Sex-determining Region Of The Y Research Articles

Mammalian gonadal differentiation: the pig model

In mammals, testicular differentiation is initiated by SRY (the sex-determining region of the Y chromosome) gene expression in Sertoli cell precursors, followed by upregulation of the SOX9 gene (SRY-related HMG box gene 9). Subsequently, differentiated testis produces two hormones that induce sexual differentiation of the internal and external genital tract. Knowledge of the molecular mechanisms involved in gonadal differentiation has increased greatly over the past decade. Several genes are involved in genital ridge formation in both sexes, and others act specifically in testicular or ovarian developmental pathways. As for other mammals, relatively few data are available on the first steps of ovarian differentiation in pigs. In this review, the expression profiles of most genes known to be involved in gonadal differentiation in pigs will be presented and compared with those observed in mice. The main feature of gonadal differentiation in the pig is fetal steroidogenesis, especially cytochrome P450 aromatase gene organization and expression. Another specific feature of gonadal differentiation in pigs is the appearance of numerous cases of XX sex-reversed animals. This intersex condition occurs as early as day 50 after coitus, during embryogenesis, and appears to be triggered genetically. It leads to a wide range of phenotypes, strikingly similar to those observed in humans. Identification of the genes involved in this pathology will improve our knowledge of mammalian gonadal differentiation and may allow the eradication of this genetic disease in pigs.

A Novel Nonsense Mutation p.L9X in the SRY Gene Causes Complete Gonadal Dysgenesis in a 46,XY Female Patient

Mammalian sex is determined by a gene localized on the Y chromosome known as SRY (sex-determining region of the Y chromosome). SRY is a transcription factor that plays a key role in the initiation of the cascade of male sexual differentiation. In 46,XY humans, SRY mutations cause complete gonadal dysgenesis (CGD) with male to female sex reversal, which results in female genitalia without testis differentiation. The aim of this study was to look for mutations of SRY gene in a 46,XY CGD Tunisian female patient by direct sequencing. This method allowed us to identify a novel nonsense mutation L9X, occurring within the NH2 terminal domain of SRY. This novel mutation led to the appearance of a premature stop codon, resulting in a truncated protein, missing the entire HMG box functional domain and the COOH terminal domain. Because of an increased risk of developing gonadoblastoma, early molecular diagnosis allows the orientation of the clinical supervision by removing the dysgenetic gonads to prevent gonadal malignancy. Furthermore, it provides valuable information for the understanding of molecular mechanisms behind the gonadal dysgenesis.

Isolation of nucleated red blood cells in maternal blood for Non-invasive prenatal diagnosis.

This paper introduces a two-step cascade enrichment method for isolating nucleated red blood cells (NRBCs) in maternal blood. The two-step enrichment platform consists of a positive enrichment process based on a red blood cell (RBC) hyperaggregation method and a negative enrichment process using microfluidic technology. An analytical evaluation using blood samples from patients with leukemia showed that the while blood cell (WBC) depletion and NRBC loss rates of the positive enrichment process were 93.98% and 6.02%, respectively. Through the two-step cascade enrichment method, 1-396 NRBCs and only 0-6 WBCs were isolated from 1mL of 18 maternal blood samples. Experimental results also showed that the WBC depletion rate of the proposed two-step method was more than 625,000-fold, and the purity of enriched NRBCs ranged from 20% to 100%. Furthermore, SRY (the sex-determining region of the Y chromosome) genes were detected in enriched NRBCs, thereby demonstrating that enriched NRBCs contain fetus-derived NRBCs.

Absent Visualization of a Hypoplastic Uterus in a 16 Year Old with Complete 46 XY Gonadal Dysgenesis (Swyer Syndrome)

Case: A 16-year-old female presented with primary amenorrhea, absent breast development, Tanner V pubic hair, sparse axillary hair and female appearing external genitalia without clitoromegaly. Further workup revealed: 46 XY karyotype with detectable SRY (sex-determining region of the Y chromosome), elevated follicle-stimulating hormone and luteinizing hormone, testosterone and androstenedione in the female range, normal dehydrotestosterone. Estrogen, estrone and ultra sensitive estradiol were in the prepubertal range. HCG stimulation did not result in an increase in testosterone levels, and the inhibin B level was undetectable; suggesting absent testicular function. AntiMullerian hormone level was <0.1. On trans-abdominal pelvic ultrasound, no ovaries, uterus or gonads were visualized. After the initiation of hormonal replacement therapy with an estrogen patch, MRI of the pelvis revealed a hypoplastic uterus and no definitive ovaries. Laparoscopic bilateral gonadectomy was performed. The pathology report showed some fallopian tissue on the left gonad with cystic changes. On the right gonad there was some ovarian stromal tissue without follicles. There was no evidence of gonadoblastoma. Summary and Conclusion: Swyer syndrome with XY complete gonadal dysgenesis may present with absent genitalia and an “absent” uterus on pelvic ultrasound. However, a uterus is in fact present and may be visualized on MRI, particularly after treatment with estrogen. It is important to correctly diagnose these patients because of the reported increase of gonadoblastoma. In addition they have the option of pregnancy (in vitro fertilization of donor egg by donor sperm, followed by embryo transfer).

