Browsing by Author "Zheng, Yi"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Differential responses to lithium in hyperexcitable neurons from patients with bipolar disorder.
    (NPG, 2015-11-05) Mertens, Jerome; Wang, Qiu-Wen; Kim, Yongsung; Yu, Diana X.; Pham, Son; Yang, Bo; Zheng, Yi; Diffenderfer, Kenneth E.; Zhang, Jian; Soltani, Sheila; Eames, Tameji; Schafer, Simon T.; Boyer, Leah; Marchetto, Maria C.; Nurnberger, John I.; Calabrese, Joseph R.; Oedegaard, Ketil J.; McCarthy, Michael J.; Zandi, Peter P.; Alda, Martin; Nievergelt, Caroline M.; Mi, Shuangli; Brennand, Kristen J.; Kelsoe, John R.; Gage, Fred H.; Yao, Jun; Department of Psychiatry, IU School of Medicine
    Bipolar disorder is a complex neuropsychiatric disorder that is characterized by intermittent episodes of mania and depression; without treatment, 15% of patients commit suicide. Hence, it has been ranked by the World Health Organization as a top disorder of morbidity and lost productivity. Previous neuropathological studies have revealed a series of alterations in the brains of patients with bipolar disorder or animal models, such as reduced glial cell number in the prefrontal cortex of patients, upregulated activities of the protein kinase A and C pathways and changes in neurotransmission. However, the roles and causation of these changes in bipolar disorder have been too complex to exactly determine the pathology of the disease. Furthermore, although some patients show remarkable improvement with lithium treatment for yet unknown reasons, others are refractory to lithium treatment. Therefore, developing an accurate and powerful biological model for bipolar disorder has been a challenge. The introduction of induced pluripotent stem-cell (iPSC) technology has provided a new approach. Here we have developed an iPSC model for human bipolar disorder and investigated the cellular phenotypes of hippocampal dentate gyrus-like neurons derived from iPSCs of patients with bipolar disorder. Guided by RNA sequencing expression profiling, we have detected mitochondrial abnormalities in young neurons from patients with bipolar disorder by using mitochondrial assays; in addition, using both patch-clamp recording and somatic Ca2+ imaging, we have observed hyperactive action-potential firing. This hyperexcitability phenotype of young neurons in bipolar disorder was selectively reversed by lithium treatment only in neurons derived from patients who also responded to lithium treatment. Therefore, hyperexcitability is one early endophenotype of bipolar disorder, and our model of iPSCs in this disease might be useful in developing new therapies and drugs aimed at its clinical treatment.
  • Thumbnail Image
    Item
    Rac and Cdc42 GTPases control hematopoietic stem cell shape, adhesion, migration, and mobilization
    (2001-05) Yang, Feng-Chun; Atkinson, Simon J; Gu, Ying; Borneo, Jovencio B; Roberts, Andrew W; Zheng, Yi; Pennington, Janice; Williams, David A
    Critical to homeostasis of blood cell production by hematopoietic stem/progenitor (HSC/P) cells is the regulation of HSC/P retention within the bone marrow microenvironment and migration between the bone marrow and the blood. Key extracellular regulatory elements for this process have been defined (cell–cell adhesion, growth factors, chemokines), but the mechanism by which HSC/P cells reconcile multiple external signals has not been elucidated. Rac and related small GTPases are candidates for this role and were studied in HSC/P deficient in Rac2, a hematopoietic cell-specific family member. Rac2 appears to be critical for HSC/P adhesion both in vitro and in vivo, whereas a compensatory increase in Cdc42 activation regulates HSC/P migration. This genetic analysis provides physiological evidence of cross-talk between GTPase proteins and suggests that a balance of these two GTPases controls HSC/P adhesion and mobilization in vivo.
