Yan Liu

Nankai University, T’ien-ching-shih, Tianjin Shi, China

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Publications (49)110.15 Total impact

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    ABSTRACT: Natural polysaccharides are biomaterials widely used for constructing scaffolds in tissue engineering. While natural polysaccharides have been shown to robustly promote tissue regeneration, the underlying molecular mechanism remains largely unknown. Here, we show that chitooligosaccharides (COS), the intermediate products of chitosan degradation, stimulate peripheral nerve regeneration in rats. Our experiment also shows that COS stimulate the proliferation of Schwann cells (SCs) during nerve regeneration. By analyzing the transcriptome and gene regulatory network, we identified the miR-27a/FOXO1 axis as the main signaling pathway for mediating the proliferative effects of COS on SCs. COS increase the expression level of miR-27a and cause a reduction of FOXO1, which subsequently accelerates the cell cycle and stimulates SC proliferation to stimulate nerve regeneration. These findings define a basic pathway for oligosaccharides-mediated cell proliferation and reveal a novel aspect of polysaccharide biomaterials in tissue engineering.
    Molecular Neurobiology 11/2014; · 5.29 Impact Factor
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    ABSTRACT: Peripheral nerve injury is a common clinical problem. Nerve growth factor (NGF) promotes peripheral nerve regeneration, but its clinical applications are limited by several constraints. In this study we found that the time-dependent expression profiles of eight let-7 family members in the injured nerve after sciatic nerve injury were roughly similar to each other. Let-7 microRNAs (miRNAs) significantly reduced cell proliferation and migration of primary Schwann cells (SCs) by directly targeting NGF and suppressing its protein translation. Following sciatic nerve injury, the temporal change in let-7 miRNA expression was negatively correlated with that in NGF expression. Inhibition of let-7 miRNAs increased NGF secretion by primary cultured SCs and enhanced axonal outgrowth from a co-culture of primaty SCs and dorsal root gangalion neurons. In vivo tests indicated that let-7 inhibition promoted SCs migration and axon outgrowth within a regenerative microenvironment. In addition, the inhibitory effect of let-7 miRNAs on SCs apoptosis might serve as an early stress response to nerve injury, but this effect seemed to be not mediated through a NGF-dependent pathway. Collectively, our results provide a new insight into let-7 miRNA regulation of peripheral nerve regeneration and suggest a potential therapy for repair of peripheral nerve injury.Molecular Therapy (2014); doi:10.1038/mt.2014.220.
    Molecular Therapy 11/2014; · 6.43 Impact Factor
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    ABSTRACT: The Wingless/Integrated (Wnt) signaling pathway plays important roles in central nervous system (CNS) development and regeneration, and β-catenin, the central component, has been considered in association with adult neurogenesis. To decipher its roles on spontaneous spinal cord regeneration, we cloned β-catenin from Gekko japonicus and examined its function in regenerating spinal cord. The protein was localized in the neurons and oligodendrocytes and maintained a stable expression levels during the spinal cord regeneration. The temporal pattern of expression has been found to be completely distinct with those of glycogen synthase kinase 3β (GSK3β). Experiments of gain-of-function by overexpression of full length β-catenin or stabilized ΔN90-β-catenin revealed that the accumulated protein attenuates the elongation of neurites and oligodendrocyte process. Knockdown of endogenous β-catenin, however, decreased proliferation of oligodendrocytes by affecting expression of downstream lef1 and c-jun. The upregulated extracellular matrix fibronectin in injured cord was found to be inefficient in regulation of β-catenin expression. Our results suggest that a tightly regulated stable expression of β-catenin is required for the spontaneous spinal cord regeneration.
