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    gaoyan09@stanford.edu
    Department: OHNS/Research Division Position: Basic Life Science Research Scientist

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  • Mail Code: 5365

All Publications

  • Defects in exosome biogenesis are associated with sensorimotor defects in zebrafish vps4a mutants. The Journal of neuroscience : the official journal of the Society for Neuroscience Shipman, A., Gao, Y., Liu, D., Sun, S., Zang, J., Sun, P., Syed, Z., Bhagavathi, A., Smith, E., Erickson, T., Hill, M., Neuhauss, S., Sui, S. F., Nicolson, T. 2024

    Abstract

    Mutations in human VPS4A are associated with neurodevelopmental defects, including motor delays and defective muscle tone. VPS4A encodes a AAA-ATPase required for membrane scission, but how mutations in VPS4A lead to impaired control of motor function is not known. Here we identified a mutation in zebrafish vps4a, T248I, that affects sensorimotor transformation. Biochemical analyses indicate that the T248I mutation reduces the ATPase activity of Vps4a and disassembly of ESCRT filaments, which mediate membrane scission. Consistent with the role for Vps4a in exosome biogenesis, vps4aT248I larvae have enlarged endosomal compartments in the CNS and decreased numbers of circulating exosomes in brain ventricles. Resembling the central form of hypotonia in VPS4A patients, motor neurons and muscle cells are functional in mutant zebrafish. Both somatosensory and vestibular inputs robustly evoke tail and eye movements, respectively. In contrast, optomotor responses, vestibulospinal, and acoustic startle reflexes are absent or strongly impaired in vps4aT248I larvae, indicating a greater sensitivity of these circuits to the T248I mutation. ERG recordings revealed intensity-dependent deficits in the retina, and in vivo calcium imaging of the auditory pathway identified a moderate reduction in afferent neuron activity, partially accounting for the severe motor impairments in mutant larvae. Further investigation of central pathways in vps4aT248I mutants showed that activation of descending vestibulospinal and midbrain motor command neurons by sensory cues is strongly reduced. Our results suggest that defects in sensorimotor transformation underly the profound yet selective effects on motor reflexes resulting from the loss of membrane scission mediated by Vps4a.Significance Statement Here we present a T248I mutation in vps4a, which causes sensorimotor defects in zebrafish larvae. Vps4a plays a key role in membrane scission. Spanning biochemical to systems level analyses, our study indicates that a reduction in Vps4a enzymatic activity leads to abnormalities in membrane-scission dependent processes such as endosomal protein trafficking and exosome biogenesis, resulting in pronounced deficits in sensorimotor transformation of visual, auditory, and vestibular cues. We suggest that the mechanisms underlying this type of dysfunction in zebrafish may also contribute to the condition seen in human patients with de novo mutations in the human VPS4A orthologue.

    View details for DOI 10.1523/JNEUROSCI.0680-24.2024

    View details for PubMedID 39455257

  • Sensory deficit screen identifies nsf mutation that differentially affects SNARE recycling and quality control. Cell reports Gao, Y., Khan, Y. A., Mo, W., White, K. I., Perkins, M., Pfuetzner, R. A., Trapani, J. G., Brunger, A. T., Nicolson, T. 2023; 42 (4): 112345

    Abstract

    The AAA+ NSF complex is responsible for SNARE complex disassembly both before and after membrane fusion. Loss of NSF function results in pronounced developmental and degenerative defects. In a genetic screen for sensory deficits in zebrafish, we identified a mutation in nsf, I209N, that impairs hearing and balance in a dosage-dependent manner without accompanying defects in motility, myelination, and innervation. Invitro experiments demonstrate that while the I209N NSF protein recognizes SNARE complexes, the effects on disassembly are dependent upon the type of SNARE complex and I209N concentration. Higher levels of I209N protein produce a modest decrease in binary (syntaxin-SNAP-25) SNARE complex disassembly and residual ternary (syntaxin-1A-SNAP-25-synaptobrevin-2) disassembly, whereas at lower concentrations binary disassembly activity is strongly reduced and ternary disassembly activity is absent. Our study suggests that the differential effect on disassembly of SNARE complexes leads to selective effects on NSF-mediated membrane trafficking and auditory/vestibular function.

