Quantification of endothelins, their receptors, and endothelin-converting enzyme mRNAs in rat genitourinary tract using real-time RT-PCR

Expression of umami-taste-related genes in the tongue: a pilot study for genetic taste diagnosis

OBJECTIVE

Expression of taste-related genes in the tongue was analysed to develop a technique for genetic diagnosis of umami taste disorders.

MATERIALS AND METHODS

Tissue samples were collected from healthy volunteers by scraping the foliate papillae of the tongue. Immunocytochemistry staining of gustducin, a taste-cell-specific G protein, and gene expression analysis by real-time polymerase chain reaction of β-actin, gustducin (GNAT3) and umami receptors (T1R1, T1R3 and mGluR1) were performed. Changes in umami receptor expression following application of umami substances onto the tongue were analysed.

RESULTS

Gustducin-positive cells were observed in the samples, indicating the presence of taste cells. Gene expression of β-actin, GNAT3, T1R1 and T1R3 was detected in all seven samples tested, while that of mGluR1 was detected in four samples. Sequence analysis by NCBI Blast showed that each polymerase chain reaction product had a 99% rate of identification of its target sequence. Stimulation of the tongue with monosodium glutamate significantly upregulated the gene expression levels of T1R1 and T1R3, indicating that this method can detect alterations in umami-related gene expression.

CONCLUSION

Evaluation of the expression of the umami receptor genes, T1R1 and T1R3, in the tongue may be clinically useful for objective genetic diagnosis of umami taste disorders.

Effects of age and hypertension on α1-adrenoceptors in the major source arteries of the rat bladder and penis

α(1)-Adrenoceptors regulate blood pressure, regional vascular resistance and tissue blood flow. As aging and hypertension may impact pelvic arterial blood flow resulting in bladder and penile dysfunction, we investigated effects of age and hypertension on α(1)-adrenoceptors in the major source arteries of the rat bladder and penis. Using radioligand receptor binding, real-time reverse transcription-polymerase chain reaction (RT-PCR) and fluorescent microsphere infusion techniques, we compared 3 and 22-month-old male Fischer rats, and male normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Twenty-two-month-old rats and SHRs had significantly higher total α(1)-adrenoceptor density in the internal iliac artery and lower blood flow to the bladder and penis than 3-month-old and WKY rats, respectively. RT-PCR data showed an age and hypertension related increase in the expression of α(1B)-adrenoceptor mRNA in the internal iliac, vesical and internal pudendal arteries and a switch from α(1A) predominance in 3-month-old and WKY rats to α(1B)>α(1A) in 22-month-old rats and SHRs. Our data indicate the presence of age and hypertension related alterations in vascular α(1)-adrenoceptor subtype distribution and in blood flow to the rat bladder and penis. These findings suggest that pharmacological blockade of the vascular α(1B)-adrenoceptor, which could increase pelvic blood flow, may contribute to the improvement of bladder and penile dysfunctions in animal models for aging and hypertension.

Effect of periodontitis on erectile function and its possible mechanism

INTRODUCTION

Periodontitis is one of the important risk factors resulting in cardiovascular diseases. Erectile dysfunction (ED) is strongly correlated with cardiovascular diseases. The expression of endothelial nitric oxide synthase (eNOS) in penile tissue has an important role in the mechanism of erection.

AIM

To investigate the effect of periodontitis on erectile function and the possible mechanism.

METHODS

After induction of periodontitis in rat, the ratio of maximum intracavernosal pressure/mean arterial pressure (ICPmax /MAP)×100, the expression of eNOS in penile tissue, the level of serum C-reactive protein (CRP) and tumor necrosis factor-α (TNF-α), and the ultrastructural changes of the cavernous tissue were examined and compared between periodontitis rats (group A) and control rats (group B).

MAIN OUTCOME MEASURE

Periodontitis significantly decrease not only the ICPmax/MAP×100 and the expression of eNOS but also the activity of NOS and the level of cyclic guanosine monophosphate (cGMP) in cavernous tissue of rat.

