Biomedical subjects
Publications and source records attributed to Xi Lin.
An allelic variant of the autophagy gene ATG16L1 (T300A) is a genetic risk factor for Crohn's disease. However, over 50% of the global population carries at least one copy. Yao et al. have demonstrated a heterozygote advantage, where the pathogen-protective effect of one allele may outweigh the disease risk in homozygotes.
BACKGROUND: Connexins have their traditional function as part of gap junction (GJ) structures, but have recently been shown to have GJ-independent roles. Although GJs and their connexin subunits are thought to be down-regulated in cancer, depending on the connexin examined, many times the expression level is preserved or even increased. This is further apparent by the importance of GJs in "bystander effects" of radiation and viral targeting treatments. METHODS: We surveyed connexin isoforms in prostate cancer cell lines and tissue with RT-PCR and immunohistochemistry. Upon modulating GJ function, we observed prostate epithelial cell behaviors. RESULTS: Advanced cells within PC-3 and LNCaP prostate cancer progression models exhibit elevated connexin 26 (Cx26) levels-a trend validated in clinical samples. When GJs were inhibited, adhesion was not affected, but invasion and migration were strikingly decreased. A link between the expression of Cx26 and integrin adhesion-linked functions are suggested by Cx26's direct interaction with focal adhesion kinase (FAK). CONCLUSIONS: These results suggest a novel mechanism for adhesion regulation by a GJ-independent Cx26 function that correlates with prostate disease progression. The increased Cx26 expression during prostate cancer progression plays a role in adhesion regulation possibly through its interaction with FAK.
A strong generic coupling between self-localized solitons and conformations of a pi-conjugated polymer chain is demonstrated through ab initio calculations and the underlying mechanisms revealed by using an extended Hubbard model. We show that significant chain bending and twisting of trans- and cis-polyacetylene result from torque imbalances among atom-centered orbitals and the steric instability at single-bond cis-centers, respectively. The soliton-induced conformational effects create sufficient strains to provide an intrinsic high-strain-rate actuation mechanism in optical excitation processes.
Dysfunction of gap junctions (GJs) caused by mutations in connexin26 (Cx26) and Cx30 accounts for nearly half of all cases of hereditary nonsyndromic deafness cases. Although it is widely held that GJs connecting supporting cells in the organ of Corti mainly provide ionic pathways for rapid removal of K+ around the base of hair cells, the function of GJs in the cochlea remains unknown. Here we show that GJs were not assembled in the supporting cells of the organ of Corti until 3 days after birth in mice and then gradually matured to connect supporting cells before the onset of hearing. In organotypic cochlear cultures that were confirmed to express GJs, GJs mediated the propagation of intracellular Ca2+ concentration waves in supporting cells by allowing intercellular diffusion of inositol 1,4,5-trisphosphate. We found that a subset of structurally mild Cx26 mutations located at the second transmembrane region (V84L, V95M, and A88S) and a Cx30 mutation located at the first cytoplasmic segment (T5M) specifically affect the intercellular exchange of larger molecules but leave the ionic permeability intact. Our results indicated that Cx26 and Cx30 mutations that are linked to sensorineural deafness retained ionic coupling but were deficient in biochemical permeability. Therefore, GJ-mediated intercellular exchange of biochemically important molecules is required for normal cochlear functions.
The mammalian auditory sensory organ, the organ of Corti, consists of sensory hair cells with uniformly oriented stereocilia on the apical surfaces and has a distinct planar cell polarity (PCP) parallel to the sensory epithelium. It is not certain how this polarity is achieved during differentiation. Here we show that the organ of Corti is formed from a thicker and shorter postmitotic primordium through unidirectional extension, characteristic of cellular intercalation known as convergent extension. Mutations in the PCP pathway interfere with this extension, resulting a shorter and wider cochlea as well as misorientation of stereocilia. Furthermore, parallel to the homologous pathway in Drosophila melanogaster, a mammalian PCP component Dishevelled2 shows PCP-dependent polarized subcellular localization across the organ of Corti. Taken together, these data suggest that there is a conserved molecular mechanism for PCP pathways in invertebrates and vertebrates and indicate that the mammalian PCP pathway might directly couple cellular intercalations to PCP establishment in the cochlea.
