Conditional knockout of the Kir4.1 channel in spinal astrocytes led to hyperalgesia; and overexpression of the Kir4.1 channel in spinal cord relieved CCI-induced hyperalgesia. Expression of spinal Kir4.1 after CCI was regulated by MeCP2. Electrophysiological recording in spinal slices showed that knockdown of Kir4.1 significantly regulated the excitability of astrocytes and then functionally changed the firing patterns of neurons in dorsal spinal cord. Therefore, targeting spinal Kir4.1 maybe an underlying treatment for hyperalgesia in chronic neuropathic pain.
Project description:Ongoing nociceptive inputs from peripheral tissues and nerve injuries lead to maladaptive alterations in central nervous system, which drive the transition from acute to chronic pain. Although astrocytes act as dynamic and active players in neuropathic pain states, the contribution of astrocytes in upper brain nucleus in this process remains unclear. Here, we revealed that prolonged neuronal inputs induced by periphery injury leads to astrocyte reactive and downregulation of inward rectifying potassium channel protein 4.1 (Kir4.1) in paraventricular thalamus(PVT). In turn, reactive PVT astrocytes could maintain the hyperexcitability of neurons, and enhanced projections from PVT to medial prefrontal cortex (mPFC) in the chronicity of neuropathic pain. Notably, we identify a neuro-glial interaction mediating pain chronification in PVT, and clarified Kir4.1 channels as a potential therapeutic target for neuropathic pain treatment.
Project description:Cyanobacteria are oxygenic photoautotrophs notable for their ability to utilize atmospheric CO2 as the major source of carbon. The prospect of using cyanobacteria in converting solar energy and high concentrations of CO2 (e.g. flue gas from coal power plants) efficiently into biomass and renewable energy sources is of interest to many research fields. In order to guide further advances in this area, a better understanding about the metabolic changes that occur under conditions of high CO2 is important. The objective of this study is to utilize genome-wide microarray expression profiling in the unicellular diazotrophic cyanobacterium Cyanothece 51142 grown in 8% CO2-enriched air and to determined the impact of high CO2 on cyanobacterial cell physiology and growth.
Project description:Six weeks old Arabidopsis plants were transferred to a low CO2 (100 ppm) environment during 24 hours and compared to control plants kept under ambient CO2 conditions. Limited CO2 availability will cause higher rates of photorespiration and affect the plant redox homeostasis. We studied the transcriptomic impact of exposing plants to a lower CO2 environment to further eliculidate the signaling pathways during photorespiratory stress.