醋酸铅致hprt基因位点突变的实验研究

目的了解醋酸铅对hprt基因位点的影响,以寻找铅致机体损伤的早期指标。方法采用多核细胞法,研究醋酸铅体外对人外周血淋巴细胞及体内对大鼠血淋巴细胞hprt基因位点的影响及突变频率。结果醋酸铅在体外实验中可诱发淋巴细胞hprt基因位点突变,且突变频率随着染毒浓度的增加而升高,突变频率Y(×10-3)与醋酸铅的浓度C(mg/kg或mg/ml)之间存在剂量-效应关系。体内实验中则是在一定范围内表现出突变频率随染毒剂量增加而增加。结论在该实验条件下,醋酸铅在体内外实验中均对血淋巴细胞hprt基因位点突变频率有影响,hprt基因突变频率检测有望作为铅接触的早期效应标志物,用于接触人群的流行病学调查中。     

Measurement of mutant frequency in T-cell receptor (TCR) gene by flow cytometry after X-irradiation on EL-4 mice lymphoma cells

It is well known that somatic mutations are induced by ionizing irradiation. We have previously reported the measurement of mutant frequency (MF) on the T-cell receptor (TCR) gene in mouse T-lymphocytes after irradiation by flow cytometry. In this study, we developed an in vitro system using murine EL-4 lymphoma cells and observed frequency of cells defective in TCR gene expression after exposure to ionizing irradiation. EL-4 cells were stained with fluorescein-labeled anti-CD4 and phycoerythrin-labeled anti-CD3 antibodies. They were analyzed with a flow cytometer to detect mutant EL-4 cells lacking surface expression of TCR/CD3 complexes which showed CD3-, CD4+ due to a somatic mutation at the TCR genes. Mutant cells could be observed at 2 days after 3 Gy irradiation. MF of EL-4 cells was 6.7x10(-4) for 0 Gy and the value increased to the maximum level of 39x10(-4) between 4 and 8 days after 3 Gy irradiation and these data were found to be best fitted by a linear-quadratic dose-response model. After the peak value the TCR MF gradually decreased with a half-life of approximately 3.2 days. We also examined the hprt mutant frequencies at seven days after irradiation and the cytokinesis-blocked micronucleus frequency at 20 hrs after irradiation. The frequencies of hprt mutation and micronuclei were found to be best fitted by a linear-quadratic dose-response model and a linear dose-response model, respectively. The method to detect mutation on TCR gene is quick and easy in comparison with other methods and is considered useful for the mutagenicity test.     

Lesch-Nyhan综合征1例的基因突变分析

目的 探讨1例Lesch-Nyhan综合征病儿的临床表现及遗传学特点。方法 回顾性分析2021年7月武汉科技大学附属天佑医院收治的1例以尿酸异常升高为主要表现的Lesch-Nyhan综合征病儿临床资料,结合其基因组测序结果,分析其遗传学特点。结果 该病儿早期临床症状不典型,基因证实为Lesch-Nyhan综合征,突变位点为新发突变位点。结论 该例LeschNyhan综合征病儿的基因突变位点为新发突变位点,目前尚未见文献报道。     

丙烯酰胺诱导人白血病HL-60和NB_4细胞hprt基因的分子突变谱

为了研究丙烯酰胺的遗传毒理作用 ,采用单细胞克隆培养 ,双向筛选计数 ,多重PCR扩增与电泳分析 ,研究了诱导HL 6 0和NB4 两种细胞hprt基因突变率及分子突变谱 .发现只有丙烯酰胺高剂量组 (70 0mg·L- 1)才对两种细胞有明确的致hprt基因突变作用 ;丙烯酰胺诱发突变主要由点突变和缺失两部分组成 (40 .0 %～ 6 6 .7% ,33.3%～ 6 0 .0 % ) ,而自发突变几乎全是点突变 (90 .0 %以上 ) ,两种细胞均无全基因缺失型 ;缺失突变可以发生于hprt基因上的每个外显子 (除外显子 7/ 8以外 ) ,较集中于基因的 3′末端 ,且诱发突变中绝大多数是点突变与单个外显子缺失 (93.3% ,86 .1% ) ,两种细胞情况类似 .结果提示 ,丙烯酰胺具有较弱的诱导hprt基因突变的作用 ,且诱发突变与自发突变的分子图谱不一样 ,这可能与其作用机理有关     

