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[Identification of mutations of SRD5A2 gene and SRY gene in patients with hypospadias].

OBJECTIVE: To identify possible molecular mechanism underlined hypospadias and any relationship of the mutations of SRD5A2 gene and SRY gene to hypospadias. METHODS: Twenty-three blood samples from the patients with hypospadias were obtained from Aug.1996 to Jan. 1998. DNA was extracted from blood leukocytes. Exons 1 to 5 of the SRD5A2 gene and exon of the SRY gene were amplified by PCR. Mutation detection was performed using PCR-SSCP/silver staining and direct DNA sequencing. RESULTS: In 3 cases (named 5R2-China-1, 5R2-China-2, and 5R2-China-3), DNA sequencing revealed that a homozygous change from nucleotide G to A occurred in 5R2-China-1 and 2, leading to a substitution of glutamine to arginine in the codon 227(Arg 227 to Gln). In the third patient (5R2-China-3), DNA sequencing revealed two different heterozygous mutations(Arg 227 to Gln, Phe 186 to Leu) in exon 4 of the SRD5A2 gene. No mutation of SRY gene was found in all patients. CONCLUSION: The mutation of SRD5A2 gene affects the differentiation of the external genitalia and may play a role in the etiology of hypospadias. Since no mutation of SRY gene was found, this study might suggest that the mutation of SRY gene is not an important event in hypospadias. Codon 227 is a hotspot site of mutation within the gene. The mutation of codon 186(Phe 186Leu) represents a new form of SRD5A2 mutation.

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

Stage-specific regulatory element of mouse Sry gene.

Sry expression is essential for initiating male sex differentiation, and the expression occurs only during a restricted period in the developing gonad. It is thought that Sry is part of a pathway of genes that regulate sex determination. Although the interactions of several genes with Sry expression have been suggested, the exact cascade of gene expression regulating Sry transcription is entirely obscure because there is no available cell line expressing Sry and reflecting an in vivo condition. The present study was carried out to investigate the cis-acting element of the mouse Sry that responds stage specifically to its expression, in part, using transgenic mice expressing GFP on the Y chromosome. Ten DNA fragments were generated by digesting the 5' upstream region (positions 5491-8039; 2,549 bp) of mouse Sry with appropriate restriction enzymes. In an electrophoretic mobility assay with these fragments, the region from position 5491 to position 5799 (309 bp) was identified as forming specific protein-DNA complexes with nuclear extracts from 11.5 days post coitus (dpc) gonads, but not from 12.5 and 13.5-dpc gonads. This region also formed specific protein-DNA complexes with the nuclear extracts from adult testicular germ cells that generate only a circular form from Sry. This stage-specific responsive region was narrowed down to positions 5559-5616 by DNase I footprinting analysis. The assay of DNase I hypersensitive (HS) using the nuclear lysates from the 11.5-dpc urogenital ridges demonstrated that the novel HS site was located in the proximity of position 5600. This region DNase I HS was also detected at the same position when the lysates from adult testicular germ cells were applied. The results indicate that the present HS site may be involved in the transcriptional regulation of the linear and/or circular molecule transcripts from mouse Sry gene.

Animals↗

Widespread expression of the testis-determining gene SRY in a marsupial.

There is compelling evidence from mutation analysis and transgenesis that the SRY gene isolated from human and mouse encodes the testis-determining factor on the mammalian Y chromosome. However, how SRY achieves this function is unclear. Although marsupials have been separated from eutherian mammals for approximately 100 million years, homologues of SRY have been localised to the Y chromosome of two unrelated marsupial species, the tammar wallaby and the Darling Downs dunnart. Gonadal development is fundamentally similar in eutherian and marsupial mammals, but the timing of morphological events is different. Fetal Sry transcripts are confined to somatic cells of the male mouse genital ridge between 10.5-12.5 days post coitum, corresponding with the onset of testis differentiation. Analysis of Sry gene expression in the genital ridge of normal and germ cell-deficient fetal mice has established that this gene acts in the somatic cell lineage, and is presumed to induce the formation of Sertoli cells. This assumption can be tested more critically in the tammar, where the equivalent stages of testis differentiation are observed over a 7-day period. We have examined the relationship of SRY expression to testis differentiation in the tammar wallaby. We show the marsupial SRY gene cannot be exclusively coupled to Sertoli cell differentiation, as this gene is expressed in the male fetus from several days before genital ridge formation until 40 days after birth. SRY transcripts are also present in a variety of extra-gonadal tissues in the developing young and adult male, a pattern of SRY expression similar to that observed in humans. These data indicate that, in addition to a role in testis determination, SRY may have other functions [corrected].

Animals↗

Amplification and application of the HMG box of bovine SRY gene for sex determination.

