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J K Reichardt

Publications and source records attributed to J K Reichardt.

At least 19 recordsLinked to original sources
PubMed2004

YY1 binding within the human HSD3B2 gene intron 1 is required for maximal basal promoter activity: identification of YY1 as the 3beta1-A factor.

The oxidation and isomerization of 3beta-hydroxy-5-ene steroids into keto-4-ene steroids, a pivotal step in the synthesis of all hormonal steroids, is catalyzed by several isoforms of 3beta-hydroxysteroid dehydrogenase. In humans, two highly homologous isoforms exist, type I expressed by the HSD3B1 gene in peripheral tissues, and type II expressed by the HSD3B2 gene in steroidogenic organs. Previously, it was shown that the HSD3B1 gene 3beta1-A element, encompassing 24 nucleotides of intron 1 not perfectly conserved between the two genes and overlapping with a conserved TG box, contributes to maximal basal promoter activity by binding the ubiquitous and unidentified 3beta1-A transcription factor. In this study for the first time we report that similarly, the HSD3B2 gene intron 1 is required for maximal basal promoter activity in reporter gene analyses, as lack of intron 1 results in a 4- to 10-fold reduction in promoter activity. Mutational analysis in gel shift assays revealed that the 3beta1-A factor binds both the HSD3B2 and HSD3B1 gene intron 1 by requiring only seven nucleotides of a conserved segment within the 3beta1-A element. By competition analysis and use of anti-YY1 antibody in both gel shift and Western blot experiments, we identified the 3beta1-A protein as the ubiquitous transcription factor YY1. In addition, we have characterized another similar YY1 binding site differently located with respect to the 3beta1-A element in both genes. Deletion and mutational analysis in transient transfections experiments revealed that contrarily to as previously shown for the HSD3B1 gene, lack of YY1 binding to the type II 3beta1-A element only results in a marginal reduction of basal promoter activity. Instead, YY1 binding to the second site, placed 35 bp downstream from the 3beta1-A element, strongly activates the HSD3B2 gene basal promoter activity, as preventing YY1 binding to this region caused a 50% decrease of basal transcription. Complete abrogation of YY1 binding within type II intron 1 resulted in a gene reporter activity identical to a reporter construct lacking the whole intron 1. These results designate YY1 as the factor responsible for the intron 1-mediated boost of the HSD3B2 gene basal promoter activity. Similarities and dissimilarities between YY1 binding within the HSD3B1 and HSD3B2 gene intron 1 are discussed involving the conserved intron 1 TG box, that suggests different mechanisms are implicated in the YY1-mediated stimulation of these two genes basal promoter activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

A genetic factor for age-related cataract: identification and characterization of a novel galactokinase variant, "Osaka," in Asians.

Galactokinase (GALK) deficiency is an autosomal recessive disorder characterized by hypergalactosemia and cataract formation. Through mass screening of newborn infants, we identified a novel and prevalent GALK variant (designated here as the "Osaka" variant) associated with an A198V mutation in three infants with mild GALK deficiency. GALK activity and the amount of immunoreactive protein in the mutant were both 20% of normal construct in expression analysis. The K(m) values for galactose and ATP-Mg(2+) in erythrocytes with homozygous A198V were similar to those of the healthy adult control subjects. A population study for A198V revealed prevalences of 4.1% in Japanese and 2.8% in Koreans, lower incidence in Taiwanese and Chinese, no incidence in blacks and whites from the United States, and a significantly high frequency (7.8%; P < .023) in Japanese individuals with bilateral cataract. This variant probably originated in Japanese and Korean ancestors and is one of the genetic factors that causes cataract in elderly individuals.

Adult↗
PubMed2001

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.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2001

Multiplex automated primer extension analysis: simultaneous genotyping of several polymorphisms.

Accurate and fast genotyping of single nucleotide polymorphisms (SNPs) is of significant scientific importance for linkage and association studies. We report here an automated fluorescent method we call multiplex automated primer extension analysis (MAPA) that can accurately genotype multiple known SNPs simultaneously. This is achieved by substantially improving a commercially available protocol (SNaPshot). This protocol relies on the extension of a primer that ends one nucleotide 5'of a given SNP with fluorescent dideoxy-NTPs (minisequencing), followed by analysis on an ABI PRisMS 377 Semi-Automated DNA Sequencer Our modification works by multiplexing the initial reaction that produces the DNA template for primer extension and/or multiplexing several primers (corresponding to several SNPs) in the same primer extension reaction. Then, we run each multiplexed reaction on a single gel lane. We demonstrate that MAPA can be used to genotype up to four SNPs simultaneously, even in compound heterozygote samples, with complete accuracy (based on concordance with sequencing results). We also show that primer design, unlike the DNA template purification method, can significantly affect genotyping accuracy, and we suggest useful guidelines for quick optimization.

