OSR1 disruption contributes to uterine factor infertility via impaired Müllerian duct development and endometrial receptivity

Three sisters, born from consanguineous parents, manifested a unique Müllerian anomaly characterized by uterine hypoplasia with thin estrogen-unresponsive endometrium and primary amenorrhea, but with spontaneous tubal pregnancies. Through whole-exome sequencing followed by comprehensive genetic analysis, a missense variant was identified in the OSR1 gene. We therefore investigated OSR1/OSR1 expression in postpubertal human uteri, and the prenatal and postnatal expression pattern of Osr1/Osr1 in murine developing Müllerian ducts (MDs) and endometrium, respectively. We then investigated whether Osr1 deletion would affect MD development, using WT and genetically engineered mice. Human uterine OSR1/OSR1 expression was found primarily in the endometrium. Mouse Osr1 was expressed prenatally in MDs and Wolffian ducts (WDs), from rostral to caudal segments, in E13.5 embryos. MDs and WDs were absent on the left side and MDs were rostrally truncated on the right side of E13.5 Osr1-/- embryos. Postnatally, Osr1 was expressed in mouse uteri throughout their lifespan, peaking at postnatal days 14 and 28. Osr1 protein was present primarily in uterine luminal and glandular epithelial cells and in the epithelial cells of mouse oviducts. Through this translational approach, we demonstrated that OSR1 in humans and mice is important for MD development and endometrial receptivity and may be implicated in uterine factor infertility.

Pharmacological blockage of the AHR-CYP1A1 axis: a call for in vivo evidence

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that can be activated by structurally diverse compounds arising from the environment and the microbiota and host metabolism. Expanding evidence has been shown that the modulation of the canonical pathway of AHR occurs during several chronic diseases and that its abrogation might be of clinical interest for metabolic and inflammatory pathological processes. However, most of the evidence on the pharmacological abrogation of the AHR-CYP1A1 axis has been reported in vitro, and therefore, guidance for in vivo studies is needed. In this review, we cover the state-of-the-art of the pharmacodynamic and pharmacokinetic properties of AHR antagonists and CYP1A1 inhibitors in different in vivo rodent (mouse or rat) models of disease. This review will serve as a road map for those researchers embracing this emerging therapeutic area targeting the AHR. Moreover, it is a timely opportunity as the first AHR antagonists have recently entered the clinical stage of drug development.

Berry fruits modulate kidney dysfunction and urine metabolome in Dahl salt-sensitive rats

Berries are rich sources of (poly)phenols which have been associated with the prevention of cardiovascular diseases in animal models and in human clinical trials. Recently, a berry enriched diet was reported to decrease blood pressure and attenuate kidney disease progression on Dahl salt-sensitive rats. However, the relationship between kidney function, metabolism and (poly)phenols was not evaluated. We hypothesize that berries promote metabolic alterations concomitantly with an attenuation of the progression of renal disease. For that, kidney and urinary metabolomic changes induced by the berry enriched diet in hypertensive rats (Dahl salt-sensitive) were analyzed using liquid chromatography (UPLC-MS/MS) and ¹H NMR techniques. Moreover, physiological and metabolic parameters, and kidney histopathological data were also collected. The severity of the kidney lesions promoted in Dahl rats by a high salt diet was significantly reduced by berries, namely a decrease in sclerotic glomeruli. In addition, was observed a high urinary excretion of metabolites that are indicators of alterations in glycolysis/gluconeogenesis, citrate cycle, and pyruvate metabolism in the salt induced-hypertensive rats, a metabolic profile counteracted by berries consumption. We also provide novel insights that relates (poly)phenols consumption with alterations in cysteine redox pools. Cysteine contribute to the redox signaling that is normally disrupted during kidney disease onset and progression. Our findings provide a vision about the metabolic responses of hypertensive rats to a (poly)phenol enriched diet, which may contribute to the understanding of the beneficial effects of (poly)phenols in salt-induced hypertension.