A fast and reliable method for bovine sexing has been developed through amplification of the bovine high motility group (HMG) box of the sex-determining region of the Y chromosome gene (SRY). Oligonucleotide primers were designed according to the conserved bovine SRY HMG box sequence motif. In agarose gel electrophoresis, a normal bull showed 1 SRY band, and a normal cow showed no SRY band. After optimization, the PCR procedure for sex determination was applied to 14 embryo biopsies. The biopsied embryos were transferred into 14 recipient cows on the same day (day 7 of the estrus cycle) that the embryos were collected and sex of the calf was confirmed after parturition. Nine calves were born and anatomical sex corresponded to those sex determined by PCR in all cases (100% accuracy). Thus, this study showed for the first time that the present method can be applied in bovine breeding programs to facilitate manipulation of the sex ratio of offspring and also allows a quick diagnosis for the XY-bovine offspring by amplification of the HMG box of the bovine SRY gene.

Animals↗

Two new novel point mutations localized upstream and downstream of the HMG box region of the SRY gene in three Indian 46,XY females with sex reversal and gonadal tumour formation.

The Y chromosome-specific gene SRY is one of the key genes involved in human sex determination. The SRY gene encodes a testis-specific transcription factor that plays a key role in sexual differentiation and development in males and is located on the distal region of the short arm of the Y chromosome. Mutations in SRY gene result in XY sex reversal and pure gonadal dysgenesis. SRY expression initiates a network of gene activity that transforms the undifferentiated gonad, genital ridge into testis. Mutations in the SRY gene have been considered to account for only 10-15% of 46,XY gonadal dysgenesis cases, whereas the majority of the remaining cases may have mutation(s) in the SRY regulatory elements or other genes involved in the sex differentiation pathway. Patients both with gonadal dysgenesis and Y-chromosome presence are at high risk of developing gonadoblastoma. Using PCR, single strand conformational polymorphism (SSCP) and automated DNA sequencing, we analysed the mutations in the SRY gene in three 46,XY sex reversal patients. Two patients demonstrated nucleotide substitution (A-->G) within the open reading frame just outside and upstream of the conserved DNA-binding motif called the high-mobility group (HMG) box, replacing glutamine at codon 57 with arginine. Altered SSCP patterns were also observed in these patients. Histological examination of gonads in patient 1 revealed the formation of gonadoblastoma. Patient 3 demonstrated A-->T substitution which replaces serine at codon 143 with cysteine, just outside but downstream of the HMG box. Results suggest the involvement of SRY gene in sex reversal which further supports the relationship between SRY alterations, gonadal dysgenesis and/or primary infertility.

Adult↗

Report of an XX male with hypospadias and pubertal gynecomastia, SRY gene negative in blood leukocytes but SRY gene positive in testicular cells.

Most XX male subjects present an anomalous translocation of the sex-determining region of the chromosome Y (SRY) gene from chromosome Y to chromosome X. Several explanations have been proposed for the differentiation of testicular tissue in the absence of SRY gene. A patient is presented in whom the SRY gene was absent in peripheral leukocytes but present in testicular tissue. This possibility should always be ruled out before diagnosing Y-negative XX maleness.

Adolescent↗

Expression of the mouse testis-determining gene Sry in male preimplantation embryos.

The testis-determining factor in the mouse is encoded by the Sry gene on the Y chromosome. Transcripts of this gene have been shown previously to be present in the genital ridge at the beginning of gonadal differentiation (11.5 days post coitum) and in adult testis. In this study, RNA transcripts of the Sry gene are also detected in male blastocyst-stage embryos (3.5 days post coitum) at approximately 40-100 copies per cell, long before overt sex differentiation. These results indicate that preimplantation mouse embryos have sexually dimorphic gene expression at least with respect to Sry transcripts. In addition, at least some of the Sry RNA transcripts in blastocysts are circular, as has been reported for Sry transcripts from adult testis. The appearance of Sry transcripts in blastocysts at this level raises the possibility that sex determination begins earlier during embryonic development than previously thought.

Animals↗

[Study of sex determination gene (SRY) in 46,XY gonadal dysgenesis].

During mammalian embryogenesis, the presence of the SRY gene determines the bipotential gonad to develop as a testis. 46,XY sex reversal has been described in man. It is associated with an essentially female phenotype and a streak gonad. In a collaborative study, we analysed 36 patients with a 46,XY sex reversal. The testis determining region of the Y chromosome was analysed by Southern blotting and by DGGE analysis of the SRY open reading frame (orf). We found a total of 7 mutations in the testis determining region including the SRY gene. This brings to 19 the total number of mutations in SRY associated with sex reversal. No relationship was found between the SRY status and the presence or absence of gonadoblastoma. However, a correlation was observed between the SRY genotype and the histology of the gonad. A mutant in SRY is associated with a completely dysgenetic gonad. The presence of immature testicular tubules is usually observed when SRY is normal. These latter results suggest the existence of as yet unidentified testis determining genes.

