Biomedical subjects

Kun Xia

Publications and source records attributed to Kun Xia.

At least 55 records · Page 3Linked to original sources

PubMed2005

Novel compound heterozygous mutations in the PANK2 gene in a Chinese patient with atypical pantothenate kinase-associated neurodegeneration.

We investigated the presence of mutations in the pantothenate kinase (PANK2) gene in a 27-year-old male Chinese patient with atypical pantothenate kinase-associated neurodegeneration (PKAN), formerly Hallervorden-Spatz syndrome. Automated DNA sequence analyses revealed compound heterozygous mutations in the exon 3 and 5. This patient had a 10-year history of PKAN characterized by a slight tremor of the right hand when writing at onset and a slow progressive rigidity of the neck and the right arm and resting tremor in upper extremities. Dysarthria, dysphagia, and dystonic-athetoid movements of the face and right fingers were marked. Magnetic resonance showed the typical "eye-of-the-tiger" sign.

Adult↗

PubMed2005

Cx31 is assembled and trafficked to cell surface by ER-Golgi pathway and degraded by proteasomal or lysosomal pathways.

Gap junctions, consisting of connexins, allow the exchange of small molecules (less than 1 KD) between adjacent cells, thus providing a mechanism for synchronizing the responses of groups of cells to environmental stimuli. Connexin 31 is a member of the connexin family. Mutations on connexin 31 are associated with erythrokeratodermia variabilis, hearing impairment and peripheral neuropathy. However, the pathological mechanism for connexin 31 mutants in these diseases are still unknown. In this study, we analyzed the assembly, trafficking and metabolism of connexin 31 in HeLa cells stably expressing connexin 31. Calcein transfer assay showed that calcein transfer was inhibited when cells were treated with Brefeldin A or cytochalasin D, but not when treated with nocodazole or a-glycyrrhetinic acid, suggesting that Golgi apparatus and actin filaments, but not microtubules, are crucial to the trafficking and assembly of connexin 31, as well as the formation of gap junction intercellular communication by connexin 31. Additionally, a-glycyrrhetinic acid did not effectively inhibit gap junctional intercellular communication formed by connexin 31. Pulse-chase assay revealed that connexin 31 had a half-life of about 6 h. Moreover, Western blotting and fluorescent staining demonstrated that in HeLa cells stably expressing connexin 31, the amount of connexin 31 was significantly increased after these cells were treated with proteasomal or lysosomal inhibitors. These findings indicate that connexin 31 was rapidly renewed, and possibly degraded by both proteasomal and lysosomal pathways.

Brefeldin A↗

PubMed2005

Identification of the alternative promoters of the KChIP4 subfamily.

The subfamily of voltage-dependent potassium (Kv) channel interacting protein 4 (KChIP4) is made up of the auxiliary interacting protein of voltage-dependent potassium channels. In this study, the structure of four splicing variants of the human KChIP4 gene was analyzed. Three of the four isoforms of the KChIP4 gene, KChIP4.1, KChIP4.2 and KChIP4.4, were amplified from mouse and human fetal brain tissues by reverse transcription-polymerase chain reaction and then identified. Based on the bioinformatics analysis of the genomic sequences of the gene, we cloned and characterized two promoter fragments from the KChIP4 gene. One was a 325 bp fragment upstream of the 5' end of the KChIP4.1 mRNA sequence and the other was an 818 bp fragment located immediately at the 5' end of the KChIP4.4 variant. Both of them can initiate the transcription of the reporter gene in HT1080 cells and Sprague-Dawley (SD) rat fetal brain neurons, and they contain CG islands, except typical TATA boxes and CAAT boxes. This shows that the KChIP4 gene expression is regulated by an alternative promoter.

Amino Acid Sequence↗

PubMed2005

Intracellular distribution, assembly and effect of disease-associated connexin 31 mutants in HeLa cells.

