Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

PCR amplification has enabled a variety of studies to be performed on the murine dystrophin transcripts. Figure 7.12 displays a summary of the features of the murine dystrophin mRNA that have been described in this article. The location of the mutation in the original mdx mouse is indicated, as are the different spliced forms of the dystrophin transcript. Also shown are the location of various PCR primer binding sites that were used to deduce the alternative splicing pattern of the gene. It is likely that conventional cloning efforts aimed at identifying the variety of dystrophin spliced forms would have taken years to perform, particularly since several of the isoforms are expressed at levels significantly below the estimated 0.02% of total mRNA that dystrophin represents in skeletal muscle (Hoffman et al., 1987a, b). Amplification of dystrophin mRNA simplifies scanning methods for the identification of DNA sequence variations. Attempts to re-isolate and sequence the 14 kb cDNA to determine the mutation in separate strains of mdx mice are not likely to be time or cost effective. PCR enables these types of questions to be answered in a relatively short period of time, and similar types of analyses can be applied to human DMD tissues. Knowledge of the transcript diversity displayed by the dystrophin gene will enable the role of these separate isoforms to be addressed. Despite considerable effort by a variety of laboratories over the last five years, the precise functional role played by dystrophin remains unclear, and it can only be assumed that the separate isoforms act to modulate the functional role of dystrophin in separate tissues or in response to differing physiological states. PCR amplification of the dystrophin isoforms has enabled the variable regions of the transcript to be subcloned (Bies et al., 1992). These clones have been used to reintroduce the variable regions into full-length mini-gene expression vectors, which are currently being tested for functional activity through the generation of transgenic mdx mice. The transgenic mice can be easily identified through the PCR-ASO assays described in this article, and the reverse transcriptase PCR assays will enable a detailed analysis of the expression pattern of the introduced mini-genes. It is hoped that such analyses will further attempts to determine the feasibility of using gene therapy as a treatment for DMD/BMD.
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PMID:PCR analysis of muscular dystrophy in mdx mice. 811 39

Duchenne and Becker muscular dystrophies (DMD and BMD) are allelic X-linked disorders arising from mutations in the (2.4 Mb) dystrophin gene at Xp21. We have applied the reverse transcriptase-polymerase chain reaction (RT-PCR) to identify a larger than normal dystrophin mRNA from a male with Duchenne muscular dystrophy and his younger affected brother. The increased size of the dystrophin mRNA was due to a splice-site mutation at the exon 26:intron 26 junction where a T to G substitution prevented normal RNA processing. A cryptic splice-site, downstream of the mutation, was activated during processing, resulting in the inclusion of 117 bases of intron 26. This insertion introduced an in-frame stop codon into the mature dystrophin mRNA. An allele-specific test was developed to identify the mutation and was applied to this family. Interestingly, the mother of the two affected boys did not carry the mutation, as determined by allele-specific amplification and direct DNA sequence analysis, indicating gonadal mosaicism. Her eldest daughter, designated as a carrier based upon conventional testing and haplotype analysis, also did not carry the family mutation. Initial haplotyping of the family appeared to be straightforward with gonadal mosaicism becoming evident only after allele-specific analysis. The application of linked markers to identify the disease allele for conventional genetic counselling would have been erroneous in this family and highlights the diagnostic power of precise identification of the disease-causing mutation.
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PMID:Identification of a point mutation and germinal mosaicism in a Duchenne muscular dystrophy family. 819 94