    Journal of Molecular Neuroscience 09/2014; · 2.76 Impact Factor
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    ABSTRACT: In order to investigate the influence of different heavy metal ions on the formation of the oxyfluoride glasses and glass ceramics, samples with different PbF2/CdF2 ratios have been prepared by the melting quenching and thermal treatment method. The different effects of Pb2+ and Cd2+ on the glass network structure are investigated by FTIR and Raman spectra. During the formation of glass network structure, Pb2+ prefers to break the Si–O–Si bond and subsequently bond to F– for charge compensation, and Cd2+ prefers to break the Si–O–Al bond and is surrounded by O2–. Pb2+ and F– gather together and form the fluoride nanocrystals, while Cd2+ remains in oxide matrix after thermal treatment. Introduction of proper CdF2 is important to adjust and control the glass network structure and crystallization process in the fabrication of the transparent glass ceramics.
    Journal of Materials Science and Technology -Shenyang- 05/2014; · 1.61 Impact Factor
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    ABSTRACT: Bone marrow mesenchymal stem cells (MSCs) can be differentiate towards a Schwann cells (SCs) lineage when exposed to pre-inducing reagents β-mercaptoethanol (BME) and retinoic acid (RA), followed by inducing factors: forskolin (FSK), basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF), and heregulin (HRG). However, the underlying mechanisms remain unclear. Here, we investigated the individual effects of these inducing factors on the differentiation of MSCs towards SC phenotype in rats. We show that the omission of either HRG or PDGF from the induction medium is not sufficient to change the SC-like phenotype or the expression level of the SC marker, S100β. However, the omission of bFGF from the induction medium effectively blocked neural induction of the MSCs. Moreover, only bFGF was found to inhibit MSC proliferation during differentiation. To clarify the mechanism responsible for the effect of bFGF, we also investigated the activation of the extracellular signal-regulated kinase (ERK) pathway in the induced cells. Our results suggest that morphological changes in MSCs induced by bFGF depend on the activation of ERK, and bFGF may be an indispensable factor that induces MSCs to differentiate into cells with SCs phenotype.
    Neuroscience Letters 12/2013; · 2.06 Impact Factor
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    ABSTRACT: Uncontrolled, excessive inflammation contributes to the secondary tissue damage of traumatic spinal cord, and HMGB1 is highlighted for initiation of a vicious self-propagating inflammatory circle by release from necrotic cells or immune cells. Several regenerative-competent vertebrates have evolved to circumvent the second damages during the spontaneous spinal cord regeneration with an unknown HMGB1 regulatory mechanism. By genomic surveys, we have revealed that HMGB1 two paralogs are broadly retained from fish onwards in the phylogeny. However, their spatial-temporal expression and effects, as shown in lowest amniote gecko, were tightly controlled in order that limited inflammation was produced in spontaneous regeneration. Gecko HMGB1 (gHMGB1) two paralogs yielded distinct injury and infectious responses, with gHMGB1b significantly upregulated in the injured cord. The intracellular gHMGB1b induced less release of inflammatory cytokines than gHMGB1a in macrophages, and the effects could be shifted by exchanging one amino acid in the inflammatory domain. Both intracellular proteins were able to mediate neuronal programmed apoptosis, which has been indicated to produce negligible inflammatory responses. In vivo studies demonstrated that the extracellular proteins could not trigger a cascade of the inflammatory cytokines in the injured spinal cord. Signal transduction analysis found that the recombinant proteins could not bind with cell surface receptors TLR2 and TLR4 to activate inflammatory signaling pathway. However they were able to interact with RAGE to potentiate oligodendrocytes migration by activation of both NFκB and Rac1/Cdc42 signaling. Our results reveal that HMGB1 does not mediate the inflammatory response in spontaneous spinal cord regeneration, but promotes CNS regeneration.