DNA Primers↗
PubMed2001

Polymorphic markers in the SRD5A2 gene and prostate cancer risk: a population-based case-control study.

It has been suggested that the activity of the steroid 5alpha-reductase type II enzyme (encoded by the SRD5A2 gene) may be associated with prostate cancer risk and that population differences in this enzyme's activity may account for part of the substantial racial/ethnic disparity in prostate cancer risk. To provide etiological clues, we evaluated the relationships of four polymorphic markers in the SRD5A2 gene, specifically, A49T (a substitution of threonine for alanine at codon 49), V89L (a substitution of leucine for valine at codon 89), R227Q (a substitution of glutamine for arginine at codon 227), and a (TA)n dinucleotide repeat, with prostate cancer risk in a population-based case-control study in China, a population with the lowest reported prostate cancer incidence rate in the world. Genotypes of these four markers were determined from genomic DNA of 191 incident cases of prostate cancer and 304 healthy controls using PCR-based assays, and serum androgen levels were measured in relation to these genotypes. All study subjects had the wild-type AA genotype of the A49T marker, and 99% had the RR genotype of the R227Q marker. For the V89L marker, prevalences of the LL, VV, and VL genotypes among controls were 35%, 21%, and 45%, respectively. Compared with men with the VV genotype, those with the LL genotype had a statistically nonsignificant 12% reduced risk (odds ratio = 0.88, 95% confidence interval, 0.53-1.47). In addition, men with the LL genotype had significantly higher serum levels of testosterone and significantly lower serum levels of 5alpha-androstane-3alpha,17beta-diol glucuronide than men with other genotypes. Men heterozygous for the (TA)0 allele of the (TA)n marker had a modest, statistically nonsignificant risk reduction (odds ratio = 0.67; 95% confidence interval, 0.39-1.12) compared with men homozygous for the (TA)0 allele, along with significantly higher serum dihydrotestosterone levels. The observed V89L genotype prevalences and the association between V89L genotypes and serum androgen levels support the hypothesis that genotypes associated with lower levels of 5alpha-reductase activity are more common in low-risk populations. Although we found no statistically significant associations of these SRD5A2 polymorphisms with prostate cancer risk, a small effect of these markers cannot be ruled out because of the rarity of certain marker genotypes. Larger studies are needed to further clarify the role of these markers and to elucidate whether genetic diversity of the SRD5A2 gene, alone or in combination with other susceptibility genes, can help explain the large racial/ethnic differences in prostate cancer risk.

Adult↗
PubMed2000

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.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2000

Evidence for an association between the SRD5A2 (type II steroid 5 alpha-reductase) locus and prostate cancer in Italian patients.

We have investigated the contributions of three polymorphic markers in the SRD5A2 gene to prostate cancer in a group of Italian patients. We have genotyped cases and controls for a polymorphic (TA)n dinucleotide repeat and two functional substitutions, A49T and V89L, substituting respectively alanine with threonine at codon 49, and valine to leucine at codon 89. We found a substantially increased but not significant risk associated with the 49T mutation and a reduction of risk for the V89L substitution. In conclusion, we report on preliminary evidence for both increased and decreased risk associated with separate markers at this locus.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2000

Prostatic steroid 5 alpha-reductase, an androgen metabolic gene.

Prostate cancer risk is highest in African Americans, lowest in Asians, and intermediate in Caucasians and Latinos. The data clearly suggest that environmental and genetic factors are involved. Investigation of the genetic factors suggests that allelic variation in the SRD5A2 gene is partially responsible for the striking racial and ethnic variations in risk.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1999

A reliable PCR amplification method for microdissected tumor cells obtained from paraffin-embedded tissue.

We report a reliable method for PCR (polymerase chain reaction) amplification of genomic DNA from PET. This method uses DNA extraction with the QIAquick kit and amplification with AmpliTaq Gold. Amplification of up to 959 bp from PET was achieved with this combination which exceeds the current reported upper limit of 800 bp. In summary, the gradual activation of the AmpliTaq Gold during thermal cycling allows both for higher-fidelity and higher-throughput PCR amplification from PET. The use of the QIAquick kit for DNA purification of PET is sensitive, reproducible and suitable for management of a high number of samples.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1999

Association of mis-sense substitution in SRD5A2 gene with prostate cancer in African-American and Hispanic men in Los Angeles, USA.