RESULTS

After electrostimulation by 3 and 5 voltage, the ratio of ICPmax /MAP×100 in group A was significantly less than that in group B (19.54±6.16 vs. 30.45±3.12; 30.91±5.61 vs. 50.52±9.52, respectively; P<0.05).The level of serum CRP and TNF-α in group A is significantly higher in group B (P<0.05).The quantitative real-time reverse transcription polymerase chain reaction study demonstrated no statistically significant difference in the expression of mRNA of eNOS in cavernous tissue between the two groups (P>0.05). But there was significant decrease in eNOS protein of the cavernous tissue in group A than in group B (P<0.05). Total NOS activity and cGMP level in cavernosal tissue were significantly lower in group A than in group B (P<0.05). There was no significant alternation occurred in the ultrastructures of penile cavernous tissue.

CONCLUSIONS

The function of penile erection is impaired by periodontitis. The decreased in the expression of eNOS and NOS activity in penile cavernous tissue caused by mild systemic inflammatory status in periodontitis may be one of the important risk factors of ED.

Molecular mechanisms regulating urogenital expression of nitric oxide synthase in spontaneously hypertensive rats

AIMS

Although doxazosin, but not nifedipine, can partially prevent a decrease in urogenital expression of nitric oxide synthase (NOS) in spontaneously hypertensive rats (SHRs), the mechanisms involved in the regulated expression of NOS are not known. Therefore, we identified differential gene expression profiles in SHRs to elucidate the molecular mechanisms regulating urogenital expression of NOS.

MAIN METHODS

SHRs and normotensive Wistar-Kyoto (WKY) rats received doxazosin (30 mg/kg/day) or nifedipine (30 mg/kg/day) orally for 4 weeks. Microarray expression data of key transcripts were verified by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis.

KEY FINDINGS

RT-PCR data, in accord with the microarray analysis, indicated that untreated SHRs had lower mRNA expression levels of cAMP responsive element binding protein 1 (Creb1) in the pelvic ganglion and vascular endothelial growth factor A (Vegfa) and kinase insert domain protein receptor (Kdr) in the penis, and higher mRNA expression levels of brain derived neurotrophic factor and neurotrophin 3 (Ntf3) in the bladder and Ntf3, Rho-kinases (Rock1 and Rock2) and caveolin 1 (Cav1) in the penis than untreated WKY rats. In SHRs, doxazosin and nifedipine caused a significant decrease in penile expression of Rock1 and Rock2, whereas the differential alterations in urogenital expression of Creb1, Vegfa, Kdr and Cav1 were attenuated by treatment with doxazosin, but not nifedipine.

SIGNIFICANCE

Our data suggest that differential alterations in the expression of several genes related to pathways that mediate NOS expression in the urogenital tissues of SHRs, which can be attenuated by doxazosin treatment, may play an important role in regulating urogenital expression of NOS.

Short- and long-term effects of silodosin, a selective alpha 1A-adrenoceptor antagonist, on ejaculatory function in rats

OBJECTIVE

To investigate the short- and long-term effects of silodosin, a selective alpha(1A)-adrenoceptor antagonist, on spontaneous seminal emission by isolated rats and on the properties of alpha(1)-adrenoceptor subtypes in the rat seminal vesicle, as silodosin produces a relatively high incidence rate of abnormal ejaculation and chronic administration of receptor antagonists causes an up-regulation in the targeted receptor.

MATERIALS AND METHODS

Rats were treated with two doses (0.1 and 3 mg/kg/day) of silodosin orally for 3 or 30 days. Spontaneous seminal emission was studied during the 3-day observation period before completing treatment. The expression levels of alpha(1A), alpha(1B) and alpha(1D)-adrenoceptor mRNAs in the rat seminal vesicle and prostate were quantified by real-time reverse transcription-polymerase chain reaction using SYBR Green I.

RESULTS

The administration of two doses of silodosin for 3 or 30 days caused a significant dose-dependent reduction in the number of ejaculatory plugs and in their dry weight. However, in rats receiving the low dose of silodosin the inhibitory effect of the drug on spontaneous seminal emission diminished significantly with chronic usage over time. Although short-term administration of silodosin did not affect expression levels of any alpha(1)-adrenoceptor subtype mRNAs in the rat seminal vesicle and prostate, long-term administration of silodosin caused a significant up-regulation in the mRNA expression of alpha(1A)-adrenoceptor in a tissue-dependent manner.

CONCLUSION

Silodosin-induced up-regulation of alpha(1A)-adrenoceptor mRNA in the rat seminal vesicle might indicate potential differences in the inhibitory effect of this drug on ejaculatory function with chronic usage over time.