Comparison of the Sensitivity of Three Methods for the Early Diagnosis of Sporotrichosis in Cats

Sporotrichosis is caused by species of fungi within the Sporothrix schenckii complex that infect man and animals. In Rio de Janeiro, Brazil, an epidemic has been observed since 1998, with most of the cases being related to transmission from infected cats. Although the definitive diagnosis of feline sporotrichosis is made by fungal culture, cytopathological and histopathological examinations are used routinely, because the long culture period may delay treatment onset. However, alternative methods are desirable in cases of low fungal burden. Immunohistochemistry (IHC) has been described as a sensitive method for diagnosing human and canine sporotrichosis, but there are no reports of its application to cats. The aim of this study was to analyse the sensitivity of cytopathological examination (Quick Panoptic method), histopathology (Grocott silver stain) and anti-Sporothrix IHC by blinded comparisons, using fungal culture as the reference standard. Samples were collected from 184 cats with sporotrichosis that exhibited skin ulcers. The sensitivities of Grocott silver stain, cytopathological examination and IHC were 91.3%, 87.0% and 88.6%, respectively. Grocott silver stain showed the best performance. IHC showed high sensitivity, as did cytopathological examination and these may be considered as alternative methodologies. When the three methods were combined, the diagnosis was established in 180 (97.8%) out of 184 cases. Taken together, these findings indicate the need to implement these methods as routine tools for the early diagnosis of sporotrichosis in cats, notably when fungal culture is not available.

Tadpoles fed supplemented diet with probiotic bacterium isolated from the intestinal tract of bullfrog Lithobates catesbeianus: Haematology, cell activity and electron microscopy

The aim of this study is to select and isolate autochthonous bacteria with probiotic potential for use in a supplemented diet for bullfrog tadpoles, Lithobates catesbeianus. A total of 20 strains of lactic acid bacteria were isolated. Nine out of these were used in the following in vitro assays: antagonism against pathogenic bacteria (ANT), antimicrobial activity from extracellular compounds (MIC), tolerance to bile salts (TBS), pH reduction, protease production, sensitivity to antimicrobial tetracycline, cell viability, growth rate and doubling time. Using these data was defined an ideotype (ideal strain) based on the best results. Distances were estimated with the Mahalanobis (D²) test, and the best candidates, presenting the shortest ideotype distances, were considered to be used. The best strain was found to be Lactobacillus plantarum because it presented 10.00 ± 0.50 mm of ANT against Aeromonas hydrophila, 3.99 ± 0.01 of MIC independent of pathogenic bacteria, 85.07 ± 0.01 of TBS, 4.20 ± 0.02 of final pH, 17.67 ± 1.15 of protease production, 13.50 ± 2.00 sensitivity to antimicrobial tetracycline, 9.36 ± 0.04 of cell viability, 0.20 ± 0.00 of growth rate and 3.46 ± 0.00 doubling time. Therefore this probiotic candidate was then supplemented (2.045 ± 1.07 × 10⁷ colony forming unities. g^-1) into the diets of bullfrog tadpoles for a period of 42 days. At the end of the trial, samples of blood and intestines were collected to verify the haematological alterations and the intestinal morphology using transmission and scanning electron microscopy. Tadpoles fed the supplemented diet showed successful lactic acid bacterium colonisation, an increased number of circulating thrombocytes, monocytes, eosinophil and LG-PAS+ and also an increase in the length and density of intestinal microvilli. This study shows the feasibility of using probiotics isolated from farmed bullfrogs as a supplement in the diets of tadpoles, providing a promising alternative for modulating the health of these animals.

N-terminal valine adduct from the anti-HIV drug abacavir in rat haemoglobin as evidence for abacavir metabolism to a reactive aldehyde in vivo

BACKGROUND AND PURPOSE

The aim of this study was to obtain evidence for the activation of the nucleoside reverse transcriptase inhibitor abacavir to reactive aldehyde metabolites in vivo. Protein haptenation by these reactive metabolites may be a factor in abacavir-induced toxic events.

EXPERIMENTAL APPROACH

The formation of N-terminal valine adducts from the abacavir-derived aldehydes was investigated in the haemoglobin of Wistar rats treated with eight daily doses (120 mg·kg(-1)) of abacavir. The analyses were conducted by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry upon comparison with synthetic standards.