    View details for DOI 10.1016/j.celrep.2023.112345

    View details for PubMedID 37027300

  • Cholesterol 25-hydroxylase protects against experimental colitis in mice by modulating epithelial gut barrier function. Scientific reports Sheng, N., Ma, Z., Zhou, Y., Xu, J., Gao, Y., Fu, X. Y. 2020; 10 (1): 14246

    Abstract

    Cholesterol 25-hydroxylase (CH25H) encodes the enzyme that converts cholesterol to 25-hydroxycholesterol (25-HC). 25-HC has been demonstrated to be involved in the pathogenesis of inflammatory bowel disease. However, the role of CH25H in experimental colitis remains unknown. Dextran sulfate sodium (DSS)-induced colitis was monitored in wild type and Ch25h-/- mice in 8-week-old male for 7 days by assessment of body weight, histology, inflammatory cellular infiltration, and colon length. The function of CH25H was investigated using loss-of-function and gain-of-function such as Ch25h-deficient mice, supplementation with exogenous 25-HC and treatment of 25-HC into Caco2 and HCT116 colonic epithelial cells. Ch25h-/- mice with DSS-induced colitis exhibited aggravated injury, including higher clinical colitis scores, severe injury of the epithelial barrier, lower tight junction protein levels and higher levels of IL-6. Supplementation with exogenous 25-HC ameliorated disease symptoms and reduced the extent of damage in DSS-induced colitis, which was characterized by lower colon damage, higher tight junction protein expression, significantly decreased local and systemic production of pro-inflammatory cytokines IL-6. In Caco2 and HCT116 cells, 25-HC induced tight junction genes expression in colon cancer epithelial cells. These effects of CH25H were obtained by promoting ATF3 expression. Taken together, our findings reveal a protective role for 25-HC in DSS-induced colitis and the ability of CH25H to maintain epithelial gut barrier function through ATF3 expression. Supplementation with exogenous 25-HC ameliorates disease symptoms, which provides a new therapeutic strategy for ulcerative colitis.

    View details for DOI 10.1038/s41598-020-71198-1

    View details for PubMedID 32859970

    View details for PubMedCentralID PMC7455728

  • lncrps25 play an essential role in motor neuron development through controlling the expression of olig2 in zebrafish. Journal of cellular physiology Gao, T., Li, J., Li, N., Gao, Y., Yu, L., Zhuang, S., Zhao, Y., Dong, X. 2020; 235 (4): 3485-3496

    Abstract

    lncrps25 is an intergenic long noncoding RNA (lncRNA), which is location close to rps25 (ribosomal protein S25) gene, is reported share high conserved sequence with NREP (neuronal regeneration-related protein) 3'-untranslated region. The function and mechanism of most of the lncRNA in embryo development remain largely unknown. In zebrafish, lncrps25 is widely expressed in the early embryonic stage and spinal cord during development. Morpholino (MO) knockdown of zebrafish lncrps25 exhibit locomotor behavior defects, caused by abnormal development of motor neurons. In addition, the defect of swimming ability and motor neurons could be recovery by microinject with lncrps25 RNA in lncrps25 morphants. By performing RNA sequencing and quantitative real-time polymerase chain reaction, we found that olig2 (oligodendrocyte transcription factor 2) messenger RNA (mRNA) was downregulated in lncrps25 morphants. Moreover, overexpression of olig2 mRNA in lncrps25 morphants partially rescued motor neurons development. Taken together, these results indicate that lncrps25 plays an essential role in the development of motor neurons in zebrafish.

    View details for DOI 10.1002/jcp.29237

    View details for PubMedID 31549395

  • Temporal Vestibular Deficits in synaptojanin 1 (synj1) Mutants. Frontiers in molecular neuroscience Gao, Y., Nicolson, T. 2020; 13: 604189