Exercise training normalizes beta-adrenoceptor expression in dogs susceptible to ventricular fibrillation

Previous studies demonstrated an enhanced beta(2)-adrenoceptor (AR) responsiveness in animals susceptible to ventricular fibrillation (VF) that was eliminated by exercise training. The present study investigated the effects of endurance exercise training on beta(1)-AR and beta(2)-AR expression in dogs susceptible to VF. Myocardial ischemia was induced by a 2-min occlusion of the left circumflex artery during the last minute of exercise in dogs with healed infarctions: 20 had VF [susceptible (S)] and 13 did not [resistant (R)]. These dogs were randomly assigned to either 10-wk exercise training [treadmill running; n = 9 (S) or 8 (R)] or an equivalent sedentary period [n = 11 (S) or 5 (R)]. Left ventricular tissue beta-AR protein and mRNA were quantified by Western blot analysis and RT-PCR, respectively. Because beta(2)-ARs are located in caveolae, caveolin-3 was also quantified. beta(1)-AR gene expression decreased ( approximately 5-fold), beta(2)-AR gene expression was not changed, and the ratio of beta(2)-AR to beta(1)-AR gene expression was significantly increased in susceptible compared with resistant dogs. beta(1)-AR protein decreased ( approximately 50%) and beta(2)-AR protein increased (400%) in noncaveolar fractions of the cell membrane in susceptible dogs. Exercise training returned beta(1)-AR gene expression to levels seen in resistant animals but did not alter beta(2)-AR protein levels in susceptible dogs. These data suggest that beta(1)-AR gene expression was decreased in susceptible dogs compared with resistant dogs and, further, that exercise training improves beta(1)-AR gene expression, thereby restoring a more normal beta-AR balance.

Increased expression of transient receptor potential vanilloid subfamily 1 in the bladder predicts the response to intravesical instillations of resiniferatoxin in patients with refractory idiopathic detrusor overactivity

OBJECTIVES

To investigate the correlation of transient receptor potential vanilloid subfamily 1 (TRPV1) mRNA expression levels and the clinical outcome of intravesical resiniferatoxin treatment in patients with idiopathic detrusor overactivity (IDO), as such treatment with vanilloids can be effective for DO.

PATIENTS AND METHODS

In all, 28 patients with IDO refractory to anticholinergics were enrolled and treated with four weekly intravesical instillations of 10 nm resiniferatoxin. Eleven patients having ureteroscopic surgery served as controls. Two bladder wall biopsies were taken from the posterior wall by rigid cystoscopy. TRPV1 expression in the bladder wall samples was determined by individual quantitative reverse transcription-polymerase chain reaction, and immunohistochemical staining. Responders to the therapy were defined as those with an improvement in an urgency scale by >/=1, and with improved general satisfaction. Baseline TRPV1 expression was compared between responders, nonresponders and controls.

RESULTS

At 3 months, 14 patients (50%) were responders and in the other 14 the treatment failed (nonresponders). Bladder biopsies were available in seven responders and 11 nonresponders. Transcript levels before treatment correlated significantly with the therapeutic effect of resiniferatoxin (P = 0.004), with higher TRPV1 mRNA expression in responders (median 1.50, range 0.89-2.78) than nonresponders (0.74, 0.34-1.32). Responders also had higher TRPV1 expression levels than a control group (P = 0.067), but the TRPV1 transcript levels of nonresponders were not significantly different from those of the control (P = 0.367).

CONCLUSION

Successful intravesical resiniferatoxin treatment is closely associated with the over-expression of TRPV1 in the bladder mucosa and submucosa in patients with IDO.

Effects of doxazosin on blood flow and mRNA expression of nitric oxide synthase in the spontaneously hypertensive rat genitourinary tract