宁波地区结核分枝杆菌基因突变位点确证及与异烟肼、利福平耐药关系研究

【摘要】： 目的 阐明宁波地区初治肺结核患者结核分枝杆菌rpoB、katG、inhA基因突变特征,深入分析基因突变与异烟肼（INH）、利福平(RFP)耐药关系,为临床抗结核治疗提供科学依据。方法 采用1%比例法对889例结核分枝杆菌临床分离株进行药敏检测,对其中的耐药菌株提取DNA,PCR扩增,对耐药菌株katG、inhA、rpoB基因测序,分析三种基因特征及基因突变与单耐药、耐多药关联性。结果 889例结核分枝杆菌临床分离株中,发现39例耐药结核分枝杆菌,其中单耐药24例,单耐药率2.70%,15例耐多药,耐多药率1.69%。39例耐药菌株中,有14例耐多药菌株发生rpoB、katG基因错义突变,突变率93.33%,3例发生inhA基因错义突变,突变率20.00%,rpoB基因450位点（ser450leu）突变率53.33%,katG基因315位点（ser315thr）突变率86.67%,463位点（arg463leu）突变率93.33%。3例单耐利福平菌株rpoB基因在463位点（arg463leu）全部发生错义突变。21例单耐异烟肼菌株中有19例发生katG基因错义突变,突变率90.47%,315位点（ser315thr）突变率63.16%,463位点（arg463leu）突变率78.95%;9例发生inhA基因错义突变,突变率42.86%,145位点（val145gly）突变率77.77%;5例发生rpoB基因错义突变,突变率23.81%,位点较分散。另外,39例耐药菌株中,有10例发生rpoB、katG、inhA多基因联合突变,突变率25.64%。结论 rpoB、katG、inhA基因突变与初治肺结核患者耐药密切相关,上述三种基因在450（ser450leu）、315（ser315thr）、463（arg463leu）、145（val145gly）等位点突变是本地区结核分枝杆菌对异烟肼、利福平耐药的重要机制之一。     

非小细胞肺癌EGFR基因胚系突变研究现状

EGFR（表皮生长因子受体）信号通路在非小细胞肺癌（Non small cell lung cancer NSCLC）的发生和发展中起重要的作用,激活后可促进肿瘤细胞的增生、分化、转移、血管生成及凋亡抑制。大约80%的NSCLC存在EGFR的表达、过度表达和突变,因此EGFR是治疗NSCLC的理想靶点。通过检测EGFR的表达和突变状态能预测EGFR酪氨酸激酶抑制剂（EGFR-TKI）治疗的疗效,成为指导晚期NSCLC临床靶向治疗的重要生物标志物。EGFR基因的体细胞突变（somatic mutation）研究为肺癌的个体化治疗提供有力的支持,但EGFR基因胚系突变（germline mutation）的研究却开展的较少。本文在于总结国际上关于EGFR基因18～21号外显子的胚系突变的研究。     

V79—6TG^s和V79—6TG^r细胞对诱变剂敏感性比较

为探讨细胞先前发生的突变对诱变剂敏感性的影响，在Ｖ７９细胞基因突变试验中用６－ＴＧ选择了抗６－ＴＧ的突变细胞。应用ＳＣＥ和微核试验比较了Ｖ７９－６ＴＧｓ（野生型细胞）和Ｖ７９－６ＴＧｒ（突变型细胞）对ＭＮＮＧ，ＭＭＳ和ＥＭＳ的敏感性。结果表明，Ｖ７９－６ＴＧｒ细胞对上述３种烷化剂较Ｖ７９－６ＴＧｓ敏感。结论指出，Ｖ７９－６ＴＧｒ细胞对诱变剂的敏感性增高可能与先前发生的ｈｐｒｔ基因突变有关。     

Relationship between the mutation of G239V point in SLC17A3 gene and primary gout

Objective To explore the relationship between the mutation of G239V point in SLC 17A3 gene and primary gout.Methods The single nucleotide polymorphism (SNP) of gene in 530 sporadic patients with primar...     