KEY RESULTS

An N-terminal valine haemoglobin adduct derived from an α,β-unsaturated aldehyde metabolite of abacavir was identified in vivo for the first time.

CONCLUSIONS AND IMPLICATIONS

This preliminary work on abacavir metabolism provides the first unequivocal evidence for the formation of an α,β-unsaturated aldehyde metabolite in vivo and of its ability to form haptens with proteins. The methodology described herein can be used to assess the formation of this metabolite in human samples and has the potential to become a valuable pharmacological tool for mechanistic studies of abacavir toxicity. In fact, the simplicity of the method suggests that the abacavir adduct with the N-terminal valine of haemoglobin could be used to investigate abacavir-induced toxicity for accurate risk/benefit estimations.

Development and validation of an assay for the simultaneous determination of zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma using liquid chromatography-tandem mass spectrometry

This paper describes the development and validation of an assay for the simultaneous quantification of the antiviral and antiretroviral drugs zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma using liquid chromatography coupled to tandem mass spectrometry. Sample pretreatment consisted of protein precipitation with 0.1% (v/v) formic acid in methanol, evaporation and reconstitution. Chromatographic separation was performed on a Synergy Polar reversed phase C18 column (150 mm × 2.0 mm ID, particle size 4 μm) using a stepwise gradient with 0.1% (v/v) formic acid in water and 0.1% (v/v) formic acid in methanol at a flow rate of 300 μL/min. A triple quadrupole mass spectrometer operating in the positive ionization mode was used for drug detection and quantification. Isotopically labeled zidovudine, lamivudine, tenofovir and ribavirin were used as internal standards. The method was validated over a clinical range of 20-2500 ng/mL for zidovudine, lamivudine and tenofovir, 4-500 ng/mL for abacavir and emtricitabine and 160-20,000 ng/mL for ribavirin. The inter and intra-assay accuracies and precisions were between -8.47% and 14.2% for zidovudine, emtricitabine and ribavirin. For abacavir, lamivudine and tenofovir, the inter and intra-assay accuracies and precisions at the lower limit of quantification were between -11.0% and 18.3%, whereas at all other levels these accuracies and precisions were between -11.7% and 12.0%. The described method is suitable for the determination of zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma in clinical practice to monitor plasma concentrations in selected cases to optimize therapy.

Comparison of acetate tape impression with squeezing versus skin scraping for the diagnosis of canine demodicosis

This study compared the sensitivity of acetate tape impression and skin squeezing with that of deep skin scraping for the diagnosis of demodicosis in dogs. Demodex canis was detected in 100% of acetate tape impressions obtained after skin squeezing and in 90% of deep skin scrapings. There was a significant difference (P < 0.001) between the techniques in the total number of mites detected. Acetate tape impression with skin squeezing was found to be more sensitive than deep skin scraping and is an alternative diagnostic method for canine demodicosis.

Effect of efavirenz on high-density lipoprotein antioxidant properties in HIV-infected patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* In previous work, we showed a long-term and concentration-dependent beneficial effect of the non-nucleoside reverse transcriptase inhibitor efavirenz (EFV) on high-density lipoproteins (HDL) in human immunodeficiency virus (HIV)-infected patients. * Furthermore, it has been suggested that instead of the current practice of only measuring HDL-chelesterol values, the evaluation of HDL function, namely its antioxidant properties, might be an improved tool for identifying subjects at increased risk for cardiovascular events. * Paraoxonase-1 (PON-1) is an enzyme associated with HDL that is responsible for HDL antioxidant function.

WHAT THIS STUDY ADDS

* In the present work, we studied the effect of EFV on the activity of PON-1 and showed, for the first time, that EFV-based antiretroviral therapy is associated with a better antioxidant function, i.e. with a higher PON-1 activity.