    Journal of Biological Chemistry 05/2013; · 4.60 Impact Factor
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    ABSTRACT: The enolase2 gene is usually expressed in mature neurons and also named neuron specific enolase (NSE). In the present study, we first obtained the NSE gene cDNA sequence by using the RACE method based on the expressed sequence tag (EST) fragment from the cDNA library of Gekko japonicus and identified one transcript of about 2.2 kb in central nervous system of Gekko japonicus by Northern blotting. The open reading frame of NSE is 1305 bp, which encodes a 435 amino-acid protein. We further investigated the multi-tissue expression pattern of NSE by RT-PCR and found that the expression of NSE mRNA was very high in brain, spinal cord and low in heart, while it was not detectable in other tissues. The real-time quantitative PCR was used to investigate the time-dependent change in the expression of the NSE mRNA level after gecko spinal cord transection and found it significantly increased at one day, reaching its highest level three days post-injury and then decreasing at the seventh day of the experiment. The recombinant plasmid of pET-32a-NSE was constructed and induced to express His fused NSE protein. The purified NSE protein was used to immunize rabbits to generate polyclonal antisera. The titer of the antiserum was more than 1:65536 determined by ELISA. Western blotting showed that the prepared antibody could specifically recognize the recombinant and endogenous NSE protein. The result of immunohistochemistry revealed that positive signals were present in neurons of the brain and the spinal cord. This study provided the tools of cDNA and polyclonal antibody for studying NSE function in Gekko japonicus.
    International Journal of Molecular Sciences 05/2013; 14(5):8787-800. · 2.34 Impact Factor
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    ABSTRACT: Gekko japonicus undergoes dramatic changes in the caudal spinal cord after tail amputation. The amputation induces cell proliferation in the caudal ependymal tube. We performed hematoxylin and eosin staining at different time points in the regeneration process to investigate the morphological characterization of the regenerated appendages. The central canal extended to the blastema post-amputation and the cartilage and muscle tissue appeared 3 weeks after injury. We performed the bromodeoxyuridine (BrdU) incorporation assay to detect proliferating cells during the regeneration process. BrdU positive cells were detected in the peri-central canal. Furthermore, nestin and neuron-specific enolase (NSE) immunocytochemistry were applied to detect neural stem/progenitor cells and neurons. Two weeks after injury, nestin-positive cells undergoing proliferation were located outside of the ependymal tube, and NSE positive cells appeared after 3 weeks of amputation. These data suggest that neurogenesis is an early event during caudal spinal cord regeneration in gecko.
    Journal of molecular histology 11/2012; 44(3). · 1.75 Impact Factor
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    ABSTRACT: SNARE complex mediates cellular membrane fusion events essential for neurotransmitter release and synaptogenesis. SNAP25, a member of the SNARE proteins, plays critical roles during the development of the central nervous system via regulation by alternative splicing and protein kinase phosphorylation. To date, little information is available regarding the protein in the spinal cord regeneration, especially for the postnatal highly expressed isoform SNAP25b. In the present study, we characterized gecko SNAP25b, which shared high identity with those of other vertebrates. Expression of gecko SNAP25b was temporally upregulated in both neurons of spinal cord and forming ependymal tube following tail amputation, coinciding with the occurrence of regenerate re-innervation. Overexpression of gecko wild type SNAP25b in the SH-SY5Y and undifferentiated PC12 cells promoted the elongation and outgrowth of neurites, while mutant constructs at Serine(187) resulted in differential effects for which S187A had a promoting role. Knockdown of endogenous SNAP25b affected the formation of neurites, which could be rescued by overexpression of SNAP25b. FM1-43 staining revealed that transfection of S187E mutant construct reduced the recruitment of vesicles. In addition, transfection of gecko SNAP25b in the astrocyte, which is absent from neuronal specific VAMP2, was capable of enhancing process elongation, indicating a potential for various alternative protein combinations. Taken together, our data suggest that gecko SNAP25b is involved in spinal cord regeneration by promoting outgrowth and elongation of neurites in a more extensive protein binding manner.