  • Thumbnail Image
    Item
    Rho GTPase CDC42 regulates directionality and random movement via distinct MAPK pathways in neutrophils
    (2006-12) Szczur, Kathleen; Xu, Haiming; Atkinson, Simon J; Zheng, Yi; Filippi, Marie-Dominique
    Neutrophil transmigration into tissue is a multiple-step process that results from a coordinated rearrangement of the cytoskeleton and adhesion complexes. Assembly and disassembly of actin and adhesion structures dictate motility behavior, while polarity and gradient sensing provide directionality to the cell movement. Here, using mice deficient in the CDC42 regulator CDC42 GTPase-activating protein (CDC42GAP), we demonstrate that CDC42 activity separately regulates neutrophil motility and directionality. CDC42GAP–/– neutrophils showed increased motility, while directed migration was defective. Podosome-like structures present at the leading edge in wild-type neutrophils were significantly reduced in CDC42GAP–/– cells. CDC42GAP–/– neutrophils also showed increased lateral and tail filopodia-like formation, and excess membrane protrusions. We further suggest that CDC42GAP-mediated extracellular signal–regulated kinase (ERK) activity regulates motility associated with podosome-like structures at the cell leading edge, while CDC42GAP-induced p38MAPK phosphorylation regulates directed migration by antagonizing filopodia assembly. Overall, this study reveals that CDC42 activity regulates both motility and directionality in neutrophils, but via distinct mitogen-activated protein kinase (MAPK) pathways.
  • Thumbnail Image
    Item
    Two-Photon Intravital Fluorescence Lifetime Imaging of the Kidney Reveals Cell-Type Specific Metabolic Signatures
    (American Society of Nephrology, 2017-08) Hato, Takashi; Winfree, Seth; Day, Richard; Sandoval, Ruben M.; Molitoris, Bruce A.; Yoder, Mervin C.; Wiggins, Roger C.; Zheng, Yi; Dunn, Kenneth W.; Dagher, Pierre C.; Medicine, School of Medicine
    In the live animal, tissue autofluorescence arises from a number of biologically important metabolites, such as the reduced form of nicotinamide adenine dinucleotide. Because autofluorescence changes with metabolic state, it can be harnessed as a label-free imaging tool with which to study metabolism in vivo Here, we used the combination of intravital two-photon microscopy and frequency-domain fluorescence lifetime imaging microscopy (FLIM) to map cell-specific metabolic signatures in the kidneys of live animals. The FLIM images are analyzed using the phasor approach, which requires no prior knowledge of metabolite species and can provide unbiased metabolic fingerprints for each pixel of the lifetime image. Intravital FLIM revealed the metabolic signatures of S1 and S2 proximal tubules to be distinct and resolvable at the subcellular level. Notably, S1 and distal tubules exhibited similar metabolic profiles despite apparent differences in morphology and autofluorescence emission with traditional two-photon microscopy. Time-lapse imaging revealed dynamic changes in the metabolic profiles of the interstitium, urinary lumen, and glomerulus-areas that are not resolved by traditional intensity-based two-photon microscopy. Finally, using a model of endotoxemia, we present examples of the way in which intravital FLIM can be applied to study kidney diseases and metabolism. In conclusion, intravital FLIM of intrinsic metabolites is a bias-free approach with which to characterize and monitor metabolism in vivo, and offers the unique opportunity to uncover dynamic metabolic changes in living animals with subcellular resolution.
  • Thumbnail Image
    Item
    Vibrio vulnificus induces mTOR activation and inflammatory responses in macrophages
    (PLOS, 2017-07-18) Xie, Dan-Li; Zheng, Meng-Meng; Zheng, Yi; Gao, Hui; Zhang, Jie; Zhang, Ting; Guo, Jian-Chun; Yang, X. Frank; Zhong, Xiao-Ping; Lou, Yong-Liang; Microbiology and Immunology, School of Medicine
    Vibrio vulnificus (V. vulnificus), a Gram-negative marine bacterium, can cause life-threatening primary septicemia, especially in patients with liver diseases. How V. vulnificus affects the liver and how it acts on macrophages are not well understood. In this report, we demonstrated that V. vulnificus infection causes a strong inflammatory response, marked expansion of liver-resident macrophages, and liver damage in mice. We demonstrated further that V. vulnificus activates mTOR in macrophages and inhibition of mTOR differentially regulates V. vulnificus induced inflammatory responses, suggesting the possibility of targeting mTOR as a strategy to modulate V. vulnificus induced inflammatory responses.