Hypertension may impact pelvic arterial blood flow resulting in reduction of nitric oxide synthase (NOS) levels. Although doxazosin, an alpha(1)-adrenoceptor antagonist, has been shown to improve erectile dysfunction as well as benign prostatic hyperplasia (BPH) and hypertension, it is not clear whether these improvements using doxazosin are primarily due to direct actions on the prostate, urinary bladder and penis, possibly via inhibition of vascular alpha(1)-adrenoceptors, or other sites of actions. Therefore, we investigated effects of doxazosin to the spontaneously hypertensive rat (SHR) on blood flow and NOS levels in the genitourinary tract. Four groups of rats were assessed: group 1, SHRs treated with doxazosin (30 mg/kg/day) for 4 weeks; group 2, SHRs treated with nifedipine (30 mg/kg/day) for 4 weeks; group 3, untreated SHRs; and group 4, untreated Wistar-Kyoto (WKY) rats. Blood flow to the ventral prostate, dorsolateral prostate, urinary bladder and penis was determined using a fluorescent microsphere infusion technique. Expression levels of nNOS and eNOS mRNAs were quantified by real-time RT-PCR using SYBR Green I. Blood flow to the ventral prostate, dorsolateral prostate, urinary bladder and penis was significantly lower in untreated SHRs than WKY rats. Treatment with doxazosin increased blood flow to each tissue studied in SHRs. RT-PCR data indicated that untreated SHRs had lower mRNA expression levels of nNOS in the bladder and penis and eNOS in the penis than WKY rats and that administration of doxazosin to the SHR caused an increase in expression levels of these genes, i.e., up-regulation of nNOS in the bladder and penis and eNOS in the penis. However, nifedipine had no significant effects on blood flow and NOS levels in the SHR genitourinary tract. Our data demonstrate that doxazosin treatment causes differential alterations in blood flow and NOS levels in the SHR genitourinary tract. These findings may provide insight into the beneficial effects of alpha(1)-adrenoceptor antagonists, on prostate, bladder and penile function, when used to treat symptoms of BPH and elevated blood pressure.

Age Related Changes in the Functional, Biochemical and Molecular Properties of α 1 -Adrenoceptors in the Rat Genitourinary Tract

PURPOSE

Because age related changes occur in the properties of alpha(1)-adrenoceptor in several mammalian tissues and alpha(1)-adrenoceptor antagonists are extensively used to treat lower urinary tract symptoms secondary to benign prostatic hyperplasia, we investigated age related changes in the functional, biochemical and molecular properties of alpha(1)-adrenoceptor in the rat genitourinary tract.

MATERIALS AND METHODS

The characteristics of alpha(1)-adrenoceptor in the ventral and dorsolateral prostate, and bladder base and dome of 3 and 22-month-old rats were determined using an isolated muscle bath, radioligand receptor binding and real-time reverse transcriptase-polymerase chain reaction techniques.

RESULTS

Old rats had significantly higher body weight, lower testosterone, a smaller ventral prostate and a larger bladder dome than young rats. Although there was no significant age dependent difference in the properties of alpha(1)-adrenoceptor in the bladder base and dome, total alpha(1)-adrenoceptor density, mRNA expression of all 3 alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B) and alpha(1D)) and the maximum contractile responses to phenylephrine were significantly lower in the ventral and dorsolateral prostate of 22 vs 3-month-old rats.

CONCLUSIONS

Age related differences in the molecular, biochemical and functional properties of alpha(1)-adrenoceptors in the rat genitourinary tract may indicate potential differences in the response to alpha(1)-adrenoceptor antagonists with aging, ie a decrease in the therapeutic response in old vs young rats in the response to alpha(1)-adrenoceptor antagonists when used to treat lower urinary tract symptoms secondary to benign prostatic hyperplasia.

Effects of chronic administration of doxazosin on alpha1-adrenoceptors in the rat prostate

PURPOSE

Although the clinical efficacy of alpha1-adrenoceptor (alpha1-AR) antagonists for the treatment of benign prostatic hyperplasia is not disputed, their mechanism of action and ability to maintain long-term effectiveness have only recently been investigated. Since it is known that chronic administration of receptor antagonists causes up-regulation in the targeted receptor, we examined the effects of chronic administration of doxazosin, a nonspecific long acting alpha1-AR antagonist, on the properties of alpha1-AR subtypes in the rat prostate.

MATERIALS AND METHODS

Rats were treated with doxazosin (2 or 4 mg/kg daily subcutaneously, supplemented with 4 mg/kg daily orally) for 8 or 12 weeks. Prostatic alpha1-AR properties at the protein and gene transcript levels were quantified by radioligand receptor binding and real-time reverse transcriptase-polymerase chain reaction, respectively.

RESULTS

Treated rats that received the highest levels of doxazosin had significantly heavier prostates compared with age matched controls. After 12 weeks of treatment radioligand binding studies with radiolabeled alpha1-AR antagonist demonstrated no significant differences in the density of total alpha1-ARs in the prostate, whereas the results of real-time reverse transcriptase-polymerase chain reaction showed up-regulation in the mRNA expression levels of all 3 alpha1-AR subtypes (alpha1A, alpha1B and alpha1D) in the ventral and dorsolateral regions of the rat prostate.