    Abstract

    The lipid phosphatase synaptojanin 1 (synj1) is required for the disassembly of clathrin coats on endocytic compartments. In neurons such activity is necessary for the recycling of endocytosed membrane into synaptic vesicles. Mutations in zebrafish synj1 have been shown to disrupt the activity of ribbon synapses in sensory hair cells. After prolonged mechanical stimulation of hair cells, both phase locking of afferent nerve activity and the recovery of spontaneous release of synaptic vesicles are diminished in synj1 mutants. Presumably as a behavioral consequence of these synaptic deficits, synj1 mutants are unable to maintain an upright posture. To probe vestibular function with respect to postural control in synj1 mutants, we developed a method for assessing the vestibulospinal reflex (VSR) in larvae. We elicited the VSR by rotating the head and recorded tail movements. As expected, the VSR is completely absent in pcdh15a and lhfpl5a mutants that lack inner ear function. Conversely, lhfpl5b mutants, which have a selective loss of function of the lateral line organ, have normal VSRs, suggesting that the hair cells of this organ do not contribute to this reflex. In contrast to mechanotransduction mutants, the synj1 mutant produces normal tail movements during the initial cycles of rotation of the head. Both the amplitude and temporal aspects of the response are unchanged. However, after several rotations, the VSR in synj1 mutants was strongly diminished or absent. Mutant synj1 larvae are able to recover, but the time required for the reappearance of the VSR after prolonged stimulation is dramatically increased in synj1 mutants. Collectively, the data demonstrate a behavioral correlate of the synaptic defects caused by the loss of synj1 function. Our results suggest that defects in synaptic vesicle recycling give rise to fatigue of ribbons synapses and possibly other synapses of the VS circuit, leading to the loss of postural control.

    View details for DOI 10.3389/fnmol.2020.604189

    View details for PubMedID 33584199

  • Similarity in gene-regulatory networks suggests that cancer cells share characteristics of embryonic neural cells JOURNAL OF BIOLOGICAL CHEMISTRY Zhang, Z., Lei, A., Xu, L., Chen, L., Chen, Y., Zhang, X., Gao, Y., Yang, X., Zhang, M., Cao, Y. 2017; 292 (31): 12842–59

    Abstract

    Cancer cells are immature cells resulting from cellular reprogramming by gene misregulation, and redifferentiation is expected to reduce malignancy. It is unclear, however, whether cancer cells can undergo terminal differentiation. Here, we show that inhibition of the epigenetic modification enzyme enhancer of zeste homolog 2 (EZH2), histone deacetylases 1 and 3 (HDAC1 and -3), lysine demethylase 1A (LSD1), or DNA methyltransferase 1 (DNMT1), which all promote cancer development and progression, leads to postmitotic neuron-like differentiation with loss of malignant features in distinct solid cancer cell lines. The regulatory effect of these enzymes in neuronal differentiation resided in their intrinsic activity in embryonic neural precursor/progenitor cells. We further found that a major part of pan-cancer-promoting genes and the signal transducers of the pan-cancer-promoting signaling pathways, including the epithelial-to-mesenchymal transition (EMT) mesenchymal marker genes, display neural specific expression during embryonic neurulation. In contrast, many tumor suppressor genes, including the EMT epithelial marker gene that encodes cadherin 1 (CDH1), exhibited non-neural or no expression. This correlation indicated that cancer cells and embryonic neural cells share a regulatory network, mediating both tumorigenesis and neural development. This observed similarity in regulatory mechanisms suggests that cancer cells might share characteristics of embryonic neural cells.

    View details for DOI 10.1074/jbc.M117.785865

    View details for Web of Science ID 000407220100015

    View details for PubMedID 28634230

    View details for PubMedCentralID PMC5546026

  • Kruppel-like factor family genes are expressed during Xenopus embryogenesis and involved in germ layer formation and body axis patterning DEVELOPMENTAL DYNAMICS Gao, Y., Cao, Q., Lu, L., Zhang, X., Zhang, Z., Dong, X., Jia, W., Cao, Y. 2015; 244 (10): 1328–46

    Abstract

    Kruppel-like factors (Klfs) are a family of transcription factors consisting of 17 members in mammals, Klf1-Klf17, which are involved in fundamental cellular physiological procedures, such as cell proliferation, differentiation, and apoptosis. However, their functions in embryonic development have been poorly understood. Our previous study has demonstrated that the pluripotency factor Klf4 participates in germ layer formation and axis patterning of Xenopus embryos by means of the regulation of key developmental signals. In the present study, we further investigated comprehensively the expression and functions of the klf family genes, klf2, klf5, klf6, klf7, klf8, klf11, klf15, and klf17, during the embryogenesis of Xenopus laevis.Spatio-temporal expression analyses demonstrate that these genes are transcribed both maternally and zygotically in Xenopus embryos, and during organogenesis and tissue differentiation, they are localized to a variety of placodes and tissues. Gain and loss of function studies manifest that Klf factors play different roles in germ layer formation and body axis patterning. Moreover, each Klf factor exhibits distinct regulatory effects on the expression of genes that are essential for germ layer formation and body axis patterning.These results suggest that Klf factors are involved in the fine-tuning of these genes during early embryogenesis.