Acute promyelocytic leukaemia (APL) is characterized by the t(15;17)(q22;q21) leading to the formation of PML-RARalpha and RARalpha-PML fusion genes which provide suitable targets for the assessment of minimal residual disease (MRD). Studies have focused upon detection of PML-RARalpha because, although assays for RARalpha-PML transcripts are more sensitive, they are not applicable to 25% of cases. Among patients receiving standard therapy (ATRA and anthracycline-based chemotherapy), qualitative assays using a nested reverse transcriptase-polymerase chain reaction (RT-PCR), which typically achieve sensitivities of 1 in 10(4), have been found to provide independent prognostic information suitable for directing an approach to treatment. Detection of PML-RARalpha at the end of consolidation, or subsequent recurrence of PCR positivity, heralds relapse, which may, however, be averted by additional therapy leading to improvements in survival for this "high-risk" subgroup of patients. MRD analysis has also proved of value in predicting response to autologous transplant procedures undertaken in second complete remission and in directing the need for additional therapy in the post-transplantation setting. Overall, these studies undertaken within the context of a relatively homogeneous disease entity confirm that MRD monitoring provides independent prognostic information, serving as a valuable model for improving treatment strategy in other molecularly defined subsets of acute myeloid leukaemia (AML). Nevertheless, conventional nested RT-PCR assays fail to detect residual disease in a significant proportion of patients who ultimately relapse, which may be a reflection of RNA quality and/or assay sensitivity. Therefore, it is hoped that "real-time" quantitative RT-PCR technology (RQ-PCR) which permits quantification of fusion gene transcripts in relation to endogenous control genes will be even more predictive of outcome and achieve greater standardization of MRD detection in the context of large-scale clinical trials.
Best Pract Res Clin Haematol 2002 Mar
PMID:The significance of minimal residual disease in patients with t(15;17). 1198 21

In many ways, chronic myeloid leukaemia (CML) serves as a paradigm for the utility of molecular methods in the diagnosis of malignancy or for monitoring the response of the patient to therapy. The Philadelphia (Ph) translocation provides an elegant example of how cytogenetic findings provided the starting point for understanding the genetic mechanisms involved in leukaemogenesis. The degree of reduction in tumour load after therapy is an important prognostic factor for CML patients. Several approaches have been introduced that can specifically detect the Ph translocation or its products; these approaches include fluorescent in situ hybridization, Southern blotting, western blotting and reverse transcriptase polymerase chain reaction (RT-PCR). Because non-quantitative RT-PCR analysis after therapy gives only limited information, quantitative or semiquantitative RT-PCR assays have been developed that enable the kinetics of residual BCR-ABL transcripts to be monitored over time in patients after allogeneic stem cell transplantation, interferon-alpha, or STI571 therapy.
Best Pract Res Clin Haematol 2002 Mar
PMID:Minimal residual disease in chronic myeloid leukaemia patients. 1198 22

Acute promyelocytic leukaemia (APL) is characterized by a unique genetic marker in virtually 100% of cases, i.e. the PML/RARalpha fusion gene which is readily amplified by the reverse transcriptase-polymerase chain reaction (RT-PCR) method. Several international groups reported the prognostic significance of minimal residual disease (MRD) assessment in APL, indicating that sequential PCR analysis should be used as a guide to therapy. In fact, such evaluation offers the possibility of identifying, after front-line treatment, either patients requiring additional therapy or patients at low risk who are presumably cured and who may be spared unnecessary toxicity. In this view, the terms molecular remission and molecular relapse are now widely employed to define a more advanced therapeutic objective and a condition necessitating anticipated salvage, respectively. The introduction of quantitative PCR through automated technologies is likely to further improve standardization of the method and comparison of results obtained in the context of large clinical trials.
Best Pract Res Clin Haematol 2003 Sep
PMID:The importance of molecular monitoring in acute promyelocytic leukaemia. 1293 66

Evidence is accruing that environmental exposures during critical periods of early development induce persisting changes in skeletal growth, and alter fracture risk in later life. We have previously demonstrated that placental calcium transport, partly determined by maternal 25-(OH) vitamin D status, may underlie this phenomenon. However, the precise relationship between expression of calcium transport proteins in the human placenta, and neonatal bone mineral accrual in the offspring, remains unknown. Tissue samples from 70 human placentae were fast frozen in liquid nitrogen and stored at -70 degrees C. A quantitative real time reverse transcriptase polymerase chain reaction was used to measure the mRNA expression of PMCA isoforms 1-4, using beta-actin as a control gene. Neonatal whole body bone area, mineral content and areal density (BA, BMC, BMD) were measured within 2 weeks of birth using DXA. PMCA3 mRNA expression predicted BA (r=0.28, p=0.02), BMC (r=0.25, p=0.04), placental weight (r=0.26, p=0.04) and birth weight (r=0.33, p=0.006) of the neonate. In a multivariate model, the relationship between placental PMCA3 expression and neonatal BMC was independent of maternal height, pre-pregnant fat stores, parity, physical activity, smoking, and calcium intake (p<0.05). Expression of the placental calcium transporter PMCA3 mRNA predicts neonatal whole body bone mineral content. This association may explain, in part, the mechanism whereby a mother's 25(OH)-vitamin D stores influence her offspring's bone mass.
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PMID:Placental calcium transporter (PMCA3) gene expression predicts intrauterine bone mineral accrual. 1733 74

