Biomedical subjects

W Wurst

Publications and source records attributed to W Wurst.

At least 37 records · Page 2Linked to original sources

PubMed1999

The caudal limit of Otx2 expression positions the isthmic organizer.

The homeobox gene Otx2 is expressed in the anterior neural tube with a sharp limit at the midbrain/hindbrain junction (the isthmic organizer). Otx2 inactivation experiments have shown that this gene is essential for the development of its expression domain. Here we investigate whether the caudal limit of Otx2 expression is instrumental in positioning the isthmic organizer and in specifying midbrain versus hindbrain fate, by ectopically expressing Otx2 in the presumptive anterior hindbrain using a knock-in strategy into the En1 locus. Transgenic offspring display a cerebellar ataxia. Morphological and histological studies of adult transgenic brains reveal that most of the anterior cerebellar vermis is missing, whereas the inferior colliculus is complementarily enlarged. During early neural pattern formation expression of the midbrain markers Wnt1 and Ephrin-A5, the isthmic organizer markers Pax2 and Fgf-8 and the hindbrain marker Gbx2 are shifted caudally in the presumptive hindbrain territory. These findings show that the caudal limit of Otx2 expression is sufficient for positioning the isthmic organizer and encoding caudal midbrain fate within the mid/hindbrain domain.

Animals↗

PubMed1999

Regulation of epidermal bullous pemphigoid antigen 1 (BPAG1) synthesis by homeoprotein transcription factors.

In a recent gene-trap screen, we identified the gene coding for Epidermal Bullous Pemphigoid Antigen 1 (BPAG1) as a putative transcriptional target of Engrailed and of other homeoproteins with a glutamine in position 50 of their homeodomain. We now show that the nuclear addressing of the homeodomains of Engrailed (EnHD) and Antennapedia (AntpHD) upregulates BPAG1e transcription in immortalized human keratinocytes (GMA24FIA) expressing En1. This upregulation is not observed with AntpHD-Q50A, a variant of AntpHD in which a single mutation abolishes its high-affinity binding to target DNA, thus strongly suggesting that BPAG1e upregulation homeodomains reflects their specific recognition of homeoprotein-binding sites in the BPAG1e locus. This is further confirmed by DNase I footprinting and electrophoretic mobility shift assays that reveal, within the cloned BPAG1e promoter, several sites of direct interaction with EnHD and Engrailed. Co-transfection experiments in GMA24FIA human keratinocytes, COS-7 simian fibroblasts, and CHP-100 human neuroepithelial cells show that Engrailed, Hoxa-5, and Hoxc-8 regulate BPAG1e promoter activity and that this regulation is context-dependent. Finally, using a mouse line with LacZ inserted within the En1 locus, we identify the keratinocytes of the ventral paws, including the epithelial cells of the eccrine tubules, as a strong site of En1 expression throughout adulthood. We therefore propose that BPAG1e, a 230 kDa keratin-binding protein expressed in keratinocytes and participating in the maintenance of hemidesmosomes at the dermis-epidermis border, is directly regulated by homeoprotein transcription factors.

Animals↗

PubMed1999

The new topical steroid ciclesonide is effective in the treatment of allergic rhinitis.

A randomized, placebo-controlled, double-blind crossover study was performed to investigate the efficacy of ciclesonide nasal spray in allergic rhinitis at the dose level of 200 micrograms per nostril. Twenty-four subjects (13 males, 11 females; median age: 28 years) with a history of allergic rhinitis but free of symptoms at screening entered the study. Ciclesonide and placebo were given for 7 days each with a washout period of at least 14 days in between. In both treatment periods, controlled intranasal allergen provocation with pollen extracts was performed on the 2 days before start of treatment (days -2 and -1) and on all treatment days (days 1 to 7) about 2 hours after administration of the study medication. At 5 and 30 minutes after each allergen provocation, rhinal airflow was measured by anterior rhinomanometry, and the subjective symptoms of obstruction, itching, and rhinorrhea were assessed by means of a standardized visual analog scale. Rhinal airflow improved significantly from day 5, while the subjective symptom of obstruction improved from day 2. Itching and rhinorrhea also improved significantly. The local and systemic tolerability of ciclesonide nasal spray was excellent. The results of this study clearly indicate that the new topical steroid ciclesonide is effective in the treatment of allergic rhinitis without producing local or systemic side effects.