    View details for DOI 10.1002/dvdy.24310

    View details for Web of Science ID 000362089300013

    View details for PubMedID 26198170

  • JmjC Domain-containing Protein 6 (Jmjd6) Derepresses the Transcriptional Repressor Transcription Factor 7-like 1 (Tcf7l1) and Is Required for Body Axis Patterning during Xenopus Embryogenesis JOURNAL OF BIOLOGICAL CHEMISTRY Zhang, X., Gao, Y., Lu, L., Zhang, Z., Gan, S., Xu, L., Lei, A., Cao, Y. 2015; 290 (33): 20273–83

    Abstract

    Tcf7l1 (also known as Tcf3) is a bimodal transcription factor that plays essential roles in embryogenesis and embryonic and adult stem cells. On one hand, Tcf7l1 works as transcriptional repressor via the recruitment of Groucho-related transcriptional corepressors to repress the transcription of Wnt target genes, and, on the other hand, it activates Wnt target genes when Wnt-activated β-catenin interacts with it. However, how its activity is modulated is not well understood. Here we demonstrate that a JmjC-domain containing protein, Jmjd6, interacts with Tcf7l and derepresses Tcf7l. We show that Jmjd6 binds to a region of Tcf7l1 that is also responsible for Groucho interaction, therefore making it possible that Jmjd6 binding displaces the Groucho transcriptional corepressor from Tcf7l1. Moreover, we show that Jmjd6 antagonizes the repression effect of Tcf7l1 on target gene transcription and is able to enhance β-catenin-induced gene activation and that, vice versa, inhibition of Jmjd6 activity compromises gene activation in both cells and Xenopus early embryos. We also show that jmjd6 is both maternally and zygotically transcribed during Xenopus embryogenesis. Loss of Jmjd6 function causes defects in anterioposterior body axis formation and down-regulation of genes that are involved in anterioposterior axis patterning. The results elucidate a novel mechanism underlying the regulation of Tcf7l1 activity and the regulation of embryonic body axis formation.

    View details for DOI 10.1074/jbc.M115.646554

    View details for Web of Science ID 000359608900027

    View details for PubMedID 26157142

    View details for PubMedCentralID PMC4536435

  • Kdm2a/b Lysine Demethylases Regulate Canonical Wnt Signaling by Modulating the Stability of Nuclear β-Catenin Developmental Cell Lu*, L., Gao*, Y., Zhang, Z., Cao, Q., Zhang, X., Zou, J., Cao, Y. 2015
  • Klf4 is required for germ-layer differentiation and body axis patterning during Xenopus embryogenesis DEVELOPMENT Cao, Q., Zhang, X., Lu, L., Yang, L., Gao, J., Gao, Y., Ma, H., Cao, Y. 2012; 139 (21): 3950–61

    Abstract

    Klf4 is a transcription factor of the family of Kruppel-like factors and plays important roles in stem cell biology; however, its function during embryogenesis is unknown. Here, we report the characterization of a Klf4 homologue in Xenopus laevis during embryogenesis. Klf4 is transcribed both maternally and zygotically and the transcript is ubiquitous in embryos during germ-layer formation. Klf4 promotes endoderm differentiation in both Nodal/Activin-dependent and -independent manners. Moreover, Klf4 regulates anteroposterior body axis patterning via activation of a subset of genes in the Spemann organizer, such as Noggin, Dkk1 and Cerberus, which encode Nodal, Wnt and BMP antagonists. Loss of Klf4 function leads to the failure of germ-layer differentiation, the loss of responsiveness of early embryonic cells to inducing signals, e.g. Nodal/Activin, and the loss of transcription of genes involved in axis patterning. We conclude that Klf4 is required for germ-layer differentiation and body axis patterning by means of rendering early embryonic cells competent to differentiation signals.

    View details for DOI 10.1242/dev.082024

    View details for Web of Science ID 000309701300007

    View details for PubMedID 22992953