Testis determination in mammals: more questions than answers

Intersex goats show different gene expression levels in the hypothalamus and pituitary compared with non-intersex goats based on RNA-Seq

The conditions for sex reversal in vertebrate species have been extensively studied, and the results highlighted numerous key factors involved in sex differentiation. However, the transcriptomes in hypothalamic and pituitary tissues from intersex goats have rarely been studied. The aim of this study was to screen candidate genes and signalling pathways related to sex reversal in Huai goats by analyzing gene expression in hypothalamic and pituitary tissues via transcriptome sequencing and bioinformatics analyses. In total, 612 and 139 differentially expressed genes (DEGs) were identified between the intersex and non‐intersex groups in the hypothalamus and pituitary, respectively. The DEGs in the hypothalamus and pituitary were significantly enriched in 41 and 16 signalling pathways, respectively, including the calcium signalling pathway, neuroactive ligand‐receptor interaction signalling pathway, and oestrogen signalling pathway, which might be related to intersex sex development disorders. A candidate gene from the tachykinin family (TACR1) was significantly enriched in the calcium signalling pathway. Thirty‐one DEGs were shared between these two comparisons and were enriched in several acetyl‐CoA‐related processes and the oestrogen signalling pathway. The results of the real‐time PCR analysis show that the transcriptome sequencing results were reliable. The transcriptome data indicate that the regulation of various physiological systems is involved in intersex goat development. Therefore, these results provide helpful data enhancing our understanding of the molecular mechanisms underlying intersex syndrome in goats.

Transcriptomic analysis of gene expression in normal goat ovary and intersex goat gonad

Intersexuality is a congenital reproductive disorder that usually occurs in hornless goats, hindering breeding of goats with hornless traits and the development of the goat industry. In this study, we aimed to identify differentially expressed genes in intersex and normal goat gonads by comparing gene transcription profiles of intersex and normal goat gonads. As intersex goats are genetically based on females, we chose female goats as controls. The goats in the control group and the experimental group were both over one-year old. We evaluated the anatomical characteristics of the reproductive organs of five intersex goats using histopathological methods. The gonads were found to be ovarian and testicular types. RNA-Seq technology was used to identify differentially expressed genes in gonads and normal goat ovary tissues. Transcription analysis results were verified by qPCR. The results showed that 2,748 DEGs were upregulated and 3,327 DEGs were downregulated in intersex ovaries unlike in controls, whereas 2006 DEGs were upregulated and 2032 DEGs were downregulated in the interstitial testes. Many of these genes play important roles in mammalian sex determination and sex differentiation, such as SOX9, WT1, GATA4, DMRT1, DHH, AMH, CYP19A1 and FST. We found that many DEGs are involved in biological developmental regulation by GO and KEGG enrichment analyses, and that most genes associated with the steroid synthesis pathway were downregulated. The DEGs identified in this study may be involved in the regulation of intersex goat sex determination and differentiation, and may increase our understanding of the molecular mechanisms of mammalian sex differentiation.

Identification of the sex-determining region in flathead grey mullet (Mugil cephalus)

Elucidation of the sex-determination mechanism in flathead grey mullet (Mugil cephalus) is required to exploit its economic potential by production of genetically determined monosex populations and application of hormonal treatment to parents rather than to the marketed progeny. Our objective was to construct a first-generation linkage map of the M. cephalus in order to identify the sex-determining region and sex-determination system. Deep-sequencing data of a single male was assembled and aligned to the genome of Nile tilapia (Oreochromis niloticus). A total 245 M. cephalus microsatellite markers were designed, spanning the syntenic tilapia genome assembly at intervals of 10 Mb. In the mapping family of full-sib progeny, 156 segregating markers were used to construct a first-generation linkage map of 24 linkage groups (LGs), corresponding to the number of chromosomes. The linkage map spanned approximately 1200 cM with an average inter-marker distance of 10.6 cM. Markers segregating on LG9 in two independent mapping families showed nearly complete concordance with gender (R²  = 0.95). The sex determining locus was fine mapped within an interval of 8.6 cM on LG9. The sex of offspring was determined only by the alleles transmitted from the father, thus indicating an XY sex-determination system.

Gonadal soma-derived factor (gsdf), a TGF-beta superfamily gene, induces testis differentiation in the teleost fish Oreochromis niloticus

The Nile tilapia, Oreochromis niloticus, is a gonochoristic teleost fish with an XX/XY genetic system and is an excellent model for gonadal sex differentiation. In the present study, we screened novel genes that were expressed predominantly in either XY or XX undifferentiated gonads during the critical period for differentiation of gonads into ovaries or testes using microarray screening. We focused on one of the isolated 12 candidate genes, #9475, which was an ortholog of gsdf (gonadal soma-derived factor), a member of the transforming growth factor-beta superfamily. #9475/gsdf showed sexual dimorphism in expression in XY gonads before any other testis differentiation-related genes identified in this species thus far. We also overexpressed the #9475/gsdf gene in XX tilapia, and XX tilapia bearing the #9475/gsdf gene showed normal testis development, which suggests that #9475/gsdf plays an important role in male determination and/or differentiation in tilapia.