Administration, Intranasal↗

PubMed1999

Pantoprazole lacks induction of CYP1A2 activity in man.

OBJECTIVE: This drug-drug interaction study investigated the potential influence of the proton pump inhibitor pantoprazole on the CYP1A2 activity as assessed by urinary excretion of caffeine metabolites. SUBJECTS, MATERIALS AND METHODS: 12 healthy, non-smoking volunteers underwent two treatment periods of 7 days each in randomized order with once-daily oral intake of 40 mg pantoprazole (test) or placebo (reference). On days 6 and 7 of both periods, 200 mg caffeine was administered two hours after pantoprazole intake, i.e. at the expected t(max) of pantoprazole serum concentrations. Urinary excretion of the caffeine metabolites 1X, 1U, AFMU, 17U was measured up to 8 hours after caffeine intake. In accordance with recent guidelines on drug-drug interactions, lack of interaction was handled as an equivalence problem. RESULTS: Point estimate and 90% confidence intervals (CI) of the respective ratios test/reference were 0.91 (0.81, 1.03) for (1X + 1U + AFMU)/17U, indicative for CYP1A2 activity, 1.03 (0.94, 1.13) for AFMU/1X (N-acetyl transferase activity) and 1.01 (0.94, 1.09) for 1U/1X (xanthine oxidase activity). CONCLUSION: Pantoprazole does not induce CYP1A2 activity, consistent with previous findings following theophylline administration, nor does it have any influence on N-acetyl-transferase or xanthine oxidase activity.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1998

Aquarius, a novel gene isolated by gene trapping with an RNA-dependent RNA polymerase motif.

In a retinoic acid (RA) gene trap screen of mouse embryonic stem (ES) cells, a novel gene, named Aquarius (Aqr), was identified and characterized. The promoterless lacZ marker was used to trap the genomic locus and to determine the expression pattern of the gene. Aqr transcripts are strongly induced in response to RA in vitro. During embryogenesis, Aqr is expressed in mesoderm, in the neural crest and its target tissues, and in neuroepithelium. Expression was first detected at 8.5 days postcoitum, when neural crest cells are visible at the lateral ridges of the neural plate. The gene-trapped Aqr locus was transmitted through the mouse germ line in three genetic backgrounds. In the F2 generation, the expected mendelian ratio of 1:2:1 was observed in all backgrounds, indicating that homozygous mice are viable. Homozygotes are normal in size and weight and breed normally. The gene trap insertion, however, does not seem to generate a null mutation, because Aqr transcripts are still present in the homozygous mutant animals. The Aqr open reading frame has weak homology to RNA-dependent RNA polymerases (RRPs) of the murine hepatitis viruses and contains an RRP motif. Aqr was mapped to mouse chromosome 2 between regions E5 through F2 by using fluorescence in situ hybridization analysis.

Amino Acid Sequence↗

PubMed1998

The winged helix transcription factor Fkh10 is required for normal development of the inner ear.

Fkhl0 is a member of the forkhead family of winged helix transcriptional regulators. Genes encoding forkhead proteins are instrumental during embryogenesis in mammals, in particular during development of the nervous system. Here we report that mice with a targeted disruption of the Fkh10 locus exhibit circling behaviour, poor swimming ability and abnormal reaching response-all common findings in mice with vestibular dysfunction. These animals also fail to elicit a Preyer reflex in response to a suprathreshold auditory stimulation, as seen in mice with profound hearing impairment. Histological examination of the inner ear reveals a gross structural malformation of the vestibulum as well as the cochlea. These structures have been replaced by a single irregular cavity in which neither proper semicircular ducts nor cochlea can be identified. We also show that at 9.5 days post coitum (dpc), Fkh10 is exclusively expressed in the otic vesicle. These findings implicate Fkh10 as an early regulator necessary for development of both cochlea and vestibulum and identify its human homologue FKHL10 as a previously unknown candidate deafness gene at 5q34.

Acoustic Stimulation↗

PubMed1998

Impaired stress response and reduced anxiety in mice lacking a functional corticotropin-releasing hormone receptor 1.

