Goat SRY induces testis development in XX transgenic mice

The testis-determining gene SRY is not well-conserved among mammals, particularly between mouse and other mammals, both in terms of protein structure and of expression regulation. To evaluate SRY phylogenic conservation in regards to its function, we expressed the goat gene (gSRY) in XX transgenic mouse gonads. Here, we show that gSRY induces testis formation, despite a goat expression profile. Our results demonstrate that sex-reversal can be induced in XX-mice by a non-mouse SRY thus suggesting a conserved molecular mechanism of action of this testis-determining gene across mammalian species.     

XY sex reversal associated with a nonsense mutation in SRY.

Sex determination in humans is mediated through the expression of a testis-determining gene on the Y chromosome. In humans, a candidate gene for the testis-determining factor (TDF) that encodes a protein with a putative DNA-binding motif and has been isolated is termed SRY. Here we describe an XY sex-reversed female with pure gonadal dysgenesis who harbors a de novo nonsense mutation in the SRY open reading frame (SRY-orf). This single-basepair substitution results directly in the formation of a termination codon in the putative SRY DNA-binding motif, presumably leading to a nonfunctional gene product. This brings the number of reported XY sex-reversed females with de novo mutations in the known SRY-orf to three, each occurring in the putative DNA-binding domain. This provides further evidence to support SRY being TDF in humans and also indicates the functional importance of the putative DNA-binding domain of the SRY protein.     

Cloning and mutational analysis of SRY.

A candidate for the male sex-determining gene has recently been isolated. This sex-determining gene (SRY) has been found to be mutated in some individuals with failed testis development, and, in mouse transgenesis, the SRY murine homologue (Sry) causes female-to-male sex reversal. The cloning of SRY should facilitate the characterisation of other genes in the testis-determining pathway and provide information on the mechanism of mammalian developmental decisions.     

Sry: the master switch in mammalian sex determination

SRY, the mammalian Y-chromosomal testis-determining gene, induces male sex determination. Recent studies in mice reveal that the major role of SRY is to achieve sufficient expression of the related gene Sox9, in order to induce Sertoli cell differentiation, which in turn drives testis formation. Here, we discuss the cascade of events triggered by SRY and the mechanisms that reinforce the differentiation of the testes in males while actively inhibiting ovarian development.     

True hermaphroditism in a 46,XY individual, caused by a postzygotic somatic point mutation in the male gonadal sex-determining locus (SRY): molecular genetics and histological findings in a sporadic case.

Recently, the gene for the determination of maleness has been identified in the sex-determining region on the short arm of the Y chromosome (SRY) between the Y-chromosomal pseudoautosomal boundary (PABY) and the ZFY gene locus. Experiments with transgenic mice confirmed that SRY is a part of the testis-determining factor (TDF). We describe a sporadic case of a patient with intersexual genitalia and the histological finding of ovotestes in the gonad, which resembles the mixed type of gonadal tissue without primordial follicle structures. The karyotype of the patient was 46,XY. By PCR amplification, we tested for the presence of PABY, SRY, and ZFY by using DNA isolated from peripheral blood leukocytes and for the presence of SRY by using DNA obtained from histological gonadal slices. The SRY products of both DNA preparations were further analyzed by direct sequencing. All three parts of the sex-determining region of the Y chromosome could be amplified from leukocytic DNA. The patient's and the father's SRY sequences were identical with the published sequence. In the SRY PCR product of gonadal DNA, the wild-type and two point mutations were present in the patient's sequence, simulating a heterozygous state of a Y-chromosomal gene: one of the mutations was silent, while the other encoded for a nonconservative amino acid substitution from leucine to histidine. Subcloning procedures showed that the two point mutations always occurred together. The origin of the patient's intersexuality is a postzygotic mutation of the SRY occurring in part of the gonadal tissue. This event caused the loss of the testis-determining function in affected cells.     