DNA-Binding Proteins↗

Preimplantation embryo sexing by polymerase chain reaction amplification of the sry gene on single mouse blastomeres.

Accurate and rapid sex determination of preimplantation embryos has great potential both in animal breeding and in human pathology. In the past, sex determination has been accomplished by cytogenetic or immunologic means and by polymerase chain reaction amplification of Y-chromosome-specific repetitive sequences. More recently, amplification of the Y-specific single-copy ZFY gene has been used in humans for sex determination of preimplantation embryos. The experiments reported here indicate that another Y-chromosome-specific single-copy gene, the sex-determining region gene (sry) can be successfully amplified from single mouse blastomeres. Blastocysts positive for sry amplification were reimplanted to foster mothers, and six of six newborns were male. We conclude that sry gene amplification can represent a good marker for embryo sex determination.

Animals↗

Early transcription of the SRY gene by bovine preimplantation embryos.

We have examined mRNA expression of two genes located on the Y chromosome, the sex-determining region Y gene (SRY) and the linked zinc finger gene (ZFY), using in vitro fertilized-in vitro cultured bovine embryos. Expression of the SRY gene, implicated in sex determination in mammals, has been reported to occur both for a short time at the sex-determining stage of development around the period of the primitive undifferentiated gonad and in the adult testis. In this study, using a sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we detected SRY but not ZFY mRNA expression as early as the 4- to 8-cell stage and through to the blastocyst stage in bovine embryos. The expression of SRY at these early stages and the previous observation that in vitro-produced male bovine embryos develop faster in culture than female embryos suggest that sex differences are evident prior to gonadal differentiation and that preimplantation bovine embryos have sexually dimorphic gene expression at least with respect to SRY transcripts.

Animals↗

Expression of SRY gene transcripts with a longer 3' untranslated sequence in adult human male lymphocytes and tumor cells.

Using 3' RACE PCR and the repeated nested-PCR method, the expression of transcripts of the sex-determining gene SRY was investigated in single lymphocytes from a human adult male and in male tumor cell lines. The gene is functionally transcribed in the early stages of embryogenesis and mRNA is also expressed in adult testes. However, in this study, SRY gene transcripts were also detected in somatic cells of adult male and in tumor cells. Moreover, this mRNA possessed a longer additional untranslated exon. Although expression of the transcripts might not have any functional meaning in these cells, these new findings support the hypothesis that any given human cell can contain illegitimate mRNAs.

Adult↗

XY female with a dysgerminoma and no mutation in the coding sequence of the SRY gene.

We report a 46,XY 11-year-old girl with pure gonadal dysgenesis who developed a dysgerminoma. The testis-determining gene SRY, a candidate for sex reversal, whose alterations seem to correlate with dysgerminoma, was analyzed and found to be normal; its coding sequence was negative for deletions and mutations. DMRT-1 gene mapping on 9p and DAX-1 on Xp21 were also normal. These results suggest the involvement of other genes in sex reversal and call into question the putative relationship between SRY alterations and dysgerminoma.

Child↗

Functional comparison of the Mus musculus molossinus and Mus musculus domesticus Sry genes.

The Sry gene functions as a genetic switch initiating testicular development of the indifferent mammalian gonad. The Mus musculus molossinus Sry open reading frame (ORF) encodes a 395-amino acid transcription factor (mSry) that specifically binds and bends DNA through its N-terminal HMG domain and activates transcription through its long C-terminal (residues 144-366) glutamine/histidine-rich activation domain. The M. m. domesticus Sry ORF encodes a highly homologous, truncated protein (dSry) of approximately 230 amino acids, and the molecular basis for truncation is a point mutation that creates an amber stop codon within the activation domain. The mSry protein activates transcription of a Sry-responsive reporter gene in HeLa cells, but dSry does not. Gene swapping and in vitro DNA binding experiments revealed that lack of transcriptional activation by dSry was not the result of polymorphisms within the first 137 amino acids of the protein. Direct analysis of the C-terminal glutamine/histidine-rich domain revealed that dSry lacked a functional transcriptional activation domain. Fusion of the GAL4 DNA-binding domain to the C-terminal deletion mutants of the GAL4-mSry chimeric protein indicated that residues 263-345 of the glutamine/histidine-rich domain were necessary for high level transactivation. Furthermore, readthrough of the premature amber stop codon by transfer RNA suppression resulted in a strong GAL4-dSry transactivator. This demonstrated that the premature stop codon is the only polymorphism responsible for the inability of the dSry glutamine/histidine-rich region to transactivate.