Teriparatide, human PTH (1-34), a new therapy for osteoporosis, elicits markedly different skeletal responses depending on the treatment regimen. In order to understand potential mechanisms for this dichotomy, the present investigation utilized microarrays to delineate the genes and pathways that are regulated by intermittent (subcutaneous injection of 80 microg/kg/day) and continuous (subcutaneous infusion of 40 microg/kg/day by osmotic mini pump) PTH (1-34) for 1 week in 6-month-old female rats. The effect of each PTH regimen was confirmed by histomorphometric analysis of the proximal tibial metaphysis, and mRNA from the distal femoral metaphysis was analyzed using an Affymetrix microarray. Both PTH paradigms co-regulated 22 genes including known bone formation genes (i.e., collagens, osteocalcin, decorin, and osteonectin) and also uniquely modulated additional genes. Intermittent PTH regulated 19 additional genes while continuous treatment regulated 173 additional genes. This investigation details for the first time the broad profiling of the gene and pathway changes that occur in vivo following treatment of intermittent versus continuous PTH (1-34). These results extend previous observations of gene expression changes and reveal the in vivo regulation of BMP3 and multiple neuronal genes by PTH treatment.
A suckling piglet model was used to study nutritional and pharmacologic means of stimulating hepatic fatty acid beta-oxidation. Newborn pigs were fed milk diets containing either long- or medium-chain triglycerides (LCT or MCT). The long-chain control diet was supplemented further with clofibric acid (0.5%) or isoproterenol (40 ppm), and growth was monitored for 10-12 days. Clofibrate increased rates of hepatic peroxisomal and mitochondrial beta-oxidation of [1-(14)C]-palmitate by 60 and 186%, respectively. Furthermore, malonyl-CoA sensitive carnitine palmitoyltransferase (CPT I) activity increased 64% (P < 0.05) in pigs receiving clofibrate. Increased CPT I activity was not congruent with changes in message, as elevated abundance of CPT I mRNA was not detected (P = 0.16) when assessed by qRT-PCR. Neither rates of beta-oxidation nor CPT activities were affected by dietary MCT or by isoproterenol treatment (P > 0.1). Collectively, these findings indicate that clofibrate effectively induced hepatic CPT activity concomitant with increased fatty acid beta-oxidation.
The ontogeny of carnitine palmitoyltransferase (CPT) was examined in liver and muscle throughout growth and development of the domestic felid. Homogenates from animals in six age categories (newborn, 24-h, 3-, 6- and 9-week-old, and adult) were examined. Hepatic CPT specific activity increased progressively from birth to 6 weeks and then declined slightly into adulthood, with maximal values for animals greater than 24 h of age [171 nmol/(min g wet tissue)] being 70% higher than for newborns [99 nmol/(min g wet tissue)] (P<.05). Specific activity in adults was similar to that in 6- and 9-week-old juveniles. Total hepatic CPT activity [nmol/(min liver)] increased linearly with age, but the activity expressed per kg body weight [nmol/(min kg BW)] declined after 3 weeks. In contrast, skeletal muscle CPT-specific activity remained unchanged from birth to 3 weeks and then increased significantly, with maximal values at 9 weeks being 90% greater than those for young animals (newborn to 3 weeks; P<.05), whereas specific activity in adults was 50% lower than that observed in 9-week-old animals (P<.05). Hepatic and muscle apparent Km's for carnitine averaged 440 microM and did not vary with age. Hepatic carnitine concentrations remained relatively constant during development, but were lower in adult lactating females, whereas skeletal muscle concentrations increased markedly with age. Hepatic concentrations were 20-50% higher than apparent Km's for carnitine in young and growing animals, but concentrations were similar to the apparent Km at 6 weeks and significantly lower than the apparent Km in adults. Carnitine concentrations in skeletal muscle were 37% lower than apparent Km during the neonatal period, but significantly higher in cats >3 weeks of age. We conclude that postnatal increases in CPT activity support increased capacity for fatty acid oxidation in the developing felid and that dietary carnitine may be required to maximize enzyme activity.