Mutations in connexin 31 (Cx31) are associated with erythrokeratodermia variabilis (EKV), hearing impairment and peripheral neuropathy; however, the pathological mechanism of Cx31 mutants remains unknown. This study analyzed 11 disease-associated Cx31 variants and one non-disease-associated Cx31 variant and compared their intracellular distribution and assembly in HeLa cells and their effect on these cells. The fluorescent localization assay showed no gap junction plaque formation in the cells expressing the recessive EKV-associated mutant (L34P) and four hearing impairment-associated mutants (66delD, 141delI, R180X and E183K), significantly reduced plaque formation in the cells with five EKV-associated dominant mutants (G12R, G12D, R42P, C86S and F137L) and no obvious change in the cells with two other mutants (I141V and 652del12). Immunoblotting analysis showed that 12 mutated Cx31s, like WT-Cx31, are able to form the Triton X-100 insoluble complex; however, the quantity of Triton X-100 insoluble complex in the transfected HeLa cells varied among different Cx31 mutants. Additionally, the expression of five EKV-associated dominant mutants (G12R, G12D, R42P, C86S and F137L) caused cell death in HeLa cells. However, the five hearing impairment-associated mutants did not induce cell death. The above results suggest that disease-associated mutants gain deleterious functions differentially. In summary, disease-associated Cx31 mutants impair the formation of normal gap junctions at different levels, and the diseases associated with Cx31 mutations may result from the abnormal assembly, trafficking and metabolism of the Cx31 mutants.

Apoptosis↗

PubMed2005

[Clinical, pathological and genetic studies in a Chinese Charcot-Marie-Tooth disease type 2 family].

OBJECTIVE: To report a Chinese Charcot-Marie-Tooth disease type 2 (CMT2) family. METHODS: All the members in the family were studied clinically,and 6 patients were studied electrophysiologically. Sural nerve biopsy was performed in the proband. PMP22 gene duplications were detected by highly polymorphic short tandem repeat. Point mutation analysis of PMP22, MPZ and NEFL gene was screened by PCR-SSCP combined with DNA direct sequencing. A genome-wide screening was carried out to the family. RESULT: Except 2 who had weakness and atrophy in both proximal and distal muscles of the lower limbs, all patients presented muscle wasting and a predominating weakness of distal parts of the lower limbs, and mild to moderate sensory impairments. In 6 patients who were subjected to elctrophysiological examinations, median-nerve conduction velocity (NCV) of the median nerve was normal. Electromyograms (EMGs) revealed signs of denervation with large motor unit potentials, fibrillation potentials and positive sharp waves. Sural nerve biopsy of the proband confirmed the presence of axonal neuropathy with an important loss of large myelinating fibers and a large number of clusters with mostly thinly myelinated axons. PMP22, MPZ and NEFL gene mutations were not found. The results of genome-wide screening revealed a linkage of CMT2 to a locus at chromosome 12q24. CONCLUSION: The results are consistent with the diagnosis of CMT2. This family represents a rare genetic type of CMT2 which can be designated as CMT2L.

Adolescent↗

PubMed2005

[Frequency analysis of autosomal dominant spinocerebellar ataxias in Han population in the Chinese mainland and clinical and molecular characterization of spinocerebellar ataxia type 6].

OBJECTIVE: To assess the frequency of spinocerebellar ataxia (SCA), including the subtypes of SCA1, SCA2, SCA3/Machado-Joseph disease(MJD), SCA6, SCA7, SCA8, SCA10, SCA12, SCA14, SCA17 and dentatorubro-pallidoluysian atrophy (DRPLA) in Han population in the Chinese mainland, and to specifically characterize the mainland Chinese patients with SCA6 in terms of clinical and molecular features. METHODS: Using a molecular approach, the authors investigated SCA in 120 families with dominantly inherited ataxias and in 60 patients with sporadic ataxias. Clinical and molecular features of SCA6 were further characterized in 13 patients from 4 families. RESULTS: SCA3/MJD was the most common type of autosomal dominant SCA in the Han population, accounting for 83 patients from 59 families(49.2%), followed by SCA2(8, 6.7%), SCA1(7, 5.8%), SCA6(4, 3.3%), SCA7(1,0.8%), SCA8 (0), SCA10 (0), SCA12(0), SCA14 (0), SCA17(0) and DRPLA(0). The genes responsible for 41(34.2%) of dominantly inherited SCA families remained undetermined. Among the 60 patients with sporadic ataxias in the present series, 3(5.0%) were found to harbor SCA3 mutations while none were found to harbor SCA6 mutations. In the 4 families with SCA6, significant anticipation was found with no genetic instability on transmission. CONCLUSION: The present authors firstly found and reported a geographic cluster of families with SCA6 subtype in the Chinese mainland, which were initially identified in Hans reported of the Chinese mainland.

Adult↗

PubMed2005

[Phenotype positioning on chromosomes in a patient with the syndrome of partial trisomy 7p21.2-->pter].