Corticotropin-releasing hormone (CRH) is a potent mediator of endocrine, autonomic, behavioural and immune responses to stress, and has been implicated in the stress-like and other aversive consequences of drug abuse, such as withdrawal from alcohol. Two CRH receptors, Crhr1 and Crhr2, have been identified in the mouse. Crhr1 is highly expressed in the anterior pituitary, neocortex, hippocampus, amygdala and cerebellum, and activation of this receptor stimulates adenylate cyclase. Here we show that in mice lacking Crhr1, the medulla of the adrenal gland is atrophied and stress-induced release of adrenocorticotropic hormone (ACTH) and corticosterone is reduced. The homozygous mutants exhibit increased exploratory activity and reduced anxiety-related behaviour under both basal conditions and following alcohol withdrawal. Our results demonstrate a key role of the Crhr1 receptor in mediating the stress response and anxiety-related behaviour.

Adrenocorticotropic Hormone↗

PubMed1998

Equipotent inhibition of gastric acid secretion by equal doses of oral or intravenous pantoprazole.

BACKGROUND: Pantoprazole is a proton pump inhibitor characterized by a low potential to interact with the cytochrome P450 system, and linear pharmacokinetics. The recommended oral dose for treatment of acid-related diseases is 40 mg. METHODS: Using a randomized, crossover study design we compared the ability of 40 mg oral and intravenous pantoprazole to elevate the intragastric pH in healthy volunteers (n = 20, 'per protocol'), during two treatment phases. The duration of each phase was 5 days. Pantoprazole 40 mg was administered once daily either as a tablet or as an intravenous injection. A 24 h pHmetry was used to record the intragastric pH on day 5 of each regimen; this was compared to the baseline curve obtained before each study period. The calculated 90% confidence intervals (90% CI) represent the mean difference in the intragastric pH, attained after intravenous or oral administration. The predefined equivalence range for the 90% CI was +/- 20% for the percentage time at which the gastric pH was at least pH 3 or 4 and +/- 1 unit for the median pH. RESULTS: Pantoprazole was well tolerated during both treatment phases. The mean of the 24 h median pH was 3.3 and 3.1 for the intravenous and oral treatments, respectively; the corresponding differences were 0.2 (90% CI: - 0.03 to 0.44). For the mean percentage time at which the pH was 3 or above, the respective calculated values were 57% and 51%, with a difference between the two administration routes of only 5.7% (90% CI: 1.8 to 9.6). At an intragastric pH of 4 or above, the mean percentage time was 420% and 38% following intravenous and oral treatment, respectively, with a difference between the treatment routes of only 4.4% (90% CI: 0.6 to 8.3). CONCLUSIONS: These results imply that the two formulations of pantoprazole can be assumed to be equipotent. Hence, the intravenous formulation of pantoprazole could be considered as an alternative route of administration.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1998

Pharmacokinetics of pantoprazole in patients with end-stage renal failure.

BACKGROUND: Pantoprazole is a selective inhibitor of the gastric H+/K+-ATPase with a low potential to interact with the cytochrome P450 enzyme system. Since pantoprazole is metabolized in the liver to metabolites which are mainly cleared by the renal route, it was the aim of this study to investigate its pharmacokinetics in patients with end-stage renal failure undergoing regular haemodialysis. METHODS: Eight patients with end-stage renal failure (creatinine clearance < 5 ml/min, age 45-65 years) on regular haemodialysis (duration of haemodialysis 4-5 h, cuprophan-dialyser Hemoflow E3, surface 1.3 m2) were given single i.v. doses of 40 mg pantoprazole one day before haemodialysis (A) and on a haemodialysis day immediately before the start of the haemodialysis (B). Concentrations of pantoprazole and metabolite M2 were determined in plasma and urine over 24 h and in timed samples of the dialysis fluid by HPLC. The protein binding was determined using equilibrium dialysis. RESULTS: The pharmacokinetic characteristics of pantoprazole AUC, t(1/2), CL and V(d area) (geometric means) were 2.4 mgxh/l, 0.63 h, 0.227 l/h/kg and 0.206 l/kg on day A (without dialysis) and 2.3 mgxh/l, 0.8 h, 0.237 l/h/kg and 0.273 l/kg on day B (with dialysis), respectively. The protein binding was 96%. Pantoprazole was found in small amounts in the dialysis fluid (max. 2.1% of the dose) but not in the urine. Pantoprazole was well tolerated. In particular, there were no clinically relevant changes in blood count, electrolytes or liver enzymes. CONCLUSIONS: Haemodialysis has no influence on the pharmacokinetic characteristics of pantoprazole. Thus, pantoprazole is not dialysed to any relevant degree, and therefore no dose-adjustment is required for patients with end-stage renal failure undergoing regular haemodialysis treatment.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1998

Pantoprazole does not interact with the pharmacokinetics of carbamazepine.