Animals↗

Circular transcripts of the testis-determining gene Sry in adult mouse testis.

Sry is expressed at higher levels in the adult testis, where no function has been determined, than in the genital ridge, its critical site of action. cDNA and 5' RACE clones isolated from testis or from Sry-transfected cell lines have an unusual structure, with 3' sequences located in a 5' position. RNAase protection assays and reverse transcription polymerase chain reactions confirmed that these unusual RNA molecules represent the most abundant transcript in testis. Furthermore, oligonucleotide hybridization and RNAase H digestion proved that these Sry RNA molecules are circular. Similar transcripts were detected in the testes of mice with Mus musculus musculus, Mus musculus domesticus, and Mus spretus Sry genes. The circular RNA is found in the cytoplasm but is not substantially bound to polysomes. We suggest that the circles arise from normal splicing processes as a consequence of the unusual genomic structure surrounding the Sry locus in the mouse.

Animals↗

SRY gene transferred to the long arm of the X chromosome in a Y-positive XX true hermaphrodite.

Yp-specific sequences, including the testicular determinant gene SRY, have been detected and located in a 46,XX true hermaphrodite individual, using PCR amplification and fluorescent in situ hybridization (FISH). Among different Y chromosome loci tested, it was only possible to detect Yp sequences. The Y-centromere and Yq sequences were absent. Unexpectedly, the Y fragment was translocated to the long arm of one of the X chromosomes, at the Xq28 level, and the derivative (X) chromosome of the patient lacked q-telomeric sequences. To our knowledge, this is the first Yp/Xq translocation reported. The coexistence of testicular and ovarian tissue in the patient may have arisen by differential inactivation of the Y-bearing X chromosome, in which Xq telomeric sequences are missing. The possible origin of the Yp/Xq translocation, during paternal meiosis or in somatic paternal cells, is discussed.

Adult↗

A familial mutation in the testis-determining gene SRY shared by both sexes.

A familial mutation in SRY, the gene coding for the testis-determining factor TDF, was identified in an XY female with gonadal dysgenesis, her father, her two brothers and her uncle. The mutation consists of a T to C transition in the region of the SRY gene coding for a protein motif known as the high mobility group (HMG) box, a protein domain known to confer DNA-binding specificity on the SRY protein. This point mutation results in the substitution, at amino acid position 109, of a serine residue for phenylalanine, a conserved aromatic residue in almost all HMG box motifs known. This F109S mutation was not found in 176 male controls. When recombinant wildtype SRY and SRYF109S mutant protein were tested in vitro for binding to the target site AAC AAAG, no differences in DNA-binding activity were observed. These results imply that the F109S mutation either is a rare neutral sequence variant, or produces an SRY protein with slightly altered in vivo activity, the resulting sex phenotype depending on the genetic background or environmental factors.

Amino Acid Sequence↗

Mapping the SRY gene in Microtus cabrerae: a vole species with multiple SRY copies in males and females.

The SRY gene is a single-copy, male-specific gene, located on the Y chromosome in most mammals. However, recently we have described the presence of multiple polymorphic copies of this gene in both males and females of the vole species Microtus cabrerae. Here, we present the chromosomal localization of SRY gene copies in this species by fluorescent in situ hybridization (FISH). This technique localized these gene copies in the short arm, and hence in the euchromatic region, of the Y chromosome. Furthermore, several copies of the SRY gene are located on the X chromosome. These copies are spread along the entire heterochromatic region of the X chromosome, occupying the whole short arm, the centromeric region, and the pericentromeric region of the long arm.

Animals↗

The human sex-determining gene SRY is a direct target of WT1.

The product of the Wilms' tumor gene, WT1, is essential for male sex determination and differentiation in mammals. In addition to causing Wilms' tumor, mutations in WT1 often cause two distinct but overlapping urogenital defects in men, Denys-Drash syndrome and Frasier syndrome. In this study we investigated the regulation of the sex determination gene SRY by WT1. Our results showed that WT1 up-regulates the SRY gene through the proximal early growth response gene-1-like DNA-binding sequences in the core promoter. Mutant WT1 proteins in Denys-Drash syndrome patients were unable to activate this promoter. These mutants did not act in a dominant negative manner, as expected over the wild-type WT1 in this promoter. We also found that WT1 could transactivate the endogenous SRY gene. These observations, together with the overlapping expression patterns of WT1 and SRY in human gonads, led us to propose that WT1 regulates SRY in the initial sex determination process in humans and activates a cascade of genes ultimately leading to the complete organogenesis of the testis.

Cell Line↗