By using the techniques of human chromosome G-banding, high resolution banding and fluorescence in situ hybridization (FISH), we investigated a patient with the karyotype of partial trisomy 7p21.2-->pter. Combining with the comparative review of the clinical data in 14 cases with partial trisomy 7p syndrome from reported literatures,we searched for the correlation between the karyotype and the phenotype and between the karyotype and the associated gene in the patients with partial trisomy 7p syndrome. The results indicated that the 7p21.2-->p22 is the critical segment of partial trisomy 7p syndrome. The phenotypes of the genital malformation and the dislocation of hip joint are associated with the duplication of 7p15. The cardiac anomalies is resulted from the dysfunctions of several genes on the long arm of chromosome 7. The gene associated with the craniosynostosis may locate on the region of 7p21.2-->p21.3.

Abnormalities, Multiple↗

PubMed2005

[ATM gene mutations in Chinese patients with ataxia telangiectasia].

OBJECTIVE: To investigate the mutation characteristics of ATM gene in Chinese patients with ataxia-telangiectasia (AT). METHODS: Mutation of ATM gene was screened by polymerase chain reaction, reverse transcription-polymerase chain reaction, polyacrylamide gel electrophoresis combined with DNA direct sequencing in two Chinese AT patients. RESULTS: A missense mutation of 1346(G>C) in exon 11, which was a homozygotic mutation, was identified in one patient; a nonsense mutation of 610 (G>T) in exon 6 combined with a missense mutation of 6679 (C>T) in exon 47, which was a compound heterozygotic mutation, were identified in the other patient. They were co-segregated with the disease and were localized within the functional domain of ATM gene. CONCLUSION: Totally three novel ATM gene mutations were identified in two Chinese AT patients.

Ataxia Telangiectasia Mutated Proteins↗

PubMed2005

[Studies on PANK2 gene mutations in Chinese patients with Hallervorden-Spatz syndrome].

OBJECTIVE: To study pantothenate kinase 2 (PANK2) gene mutations in Chinese patients with Hallervorden-Spatz syndrome (HSS). METHODS: PANK2 gene mutations were detected by PCR, DNA sequence analyses, restriction enzyme digestion and PCR-single strand conformation polymorphism in 5 patients, 3 unaffected family members and 51 unrelated healthy persons. RESULTS: Novel compound heterozygous PANK2 gene mutations, A803G and T1172A, in exons 3 and 5, respectively, were found in one patient. At the same time, 3 types of single nucleotide polymorphisms, -38 t>a in 5'-UTR, IVS1+42 c>a and G77C in exon 1, were confirmed; among them, -38 t>a, IVS1+42 c>a, were first reported. CONCLUSION: PANK2 gene mutations can cause HSS in Chinese patients.

Adolescent↗

PubMed2005

[Mutation analysis of gene CX31.1 in the hereditary hearing loss pedigrees].

OBJECTIVE: To make clear of the relation between CX31.1 and hereditary hearing loss by the mutation detect of gene CX31.1 in nonsyndromic hearing loss pedigrees. METHOD: Thirty-seven pedigrees of autosomal recessive inheritance hereditary hearing loss and twenty-four pedigrees of autosomal dominant inheritance hereditary hearing loss were collected from decades provinces of China. By using polymerase chain reaction and direct sequence, we screened the members of this pedigrees for the mutations of gene CX31.1. RESULT: One polymorphism and one synonymous mutation of gene CX31.1 and two absent pieces in the introns of CX31.1 were found. CONCLUSION: Though we have not found mutations of CX31.1 which can induce corresponding hereditary deafness of the pedigrees inspected before, we don't think we can deny gene CX31.1 is a nosogenesis gene of hereditary hearing loss, and what we can do is to collect enough pedigrees to continue our research.

Connexins↗

PubMed2005

[Effect of glycoprotein alpha II bA2334C mutation on the biosynthesis and transportation of alpha II bbeta3 complex].

OBJECTIVE: To study the effect of glycoprotein (GP) alpha II bA2334C mutation on the biosynthesis and expression of alpha II bbeta3 complex. METHODS: The GP alpha II bA2334C eukaryotic expression plasmid pc3.1-2334M2b was constructed. Chinese hamster ovary (CHO) cells were transfected with the plasmid with or without integrin beta3 expression plasmid pc3.1-3a. The whole expression of alpha II bA2334C was confirmed by Western blot and the membrane expression was analyzed by flow cytometry. A newly constructed alpha II bA2334C GFP fusion protein expressing plasmid was used to determine its subcellular localization by laser confocal scanning microscopy. RESULTS: Expression of the mutant protein, alpha II bA2334C, in the transfected CHO cells was confirmed by Western blot with a lower rate of the mature type than the wild type control. The expression on membrane was only 25% of the normal. Subcellular localization analysis showed that alpha II bA2334C GFP was able to be expressed in CHO cells and could be transported from endoplasmic reticulum to Golgi apparatus. CONCLUSIONS: The mutant alpha II bA2334C can be synthesized in CHO cells and form alpha II bbeta3 complex. However, only a small fraction of the premature alpha II bA2334C can be transported to Golgi apparatus and transformed to mature alpha II b. The possible pathogenesis of this type II thrombasthenia may be that the misfolded alpha II bA2334C is partially degraded in the endoplasmic reticulum causing lower expression of alpha II bbeta3 complex on the membrane and resulting in impared function of platelets than normal alpha II b.