CONCLUSIONS

These data demonstrate that chronic treatment with doxazosin causes an alteration in the properties of the alpha1-AR system in the rat prostate. These findings may provide insight into the long-term effectiveness of alpha1-AR antagonists in the treatment of benign prostatic hyperplasia.

Analysis of fibroblast growth factor 2 (FGF2) gene transcription and protein distribution in the bovine testis

Several fibroblast growth factors (FGFs) are implicated in proliferation and differentiation of both somatic and germ cells during testicular development, as well as in spermatogenesis of adult testis. The expression of FGF2 was studied in the adult bovine testis using quantitative RT-PCR, RNA in situ hybridization, and immunohistochemistry. Quantitative RT-PCR revealed consistent levels of FGF2 mRNA in parenchymal samples of the bovine testis. In situ hybridization localized FGF2 transcripts only in a constant fraction of Leydig and Sertoli cells as well as in modified Sertoli cells of the terminal segments. Immunohistochemistry revealed (a) no FGF2 protein in Sertoli cells (b) moderate cytoplasmic staining in Leydig cells and spermatogonia and (c) strong nuclear and faint cytoplasmic staining in myofibroblasts, in epithelial cells of straight tubules and rete testis and in blood vessels. These observations indicate a pleiotropic effect of FGF2 on the control of spermatogenesis in a paracrine and/or autocrine manner.

Doxazosin-induced up-regulation of alpha 1A-adrenoceptor mRNA in the rat lower urinary tract

Alpha1-adrenoceptor (AR) antagonists can provide effective treatment of symptoms caused by benign prostatic hyperplasia. However, their mechanisms of action have not been fully elucidated. We previously reported that chronic administration of doxazosin causes an up-regulation in the mRNA expression of all three alpha1-AR subtypes in the rat prostate. As alpha1-AR antagonists might also affect the properties of alpha1-ARs in the lower urinary tract, we examined the effects of doxazosin (2 or 4 mg/kg daily subcutaneously, supplemented with 4 mg/kg daily orally for 8 or 12 weeks) on alpha1-AR subtype mRNAs in the rat bladder dome, bladder base, and urethra using real-time reverse transcription PCR. Rats that received the highest doses of doxazosin had significantly heavier bladder base and prostatic urethra than controls. PCR data showed that all three alpha1-AR subtypes were expressed in all tissues studied. Doxazosin treatment caused an up-regulation in the mRNA levels of alpha1A-AR in the rat bladder base and prostatic urethra, indicating that chronic doxazosin treatment may cause an alteration in the properties of alpha1A-AR subtype mRNA in these two areas. Furthermore, the heavier bladder base and prostatic urethra in the doxazosin-treated rats suggest that alpha1-AR antagonist treatment might also influence the growth process in these areas of the rat lower urinary tract.

Molecular classification of doxazosin-induced alterations in the rat prostate using gene expression profiling

We investigated molecular changes that occurred during chronic administration of doxazosin, an alpha1-adrenoceptor (AR) antagonist, using Affymetrix GeneChip analysis of gene expression. Rats were treated with doxazosin (4 mg/kg/day subcutaneously, supplemented with 4 mg/kg/day orally) for 12 weeks. Labeled cRNA was prepared and the subsequent hybridization to rat 230A arrays was performed. The alterations in gene expression levels of candidate genes identified by microarray analysis with potential biological relevance were verified by real-time reverse transcription polymerase chain reaction (RT-PCR) using SYBR Green I. Doxazosin treated rats had significantly heavier prostates compared to control rats. Microarray analysis revealed that chronic doxazosin treatment caused changes in the expression levels of 625 genes, of which 39 were related to cell death, necrosis, growth, proliferation and G-protein signalling pathways in the rat prostate. Furthermore, RT-PCR experiments, in accord with the microarray analysis, indicated that chronic doxazosin treatment caused an up-regulation in the mRNA expression level of clusterin, an antiapoptotic mediator, and epiregulin, a mitogen, in the ventral and dorsolateral prostate, respectively. These findings, that demonstrate chronic doxazosin administration causes significant changes in the expression of several hundred genes in the rat prostate, may provide insight into the long-term efficacy of alpha1-AR antagonists in the treatment of benign prostatic hyperplasia.