    The international journal of biochemistry & cell biology 09/2012; 44(12):2288-2298. · 4.89 Impact Factor
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    ABSTRACT: The tubulin beta III (TUBB3) gene encodes a class III member of the beta tubulin protein family that is primarily expressed in neurons and is considered to play a critical role in proper axon guidance and maintenance. This protein is generally used as a specific marker of neurons in the central nervous system. We obtained the full length cDNA sequence of TUBB3 by using the RACE method based on the EST fragment from the brain and spinal cord cDNA library of Gekko japonicus. We further investigated the multi-tissue expression pattern by RT-PCR and identified one transcript of TUBB3 about 1.8 kb in the central nervous system of Gekko japonicus by Northern blotting. The completed cDNA of gecko TUBB3 is 1 790 bp with an open reading frame of 1 350 bp, encoding a 450 amino-acid protein. The recombinant plasmid of pET-32a-TUBB3 was constructed and induced to express His-tagged TUBB3 protein in prokaryotic BL21 cells. The purified TUBB3 protein was then used to immunize rabbits to generate polyclonal antisera. The titer of the antiserum was more than 1:65 536 determined by ELISA. The result of western blotting showed that the TUBB3 antibody could specifically recognize the recombinant TUBB3 protein and endogenous TUBB3 protein. Our findings provide the tools to further understand the TUBB3 gene and investigate the regeneration of the central nervous system in Gekko japonicas.
    Zoological Research 08/2012; 33(4):395-401.
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    ABSTRACT: Solid tissues in the body possess a range of stiffness and provide cells with an instructive microenvironment. Scaffolds in tissue engineering should be rationally designed to become an adhesion substrate friendly to cells. Schwann cells are the principal glial cell in the peripheral nervous system and used as support cells for generating tissue-engineered nerve grafts. Although an important mechanical cue, substrate stiffness, has been documented to make significant effects on many types of cells cultured on the substrate, such a study for Schwann cells is still lacking. In this study, we investigated cell adhesion, survival, proliferation, migration, cytoskeleton, and neurotrophic actions of Schwann cells cultured on polyacrylamide gel substrates with different stiffness, and determined an optimal elastic modulus value for these substrates. Our data not only highlight the importance of substrate stiffness in the crosstalk between Schwann cells and surrounding microenvironment, but also introduce a new parameter, in addition to biocompatibility, biodegradability, and neuroaffinity, for designing scaffolds in nerve tissue engineering.
    Biomaterials 06/2012; 33(28):6672-81. · 8.31 Impact Factor
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    ABSTRACT: It has been an open question whether Nd3+ ions are incorporated into the crystalline phase in oxyfluoride glass ceramics or not. Moreover, relative research has indicated that spectra characters display minor differences between before and after heat treatment in oxyfluoride glass compared to similar Er3+-, Yb3+-, Tm3+-, Eu3+-, etc.-doped materials. Here, we have studied the distribution of Nd3+ ions in oxyfluoride glass ceramics by X-ray diffraction quantitative analysis and found that almost none of the Nd3+ ions can be incorporated into the crystalline phase. In order to confirm the rationality of the process, the conventional mathematical calculation and energy-dispersive spectrometry line scanning are employed, which show good consistency. The distribution of Nd3+ ions in oxyfluoride glass ceramics reported here is significant for further optical investigations and applications of rare-earth doped oxyfluoride glass ceramics.
    Nanoscale Research Letters 05/2012; 7:275. · 2.48 Impact Factor
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    ABSTRACT: The growth-associated protein 43 (GAP-43) gene of Gekko japonicus was obtained from a brain and spinal cord cDNA library. The results of northern blot analysis showed the gecko GAP-43 gene transcript is 1.7 kb in length, and it was abundantly expressed in tissues of brain, spinal cord and ovary. Gecko GAP-43 promoted the outgrowth of Gsn3 cells and PC12 cell in vitro, and phosphorylation at serine 42 modulated the effect of GAP-43 on cell spreading and morphology. The change in GAP-43 expression in the spinal cord after tail amputation was examined by reverse transcription polymerase chain reaction (RT-PCR). The level of GAP-43 in the spinal cord was increased during the time course we examined, indicating a possible correlation between GAP-43 expression and the spinal cord injury and regeneration.