OBJECTIVE: Pantoprazole is a H+/K+-ATPase inhibitor with a minimized potential of interaction with the cytochrome P450 system. Imidazole derivatives such as cimetidine and omeprazole have been shown to markedly interact with carbamazepine, a major anticonvulsant with a narrow therapeutic range. Therefore, the influence of steady-state pantoprazole on the pharmacokinetics of carbamazepine was investigated. SUBJECTS AND METHODS: N = 20 healthy volunteers (12 male/8 female) completed a double-blind, placebo-controlled, randomized crossover study. During the test period they received 40 mg pantoprazole p.o. once daily for 11 days and concomitantly a single oral dose of 400 mg carbamazepine on day 5. In the reference period placebo was administered instead of pantoprazole. RESULTS: Serum concentrations of carbamazepine and its active metabolite carbamazepine-10,11-epoxide were measured until day 11. Geometric means of AUC (extent characteristic) and Cmax/AUC (rate characteristic) of carbamazepine were 292 and 287 mgxh/l, and 0.0150 and 0.0144 l/h (reference and test), respectively. Point estimates and 90% confidence intervals of the ratios were 0.98 (0.95, 1.01) for AUC, and 0.96 (0.92, 1.00) for Cmax/AUC, respectively. Since the 90% confidence intervals of the primary characteristics, AUC and Cmax/AUC were entirely within the predefined equivalence range of 0.80 - 1.25, lack of interaction of pantoprazole with the pharmacokinetics of carbamazepine was demonstrated. Equivalence was also demonstrated for carbamazepine-10,11-epoxide using the characteristics AUC and Cmax. CONCLUSION: No dose adjustment of carbamazepine is therefore required during concomitant treatment with pantoprazole.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1997

Phase I and pharmacokinetic study of the P-glycoprotein modulator dexniguldipine-HCL.

Dexniguldipine (DNIG) is the R-enantiomer of the dihydropyridine derivate niguldipine. DNIG showed a binding affinity to the P-glycoprotein (P-gp) and therefore it is to be assumed to block the P-gp pumping mechanism. This open phase I study was conducted to determine the maximal tolerated dose (MTD) and safety of intravenously administered DNIG alone and in combination with vinblastine in patients with a metastatic or locally advanced cancer. Additionally, serum levels of DNIG were assessed and compared between dosage groups to investigate the intravenous dose linearity. The study was divided into two parts concerning DNIG administration. In part I the patients received DNIG for four hours daily over four consecutive days and additionally 0.15 mg/kg vinblastine at day 3. Treatment was started with 1 mg/kg/4h, and whenever the drug was well tolerated the dosage was increased. In part II the patients received up to three courses of a four-hour infusion (5 and 7 mg/kg/4h) of DNIG followed by a continuous infusion for 48 hours (5 and 7 mg/kg/24h). Twenty-six patients entered this trial and were given at least one infusion of DNIG; vinblastine was given immediately after the 4-hour infusion. One to seven courses and dosages from 1-11 mg/kg were administered. In five patients the dose limiting toxicity was seen in cardiovascular adverse events such as a drop in blood pressure, decreased heart rate and in one patient an AV block III. Most frequent adverse events were nausea, dizziness, vomiting, peripheral paresthesia, atactic gait, mild constipation, polyuria, hypocalcemia; all disappeared within 24 hours after discontinuation of infusion. A linear increase in DNIG serum concentration with increasing doses was found following intravenous infusion of DNIG over a four-hour period. Long-term infusion regimes over a period of two or five days resulted in reasonably constant DNIG serum levels. MTD was determined at 5 mg/kg/4h. It is to be assumed that the MTD for continuous infusion of DNIG is higher than 5 mg/kg/24h, but this was not followed up in the study and must be the aim of a later trial.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Considerations on genetic and environmental factors that contribute to resistance or sensitivity of mammals including humans to toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. Part 1: Genetic factors affecting the toxicity of TCDD.