AIMS

A long-term and concentration-dependent beneficial effect of efavirenz (EFV) on cholesterol associated with high-density lipoprotein (HDL-c) in human immunodeficiency virus (HIV)-infected patients has been documented. Furthermore, it has been suggested that, instead of the current practice of only measuring HDL-c values, the evaluation of HDL quality might be an improved tool for identifying subjects at increased risk of cardiovascular events. Paraoxonase-1 (PON-1) is an enzyme associated with HDL that is involved in the onset of cardiovascular disease and responsible for HDL antioxidant function. The aim of the present study was to investigate the effect of EFV on the circulating activity of PON-1 in HIV-infected patients.

METHODS

The patients included were adults with a documented HIV-1 infection, nontreated or treated with antiretroviral regimens including EFV 600 mg once daily as first therapeutic regimen for at least 3 months. The influence of treatment with EFV, HDL-c and CD4 cell count on PON-1 activity was analysed.

RESULTS

HIV-infected White patients treated with EFV had higher PON-1 activity [77.35 U l(-1) (65.66, 89.04)] (P < 0.05) and higher PON-1 activity : HDL-c ratio [1.88 (1.49, 2.28)] (P < 0.01) than untreated patients. PON-1 activity was higher in Black patients (P < 0.001) and in patients with a CD4 cell count >500 cells ml(-1) (P= 0.0120).

CONCLUSIONS

EFV-based antiretroviral regimens are associated with HDL particles with a better antioxidant function, i.e. with a higher PON-1 activity. The PON-1 activity of Black patients is higher than that found in Whites regardless of treatment. Ethnicity should be taken into consideration when studying drug effects on PON-1 activity.

Response to azolic antifungal agents for treating feline sporotrichosis

The effectiveness and safety of treatment with ketoconazole and itraconazole were compared in 773 sporotrichosis-infected cats over a four-year period (2002 to 2005). Five hundred and ninety-eight cats received oral ketoconazole and 175 received oral itraconazole. Treatment was successful in 238 (30.8 per cent) cats, of which 171 (28.6 per cent) of 598 received 13.5 to 27.0 mg/kg/day ketoconazole and 67 (38.3 per cent) of 175 received 8.3 to 27.7 mg/kg/day itraconazole. Adverse effects were reported in 306 (39.6 per cent) of the cats, 105 (13.6 per cent) died and 430 (55.6 per cent) dropped out of treatment or were still under treatment at the time of data analysis.

Mycological evaluation of bronchoalveolar lavage in cats with respiratory signs from Rio de Janeiro, Brazil

Twenty-three cats with respiratory signs who had domiciliary contact with cats with sporotrichosis were studied. Sneezing was the predominant extracutaneous sign. Twelve cats had no skin lesions and 11 had ulcerated skin lesions. Mycological culture of material obtained from the nasal cavity, oral cavity, bronchoalveolar lavage (BAL) and skin lesions, when present, was performed for all cats. In the case of autopsy, lung fragments were cultured. Sporothrix schenckii was isolated from four of the 12 cats without skin lesions: BAL (one cat) and oral and/or nasal cavity (three cats). The latter three animals developed nasal and distant skin lesions within the following 2-4 weeks. The cat with S. schenckii isolated from BAL did not develop skin lesions or lower respiratory tract symptoms during the 6 months of follow-up. S. schenckii was isolated from one or more biological samples of all 11 cats with skin lesions: oral cavity (five), nasal cavity (eight), BAL fluid (four), skin lesions (eight), and blood culture (one). No yeast-like structures were observed upon BAL cytology in any of the 23 cats. The results suggest that S. schenckii can cause infection of skin contiguous to the natural facial orifices through colonisation of the mucosal surfaces of the upper airways.

Estimation of the critical effect level for pollution prevention based on oyster embryonic development toxicity test: the search for reliability