BACKGROUND: Prostate cancer is a very common disease in more-developed countries, but its cause is largely unknown. It is an androgen-dependent cancer, and androgens have been proposed as having a substantial role in predisposition to the disease. Thus, variations in androgen metabolism genes may affect risk of this disease. METHODS: We screened 216 African-American and 172 Hispanic men with prostate cancer, and 261 African-American and 200 Hispanic healthy men (controls), from a large prospective cohort study (the Hawaii-Los Angeles Multiethnic Cohort Study) for a mis-sense substitution in the human prostatic (or type II) steroid 5alpha-reductase (SRD5A2) gene, the product of which controls metabolic activation of testosterone to dihydrotestosterone. This mis-sense substitution results in an alanine residue at codon 49 being replaced with threonine (A49T). We also reconstructed this mutation in the SRD5A2 cDNA, and overexpressed the enzyme in mammalian tissue culture cells. FINDINGS: The A49T aminoacid substitution in the SRD5A2 gene increased the risk of clinically significant disease 7.2-fold in African-American men (95% CI=2.17-27.91; p=0.001) and 3.6-fold in Hispanic men (1.09-12.27; p=0.04). The mutant enzyme had a higher in-vitro Vmax than the normal enzyme (9.9 vs 1.9 nmol min(-1) mg(-1)). INTERPRETATION: The A49T variant of the SRD5A2 gene may be a significant contributor to the incidence of prostate cancer in African-American and Hispanic men in Los Angeles. We estimate that the population attributable risk due to this aminoacid substitution for clinically significant disease is about 8% in both populations. Increased conversion of testosterone to dihydrotestosterone catalysed by this variant steroid 5alpha-reductase enzyme may be the cause of the increased risk.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1999

GEN GEN: the genomic genetic analysis of androgen-metabolic genes and prostate cancer as a paradigm for the dissection of complex phenotypes.

Prostate cancer will be diagnosed in about 179,300 men in the US in 1999 alone. Some 37,000 individuals die of this disease annually. Prostate cancer is characterized by a substantial racial/ethnic variation in risk: highest in African-American men, lowest in Asian men and intermediate in Caucasian and Latino men. We set out to investigate as our central hypothesis that genetic variants of genes involved in androgen metabolism by themselves and in combination significantly contribute to prostate cancer progression and its racial/ethnic variation. Specifically, we examined the hypothesis that DNA sequence (allelic) variations in the type II (or prostatic) steroid 5alpha-reductase (SRD5A2) gene contribute substantially to the risk and progression of prostate cancer particularly across racial/ethnic lines. The "candidate gene", SRD5A2, was chosen because the reaction product [i.e. dihydrotestosterone (DHT)] of the enzyme encoded by this gene modulates directly cell division in the prostate. DHT binds to the androgen receptor (AR) and the DHT-AR complex leads to the transactivation of a variety of genes which ultimately modulates cell division in the prostate. Epidemiologic evidence suggests that variation in DHT levels play an important role in risk of prostate cancer. Thus, steroid 5alpha-reductase activity encoded by SRD5A2 variant alleles may be important in regulating intraprostatic DHT steady state levels by controlling its biosynthesis. A second candidate gene, the type II 3beta-hydroxysteroid dehydrogenase (HSD3B2) gene, encodes the enzyme that initiates the metabolic inactivation of testosterone (T) to DHT. We have identified allelic variants in this gene as well. Here I review our strategy for identifying candidate genes for prostate cancer, a multifactorial disease. I summarize the significant findings, particularly of allelic variants in the HSD3B2 and SRD5A2 genes and discuss how they by themselves, in combination and through interactions with the environment may play a role in prostate cancer predisposition and its progression. Our approach, a multidisciplinary genomic genetic (GEN GEN) attack on the problem, may be useful in the analysis of other complex phenotypes as well.

3-Hydroxysteroid Dehydrogenases↗
PubMed1999

Identification of mutations in the galactose-1-phosphate uridyltransferase (GALT) gene in 16 Turkish patients with galactosemia, including a novel mutation of F294Y. Mutation in brief no. 235. Online.

Classical galactosemia caused by deficiency of galactose-1-phosphate uridyltransferase (GALT) is a severe autosomal recessive disorder. We report here molecular analysis of 16 unrelated Turkish galactosemia index cases without GALT activity. Almost 84% of all mutant alleles were identified in this study. The most common molecular defect observed in the Turkish population was Q188R (replacement of glutamine-188 by arginine) (57%). In order to facilitate the determination of unknown mutations in the entire coding region of GALT, we established an approach based on GALT cDNA synthesis and direct sequencing. We have identified one novel candidate galactosemia mutation, a T-to-A transversion at the codon 294 (F294Y) in exon 9 in addition to previously reported three missense (M142K K285N, A320T), one stop codon (E340X), and one silent (L218L) mutations in galactosemia patients which reflect considerable genetic heterogeneity in the Turkish population.

Alleles↗
PubMed1999

Androgen metabolism and prostate cancer: establishing a model of genetic susceptibility.