The marked species differences in short-term toxicity (30-day LD50) of ca. 10,000 (LD50: guinea pigs ca. 1 microgram/kg body wt and Han/Wistar Kuopio rats more than 9600 micrograms/kg body wt) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is one of the central issues of the controversies that have developed on the validity of risk assessment strategies for TCDD and related compounds. One of the most challenging issues that toxicologists face today is the identification of genes that contribute to or are responsible for increased resistance or sensitivity to TCDD and related compounds. It is assumed that most, if not all, toxic effects of TCDD are mediated more or less through the binding affinity to the Ah receptor. This hypothesis was extended and tries to explain the differences in sensitivity/resistance of animals including humans to TCDD by their total fat (lipid) content. In this respect the gene or genes which is or are responsible for obesity of mammals including humans are of great interest. An obvious linear positive logarithmic relationship between the oral 30-day LD50 (microgram/kg) of TCDD in different species and strains of mammals and their total body fat content (TBF%) was found: log LD50 = 5.30 x log (TBF)-3.22, or LD50 = 0.000603 x (TBF)5.30. By means of this regression the toxicity of TCDD in mammals including humans of different age and/or body weight can be predicted if their total body fat content is known. Examples of single-gene and polygenic disease models in different mammals, such as nonobese diabetic, diabetic, viable yellow, obese, and fat mice, as well as transgenic mice, and other suitable animal models, such as fatty Zucker rats, Han/Wistar (Kuopio) rats, and minipigs, are discussed, and predicted LD50 values of TCDD in these animals and humans are presented.

Animals↗

PubMed1997

Transcranial Doppler echo contrast studies using different colour processing modes.

OBJECTIVES: To study the effects of different colour imaging modes on the contrast-medium-enhanced image of the intracranial cerebral arteries. METHODS: Twelve healthy volunteers were studied transcranially after administration of 10 ml BY963 successively with Power Doppler (p-TCCS) and with colour Doppler frequency imaging mode (f-TCCS) in a randomized order. RESULTS: The latency time (mean+/-SD) from the injection until the signal enhancement in the middle cerebral artery was 17.1+/-5.8 s for p-TCCS and 17.8+/-4 s for f-TCCS, and the duration of the optimal diagnostically useful signal enhancement was 44.2+/-8.2 s and 40.2+/-12.6 s respectively. CONCLUSIONS: Based on the measured parameters, both imaging modes were of equal value. Theoretical differences in sensitivity of the two methods play no particular role facing the immense signal enhancement after echo contrast application.

Adult↗

PubMed1996

The mouse Pax2(1Neu) mutation is identical to a human PAX2 mutation in a family with renal-coloboma syndrome and results in developmental defects of the brain, ear, eye, and kidney.

We describe a new mouse frameshift mutation (Pax2(1Neu)) with a 1-bp insertion in the Pax2 gene. This mutation is identical to a previously described mutation in a human family with renal-coloboma syndrome [Sanyanusin, P., McNoe, L. A., Sullivan, M. J., Weaver, R. G. & Eccles, M. R. (1995) Hum. Mol. Genet. 4, 2183-2184]. Heterozygous mutant mice exhibit defects in the kidney, the optic nerve, and retinal layer of the eye, and in homozygous mutant embryos, development of the optic nerve, metanephric kidney, and ventral regions of the inner ear is severely affected. In addition, we observe a deletion of the cerebellum and the posterior mesencephalon in homozygous mutant embryos demonstrating that, in contrast to mutations in Pax5, which is also expressed early in the mid-hindbrain region, loss of Pax2 gene function alone results in the early loss of the mid-hindbrain region. The mid-hindbrain phenotype is similar to Wnt1 and En1 mutant phenotypes, suggesting the conservation of gene regulatory networks between vertebrates and Drosophila.

Abnormalities, Multiple↗

PubMed1996

The mouse Engrailed-1 gene and ventral limb patterning.

During vertebrate limb development, positional information must be specified along three distinct axes. Although much progress has been made in our understanding of the molecular interactions involved in anterior-posterior and proximal-distal limb patterning, less is known about dorsal-ventral patterning. The genes Wnt-7a and Lmx-1, which are expressed in dorsal limb ectoderm and mesoderm, respectively, are thought to be important regulators of dorsal limb differentiation. Whether a complementary set of molecules controls ventral limb development has not been clear. Here we report that Engrailed-1, a homeodomain-containing transcription factor expressed in embryonic ventral limb ectoderm, is essential for ventral limb patterning. Loss of Engrailed-1 function in mice results in dorsal transformations of ventral paw structures, and in subtle alterations along the proximal-distal limb axis. Engrailed-1 seems to act in part by repressing dorsal differentiation induced by Wnt-7a, and is essential for proper formation of the apical ectodermal ridge.