In spite of the consideration that toxicity testing is a reduced approach to measure the effects of pollutants on ecosystems, the early-life-stage (ELS) tests have evident ecological relevance because they reflect the possible reproductive impairment of the natural populations. The procedure and validation of Crassostrea rhizophorae embryonic development test have shown that it meets the same precision as other U.S. EPA tests, where EC(50) is generally used as a toxicological endpoint. However, the recognition that EC(50) is not the best endpoint to assess contaminant effects led U.S. EPA to recently suggest EC(25) as an alternative to estimate xenobiotic effects for pollution prevention. To provide reliability to the toxicological test results on C. rhizophorae embryos, the present work aimed to establish the critical effect level for this test organism, based on its reaction to reference toxicants, by using the statistical method proposed by Norberg-King (Inhibition Concentration, version 2.0). Oyster embryos were exposed to graded series of reference toxicants (ZnSO(4) x 7H(2)O; AgNO(3); KCl; CdCl(2)H(2)O; phenol, 4-chlorophenol and dodecyl sodium sulphate). Based on the obtained results, the critical value for C. rhizophorae embryonic development test was estimated as EC(15). The present research enhances the emerging consensus that ELS tests data would be adequate for estimating the chronic safe concentrations of pollutants in the receiving waters. Based on recommended criteria and on the results of the present research, zinc sulphate and 4-chlorophenol have been pointed out, among the inorganic and organic compounds tested, as the best reference toxicants for C. rhizophorae ELS-test.

Estimating the gasoline components and formulations toxicity to microalgae (Tetraselmis chuii) and oyster (Crassostrea rhizophorae) embryos: an approach to minimize environmental pollution risk

Even though petrochemical contamination frequently occurs in the form of oil spills, it is thought that a greater danger to coastal habitats is posed by chronic petrochemical toxicity associated with urban run-off, in which gasoline water-soluble-fraction (WSF) plays an important role. The hypothesis of the entrepreneurs, who were associated to the scientists uncharged of this research, was that recycled petrochemical waste may provide different gasoline formulations, having different toxic properties; the correlation between the gasoline formulations and their components' toxicological effects might contribute to the reformulation of the products, in such a way that the gasoline generated could be less toxic and less harmful to the environment. The aim of this research was to determine the toxic effects of 14 different types of gasoline (formulated, in accordance with National Petroleum Agency standards, from petrochemical waste), on Tetraselmis chuii (microalgae culture) and Crassostrea rhizophorae (embryos). Microalgae and oyster embryos were exposed to different gasoline formulations water-soluble fractions (WSF) at a range of concentrations (0%, 4.6%, 10.0%, 22.0%, 46.0%, and 100%), for 96 and 24h, respectively. The tests were carried out under controlled conditions. End-points have been CI50-96h (concentration causing 50% growth inhibition in microalgae cultures) and EC50-24h (concentration causing abnormalities on 50% of the exposed embryos). Through these procedures, gasoline formulations, which represent the lowest environmental risk, were selected. Bioassays carried out on the 8 different gasoline components aimed to correlate gasoline toxicity with the toxic potential of its components. The analysis of principal components showed that the C9DI, a mixture of aromatic hydrocarbons of 9 carbon atoms, had the highest level of toxic potential, followed by C9S (a mixture of aromatics with 9-11 carbon atoms) and heavy naphtha. The results showed gasoline formulations 1-4 (monoaromatic hydrocarbons being the most conspicuous components) to be the least toxic, whilst formulations 12-14 (having higher content of C9DI, C9S and naphtha) were found to be the most harmful to organisms. This study led to the identification of the most toxic WSF gasoline components (C9DI and C9S), and to the possibility of developing more eco-compatible gasoline formulations.

Mixed infection with Leishmania (Viannia) braziliensis and Leishmania (Leishmania) chagasi in a naturally infected dog from Rio de Janeiro, Brazil

We report here the first case of co-infection with Leishmania (Viannia) braziliensis and Leishmania (Leishmania) chagasi in a naturally infected dog from Rio de Janeiro, Brazil. Isoenzyme characterisation identified the parasites isolated in culture from the cutaneous lesion as L. (V.) braziliensis and the isolates from blood and lymph node as L. (L.) chagasi. PCR analysis using specific primers followed by molecular hybridisation for direct Leishmania species identification in tissue fragments confirmed the presence of L. (V.) braziliensis DNA in the cutaneous lesion and of L. (L.) chagasi DNA in spleen and popliteal lymph node fragments. This report emphasises the importance of identification of Leishmania species infecting seropositive dogs in endemic areas, and the consequent re-assessment of control and epidemiological surveillance measures for the control of leishmaniasis, as is the case in Brazil.

