A human XY female with a frame shift mutation in the candidate testis-determining gene SRY

The primary decision about male or female sexual development of the human embryo depends on the presence of the Y chromosome, more specifically on a gene on the Y chromosome encoding a testis-determining factor, TDF. The human sex-determining region has been delimited to a 35-kilobase interval near the Y pseudoautosomal boundary. In this region there is a candidate gene for TDF, termed SRY, which is conserved and specific to the Y chromosome in all mammals tested. The corresponding gene from the mouse Y chromosome is deleted in a line of XY female mutant mice, and is expressed at the expected stage during male gonadal development. We have now identified a mutation in SRY in one out of 12 sex-inversed XY females with gonadal dysgenesis who do not lack large segments of the short arm of the Y chromosome. The four-nucleotide deletion occurs in a sequence of SRY encoding a conserved DNA-binding motif and results in a frame shift presumably leading to a non-functional protein. The mutation occurred de novo, because the father of the sporadic XY female that bears it has the normal sequence at the corresponding position. These results provide strong evidence for SRY being TDF.     

Genetic evidence equating SRY and the testis-determining factor

The testis-determining factor gene (TDF) lies on the Y chromosome and is responsible for initiating male sex determination. SRY is a gene located in the sex-determining region of the human and mouse Y chromosomes and has many of the properties expected for TDF. Sex reversal in XY females results from the failure of the testis determination or differentiation pathways. Some XY females, with gonadal dysgenesis, have lost the sex-determining region from the Y chromosome by terminal exchange between the sex chromosomes or by other deletions. If SRY is TDF, it would be predicted that some sex-reversed XY females, without Y chromosome deletions, will have suffered mutations in SRY. We have tested human XY females and normal XY males for alterations in SRY using the single-strand conformation polymorphism assay and subsequent DNA sequencing. A de novo mutation was found in the SRY gene of one XY female: this mutation was not present in the patient's normal father and brother. A second variant was found in the SRY gene of another XY female, but in this case the normal father shared the same alteration. The variant in the second case may be fortuitously associated with, or predisposing towards sex reversal; the de novo mutation associated with sex reversal provides compelling evidence that SRY is required for male sex determination.     

Male development of chromosomally female mice transgenic for Sry

The initiation of male development in mammals requires one or more genes on the Y chromosome. A recently isolated gene, termed SRY in humans and Sry in mouse, has many of the genetic and biological properties expected of a Y-located testis-determining gene. It is now shown that Sry on a 14-kilobase genomic DNA fragment is sufficient to induce testis differentiation and subsequent male development when introduced into chromosomally female mouse embryos.     

Zfy gene expression patterns are not compatible with a primary role in mouse sex determination

The Y chromosome determines maleness in mammals. A Y chromosome-linked gene diverts the indifferent embryonic gonad from the default ovarian pathway in favour of testis differentiation, initiating male development. Study of this basic developmental switch requires the isolation of the testis-determining gene, termed TDF in humans and Tdy in mice. ZFY, a candidate gene for TDF, potentially encodes a zinc-finger protein, and has two Y-linked homologues, Zfy-1 and Zfy-2, in mice. Although ZFY, Zfy-1 and Zfy-2 seem to map to the sex-determining regions of the human and mouse Y chromosomes, there is no direct evidence that these genes are involved in testis determination. We report here that Zfy-1 but not Zfy-2 is expressed in differentiating embryonic mouse testes. Neither gene, however, is expressed in We/We mutant embryonic testes which lack germ cells. These observations exclude both Zfy-1 and Zfy-2 as candidates for the mouse testis-determining gene.     

Separation of the genetic loci for the H-Y antigen and for testis determination on human Y chromosome

The mammalian Y chromosome encodes a testis-determining factor (termed TDF in the human), a master regulator of sex differentiation. Embryos with a Y chromosome develop testes and become males whereas embryos lacking a Y chromosome develop ovaries and become females. Expression of H-Y, a minor histocompatibility antigen, may also be controlled by a gene on the Y chromosome, and it has been proposed that this antigen is the testis-determining factor. We have tested the postulated identity of H-Y and TDF in the human. H-Y typing with T cells was carried out on a series of sex-reversed humans (XX males and XY females), each shown by DNA hybridization to carry part but not all of the Y chromosome. This deletion analysis maps the gene for H-Y to the long arm or centromeric region of the human Y chromosome, far from the TDF locus, which maps to the distal short arm.     