A case report of an XX male with complete masculinization but absence of the SRY gene

Abstract A 34-year old man with complete masculinization and a history of several years of infertility was referred to us for genetic reviewing. His semen analysis showed azoospermia. Conventional chromosomal analysis indicates a 46,XX karyotype, molecular analyses excluded the presence of SRY (the sex-determining region of the Y chromosome) gene. This case is one of the rare cases reported in the literature in whom testicular differentiation and complete virilization were found in a 46,XX chromosomal constitution, with the absence of SRY gene. This finding suggests that other genes downstream from SRY play an important role in sex determination. Through reporting this rare case and reviewing previous literatures, the aim of this report is to highlight the value of genetically screening all males with azoospermia who present for evaluation of infertility, since the phenotype does not always correlate with the genotype.

Loss of Mitogen-Activated Protein Kinase Kinase Kinase 4 (MAP3K4) Reveals a Requirement for MAPK Signalling in Mouse Sex Determination

Author SummaryIn mammals, whether an individual develops as a male or female depends on its sex chromosome constitution: those with a Y chromosome become males because of the development of the embryonic gonad into a testis. The Y-linked sex determining gene SRY regulates this process by initiating a pathway of gene and protein expression, including the expression of critical autosomal genes such as SOX9. We identified a mouse mutant that causes embryonic gonadal sex reversal: the development of ovaries in an XY embryo. This mutant, which we called boygirl (byg), was shown to contain an early stop codon that disrupts the autosomal gene encoding MAP3K4, a component of the mitogen-activated protein kinase (MAPK) signaling pathway. Analysis of embryonic XY gonads suggests that sex reversal is caused by delayed and reduced expression of the sex-determining gene SRY. Our data indicate, for the first time, a requirement for MAPK signaling in the developing XY gonad in order to facilitate normal expression of SRY and the downstream testis-determining genes and also suggest that reduced dosage of MAP3K4 may be the cause of a previously described autosomal sex-reversing mutation in the mouse. We predict that loss of MAP3K4 or other MAPK components may underlie disorders of sexual development (DSD) in humans as well.

A 46,XX SRY-negative man with complete virilization and infertility as the main anomaly

To report a case of a 46,XX SRY-negative man with a male phenotype and azoospermia. Case report. Molecular and Cytogenetic Unit in a University Hospital. A 35-year-old man with complete masculinization who referred to our institution because of a history of several years of infertility. Lymphocytic karyotype and genetic counseling. Peripheral blood metaphases were analyzed by standard G-banding and Q-banding. Fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) analyses were performed. Semen analysis showed azoospermia. Chromosome analysis revealed a 46,XX karyotype; molecular and cytogenetic analyses excluded the presence of SRY (the sex-determining region of the Y chromosome) gene. This case is one of the rare patients reported in the literature in whom testicular differentiation and a complete virilization in a 46,XX chromosomal constitution does not account for a translocation of the SRY gene to the X chromosome or to the autosomes. This finding suggests that other genes downstream from SRY, not yet identified, play an important role in sex determination.

Defective importin beta recognition and nuclear import of the sex-determining factor SRY are associated with XY sex-reversing mutations.

The architectural transcription factor SRY (sex-determining region of the Y chromosome) plays a key role in sex determination as indicated by the fact that mutations in SRY are responsible for XY gonadal dysgenesis in humans. Although many SRY mutations reduce DNA-binding/bending activity, it is not clear how SRY mutations that do not affect interaction with DNA contribute to disease. The SRY high-mobility group domain harbors two nuclear localization signals (NLSs), and here we examine SRY from four XY females with missense mutations in these signals. In all cases, mutant SRY protein is partly localized to the cytoplasm, whereas wild-type SRY is strictly nuclear. Each NLS can independently direct nuclear transport of a carrier protein in vitro and in vivo, with mutations in either affecting the rate and extent of nuclear accumulation. The N-terminal NLS function is independent of the conventional NLS-binding importins (IMPs) and requires unidentified cytoplasmic transport factors, whereas the C-terminal NLS is recognized by IMPbeta. The SRY-R133W mutant shows reduced IMPbeta binding as a direct consequence of the sex-reversing C-terminal NLS mutation. Of the N-terminal NLS mutants examined, SRY-R62G unexpectedly shows a marked reduction in IMPbeta binding, whereas SRY-R75N and SRY-R76P show normal IMPbeta binding, suggesting defects in the IMP-independent pathway. We conclude that SRY normally requires the two distinct NLS-dependent nuclear import pathways to reach sufficient levels in the nucleus for sex determination. This study documents cases of human disease being explained, at a molecular level, by the impaired ability of a protein to accumulate in the nucleus.