Activated T lymphocytes in Type 2 diabetes: implications from in vitro studies

The number of subjects with Type 2 diabetes (DM2) has risen significantly in the last ten years. Obtaining sufficient human tissue to study this disease process as well as many other diseases is generally difficult. T lymphocytes offer a unique opportunity for these studies. Although resting human peripheral T-lymphocytes are devoid of insulin receptors, these receptors emerge upon activation of cells by specific antigens or mitogens. Concomitant with the insulin receptors, two other growth factor receptors (IGF-1 and IL-2) also emerge on the T lymphocyte cell surface along with intracellular signal transduction mechanisms and insulin degrading enzyme (IDE). After binding to its receptor, insulin has been shown to exert its classical effects on carbohydrate metabolism in the stimulated T- cell; thereby, validating the use of activated T-lymphocytes for studying the pathogenesis of metabolic and immune disorders and the mechanism(s) by which insulin exerts its effects. In activated T-lymphocytes, insulin stimulates glucose uptake, glucose oxidation, pyruvate flux and pyruvate dehydrogenase activity, amino acid transport, lipid metabolism and protein synthesis. Through its ability to enhance nutrient uptake and raise the levels of intermediary cellular metabolism, insulin is believed to maintain the allo-activated state of lymphocytes, enhance T-Lymphocyte responsiveness, and support or possibly promote the actions of immuno-derived regulatory growth and differential factors. Since insulin enhances energy requirements and protein synthesis necessary for appropriate T-cell functions, defects in insulin action may lead to inappropriate immunoresponses in various metabolic states such as in diabetes. Studies from our lab have found insulin binding, processing, and responsiveness in phytohemagglutinin(PHA)-activated T-cells are reflective of the donor's glycemic status and ambient insulin levels in subjects with Type 1 and Type 2 diabetes (DM2) and other insulin resistant states. Our studies show that patients with diabetic ketoacidosis and hyperglycemia have increased proinflammatory cytokines and activated CD4+ and CD8+ T lymphocytes. The diabetic state, where effective insulin concentrations are low and both glucose and free fatty acids are high, provides an environment of oxidative stress and activation of the inflammatory pathways. The mechanisms underlying insulin action, in general, or in the CD4+ and CD8+ T-lymphocytes, in particular, have not been clearly elucidated. Due to the accessibility of obtaining these cells from patients, activated T-lymphocytes offer the potential of studying diabetes and other disease in human subjects.     

Identification and functional analysis of two rare allelic variants of the thiopurine S-methyltransferase gene, TPMT*16 and TPMT*19

Human thiopurine S-methyltransferase (TPMT) catalyses the S-methylation of thiopurine drugs. TPMT is genetically polymorphic and is associated with large interindividual variations in thiopurine drug toxicity and therapeutic efficacy. During routine genotyping of patients with Crohn's disease, one novel missense mutation, 365A>C (TPMT*19, Lys(122)Thr), and a recently described missense mutation, 488G>A (TPMT*16, Arg(163)His), were identified in a Caucasian and a Moroccan patient, respectively. Using a heterologous yeast expression system, kinetic parameters (K(m) and V(max)) of the two variants with respect to 6-thioguanine S-methylation were determined and compared with those obtained with the wild-type enzyme. The Lys(122)Thr exchange did not significantly decrease the intrinsic clearance value (V(max)/K(m)) of the variant enzyme. In contrast, the Arg(163)His substitution significantly decreased the intrinsic clearance value by three-fold. The Arg(163) is located in a highly conserved region of the human TPMT protein and, as such, the Arg(163)His substitution is expected to result in a marked reduction of enzyme activity, as confirmed by the in vitro data. Phenotyping by measurement of red blood cell TPMT activity indicated that the patient heterozygous for the Lys(122)Thr mutation had normal TPMT activity, whereas the patient heterozygous for the Arg(163)His mutation was an intermediate methylator, which demonstrated a positive correlation between TPMT phenotyping and the in vitro data. The identification of a novel non-functional allele of the TPMT gene improves our knowledge of the genetic basis of interindividual variability in TPMT activity. These data further enhance the efficiency of genotyping methods to predict patients at risk of an inadequate response to thiopurine therapy.     