Studies in the past decades have shown that active hepatitis B virus (HBV) replication is the key driver of liver injury and disease progression, and thus sustained viral suppression is of paramount importance in the management of chronic HBV infection. The nucleos(t)ide analogues lamivudine, adefovir, entecavir, telbivudine and tenofovir are potent inhibitors of HBV polymerase/reverse transcriptase activity and are highly effective in the suppression of HBV replication, but rarely eliminate the virus. Long-term therapy is usually required to achieve sustained hepatitis B e antigen seroconversion, HBV DNA suppression, ALT normalization and fibrosis reversal. Maintained long-term therapy has been demonstrated to significantly lower the rate of hepatic decompensation and development of cirrhosis or hepatocellular carcinoma. However, drug resistance is a serious risk on prolonged nucleos(t)ide analogue therapy, and this poses a critical challenge. Prevention and proper management of drug resistance are crucial to ensure long-term success.
Best Pract Res Clin Gastroenterol 2008
PMID:Nucleos(t)ide analogues for hepatitis B virus: strategies for long-term success. 1918 68

Molecular monitoring of chronic myeloid leukaemia (CML) patients by real time quantitative reverse transcriptase PCR (RQ-PCR) is of clinical value, but the use of diverse laboratory protocols and units of measurement make it difficult to compare results between and sometimes within centres. This review explores the intrinsic difficulties in standardising the RQ-PCR analysis, summarises the progress that has been made following the proposal for a new International Scale for BCR-ABL measurement and discusses how further improvements are likely to be made.
Best Pract Res Clin Haematol 2009 Sep
PMID:Standardisation of molecular monitoring for chronic myeloid leukaemia. 1995 86

HIV-associated lipodystrophy is clinically characterized by body fat changes including subcutaneous fat loss (lipoatrophy) with or without truncal fat accumulation (lipohypertrophy). Thymidine nucleoside reverse transcriptase inhibitors, stavudine and to a lesser extent zidovudine, are major contributors for lipoatrophy. Drug factors are not clear for lipohypertrophy. Restoration to health with effective viral suppression and weight gain may be factors playing significant roles in lipohypertrophy. Mitochondrial dysfunction and inflammation in subcutaneous adipose tissue are key factors in the pathogenesis of HIV-associated lipoatrophy. The pathogenesis of lipohypertrophy is less well understood. Switching from thymidine nucleoside reverse transcriptase inhibitors restores subcutaneous fat in patients with HIV-associated lipoatrophy, but improvement is slow and limited. Surgical filling cosmetically improves facial lipoatrophy. Exercise and diet may reduce increased visceral adipose tissue. Liposuction may be useful to remove superficial, localized fat accumuli.
Best Pract Res Clin Endocrinol Metab 2011 Jun
PMID:Disorders of fat partitioning in treated HIV-infection. 2166 36

Identification and characterization of the molecular mechanisms contributing to the high incidence of insulin resistance in HIV infected patients treated with combined antiretroviral therapy remains a critically important goal in the quest to improve the safety of antiretroviral treatment regimens. The use of in vitro model systems together with the investigation of drug-mediated effects on glucose homeostasis in animals and healthy human volunteers has provided important insight into the contribution of individual drugs to insulin resistance and affected cellular pathways. HIV protease inhibitor mediated blockade of glucose transport and nucleoside reverse transcriptase inhibitor mediated mitochondrial toxicity have been well characterized. Together with growing understanding of mediators of insulin resistance in non-HIV metabolic syndrome, additional cellular effects including the induction of endoplasmic reticulum and oxidative stress, altered adipocytokine secretion, and lipotoxicity have been integrated into this developing picture. Further elucidation of these mechanisms provides potential for the continued development of safer antiviral drugs and targeted treatment of insulin resistance in affected patients.
Best Pract Res Clin Endocrinol Metab 2011 Jun
PMID:Molecular mechanisms for insulin resistance in treated HIV-infection. 2166 39


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