棕色田鼠性别决定研究进展

哺乳动物性别决定方式属于雄性异配型性别决定, 依赖于Y染色体, SRY基因是性别决定中最重要的基因。文章报道了棕色田鼠指名亚种有Y染色体, 但是Y染色体上没有SRY基因, 性别决定不依赖于SRY基因, 排除了R-spondin 1基因是性别决定基因, 同时讨论了棕色田鼠指名亚种SRY基因缺失后可能的性别决定 机制。     

中国人SRY基因的分离、克隆和核苷酸序列分析

睾丸决定因子基因(Testis-determining factor,TDF)位于Y染色体短臂上,它的表达产物诱导睾丸组织的发生。SRY基因(Sex-determining Region of the Y)位于Y染色体的性别决定区内,许多特征显示SRY就是TDF。我们选用与SRY基因相应的引物,用PCR技术对正常人男女各10例的基因组DNA进行扩增。将特异扩增的男性SRY基因片段重组到质粒PUC12中,得到含有中国人SRY基因片段的克隆,命名为PSY-1、PSY-2。用[~(32)p]标记重组质粒中的SRY基因片段作探针,与PCR结果进行Southern杂交,男性样品均显示特异杂交带,女性样品为阴性。用末端终止法测定克隆的SRY基因片段的全部核苷酸序列为299bp,含有SRY基因中高度保守及功能特异性区域的240bp,我们对此进行了讨论。     

Z and W chromosomes of chickens: studies on their gene functions in sex determination and sex differentiation

Since the discovery of SRY/SRY as a testis-determining gene on the mammalian Y chromosome in 1990, extensive studies have been carried out on the immediate target of SRY/SRY and genes functioning in the course of testis development. Comparative studies in non-mammalian vertebrates including birds have failed to find a gene equivalent to SRY/SRY, whereas they have suggested that most of the downstream factors found in mammals including SOX9 are also involved in the process of gonadal differentiation. Although a gene whose function is to trigger the cascade of gene expression toward gonadal differentiation has not been identified yet on either W or Z chromosomes of birds, a few interesting genes have been found recently on the sex chromosomes of chickens and their possible roles in sex determination or sex differentiation are being investigated. It is the purpose of this review to summarize the present knowledge of these sex chromosome-linked genes in chickens and to give perspectives and point out questions concerning the mechanisms of avian sex determination.     

Familial case with sequence variant in the testis-determining region associated with two sex phenotypes.

The human Y chromosome encodes a testis-determining factor (TDF) which is responsible for initiating male sex determination. Recently a region of the Y chromosome (SRY) was identified as part of the TDF gene. We have identified a three-generation family (N) in which all XY individuals have a single base-pair substitution resulting in a conservative amino acid change in the conserved domain of the SRY open reading frame. Three individuals are XY sex-reversed females, and two are XY males. Several models are proposed to explain association between a sequence variant in SRY and two sex phenotypes.     

The rise and fall of SRY

Comparisons between species reveal when and how SRY, the testis-determining gene, evolved. SRY is younger than the Y chromosome, and so was probably not the original mammal sex-determining gene that defined the Y. SRY is typical of genes on the Y chromosome. It arose from a gene on the proto-sex chromosome pair with a function (possibly brain-determination) in both sexes. It has been buffeted in evolution, and shows variation in copy number, structure and expression. And it is dispensable, having been lost at least twice independently in different rodent lineages. At the observed rate of attrition, the human Y chromosome will be gone in 5-10 million years. This could lead to the extinction of our species or to a burst of hominid speciation.     

Evidence for increased prevalence of SRY mutations in XY females with complete rather than partial gonadal dysgenesis.

The Y chromosome gene SRY (sex-determining region, Y gene) has been equated with the mammalian testis-determining factor. The SRY gene of five subjects with 46,XY complete gonadal dysgenesis (46,XY karyotype, completely female external genitalia, normal Müllerian ducts, and streak gonads) was evaluated for possible mutations in the coding region by using both single-strand conformation polymorphism (SSCP) assay and DNA sequencing. Mutations were identified in three subjects, of which two gave altered SSCP patterns. Two of them were point mutations causing amino acid substitutions, and the third was a single-base deletion causing a frameshift. All three mutations caused alterations in the putative DNA-binding region of the SRY protein. Genomic DNA was obtained from the fathers of two of the three mutant patients: one mutation was demonstrated to be de novo, and the other was inherited. The presence of SRY mutations in three of five patients suggests that the frequency of SRY mutations in XY females is higher than current estimates.     