Spinocerebellar ataxia type 10 (SCA10) is a dominantly inherited ataxia caused by expansion of ATTCT pentanucleotide repeat in intron 9 of a novel gene, E46L, on chromosome 22q13.3. SCA10 is a complex neurodegenerative condition. Initial studies characterized SCA10 as pure cerebellar ataxia associated with seizures. Recent identification of new SCA10 families revealed more diverse phenotypes, including polyneuropathy, pyramidal signs, cognitive and neuropsychiatric impairment. Moreover, several families manifest with ataxia without seizures. Thus a complete clinical spectrum is emerging. Progress has also been made in understanding the molecular and genetic mechanisms of pathogenesis. The length of expanded ATTCT repeats is variable in different tissues and highly unstable during paternal transmission, revealing complex genetic and pathogenetic processes. Under torsional stress, ATTCT repeats form unpaired DNA structure and may serve as an erroneous DNA replication origin, potentially contributing to repeat instability and aberrant cell cycle entry. E46L is a cytoplasmic protein with unknown function. Reduced expression of E46L in primary neuronal cultures from cerebellum and cortex by small interfering RNAs (siRNAs) caused increased apoptosis, raising the possibility that reduced expression of E46L might also play an important role in SCA10 pathogenesis.
AIM: To investigate the fibrin(ogen)olytic character of FIIa isolated from Agkistrodon acutus venom in vitro and in vivo. METHODS: 125I-labeled human plasma clot lysis was measured in vitro and rabbit carotid artery thrombosis was as an in vivo model. RESULTS: In vitro, urokinase (UK) at 25, 35, 40, 45, 60 kU/L and FIIa at 0.08, 0.23, 0.4, 0.5, and 0.7 g/L resulted an equivalent clot lysis (20%, 40%, 50%, 60%, and 80%). UK at 25 to approximately 60 kU/L induced 27.3%+/-3.6%, 35.2%+/-2.3%, 39.3%+/-2.4%, 44.2%+/-4.6%, and 51.1%+/-1.2% fibrinogen degradation. But FIIa at 0.08 approximately -0.7 g/L induced 95.4%+/-0.3%, >95.6%, >95.6%, >95.6%, >95.6% fibrinogen degradation respectively. In vivo, UK 40 kU/kg and FIIa 1.0 mg/kg reduced the weight of residual thrombus to 9.0+/-2.5 mg and 7.8+/-3.5 mg compared with negative control group (30.0+/-5.4 mg). But the fibrinogen degradation rate after UK 40 kU/kg and FIIa 1.0 mg/kg treatment was 24.4%+/-6.2% and 4.1%+/-7.8%, respectively (P<0.05, n=6). The order of the lysis speed after UK 125 kU/L treatment was platelet poor plasma (PPP) clots>the whole blood clots>platelet rich plasma (PRP) clots. The sequence for FIIa 0.4 g/L was PRP >PPP >whole blood clots. CONCLUSION: At the same percentage of clot lysis, FIIa degraded more fibrinogen than UK did in vitro but less fibrinogen than UK did in vivo. The order of the lysis speed was PPP>whole blood clots>PRP clots for UK and PRP>PPP>whole blood clots for FIIa.
The importance of connexins (Cxs) in cochlear functions has been demonstrated by the finding that mutations in Cx genes cause a large proportion of sensorineural hearing loss cases. However, it is still unclear how Cxs contribute to the cochlear function. Recent data (33) obtained from Cx30 knockout mice showing that a reduction of Cx diversity in assembling gap junctions is sufficient to cause deafness suggest that functional interactions of different subtypes of Cxs may be essential in normal hearing. In this work we show that the two major forms of Cxs (Cx26 and Cx30) in the cochlea have overlapping expression patterns beginning at early embryonic stages. Cx26 and Cx30 were colocalized in most gap junction plaques in the cochlea, and their coassembly was tested by coimmunoprecipitation. To compare functional differences of gap junctions with different molecular configurations, homo- and heteromeric gap junctions composed of Cx26 and/or Cx30 were reconstituted by transfections in human embryonic kidney-293 cells. The ratio imaging technique and fluorescent tracer diffusion assays were used to assess the function of reconstituted gap junctions. Our results revealed that gap junctions with different molecular configurations show differences in biochemical coupling, and that intercellular Ca(2+) signaling across heteromeric gap junctions consisting of Cx26 and Cx30 was at least twice as fast as their homomerically assembled counterparts. Our data suggest that biochemical permeability and the dynamics of intercellular signaling through gap junction channels, in addition to gap junction-mediated intercellular ionic coupling, may be important factors to consider for studying functional roles of gap junctions in the cochlea.