Animals↗

PubMed2005

Research on screening and identification of proteins interacting with ataxin-3.

OBJECTIVE: This study sought to isolate and identify the proteins that interact with ataxin-3, to confirm the interacted domain, and to provide new clues for exploring the function of ataxin-3 and the pathogenesis of spinocerebellar ataxia type 3 and Machado-Joseph disease (SCA3/MJD). METHODS: Yeast two-hybrid screen (MATCHMAKER GAL4 Two-Hybrid System 3) and regular molecular biologic techniques were undertaken to screen human brain cDNA library with mutant ataxin-3 bait. Two baits from both normal and mutant C-terminus of ataxin-3 were created by subcloned methods to determine which domain of ataxin-3 interacts with the putative associated proteins and to find out optimal candidate proteins that interact with C-terminus of ataxin-3. Confocal microscope was used to observe whether ataxin-3 co-localized with the obtained interacting proteins in mammalian cells. RESULTS: Five novel ataxin-3 interacting proteins were obtained, among which were three known proteins, namely human rhodopsin guanosine diphosphate dissociation inhibitor alpha, small ubiquitin-like modifier 1, and human neuronal amiloride-sensitive cation channel 2; the other two were unknown. Interacting domain analysis revealed that an unknown protein interacted with the C-terminus near the polyglutamine tract of ataxin-3, the other four all interacted with the N-terminus. In the nucleus of SH-SY5Y cell, small ubiquitin-like modifier 1 co-localized with the wild-type ataxin-3 and with the intranuclear aggregates formed by the mutant ataxin-3. CONCLUSION: An unknown protein probably interacting with C-terminus of ataxin-3 is firstly discovered, and the initiative findings suggest first that the interaction of small ubiquitin-like modifier 1 with N-terminus of ataxin-3 and the relevant sumoylation probably participate in the post-translation modifying of ataxin-3 and in the pathogenesis of SCA3/MJD.

Acid Sensing Ion Channels↗

PubMed2005

[Stable suppression of beta-catenin expression in prostate cancer cell line by retrovirus mediated RNAi].

OBJECTIVE: To set up a prostate cancer cell line in which beta-catenin expression is stably suppressed and to investigate the role of Wnt/beta-catenin signaling pathway in prostate tumorgenesis. METHODS: We select 3 sites in the complete coden sequence region of beta-catenin gene as the RNAi targets, ligated the annealed double pre-DNA strands into the retroviral vectors pSUPER-retro and transfected them into the packaging cells PA317, and then collected supernatant with retrovirus to infect DU145. After selection by puromycin and culture expansion, the stable cell clones were attained. Expression of the 2 target genes of Wnt/beta-catenin signaling pathway cyclinD1 and c-myc, was detected in the beta-catenin RNAi cells by Western blot. The effect of suppressing beta-catenin by RNAi on cell proliferation was quantified by methylthiazoletetrazolium (MTT) assay. RESULTS: Western blotting and RT-PCR showed that the expression level of beta-catenin in the 2 stable cell clones apparently decreased. CyclinD1 and c-myc expression decreased in the beta-catenin RNAi cells. MTT showed that the cell number of beta-catenin expression suppression cell clones decreased significantly (P < 0. 05), suggesting the cell proliferation was prevented. CONCLUSION: The beta-catenin gene stable suppression cell line was successfully established.

Cell Line, Tumor↗

PubMed2005

Mutation analysis of small heat-shock protein 22 gene in Chinese patients with Charcot-Marie-Tooth disease.