鲤鱼中5个Sox基因保守区的克隆和比较

SRY/Sry基因已被公认为是哺乳动物的睾丸决定因子(TestisDeterminingFactor,TDF)基因,它的正确的时空表达是雄性生殖腺形成的关键,即导致哺乳动物胚胎性别决定的开关基因.作为一个大基因家族的首位成员,它的发现诱发了Sox基因家族的研究热潮.Sox基因家族是在动物中发现的一类新的编码转录因子的基因家族,其产物具有一个HMG基序保守区,参与诸如性别决定、骨组织的发育、血细胞生成过程、神经系统的发育、晶状体的发育等多种早期胚胎发育过程.鱼类是脊椎动物中进化地位较低的一类生物,除了个别种类出现了与性别相关的染色体外,绝大多数都无异形性染色体,说明了鱼类正处于性别染色体进化的重要时刻.研究鱼类中的Sox基因对于研究SRY的发生、性别染色体的进化以及性别的决定机制有着重要的意义.本实验利用兼并引物PCR的方法,参照Sox基因的HMG-box区氨基酸序列设计简并引物,对鲤鱼(Cyrinuscarpio)的基因组进行扩增,获得5个新的基因片段.经过在Genbank中进行同源性比较和分析,证明它们是鲤鱼的Sox基因并分别命名为CcSox3、CcSox4、CcSox11、CcSox14、CcSox21.与鲤鱼中的这些Sox基因具有最高同源性的基因分别是OlSox3,同源性为94.03%;CvSox4基因,同源性为88.06%;DrSox11基因,同源性为97.01%;MmSox14和HsSox14基?     

Exchange of terminal portions of X- and Y-chromosomal short arms in human XX males

In most human 'XX males', DNA sequences normally found on Yp, the short arm of the Y chromosome, are present on Xp, the short arm of the X chromosome. To establish whether this transfer involves a terminal portion of Yp, and whether a terminal portion of Xp is lost in the process, we followed the inheritance of pseudoautosomal restriction fragment length polymorphisms in two XX-male families. One XX male apparently inherited the entire pseudoautosomal region of his father's Y chromosome and no part of the pseudoautosomal region of his father's X chromosome. The second XX male also inherited the entire pseudoautosomal region of his father's Y, but in addition inherited a proximal portion of the pseudoautosomal region of his father's X. These findings argue that XX males result from the transfer of a terminal portion of Yp onto Xp in exchange for a terminal portion of Xp (ref. 7). This implies that the testis-determining factor gene (TDF) maps distally in the strictly sex-linked portion of Yp, near the pseudoautosomal domain. The XX males described here appear to result from single (and, at least in the second case, unequal) crossovers proximal to the pseudoautosomal region on Yp and proximal to or within the pseudoautosomal region on Xp.     

Expression of a candidate sex-determining gene during mouse testis differentiation

The development of a eutherian mammal as a male is a consequence of testis formation in the embryo, which is thought to be initiated by a gene on the Y chromosome. In the absence of this gene, ovaries are formed and female characteristics develop. Sex determination therefore hinges on the action of this testis-determining gene, known as Tdy in mice and TDF in humans. In the past, several genes proposed as candidates for Tdy/TDF have subsequently been dismissed on the grounds of inappropriate location or expression. We have recently described a candidate for Tdy, which maps to the minimum sex-determining region of the mouse Y chromosome. To examine further the involvement of this gene, Sry, in testis development, we have studied its expression in detail. Fetal expression of Sry is limited to the period in which testes begin to form. This expression is confined to gonadal tissue and does not require the presence of germ cells. Our observations strongly support a primary role for Sry in mouse sex determination.     