Ion channels in the degenerin-epithelial sodium channel (DEG-ENaC) family perform diverse functions, including mechanosensation. Here we explored the role of the vertebrate DEG-ENaC protein, acid-sensing ion channel 2 (ASIC2), in auditory transduction. Contributions of ASIC2 to hearing were examined by comparing hearing threshold and noise sensitivity of wild-type and ASIC2 null mice. ASIC2 null mice showed no significant hearing loss, indicating that the ASIC2 was not directly involved in the mechanotransduction of the mammalian cochlea. However, we found that (1) ASIC2 was present in the spiral ganglion (SG) neurons in the adult cochlea and that externally applied protons induced amiloride-sensitive sodium currents and action potentials in SG neurons in vitro, (2) proton-induced responses were greatly reduced in SG neurons obtained from ASIC2 null mice, indicating that activations of ASIC2 contributed a major portion of the proton-induced excitatory response in SG neurons, and (3) ASIC2 null mice were considerably more resistant to noise-induced temporary, but not permanent, threshold shifts. Together, these data suggest that ASIC2 contributes to suprathreshold functions of the cochlea. The presence of ASIC2 in SG neurons could provide sensors to directly convert local acidosis to excitatory responses, therefore offering a cellular mechanism linking hearing losses caused by many enigmatic causes (e.g., ischemia or inflammation of the inner ear) to excitotoxicity.
Several basic helix-loop-helix (bHLH) genes have been shown to be essential for the generation of the auditory sensory hair cells or the spiral ganglion (SG) neurons that innervate the hair cells in the cochlea, as well as a variety of cell types in the other nervous systems. However, it remains elusive what cellular context-dependent mechanisms confer the inner ear-specific neuronal or sensory competency/identities. We explored the possibility that one of the mechanisms responsible for generating cellular diversity in the nervous system through cooperative action of bHLH and LIM-homeodomain (LIM-HD) transcriptional factors might also contribute to the inner ear-specific sensory and/or neuronal competency. Here, we show that Islet1 (Isl1), a LIM-HD protein, is expressed early in the otocyst in the region that gives rise to both the auditory sensory organ, the organ of Corti, and SG neurons. Subsequently, the expression of Isl1 is maintained in SG neurons but is transitory in the sensory lineage. At embryonic day 12 (E12) in mice, the expression of Isl1 marks distinctively the ventral portion of the nascent cochlear epithelium encompassing the primordial organ of Corti. At E13, Isl1 is maintained at relatively high levels in the sensory primordium while down-regulated in the other regions of the cochlear duct. As the sensory epithelium starts to differentiate, it is down-regulated in the entire cochlear epithelium. The expression of Isl1 in the developing inner ear reveals an early and likely a common step in the development of both sensory and neuronal lineages of the inner ear, and suggests its potential role in the inner ear-specific sensory and neuronal cell development.
Spinocerebellar ataxia type 10 (SCA10) is an autosomal dominant disorder characterized by ataxia, seizures, and anticipation. It is caused by an expanded ATTCT pentanucleotide repeat in intron 9 of a novel gene, designated "SCA10." The ATTCT expansion in SCA10 represents a novel class of microsatellite repeat and is one of the largest found to cause human diseases. The expanded ATTCT repeat is unstably transmitted from generation to generation, and an inverse correlation has been observed between size of repeat and age at onset. In this multifamily study, we investigated the intergenerational instability, somatic and germline mosaicism, and age-dependent repeat-size changes of the expanded ATTCT repeat. Our results showed that (1) the expanded ATTCT repeats are highly unstable when paternally transmitted, whereas maternal transmission resulted in significantly smaller changes in repeat size; (2) blood leukocytes, lymphoblastoid cells, buccal cells, and sperm have a variable degree of mosaicism in ATTCT expansion; (3) the length of the expanded repeat was not observed to change in individuals over a 5-year period; and (4) clinically determined anticipation is sometimes associated with intergenerational contraction rather than expansion of the ATTCT repeat.