American cutaneous leishmaniasis in two cats from Rio de Janeiro, Brazil: first report of natural infection with Leishmania (Viannia) braziliensis

We describe the isolation of Leishmania (Viannia) braziliensis from two female cats with American cutaneous leishmaniasis in Rio de Janeiro, Brazil. The isolates were identified as L. (V.) braziliensis by isoenzyme electrophoresis.

Expression of cell-cycle regulatory proteins and their prognostic value in superficial low-grade urothelial cell carcinoma of the bladder

AIMS

Cell-cycle regulatory proteins are important indicators in determining progression trough the cell-cycle and progression to invasive cancer in patients presenting with superficial bladder cancer. We performed an immunohistochemical study in order to evaluate the prognostic value of the expression of p16, p27, pRb, p53 and Ki-67 in superficial grade I and II papillary urothelial cell carcinoma of the bladder.

METHODS

p16, p27, p53, pRb and Ki-67 immunoexpression was studied in 14 pTa, 35 pT1a and 7 pT1b bladder tumours at presentation and at recurrence of their tumours. The recurrence-free survival and the progression-free survival were analysed according to these regulatory cell-cycle proteins expression.

RESULTS

For survival in univariate analysis a high Ki-67 labelling index was a poor prognostic factor for recurrence-free and progression-free survival (P=0.0014 and P=0.012, respectively). Ki-67 labelling index was also an independent recurrence-free survival prognostic factor (P=0.0005). The p16, p27, p53 and pRb immunoreactivity was not significantly associated with recurrence or progression rate in this group of bladder carcinomas.

CONCLUSIONS

These data suggest that the Ki-67 labelling index can be a reliable marker in predicting recurrence and/or progression in superficial low-grade bladder carcinomas and may be relevant in planning adjuvant therapy.

Glucose-6-phosphate dehydrogenase aveiro: a de novo mutation associated with chronic nonspherocytic hemolytic anemia

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common X-linked enzyme abnormality. The clinical phenotype is variable but often predictable from the molecular lesion. Class I variants (the most severe forms of the disease) cluster within exon 10, in a region that, at the protein level, is believed to be involved in dimerization. Here we describe a de novo mutation (C269Y) of a new class I variant (G6PD Aveiro) that maps to exon 8. Mutant and normal alleles were found in both hematopoietic and buccal cells, indicating the presence of mosaicism. The available model of the protein predicts that this lesion lies in proximity to the dimer interface of the molecule. A possible mechanism to explain the severity of the defect is proposed. (Blood. 2000;95:1499-1501)

[The weight of the spleen in chronic chagasics]

During the course of systemic inflammatory reactions and chronic venous congestion, the documented phenomenon of increased spleen size is respectively called reactional hyperplasia and congestive splenomegaly. In Chagas' disease, the inflammatory process observed in the heart of chronically infected patients can result in heart failure and ultimately in congestive failure. In order to evaluate the spleen response to both inflammatory and cardiac processes, in this retrospective study we compare the weight of spleens from normal and chagasic patients, with or without congestive failure. Information about patient age, sex, race and spleen weight was collected from autopsy reports. Eighty-eight selected cases were divided into four groups: 1) chagasic patients with congestive failure, 2) chagasic patients without congestive failure, 3) non-chagasic patients with congestive failure, 4) non-chagasic patients without congestive failure. The average age was 44.9 +/- 15.4 years, 53.4% were Caucasians and 70.5% were males, and no significant difference in these parameters was observed between the four groups. The spleen weight for the groups presenting congestive failure was 183.7 +/- 85.9 g for chagasic and 206.3 +/- 101.0 g for non-chagasic patients; for the groups without congestive failure the average spleen weight was 173.7 +/- 118.9 g for the chagasic and 117.2 +/- 52.0 g for non-chagasic patients. The spleen weight was significantly higher for the chagasic patients without congestive failure when compared to the non-chagasic group without congestive failure. These results suggest that the inflammatory component in Chagas' disease plays an important role in the increase of spleen weight together with hemodynamic alterations arising from congestive heart failure.