A metabolically competent human cell line expressing five cDNAs encoding procarcinogen-activating enzymes: application to mutagenicity testing.

A human B-lymphoblastoid cell line, designated MCL-5, constitutively expressing human cytochrome P-450 CYP1A1 and also expressing five transfected human cDNAs encoding drug-metabolizing enzymes, has been developed. cDNAs encoding CYP1A2, CYP2A6, and microsomal epoxide hydrolase (mEH) were introduced by using a vector conferring hygromycin B resistance, and cDNAs encoding CYP2E1 and CYP3A4 were introduced by using a vector conferring resistance to 1-histidinol. MCL-5 cells stably expressed all five cDNAs and the native CYP1A1 as determined by measurement of form-specific enzyme activity levels. The mutagenicity of seven model procarcinogens to MCL-5 cells was examined at the hypoxanthine guanine phosphoribosyltransferase (hprt) and thymidine kinase (tk) loci. Exposure to benzo[a]pyrene (BP), 3-methylcholanthrene (3MC), N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), aflatoxin B1, (AFB1), 2-(acetylamino)fluorene (AAF), or benzidine (BZD) induced a statistically significant increase in mutant frequency. Linear interpolation of the concentration of procarcinogen necessary to produce a doubling of the mutant fraction at the hprt locus in MCL-5 cells and the parent AHH-1 cell line revealed that, for each of the chemicals examined, except BZD, MCL-5 cells were significantly more sensitive than the parent AHH-1 cells. The increase in sensitivity to mutagenicity ranged from 3-fold for AAF to greater than 40,000-fold for NDMA. MCL-5 cells have great potential as a screening system for the analysis of human procarcinogen/promutagen activation.     

Pharmacogenetics of human androgens and prostatic diseases

Prostate cancer (PCa) and benign prostatic hypertrophy (BPH) are two common and growing public health problems in the Western world. We review here the recent biochemical and pharmacogenetic literature related to these two prostatic disorders. We focus first on constitutional ('germline') single nucleotide polymorphism (SNPs) at the steroid 5 alpha-reductase (SRD5A2) locus, which encodes the human prostatic (or Type II) steroid 5 alpha-reductase enzyme. The investigations reviewed point to several uses of personalised medicine at the SRD5A2 locus. In addition, we report on recent identification of somatic pharmacogenetic alterations at the androgen receptor (AR) locus, which encodes the human androgen receptor, suggesting that this also may be a fruitful field of investigation, with important clinical applications. Pharmacogenomic investigation of constitutional and somatic DNA changes in human genes predisposing to cancer may lead to significant advances in chemoprevention, presymptomatic diagnosis and improved treatment of PCa.     

The absence of interaction between drug metabolizing enzyme genotypes and maternal lifestyle factors on glycophorin A somatic mutation frequency levels in newborns

Prenatal exposure to carcinogens results in newborn DNA damage which in turn is associated with impaired health conditions in both childhood and adulthood. The present study aimed to evaluate whether phase I and II biotransformation enzyme genetic polymorphisms in combination with environmental exposures during pregnancy result in elevated levels of newborn DNA damage. Maternal peripheral and umbilical cord blood samples from 406 mother/newborn pairs were genotyped for a panel of phase I/II metabolic enzymes (CYP1A1, CYP2E1, GSTM1, GSTT1 and NAT2) responsible for the metabolism of tobacco and lifestyle-related mutagens and carcinogens. DNA damage was measured by somatic cell mutation frequency at the glycophorin A (GPA) locus in newborns. No association with elevated somatic cell mutation frequency was observed between the combination of maternal/newborn genotypes and cigarette smoke or lifestyle exposures. The observed variation in newborn GPA frequency might be due to either environmental factors not assessed in this study or inter-individual differences in alternative metabolic or DNA repair pathways.     