Sequences homologous to ZFY, a candidate human sex-determining gene, are autosomal in marsupials

Sexual differentiation in placental mammals results from the action of a testis-determining gene encoded by the Y chromosome. This gene causes the indifferent gonad to develop as a testis, thereby initiating a hormonal cascade which produces a male phenotype. Recently, a candidate for the testis-determining gene (ZFY, Y-borne zinc-finger protein) has been cloned. The ZFY probe detects a male-specific (Y-linked) sequence in DNA from a range of eutherian mammals, as well as an X-linked sequence (ZFX) which maps to the human X chromosome. In marsupials it is also the Y chromosome that seems to determine the fate of the gonad, but not all sexual dimorphisms. Using the ZFY probe we find, surprisingly, that the ZFY homologous sequences are not on either the X or the Y chromosome in marsupials, but map to the autosomes. This implies ZFY is not the primary sex-determining gene in marsupials. Either the genetic pathways of sex determination in marsupials and eutherians differ, or they are identical and ZFY is not the primary signal in human sex determination.     

Spermatogenic failure in male mice lacking H-Y antigen

The mammalian Y chromosome carries a factor that initiates male sexual development by directing the fetal gonads to form testes. Wachtel and his colleagues proposed that this testis-determining function of the Y is mediated by the male-specific cell-surface antigen H-Y, originally defined by skin grafting. This attractive hypothesis, which has been widely accepted, was based on the assumption that serological tests using antisera raised against male cells were recognizing H-Y antigen. Although disputed this assumption is supported by some recent studies. However, mice have been described which develop testes but lack the cell-surface H-Y antigen as defined by T-cell-mediated transplantation tests. Thus, although it remains possible that a serologically detected male-specific antigen is responsible for testis determination, it seems that H-Y, as originally defined, is not. We show here that H-Y negative male mice, in losing the genetic information that encodes H-Y, have also lost genetic information required for spermatogenesis. This result identifies a gene on the mouse Y, distinct from the testis-determining gene, which is necessary for spermatogenesis, and raises the intriguing possibility that the product of this 'spermatogenesis gene' is H-Y antigen.     

SRY基因在部分动物类群系统进化中保守性研究

用特异于人 HMG- box区域的一对引物 ,对脊推动物 5个纲 10个物种及 2种无脊推动物的基因组 DNA进行 PCR扩增 ,并以 dig标记的人 SRY基因为探针 ,与扩增产物进行 Southern杂交 ,结果表明 :在这 12个物种中都存在 SRY基因的同源序列 ,无脊推动物克氏螯虾及背角无齿蚌杂交中显色较慢 ,表明 SRY基因在系统进化中具有高度的保守性且同源程度与物种在进化上的地位有关     

A candidate spermatogenesis gene on the mouse Y chromosome is homologous to ubiquitin-activating enzyme E1.

The human X-linked gene A1S9 complements a temperature-sensitive cell-cycle mutation in mouse L cells, and encodes the ubiquitin-activating enzyme E1. The gene has been reported to escape X-chromosome inactivation, but there is some conflicting evidence. We have isolated part of the mouse A1s9 gene, mapped it to the proximal portion of the X chromosome and shown that it undergoes normal X-inactivation. We also detected two copies of the gene on the short arm of the mouse Y chromosome (A1s9Y-1 and A1s9Y-2). The functional A1s9Y gene (A1s9Y-1) is expressed in testis and is lost in the deletion mutant Sxrb. Therefore A1s9Y-1 is a candidate for the spermatogenesis gene, Spy, which maps to this region. A1s9X is similar to the Zfx gene in undergoing X-inactivation, yet having homologous sequences on the short arm of the Y chromosome, which are expressed in the testis. These Y-linked genes may form part of a coregulated group of genes which function during spermatogenesis.     