A novel postzygotic nonsense mutation in SRY in familial XY gonadal dysgenesis

The Y chromosome gene SRY plays an important role in normal male sexual development and is thought to be the testis-determining factor. We describe a familial nonsense mutation in SRY, shared by two XY sisters with complete gonadal dysgenesis and, in a mosaic manner, by their father. This mutation, consisting of a C to T transition in position 1 of codon 97 of SRY, results in a truncated peptide with an incomplete DNA-binding domain. The mutation is also present in the father of the two cases, but a portion of wild-type SRY also remains. Our data suggest that the father suffered a postzygotic mutation early in development, but that he retained a remnant of functional SRY protein that accounts for his normal development. Received: 18 September 1995 / Revised: 21 November 1995     

Molecular analysis of the sex-determining region from the Y chromosome in two patients with Frasier syndrome.

In the Frasier syndrome there is an association between XY gonadal dysgenesis and chronic renal failure. Owing to an observed sex reversal, the Y chromosomes of two girls with this syndrome have been analyzed. Using molecular-biology techniques, no major alterations of the known sex-determining area of the Y chromosome were found. Furthermore, the sequence did not reveal impairment of the recently described testis-determining factor SRY. These data suggest that in the Frasier syndrome, XY sex reversal and renal failure could be the result of either faulty gene(s) located downstream in the sex differentiation pathway during embryogenesis, or impaired SRY regulation. Preliminary results on the Wilms' tumor suppressor gene WT1, a candidate for acting downstream to SRY, are also provided.     

SRY protein is expressed in ovotestis and streak gonads from human sex-reversal

In mammals, a master gene located on the Y chromosome, the testis-determining gene SRY, controls sex determination. SRY protein is expressed in the genital ridge before testis determination, and in the testis it is expressed in Sertoli and germ cells. Completely sex-reversed patients are classified as either 46,XX males or 46,XY females. SRY mutations have been described in only 15% of patients with 46,XY complete or partial gonadal dysgenesis. However, although incomplete or partial sex-reversal affects 46,XX true hermaphrodites, 46,XY gonadal dysgenesis, and 46,XX/46,XY mosaicism, only 15% of the 46,XX true hermaphrodites analyzed have the SRY gene. Here, we demonstrate that the SRY protein is expressed in the tubules of streak gonads and rete testis, indicating that the SRY protein is normally expressed early during testis determination. Based on these results, we propose that some factors downstream from SRY may be mutated in these 46,XY sex-reversal patients. We have also analyzed SRY protein expression in the ovotestis from 46,XX true hermaphrodites and 46,XX/46,XY mosaicism, demonstrating SRY protein expression in both testicular and ovarian portions in these patients. This suggests that the SRY protein does not inhibit ovary development. These results confirm that other factors are needed for complete testis development, in particular, those downstream of the SRY protein.     

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 SRY^F109S 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 back-ground or environmental factors.This paper is dedicated by G. S. to Professor Ulrich Wolf on the occasion of his 60th birthday     

Monozygotic twins of opposite sex

Although discordant karyotypes are known in identical twins, cases involving differences in sex phenotype are rare. We studied identical twins with the 46,XY karyotype - a male with mixed gonadal dysgenesis and a female with "pure" gonadal dysgenesis. The testis-determining SRY gene was present in DNA from both twins but no mutations were detected in the SRY conserved motif. Monozygosity was indicated by short tandem repeat polymorphism analysis. These observations could be attributed to (i) mutation and mosaicism involving "downstream" sex-determining loci, (ii) variable penetrance of genes such as DSS/NR0B1, duplication of which can disrupt the male-determining pathway, or (iii) occurrence of cryptic 45,X gonadal cell lines.     

Characterization and mapping of the human SOX4 gene

The SOX genes comprise a large family related by homology to the HMG-box region of the testis-determining gene SRY. We have cloned and sequenced the human SOX4 gene. The open reading frame encodes a 474 amino acid protein, which includes an HMG-box. The non-box sequence is particularly rich in serine residues and has several polyglycine and polyalanine stretches. With somatic cell hybrids, human SOX4 has been mapped to Chromosome (Chr) 6p distal to the MHC region. There is no evidence for clustering of other members of the SOX1,-2, and-3 or SOX4 gene families around the SOX4 locus.