Biochemical and pharmacogenetic dissection of human steroid 5 alpha-reductase type II

Human prostatic steroid 5alpha-reductase, encoded by the SRD5A2 gene on chromosome band 2p23, catalyses the irreversible conversion of testosterone to dihydrotestosterone (DHT), the most active androgen in the prostate, with NADPH as its cofactor. This enzyme has never been purified but a number of competitive inhibitors have been developed for this enzyme since increased steroid 5alpha-reductase activity may cause benign prostatic hypertrophy and prostate cancer. We report here the detailed biochemical and pharmacogenetic dissection of the human enzyme by analysing 10 missense substitutions and three double mutants which are all naturally found in humans. Nine of these 13 mutants reduce activity (measured as Vmax) by 20% or more, three increase steroid 5alpha-reductase by more than 15% and one results in essentially unaltered kinetic properties suggesting that it is a truly neutral ('polymorphic') amino acid substitution. Substantial pharmacogenetic variation among the mutants was also observed when three competitive inhibitors, finasteride, GG745 (dutasteride) and PNU157706, were investigated. Our studies not only define the substrate and cofactor binding sites of human steroid 5alpha-reductase, but also have significant consequences for the pharmacological usage of steroid 5alpha-reductase inhibitors in human patients treated for prostatic conditions.     

柱前衍生反相高效液相法定量检测烧伤患者血清氨基酸的含量

目的：应用柱前衍生的高效液相色谱法,定量测定重症烧伤病人血清中氨基酸的含量。方法：以2、4－二硝基氟苯（DNFB）为衍生剂,用反相高效液相色谱法在360nm处测定血清中17种游离氨基酸的含量。并以外标法进行计算。结果：在27分内分出17种氨基酸,分离完全。DNFB省生的氨基酸其回收率在97.32％－104.26%之间,变异系数为1.5%-4.8%。在重症务病人组,血清中多种氨基酸含量发生显著改变。结论：本法操作简便,快速准确,重复性好,适用于临床检测的需要。     

Prediction of response of mutated alpha-galactosidase A to a pharmacological chaperone

OBJECTIVE: To examine the relationship between types and locations of mutations of the enzyme alpha-galactosidase (Gal) A in Fabry disease and the response to the pharmacological chaperone 1-deoxygalactonojirimycin (DGJ). METHODS: T cells grown from normal individuals or from patients with Fabry disease were tested for response to treatment with DGJ by increased activity of alpha-Gal A. RESULTS: Cells from normal controls responded with a 28% increase in alpha-Gal A activity, whereas response in Fabry individuals was mutation dependent ranging from no increase to fully normal activity. Nine truncation mutations (all nonresponsive) and 31 missense mutations were tested. Three groups of missense mutations were categorized: responders with activity more than 25% of normal, nonresponders, with less than 7% and an intermediate response group. In normal cells and in responders an increase in the mature lysosomal form of alpha-Gal A was observed after DGJ treatment. Nonresponders showed little or no protein with or without DGJ. The intermediate response group showed an increase in band intensity but incomplete processing of the enzyme to the mature form. CONCLUSION: Mapping the missense mutations to the structure of alpha-Gal A identified several factors that may influence response. Mutations in regions that are not in alpha-helix or beta-sheets, neither involved in disulfide bonds nor with an identified functional or structural role were more likely to respond. Predictability is, however, not precise and testing of each mutation for response to pharmacological chaperone therapy is necessary for Fabry disease and related lysosomal storage disorders.     

Somatic mutations in epidermal growth factor receptor underlying complete responsiveness to gefitinib in a Taiwanese female patient with metastatic adenocarcinoma of lung

A 61-year-old never-smoker female suffered from adenocarcinoma of the lung with chest wall invasion and peri-adrenal lymph node metastases. After palliative resection of all clinically detectable primary and metastatic adenocarcinoma, she received cisplatin and gemcitabine combination chemotherapy for a total of 3 cycles. New metastatic lesions were found in spleen and para-aortic lymph nodes. Her tumor tissue was subjected to mutation analysis for epidermal growth factor receptor (EGFR) and had been shown to have a T-->G missense mutation in nucleotide 2819 of EGFR full-length cDNA (accession no. NM_005228.3), within exon 21 of the EGFR gene, resulting in amino acid substitutions from leucine to arginine at codon 858 (L858R) as expected. She received oral gefitinib 250 mg/day after mutation analysis. She had a very good tumor response with more than 90% tumor reduction shown by abdominal computed tomographic scan, normalization of previously elevated carcinoembryonic antigen level, and complete resolution of previous uptake signals in spleen and para-aortic lymph nodes shown by positron emission tomographic scan. She has been kept in clinical complete remission for 11+ months after the initiation of gefitinib treatment. Our patient supports the proposition that somatic mutation L858R in exon 21 of the EGFR gene accounts for complete responsiveness to gefitinib in a Taiwanese female patient with metastatic adenocarcinoma of lung.     