Breakpoints in the human T-cell antigen receptor alpha-chain locus in two T-cell leukaemia patients with chromosomal translocations

Specific chromosomal translocations have been observed in several human and animal tumours and are believed to be important in tumorigenesis. In many of these translocations the breakpoints lie near cellular homologues of transforming genes, suggesting that tumour development is partly due to the activation of these genes. The best-characterized example of such a translocation occurs in mouse plasmacytoma and human B-cell lymphoma, where c-myc, the cellular homologue of the viral oncogene myc, is brought into close proximity with either the light- or heavy-chain genes of the immunoglobulin loci, resulting in a change in the regulation of the myc gene. T-cell malignancies also have characteristic chromosomal abnormalities, many of which seem to involve the 14q11-14q13 region. This region has recently been found to contain the alpha-chain genes of the human T-cell antigen receptor. Here we determine more precisely the chromosome breakpoints in two patients whose leukaemic T cells contain reciprocal translocations between 11p13 and 14q13. Segregation analysis of somatic cell hybrids demonstrates that in both patients the breakpoints occur between the variable (V) and constant (C) region genes of the T-cell receptor alpha-chain locus, resulting in the translocation of the C-region gene from chromosome 14 to chromosome 11. As the 11p13 locus has been implicated in the development of Wilms' tumour, it is possible that either the Wilms' tumour gene or a yet unidentified gene in this region is involved in tumorigenesis and is altered as a result of its translocation into the T-cell receptor alpha-chain locus.     

Comparative chromosome mapping of a conserved homoeo box region in mouse and human

Specific genes are assumed to regulate pattern formation in the mammalian embryo, but as yet none has been identified unequivocally. It is possible that such genes in mammals may be identified by virtue of a conserved coding sequence, because many of the Drosophila melanogaster homoeotic and segmentation genes, which have crucial roles in the regulation of segmental pattern formation during embryonic development, contain a 180-base pair (bp) DNA sequence, the homoeo box, and that sequences homologous to the Drosophila homoeo box are also present in 6-10 copies in higher animals, including mammals. Although the assumption that the homoeo box identifies genes responsible for pattern formation in mammals remains to be validated, it is a particularly attractive hypothesis given the strong conservation of homoeo boxes over vast evolutionary distances. Here we report the localization of a human homoeo box region, previously cloned and shown to contain two homoeo boxes within a sequence of 5-kilobases (kb), to the long arm of chromosome 17. We show that two single-copy homoeo box-flanking probes derived from this region strongly hybridize to single-copy restriction fragments in mouse genomic DNA and that these conserved homoeo box-flanking sequences map to mouse chromosome 11. This may be significant as several genes that map to chromosome 17 in human also map to chromosome 11 in the mouse, implying that a segment of mouse chromosome 11 is homologous to a region of human chromosome 17. Taken together, these data suggest that the homoeo box region detected with our probes is highly conserved in human and mouse.     

A primitive Y chromosome in papaya marks incipient sex chromosome evolution

Many diverse systems for sex determination have evolved in plants and animals. One involves physically distinct (heteromorphic) sex chromosomes (X and Y, or Z and W) that are homozygous in one sex (usually female) and heterozygous in the other (usually male). Sex chromosome evolution is thought to involve suppression of recombination around the sex determination genes, rendering permanently heterozygous a chromosomal region that may then accumulate deleterious recessive mutations by Muller's ratchet, and fix deleterious mutations by hitchhiking as nearby favourable mutations are selected on the Y chromosome. Over time, these processes may cause the Y chromosome to degenerate and to diverge from the X chromosome over much of its length; for example, only 5% of the human Y chromosome still shows X-Y recombination. Here we show that papaya contains a primitive Y chromosome, with a male-specific region that accounts for only about 10% of the chromosome but has undergone severe recombination suppression and DNA sequence degeneration. This finding provides direct evidence for the origin of sex chromosomes from autosomes.     

The sex reversal of two mosaics with 45, XO/46, XX and 46, XY/47, XXY

Sex-reversed males with 45, XO and 46, XX are associated with patients carrying a small male-determining region-SRY gene of the Y chromosome, while some 46, XY females can be the result of SRY gene mutations on Y chromosome. Duplication of DSS gene on Xp21 can also cause 46, XY individual with normal Y chromosome and an intact SRY gene develops as phenotypically sex reversed female. We report two patients of the sex reversal, one develops as a male carrying the karyotype 45, XO/46, XX, the other is a phenotypically female with karyotype 46, XY/47, XXY. The mosaic with 46, XY/47, XXY female might be reported for the first time. Xu Yaoxian: born in Dec., 1956, Lecturer