Acute phencyclidine induces schizophrenia-like symptoms in healthy humans and psychotic episodes in schizophrenics. Although phencyclidine is known as a N-methyl d-aspartate receptor antagonist (NMDA-R), the molecular events underlying the behavioral symptoms remain largely unknown. Statistical analysis of oligonucleotide microarray data was used to identify phencyclidine-induced alterations in rat cortical gene expression. Acute phencyclidine produced a statistically significant change in 477 genes in rat prefrontal cortex (PFC), a brain area associated with cognitive dysfunction in schizophrenics. Real-time quantitative PCR (RTQ-PCR) confirmed a subset of these changes ranging from -59% to 255% (smallest confirmation: -19%). Subsequent time-course and dose-response studies using RTQ-PCR confirmed and extended the original microarray results. At the molecular level, genes altered by phencyclidine are related to diverse biological processes including stress, inflammatory response, growth and development, neural plasticity and signal transduction. Further analysis, aimed at assessing the relevance of our results to schizophrenia, revealed dysregulation of genes related to: (i) thalamocortical projections, (ii) neurotransmission and neuromodulation, (iii) thyroid hormone activity, (iv) oligodendrocyte linage, (v) brain lipid metabolism, (vi) sleep architecture and (viii) the velocardiofacial syndrome.
INTRODUCTION: The hybridization intensities derived from microarray experiments, for example Affymetrix's MAS5 signals, are very often transformed in one way or another before statistical models are fitted. The motivation for performing transformation is usually to satisfy the model assumptions such as normality and homogeneity in variance. Generally speaking, two types of strategies are often applied to microarray data depending on the analysis need: correlation analysis where all the gene intensities on the array are considered simultaneously, and gene-by-gene ANOVA where each gene is analyzed individually. AIM: We investigate the distributional properties of the Affymetrix GeneChip signal data under the two scenarios, focusing on the impact of analyzing the data at an inappropriate scale. METHODS: The Box-Cox type of transformation is first investigated for the strategy of pooling genes. The commonly used log-transformation is particularly applied for comparison purposes. For the scenario where analysis is on a gene-by-gene basis, the model assumptions such as normality are explored. The impact of using a wrong scale is illustrated by log-transformation and quartic-root transformation. RESULTS: When all the genes on the array are considered together, the dependent relationship between the expression and its variation level can be satisfactorily removed by Box-Cox transformation. When genes are analyzed individually, the distributional properties of the intensities are shown to be gene dependent. Derivation and simulation show that some loss of power is incurred when a wrong scale is used, but due to the robustness of the t-test, the loss is acceptable when the fold-change is not very large.
OBJECTIVE: To study the changes of the intramembrane protein particles of erythrocyte from Duchenne muscular dystrophy (DMD) patients and the gene carriers and to explore the pathogenesis of DMD and the diagnostic value of erythrocyte freeze-fracture technology. METHODS: The fixed erythrocyte mass was treated to form replica membrane by means of the freeze-fracture technology. Then the replica membrane was observed and a picture was taken under electron microscope. The protein particles of extracellular face(EF) and protoplasmic face(PF) per square were counted. The statistical comparative analysis was performed. RESULTS: The protein particle counts of EF face and PF face of erythrocyte membrane from DMD patients and DMD carriers decreased obviously in comparison with the normal control group (P<0.001). CONCLUSION: The erythrocyte freeze-fracture electron microscopic technology may serve as a method for accessory examination of diagnosing DMD patients and a method for detecting DMD carriers. This investigation material supplies reliable evidence for the theory of the systemic membrane defect of DMD.
OBJECTIVE: To observe Trichomonas vaginalis (T. vaginalis) adhering to and phagocytizing male genitourinary epithelial cells in order to study the pathogenetic mechanism of male trichomoniasis. METHODS: Cultured T. vaginalis bodies were incubated with male genitourinary epithelial cells, and then the ultrastructure was observed with transmission electron microscopy. RESULTS: T. vaginalis adhered to epithelial cells like amoeba, and formed pseudopodium or surface invagination surrounding or nibbling other parts of the epithelial cytoplasm. CONCLUSIONS: T. vaginalis has the speciality of adhering to and phagocytizing to male genitourinary epithelial cells. Genitourinary epithelial cells may be injured directly by the phagocytosis of T. vaginalis. Attention has to be paid to the correlation.