Somatic Mutation Detection in Human Biomonitoring

Abstract: Somatic cell gene mutation arising in vivo may be considered to be a biomarker for genotoxicity. Assays detecting mutations of the haemoglobin and glycophorin A genes in red blood cells and of the hypoxanthine-guanine phosphoribos-yltransferase and human leucocyle antigenes in T-lymphocytes are available in humans. This MiniReview describes these assays and their application to studies of individuals exposed to genotoxic agents. Moreover, with the implementation of techniques of molecular biology mutation spectra can now be defined in addition to the quantitation of in vivo mutant frequencies. We describe current screening methods for unknown mutations, including the denaturing gradient gel electrophoresis, single strand conformation polymorphism analysis, heteroduplex analysis, chemical modification techniques and enzymatic cleavage methods. The advantage of mutation detection as a biomarker is that it integrates exposure and sensitivity in one measurement. With the analysis of mutation spectra it may thus be possible to identify the causative genotoxic agent.     

Treatment of fabry disease: current and emerging strategies

Fabry disease is an X-linked lysosomal storage disorder (LSD) due to deficiency of the enzyme α-galactosidase A (GLA). Absent or reduced enzyme activity leads to impaired catabolism of neutral glycosphingolipids, particularly globotriaosylceramide (Gb3), resulting in intracellular deposition of such lipids. Clinical manifestations in hemizygote males include angiokeratoma, hypohydrosis, acroparesthesia, abdominal pain, proteinuria, renal insufficiency, left ventricular hypertrophy and cerebrovascular accidents. Heterozygote women may present with mild to severe signs and symptoms. Since year 2001, enzyme replacement therapy (ERT) is the only specific treatment for Fabry disease. The beneficial effect of ERT on different organs/systems has been extensively evaluated, and an improvement in renal function, cardiac mass and quality of life has been reported. Different treatment approaches are currently on development. One of them implies the use of the active-site-specific chaperone 1-deoxygalactonojirimycin that acts facilitating folding of mutant GLA in the endoplasmic reticulum and increasing its lysosomal residual activity. Reduction of Gb3 deposits has been shown in lymphoblasts from Fabry patients with missense mutations and transgenic mouse model expressing a missense mutation GLA. Gene therapy has been also developed as a potential option for treatment of Fabry disease. This review will discuss these novel therapeutic options along with their advantages and limitations.     

Human NADPH-P450 oxidoreductase: complementary DNA cloning, sequence and vaccinia virus-mediated expression and localization of the CYPOR gene to chromosome 7

The cDNA containing the full coding sequence of human NADPH-P450 oxidoreductase was isolated and completely sequenced. The cDNA contained 2398 base pairs, including 9 and 358 base pairs of 5' and 3' noncoding sequences, respectively. The human NADPH-P450 oxidoreductase protein deduced from the cDNA has 677 amino acids, with a calculated molecular weight of 76,656. The cDNA nucleotide and deduced amino acid sequences displayed 83 and 92% similarities, respectively, with those of the rat NADPH-P450 oxidoreductase. By use of somatic cell hybrids, the NADPH-P450 oxidoreductase gene was regionally localized to human chromosome 7 (7p15-q35). The levels of NADPH-P450 oxidoreductase protein and mRNA were analyzed in 13 human liver specimens and less than 3-fold variation was found among the different livers. The NADPH-P450 oxidoreductase cDNA was inserted into vaccinia virus and expressed in cell culture. The cDNA-expressed enzyme was active in reducing the electron acceptor cytochrome c. In addition, the NADPH-P450 oxidoreductase stimulated the enzymatic activity of vaccinia virus-expressed human P3(450) when both recombinant viruses were used to coinfect human cells in culture. An approximate equal mole level of NADPH-P450 oxidoreductase and P3(450) was required to achieve maximal activity for both ethoxycoumarin O-deethylase and aryl hydrocarbon hydroxylase.