Aromatic amino-acid biosynthesis in Candida albicans: identification of the ARO4 gene encoding a second DAHP synthase

The primary step in the aromatic amino-acid biosynthetic pathway in Saccharomyces cerevisiae is catalyzed by two redundant isozymes of 3-deoxy-d-arabinoheptulosonate-7-phosphate (DAHP) synthase, either of which alone is sufficient to permit growth on synthetic complete media lacking aromatic acids (SC-Aro). The activity of one isozyme (encoded by the ARO3 gene) is feedback-inhibited by phenylalanine, whereas the activity of the other isozyme (encoded by the ARO4 gene) is feedback-inhibited by tyrosine. Transcription of both genes is controlled by GCN4. We previously cloned the ARO3 gene from the opportunistic pathogen Candida albicans and found that: (1) it can complement an aro3 aro4 double mutation in S. cerevisiae, an effect inhibited by excess phenylalanine; and (2) its expression is induced in response to amino-acid deprivation, consistent with the presence of two putative GCN4-responsive promoter elements (Pereira and Livi 1993, 1995). To determine whether other DAHP synthases exist in C. albicans, we have constructed a homozygous aro3-deletion mutant strain. Such a mutant was found to be phenotypically Aro+, i. e., capable of normal growth on SC-Aro media, suggesting the presence of at least one additional isozyme. To confirm this result, a 222-bp DNA fragment was amplified by the polymerase chain reaction (PCR) from genomic DNA prepared from the homozygous aro3-deletion mutant, using a degenerate primer based on a conserved N-terminal region of Aro3p plus a degenerate comeback primer encoding a conserved region of the protein that lies within the deleted portion of the gene. The nucleotide sequence of this PCR fragment predicts a 74-amino acid DAHP synthase-related protein which shows strong homology to Aro3p from S. cerevisiae and C. albicans, but even greater homology (78% identity) to S. cerevisiae Aro4p. We conclude that cells of C. albicans contain a second Aro4p-related DAHP synthase.

A GCN-like response in Candida albicans

The control of amino acid and purine biosynthesis in the yeast Saccharomyces cerevisiae is mediated by the transcriptional activator GCN4. We previously identified the presence of two putative GCN4 responsive elements (GCREs) in the promoter sequence of the Candida albicans ARO3 gene, which encodes an enzyme in the aromatic amino acid pathway. We now show that amino acid deprivation results in a dramatic rise in the steady-state level of ARO3-specific mRNA, indicative of a GCN-like pathway in C. albicans.

Cloning and expression of the ARO3 gene encoding DAHP synthase from Candida albicans

In Saccharomyces cerevisiae, the primary step in the aromatic (ARO) amino acid (aa) biosynthetic pathway is catalyzed by two isozymes of 3-deoxy-D-arabinoheptulosonate-7-phosphate synthase (DAHPS). The activity of one DAHPS isozyme (encoded by the ARO3 gene) is feedback inhibited by phenylalanine, whereas the other (encoded by the ARO4 gene) is inhibited by tyrosine. The expression of these genes is also regulated at the transcriptional level by the general control activator GCN4. We took advantage of the high degree of aa sequence homology between DAHPSs from several species to isolate ARO3 homologues from the pathogenic yeast Candida albicans. An ARO3/ARO4-specific sequence was generated from C. albicans genomic DNA by polymerase chain reaction amplification and used as a probe to screen a C. albicans cDNA library. A 1.3-kb cDNA clone was isolated and sequenced. The cDNA contains a long open reading frame predicting a 368-aa protein with significant homology to known DAHPSs, including both the S. cerevisiae ARO3 and ARO4 products (68.5% and 58.5% identity, respectively). Northern analysis of yeast and mycelial poly(A)+ RNA revealed equivalent expression of a 1.3-kb transcript in both cell types. A genomic clone was isolated by cross-hybridization, and analysis of the 5' untranslated region revealed the presence of a putative GCN4-binding site. This clone complemented an aro3 mutation in S. cerevisiae; functional complementation was inhibited by the presence of excess phenylalanine (but not tyrosine) in the growth medium, confirming that the cloned gene is the C. albicans homologue of ARO3.