    Molecular Biology Reports 03/2012; 39(7):7769-75. · 1.96 Impact Factor
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    ABSTRACT: GSK-3β signaling is involved in regulation of both neuronal and glial cell functions, and interference of the signaling affects central nervous system (CNS) development and regeneration. Thus, GSK-3β was proposed to be an important therapeutic target for promoting functional recovery of adult CNS injuries. To further clarify the regulatory function of the kinase on the CNS regeneration, we characterized gecko GSK-3β and determined the effects of GSK-3β inactivation on the neuronal and glial cell lines, as well as on the gecko tail (including spinal cord) regeneration. Gecko GSK-3β shares 91.7-96.7% identity with those of other vertebrates, and presented higher expression abundance in brain and spinal cord. The kinase strongly colocalized with the oligodendrocytes while less colocalized with neurons in the spinal cord. Phosphorylated GSK-3β (pGSK-3β) levels decreased gradually during the normally regenerating spinal cord ranging from L13 to the 6th caudal vertebra. Lithium injection increased the pGSK-3β levels of the corresponding spinal cord segments, and in vitro experiments on neurons and oligodendrocyte cell line revealed that the elevation of pGSK-3β promoted elongation of neurites and oligodendrocyte processes. In the normally regenerate tails, pGSK-3β kept stable in 2 weeks, whereas decreased at 4 weeks. Injection of lithium led to the elevation of pGSK-3β levels time-dependently, however destructed the regeneration of the tail including spinal cord. Bromodeoxyuridine (BrdU) staining demonstrated that inactivation of GSK-3β decreased the proliferation of blastemal cells. Our results suggested that species-specific regulation of GSK-3β was indispensable for the complete regeneration of CNS.
    Journal of Cellular Biochemistry 01/2012; 113(6):1842-51. · 3.37 Impact Factor
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    ABSTRACT: Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant disorder characterized by a mixture of hyperpigmented and hypopigmented macules localized on the back of the extremities and caused by the mutations in the DSRAD gene. Two Chinese pedigrees of typical DSH were subjected to mutation detection in DSRAD. Direct sequencing of all PCR products of the whole coding regions of DSRAD was performed to identify the mutation. The c.1615delG (p.V539fs) mutation was found in the affected members but not in the healthy individuals in family 1 and the c.ins1372-9 CCACAGAT (p.D458fs) mutation was found in patients but not in the healthy members of family 2. Our study found two novel frameshift mutations in the DSRAD gene. We add new variants to the knowledge of DSRAD mutations in DSH.
    International journal of dermatology 11/2011; 51(8):920-2. · 1.23 Impact Factor
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    ABSTRACT: Tissue-engineered nerve grafts (TENGs) constitute a promising alternative to nerve autografts that are recognized as the gold standard for surgical repair of peripheral nerve gaps. To investigate the feasibility of using TENGs for bridging extra large peripheral nerve gaps in large animals. TENGs were constructed by incorporating autologous bone marrow mesenchymal stem cells (MSCs) into a neural scaffold that consisted of a chitosan conduit inserted with poly(lactic-co-glycolic acid) (PLGA) fibers. A 60-mm-long sciatic nerve gap in dogs was bridged by TENGs, chitosan/PLGA scaffolds, or nerve autografts. At 12 months postsurgery, behavioral analysis, electrophysiology, retrograde fluorogold tracing, and histological examination were performed. The outcomes of TENGs were similar to those of autografts and better than those of scaffolds alone. Introduction of autologous MSCs to a chitosan/PLGA scaffold improved the repair and rehabilitation of a large gap after peripheral nerve injury in dogs. Autologous MSCs may be a source of support cells for neural tissue engineering.
    Neurorehabilitation and neural repair 09/2011; 26(1):96-106. · 4.62 Impact Factor
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    ABSTRACT: Several adult reptiles, such as Gekko japonicus, have the ability to precisely re-create a missing tail after amputation. To ascertain the associated acquisition of positional information from blastemal cells and the underlying molecular mechanism of tail regeneration, a candidate molecule CD59 was isolated from gecko. CD59 transcripts displayed a graded expression in the adult gecko spinal cord with the highest level in the anterior segment, with a stable expression along the normal tail. After tail amputation, CD59 transcripts in the spinal cord proximal to the injury sites increased markedly at 1 day and 2 weeks; whereas in the regenerating blastema, strong CD59 positive signals were detected in the blastemal cells anterior to the blastema, with a gradual decrease along the proximodistal (PD) axis. When treated with RA following amputation, CD59 transcripts in the blastema were up-regulated. PD confrontation assays revealed that the proximal blastema engulfed the distal one after in vitro culture, and rabbit-anti human CD59 antibody was able to block this PD engulfment. Overexpression of the CD59 during tail regeneration causes distal blastemal cells to translocate to a more proximal location. Our results suggest that position identity is not restricted to amphibian limb regeneration, but has already been established in tail blastema of reptiles. The CD59, a cell surface molecule, acted as a determinant of proximal-distal cell identity.