Steroidogenic factor-1 contributes to the cyclic-adenosine monophosphate down-regulation of human SRY gene expression.

In mammals, male sex determination is initiated by SRY (sex-determining region of the Y chromosome) gene expression and followed by testicular development. This study describes specific down-regulation of the human SRY gene transcription by cAMP stimulation using reverse transcription-polymerase chain reaction experiments. Using transfection experiments, conserved nuclear hormone receptor (NHR1) and Sp1 consensus binding sites were identified as essential for this cAMP transcriptional response. Steroidogenic factor-1 (SF-1), a component of the sex-determination cascade, binds specifically to the NHR1 site and activates the SRY promoter. Activation of SF-1 was abolished by cAMP pretreatment of the cells, suggesting a possible effect of cAMP on the SF-1 protein itself. Indeed, human SF-1 protein contains at least two in vitro cAMP-dependent protein kinase (PKA) phosphorylation sites, leading after phosphorylation to a modification of both DNA-binding activity and interaction with general transcription factors such as Sp1. Taken together, these data suggest that cAMP responsiveness of human SRY promoter involves both SF-1 and Sp1 sites and could act via PKA phosphorylation of the SF-1 protein itself.

Multiple mono- and polymorphic Y-linked copies of the SRY HMG-box in Microtidae

Sex determination in mammals is controlled by SRY (sex-determining region of the Y chromosome), a single-copy gene located on the Y-specific region. Several exceptions to this rule have been described: some rodent species present Y-specific multiple copies (either mono- or polymorphic) of this gene, and two Ellobius species and one Tokudaia species determine sex without a Y chromosome or the SRY gene. Recently, we have described multiple polymorphic copies of the SRY gene in both males and females of the vole species Microtus cabrerae. The female location and the presence of stop codons in some copies from males and females also suggest that they are nonfunctional copies of this gene (pseudogenes). We have investigated the SRY HMG-box in nine species of the family Microtidae; we report here the presence, in eight of these species, of multiple mono- or polymorphic copies of the SRY gene located on the Y chromosome.

Seminoma in a postmenopausal woman with a Y;15 translocation in peripheral blood lymphocytes and a t(Y;15)/45,X Turner mosaic pattern in skin fibroblasts.

We report an unusual case of a 55 year old Japanese woman with a seminoma but relatively normal menses. The patient was a phenotypic female with late onset menarche (18...

The role of SRY in mammalian sex determination.

The gene SRY (sex determining region of the Y), located at the distal region of the short arm of the Y chromosome, is necessary for male sex determination in mammals. SRY initiates the cascade of steps necessary to form a testis from an undifferentiated gonad. The SRY gene encodes an HMG (High Mobility Group) protein which may act as a transcription factor by binding to double stranded DNA and then bending the DNA. Mutations in SRY have been identified in some subjects with 46,XY pure gonadal dysgenesis. However the role for other autosomal and X-linked genes in testis determination is evident by the presence of a normal SRY gene in the majority of females with 46,XY pure gonadal dysgenesis and the lack of SRY in a minority of males with 46,XY maleness.

PCR amplification of SRY-related gene sequences reveals evolutionary conservation of the SRY-box motif.

SRY (sex-determining region of the Y chromosome) has recently been identified as a key regulatory gene in mammalian sex determination. The open reading frame of this gene contains an 80-amino-acid motif, the SRY-box, which shares a high degree of homology with a DNA-binding domain found in the high-mobility-group (HMG) proteins HMG1 and HMG2. The SRY box motif is highly conserved in several sequence-specific DNA-binding proteins that are known to act as transcription factors. Here we describe the use of degenerate PCR primers to identify SRY-related sequences containing the SRY-box motif from the genomic DNA of a variety of species. The results of this study suggest that in a diverse array of species SRY-related genes may serve as transcription factors that regulate a variety of developmental pathways, including sex determination.