Animals↗

PubMed1996

An induction gene trap screen in embryonic stem cells: Identification of genes that respond to retinoic acid in vitro.

We have developed a novel induction gene trap approach that preselects in vitro for integrations into genes that lie downstream of receptor/ligand-mediated signaling pathways. Using this approach, we have identified 20 gene trap integrations in embryonic stem cells, 9 of which were induced and 11 of which were repressed after exposure to exogenous retinoic acid (RA). All but one of these integrations showed unique spatially restricted or tissue-specific patterns of expression between 8.5 and 11.5 days of embryogenesis. Interestingly, expression was observed in tissues that are affected by alterations in RA levels during embryogenesis. Sequence analysis of fusion transcripts from six integrations revealed five novel gene sequences and the previously identified protooncogene c-fyn. To date, germ-line transmission and breeding has uncovered one homozygous embryonic lethal and three homozygous viable insertions. These studies demonstrate the potential of this induction gene trap approach for identifying and mutating genes downstream of signal transduction pathways.

Animals↗

PubMed1996

Lack of pharmacodynamic and pharmacokinetic interaction between pantoprazole and phenprocoumon in man.

OBJECTIVE: Pantoprazole is a selective proton pump inhibitor characterized by a low potential to interact with the cytochrome P450 enzymes in man. Due to the clinical importance of an interaction with anticoagulants, this study was carried out to investigate the possible influence of pantoprazole on the pharmacodynamics and pharmacokinetics of phenprocoumon. METHODS: Sixteen healthy male subjects were given individually adjusted doses of phenprocoumon to reduce prothrombin time ratio (Quick method) to about 30-40% of normal within the first 5-9 days and to maintain this level. The individual maintenance doses remained unaltered from day 9 on and were administered until day 15. Additionally, on study days 11-15, pantoprazole 40 mg was given per once daily. As a pharmacodynamic parameter, the prothrombin time ratio was determined on days 9 and 10 (reference value) and on days 14 and 15 (test value), and the ratio test/reference was evaluated according to equivalence criteria. RESULTS: The equivalence ratio (test/reference) for prothrombin time ratio was 1.02 (90% confidence interval 0.95-1.09), thus fulfilling predetermined bioequivalence criteria (0.70-1.43). The pharmacokinetic characteristics AUC0-24h and Cmax of S(-)- and R(+)-phenprocoumon were also investigated using equivalence criteria. Equivalence ratios and confidence limits of AUC0-24h and of Cmax of S(-)-phenprocoumon (0.93, 0.87-1.00 for AUC0-24h; 0.95, 0.88-1.03 for Cmax) and of R(+)-phenprocoumon (0.89, 0.82-0.96; 0.9, 0.83-0.98) were within the accepted range of 0.8-1.25. CONCLUSION: Pantoprazole does not interact with the anticoagulant phenprocoumon on a pharmacodynamic or pharmacokinetic level. Concomitant treatment was well tolerated.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1996

A novel family of repeat sequences in the mouse genome responsive to retinoic acid.

Repetitive DNA sequences form a substantial portion of eukaryotic genomes and exist as members of families that differ in copy number, length, and sequence. Various functions, including chromosomal integrity, gene regulation, and gene rearrangement have been ascribed to repetitive DNA. Although there is evidence that some repetitive sequences may participate in gene regulation, little is known about how their own expression may be regulated. During the course of gene trapping experiments with embryonic stem (ES) cells, we identified a novel class of expressed repetitive sequences in the mouse, using 5' rapid amplification of cDNA ends-polymerase chain reaction (5' RACE-PCR) to clone fusion transcripts from these lines. The expression of these repeats was induced by retinoic acid (RA) in cultured ES cells examined by Northern blot analyses. In vivo, their expression was spatially restricted in embryos and in the adult brain as determined by RNA in situ hybridization. We designated this family of sequences as Dr (developmentally regulated) repeats. The members of the Dr family, identified by cDNA cloning and through database search, are highly similar in sequence and show peculiar structural features. Our results suggest the expression of Dr-containing transcripts may be part of an ES cell differentiation program triggered by RA.

Animals↗