OBJECTIVE: To study the characteristics of the mutation of small heat-shock protein 22 (HSP22) gene in Chinese patients with Charcot-Marie-Tooth (CMT) disease. METHODS: A CMT2L proband with 423(G--> T) mutation in HSP22 gene had been studied and reported by the present authors. In this study, mutation analysis of HSP22 gene was performed using polymerase chain reaction and DNA direct sequencing in 114 CMT probands. RESULTS: In the 114 CMT probands, a 582(C--> T)(T194T)samesense mutation was found in two unrelated families. CONCLUSION: The rate of HSP22 gene mutation in Chinese patients with CMT is as low as 0.87%(1/115).

Asian People↗

PubMed2005

Molecular analysis of SLC26A4 gene in a Chinese deafness family.

OBJECTIVE: To identify the pathogenic gene for a non-syndromic hearing loss family. METHODS: Mutation analysis was carried out by polymerase chain reaction and direct sequencing of all exons of SLC26A4 (solute carrier family 26, member 4) gene. RESULTS: Compound heterozygous mutations N392Y and S448X were detected in the proband of the family, heterozygous mutation S448X was detected in the father, heterozygous mutation N392Y was detected in the mother. CONCLUSION: The proband's hearing loss resulted from the compound heterozygous mutations N392Y and S448X for SLC26A4 gene.

Adult↗

PubMed2005

[Prenatal diagnosis of prelingual deafness by determination of SLC26A4 gene mutation].

OBJECTIVE: To identify deafness related gene and provide its prenatal diagnosis to avoid deaf fetus delivery. METHODS: DNA was extracted from amniotic cells in a pregnant woman close to 21 weeks' gestation, as well as from peripheral blood cells of the pregnant woman, her husband and their two sons. Screening for GJB2 and SLC26A4 gene mutations was firstly performed in the deafness proband (the first son of the couple), and then it was carried out in the fetus and the rest family members. RESULTS: The first child of the family, i.e., the proband, was homozygous in the IVS7-2A > G mutation of SLC26A4, the parents and the second child were carriers of the same mutation, while the fetus had a wild-type form. CONCLUSION: It is feasible to identify deafness related genes by screening for GJB2 and SLC26A4 mutation, thus providing correct prenatal diagnosis and avoiding deaf delivery of baby.

Adult↗

PubMed2005

A minidystrophin-EGFP fusion gene expressed in Cos-7 cells mediated by human source vector.

OBJECTIVE: To construct a human source vector containing minidystrophin-EGFP fusion gene and investigate its expression in Cos-7 cells. METHODS: The recombinant human source vector named pHrnDysG was constructed with PCR-clone methods. Three fragments of dystrophin gene were PCR amplified from normal human dystrophin gene cDNA (GenBank NM04006). These three fragments were ligated to generate a minidystrophin gene. The enhanced green fluorescent protein (EGFP) gene was fused to the C terminal of the minidystrophin gene, and then the pHrnDysG was finally obtained by cloning the fusion gene to pHrneo. Fluorescence microscope and RT-PCR were used to detect the expression of minidystrophin-EGFP fusion gene after the recombinant construct was transfected into Cos-7 cells by lipofectamine. RESULTS: Restrictive enzyme digestion analysis and sequencing confirmed that pHrnDysG vector was constructed successfully. After the recombinant pHrnDysG was transfected to Cos-7 cells, RT-PCR demonstrated that the fusion gene was successfully transcribed, and the green fluorescence was observed at the cell membrane. CONCLUSION: The minidystrophin-EGFP fusion gene mediated by pHrneo vector could express in Cos-7 cells and its products' localization in the cell membrane was the same as that of full length dystrophin. These results suggested that the recombinant human source vector pHrnDysG might be potentially used in studies on the gene therapy of Duchenne muscular dystrophy.

Animals↗

PubMed2005

[Mutation analysis of small heat shock protein 27 gene in Chinese patients with Charcot-Marie-Tooth disease].

OBJECTIVE: To investigate the features of small heat shock protein 27 (HSP27) gene mutation in Chinese patients with Charcot-Marie-Tooth disease (CMT). METHODS: DNA samples from 114 CMT probands were screened for mutations in HSP27 gene by polymerase chain reaction and direct sequencing, and haplotype analysis was further carried out on the mutation detected families. RESULTS: One missense mutation C379T was detected in 4 autosomal dominant CMT2 families. Haplotype analysis indicated that the 4 families probably had a common ancestor. CONCLUSION: To the authors' knowledge, this is the first report of HSP27 gene mutation in Chinese patients with CMT, but it may be not common(0.90%). The C379T mutation in HSP27 gene also causes CMT2 except for distal hereditary motor neuropathy, thus providing further evidence that even the same mutation in the same gene may lead to distinct phenotypes.

Asian People↗