The prostate is an androgen-regulated organ, which has led to longstanding interest in the role of androgens in prostate carcinogenesis. Although evidence of a hormonal etiology for prostate cancer is strong, it is almost entirely circumstantial. Much of the problem in proving a causal relationship relates to the continued difficulties in reliably measuring human tissue-specific exposure to endogenous steroid hormones. The international and racial-ethnic variations in prostate cancer incidence, combined with the effects of migration on risk patterns, have suggested that genetic factors play a central role in determining prostate cancer risk. We are developing a polygenic model of prostate carcinogenesis, focused around a series of genes involved in androgen biosynthesis, transport and metabolism. We have begun to develop this model by utilizing sequence variants to study how polymorphic markers in two genes (SRD5A2 and AR) are related to prostate cancer risk within and between racial-ethnic groups. We are now collaborating with the Whitehead Institute/MIT, Center for Genome Research, to screen for single nucleotide polymorphisms in additional genes relevant to the androgen pathway and prostate cell growth. The model when fully developed can potentially provide a basis for targeting populations for screening interventions and for implementing primary preventive strategies.

Androgens↗
PubMed1999

Somatic mutations at the SRD5A2 locus encoding prostatic steroid 5alpha-reductase during prostate cancer progression.

Prostate cancer is a serious public health problem in many industrialized countries. Androgens appear to play a critical role in its etiology. Specifically, the active androgen in the prostate, dihydrotestosterone (DHT) which is synthesized by the enzyme steroid 5alpha-reductase from testosterone (T), acts as a mitogen. Hence androgen-deprivation is commonly used during prostate cancer therapy. Two isozymes for steroid 5alpha-reductase have been reported. The type II enzyme is prostate-specific and encoded by the SRD5A2 gene. We have investigated a polymorphic (TA)n dinucleotide repeat in the 3' UTR (untranslated region) of the SRD5A2 gene in 30 matched samples of constitutional ("germline") DNA from peripheral blood lymphocytes and microdissected, pure tumor DNA. We report here 8 LOH (loss of heterozygosity) events and 9 cases of microsatellite instability at this marker. Therefore, almost 57% of the samples examined showed evidence of somatic mutations at the 3' UTR of the SRD5A2 locus. Our data suggest that the SRD5A2 gene may be involved in prostate cancer progression and that this may have relevance for treatment of the disease.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1998

Androgen metabolism and prostate cancer: establishing a model of genetic susceptibility.

The prostate is an androgen-regulated organ, which has led to long-standing interest in the role of androgens in prostate carcinogenesis. Although evidence of a hormonal etiology for prostate cancer is strong, it is almost entirely circumstantial. Much of the problem in proving a causal relationship relates to the continued difficulties in reliably measuring human tissue-specific exposure to endogenous steroid hormones. The international and racial-ethnic variations in prostate cancer incidence, combined with the effects of migration on risk patterns, have suggested that whereas environmental factors are likely to be important, genetic factors might also play a central role in determining prostate cancer risk. We are developing a polygenic model of prostate carcinogenesis focused around a series of genes involved in androgen biosynthesis and androgen activation, transport, and metabolism in the prostate. In this developing model, we have initially targeted four genes based on three main criteria: (a) all encode products that play important roles in inducing androgen stimulation in the prostate; (b) all are polymorphic; and (c) all show substantial allelic variation in the polymorphic marker among the racial-ethnic groups of greatest interest in terms of prostate cancer risk. In addition to studying how the polymorphic markers of interest are related to prostate cancer development within and between racial-ethnic groups, we are concurrently evaluating whether genotypic variations correlate in the anticipated direction with biochemical parameters in vitro and in vivo. We summarize the development of this model and the state of knowledge related to each of the genes comprising the current model. We discuss the extent to which the current model can explain demographic variation in prostate cancer risk as well as the potential for future expansion of the model to incorporate environmental risk factors as well as additional genes. The model, when fully developed, can potentially provide a basis for targeting populations for screening interventions and/or preventive strategies aimed at the multigene products or at the genes themselves.

3-Hydroxysteroid Dehydrogenases↗
PubMed1998

The fundamental importance of human galactose metabolism: lessons from genetics and biochemistry.

Cloning and characterization of all three human galactose-metabolic genes (GALK, GALT and GALE) has led to the identification of a number of mutations which are generally of the missense type in patients with galactosemia, an inborn error of metabolism. The predominance of missense mutations is interesting, considering the general importance of galactose metabolism for cellular energy production and proper modification of glycoproteins and glycolipids. Abnormalities in both of these macromolecules have been described in transferase-deficiency galactosemia, the most common and best-studied form of galactosemia. Thus, the parallel biochemical and molecular genetic analyses of human galactose metabolism are shedding light on this under-appreciated metabolic pathway that is critical for cellular energy production, modification of cellular macromolecules and normal human development.

Carbohydrate Sequence↗