    PLoS ONE 03/2011; 6(3):e17878. · 3.53 Impact Factor
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    ABSTRACT: Glial fibrillary acidic protein (GFAP) is a principal intermediate filament in mature astrocytes of the central nervous system (CNS), and the regulation of GFAP transcription has not been well understood yet. In the present study, we reported paired box 3 protein (Pax3) as a novel regulator of GFAP transcription, which could bind the promoter region of GFAP and down regulate the GFAP level during the serum-induced astrocyte differentiation of neural stem cells (NSCs). Moreover, the overexpression and suppression of Pax3 could inhibit and promote NSC differentiation, respectively. These data suggest that Pax3 negatively regulates GFAP expression during astrocyte differentiation in vitro.
    FEBS letters 02/2011; 585(7):1014-20. · 3.54 Impact Factor
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    ABSTRACT: The glial fibrillary acidic protein (GFAP) is an astrocyte-specific member of the class III intermediate filament proteins. It is generally used as a specific marker of astrocytes in the central nervous system (CNS). We isolated a GFAP cDNA from the brain and spinal cord cDNA library of Gekko japonicus, and prepared polyclonal antibodies against gecko GFAP to provide useful tools for further immunochemistry studies. Both the real-time quantitative PCR and western blot results revealed that the expression of GFAP in the spinal cord after transection increased, reaching its maximum level after 3 days, and then gradually decreased over the rest of the 2 weeks of the experiment. Immunohistochemical analyses demonstrated that the increase in GFAP-positive labeling was restricted to the white matter rather than the gray matter. In particular, a slight increase in the number of GFAP positive star-shaped astrocytes was detected in the ventral and lateral regions of the white matter. Our results indicate that reactive astrogliosis in the gecko spinal cord took place primarily in the white matter during a short time interval, suggesting that the specific astrogliosis evaluated by GFAP expression might be advantageous in spinal cord regeneration.
    Cellular & Molecular Biology Letters 12/2010; 15(4):582-99. · 1.95 Impact Factor
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    ABSTRACT: Darier disease (DD; OMIM 124200) is a rare, autosomal dominant hereditary skin disorder characterized by abnormal keratinization and acantholysis. The causes of DD are defects in the ATP2A2 gene, which encodes the sarco/endoplasmic reticulum Ca(2+) ATPase isoform 2 (SERCA2). The aim of this study was to report a novel splice-site mutation and to examine the relative quantity expression of ATP2A2 gene in a Chinese family with DD. Polymerase chain reaction (PCR) was carried out to amplify the exons and flanking intron boundaries of the ATP2A2 gene followed by direct sequencing. A novel splice-site mutation (IVS20-6T>A) was found in the family, which was confirmed by creating a novel HinfI (NEB Inc) recognition site and RT-PCR. Real-time quantitative PCR showed approximately 53 and 52% reduction of ATP2A2 expression of the proband and his father, respectively. The results support the proposition that haploinsufficiency is a common mechanism for the dominant inheritance of DD.
    Archives for Dermatological Research 12/2010; 302(10):769-72. · 2.27 Impact Factor

Publication Stats

132 Citations
110.15 Total Impact Points


  • 2012–2014
    • Nankai University
      • Department of Physics
      T’ien-ching-shih, Tianjin Shi, China
  • 2006–2012
    • Nantong University
      Tungchow, Jiangsu Sheng, China
  • 2006–2007
    • Xi'an Jiaotong University
      • Department of Dermatology
      Ch’ang-an, Shaanxi, China