Age-related changes in the properties of the endothelin receptor system at protein and mRNA levels in the rat vas deferens

As age-related changes occur in the properties of the endothelin (ET) receptor system in several mammalian tissues, and as there are significant amounts of functional ET receptors in the vas deferens, we investigated the age-related changes in the ET receptor system at the protein and mRNA levels in the rat vas deferens. The ET system was investigated in the vasa deferentia of 3 weeks, 3 months and 22 months old rats. ET receptors were characterized and quantified at the protein level by radioligand receptor binding, and gene transcript levels of ET-1, ET-3, ET converting enzyme-1 (ECE-1), and ET(A) and ET(B) receptor subtypes were quantified by real-time reverse transcription polymerase chain reaction (RT-PCR). The results of radioligand receptor binding assays demonstrate that there is a higher density of total ET receptors in the vas deferens of 3 weeks old rats than in 3 months and 22 months old rats, and that the predominant ET receptor is of the ET(A) subtype in all three ages. Real-time RT-PCR data show that the predominant mRNA expression of ETs and their receptors in all age groups studied are ET-1 and the ET(A) receptor subtype, respectively. Furthermore, ET-1, ET-3, ECE-1, and ET(A) and ET(B) receptor subtype mRNAs are expressed at higher levels in the 3 weeks old rats as compared with the other two age groups. These results demonstrate the presence of age-related changes in the properties of the ET receptor system at both protein and mRNA levels in the rat vas deferens.

Doxazosin treatment causes differential alterations of alpha 1-adrenoceptor subtypes in the rat kidney, heart and aorta

We have previously demonstrated that long-term administration of doxazosin, an alpha(1)-adrenoceptor (alpha(1)-AR) antagonist, causes an up-regulation in the expression of alpha(1)-AR subtype mRNAs in the rat genitourinary tract and suggested that these changes may affect long-term effectiveness of alpha(1)-AR antagonists when used to treat the lower urinary tract symptoms of benign prostatic hyperplasia. As chronic administration of alpha(1)-AR antagonists may cause similar alterations in other tissues in which alpha(1)-ARs play a physiologic role, we examined the effects of long-term administration of doxazosin on the expression of alpha(1)-AR subtype mRNAs in several rat tissues. Rats were treated with doxazosin (4 mg/kg/day subcutaneously, supplemented with 4 mg/kg/day orally) for 12 weeks. The cDNA was prepared by reverse transcription of RNA extracted from the rat kidney, heart and aorta. alpha(1A), alpha(1B) and alpha(1D)-AR mRNA expression levels were quantified by real-time reverse transcription polymerase chain reaction. The rank order of expression levels of the alpha(1)-AR mRNAs in rat tissues were: alpha(1A)-AR, kidney > heart > aorta; alpha(1B)-AR, heart > kidney > aorta; alpha(1D)-AR, aorta > kidney = heart. Chronic administration of doxazosin caused an up-regulation in the mRNA level of alpha(1A), alpha(1B) and alpha(1D)-ARs in the rat kidney, heart and aorta, respectively. Our data demonstrate that doxazosin treatment causes differential alterations in the expression of alpha(1)-AR subtype mRNAs in different rat tissues. These findings may provide insight into the long-term effects of alpha(1)-AR antagonists in the treatment of diseases involving tissues whose function is regulated by alpha(1)-ARs.

DNA methylation-mediated control of Sry gene expression in mouse gonadal development

DNA methylation at CpG sequences is involved in tissue-specific and developmentally regulated gene expression. The Sry (sex-determining region on the Y chromosome) gene encodes a master protein for initiating testis differentiation in mammals, and its expression is restricted to gonadal somatic cells at 10.5-12.5 days post-coitum (dpc) in the mouse. We found that in vitro methylation of the 5'-flanking region of the Sry gene caused suppression of reporter activity, implying that Sry gene expression could be regulated by DNA methylation-mediated gene silencing. Bisulfite restriction mapping and sodium bisulfite sequencing revealed that the 5'-flanking region of the Sry gene was hypermethylated in the 8.5-dpc embryos in which the Sry gene was not expressed. Importantly, this region was specifically hypomethylated in the gonad at 11.5 dpc, while the hypermethylated status was maintained in tissues that do not express the Sry gene. We concluded that expression of the Sry gene is under the control of an epigenetic mechanism mediated by DNA methylation.