A very rare clinical case of a holstein heifer with two vulvae and a scrotum

The physical and gynecological examination of a Holstein heifer single-born with a disorder of sexual development showed anatomical abnormalities such as the presence of a scrotum and 2 vulvae and an anal sphincter that was positioned on the right side of the body. Also, an early pregnancy was diagnosed. Cytogenetic and hormone analysis was requested, and the animal showed normal female metaphases (60,XX) and hormonal profiles. However, in gross anatomy and histological examinations, a structure compatible with a penis, the absence of a uterine body, 2 exophytic structures, and a septum in the vagina were detected.

The intra-abdominal testis: lessons from the past, and ideas for the future

The intra-abdominal testis (IAT) has been always an enigma for both diagnosis and treatment. Imaging techniques are known for low sensitivity for localizing the IAT. It has been universally accepted that the gold standard for localizing the IAT is diagnostic laparoscopy. Orchiopexy techniques for IAT are complicated and attended with a higher rate of failure and complication than those for the palpable testis. For the low-lying abdominal testis, a one-stage procedure without interruption of the vessels has a high success rate. The Prentiss maneuver bridges the borders of normal pathway to gain a straighter course to the scrotum. The interruption of the main vascular supply of the testis, depending on collateral circulation, has been used for many years but with questionable effects on the microscopic delicate structure of the testis. Microvascular autotransplantation was intended to avoid this effect, but it is technically demanding and requires special expertise. The principle of traction has been used in the past but was abandoned due to high rate of atrophy. Recently, traction has been revisited with a new approach with very encouraging results. The key to success in any technique for orchiopexy is the complete absence of tension.

A fresh look at the male-specific region of the human Y chromosome

The Chromosome-centric Human Proteome Project (C-HPP) aims to systematically map the entire human proteome with the intent to enhance our understanding of human biology at the cellular level. This project attempts simultaneously to establish a sound basis for the development of diagnostic, prognostic, therapeutic, and preventive medical applications. In Iran, current efforts focus on mapping the proteome of the human Y chromosome. The male-specific region of the Y chromosome (MSY) is unique in many aspects and comprises 95% of the chromosome's length. The MSY continually retains its haploid state and is full of repeated sequences. It is responsible for important biological roles such as sex determination and male fertility. Here, we present the most recent update of MSY protein-encoding genes and their association with various traits and diseases including sex determination and reversal, spermatogenesis and male infertility, cancers such as prostate cancers, sex-specific effects on the brain and behavior, and graft-versus-host disease. We also present information available from RNA sequencing, protein-protein interaction, post-translational modification of MSY protein-coding genes and their implications in biological systems. An overview of Human Y chromosome Proteome Project is presented and a systematic approach is suggested to ensure that at least one of each predicted protein-coding gene's major representative proteins will be characterized in the context of its major anatomical sites of expression, its abundance, and its functional relevance in a biological and/or medical context. There are many technical and biological issues that will need to be overcome in order to accomplish the full scale mapping.

SRY mutation analysis by next generation (deep) sequencing in a cohort of chromosomal Disorders of Sex Development (DSD) patients with a mosaic karyotype

Background

The presence of the Y-chromosome or Y chromosome-derived material is seen in 4-60% of Turner syndrome patients (Chromosomal Disorders of Sex Development (DSD)). DSD patients with specific Y-chromosomal material in their karyotype, the GonadoBlastoma on the Y-chromosome (GBY) region, have an increased risk of developing type II germ cell tumors/cancer (GCC), most likely related to TSPY. The Sex determining Region on the Y gene (SRY) is located on the short arm of the Y-chromosome and is the crucial switch that initiates testis determination and subsequent male development. Mutations in this gene are responsible for sex reversal in approximately 10-15% of 46,XY pure gonadal dysgenesis (46,XY DSD) cases. The majority of the mutations described are located in the central HMG domain, which is involved in the binding and bending of the DNA and harbors two nuclear localization signals. SRY mutations have also been found in a small number of patients with a 45,X/46,XY karyotype and might play a role in the maldevelopment of the gonads.

Methods

To thoroughly investigate the presence of possible SRY gene mutations in mosaic DSD patients, we performed next generation (deep) sequencing on the genomic DNA of fourteen independent patients (twelve 45,X/46,XY, one 45,X/46,XX/46,XY, and one 46,XX/46,XY).

Results and conclusions

The results demonstrate that aberrations in SRY are rare in mosaic DSD patients and therefore do not play a significant role in the etiology of the disease.

Sex reversal in C57BL/6J XY mice caused by increased expression of ovarian genes and insufficient activation of the testis determining pathway

Sex reversal can occur in XY humans with only a single functional WT1 or SF1 allele or a duplication of the chromosome region containing WNT4. In contrast, XY mice with only a single functional Wt1, Sf1, or Wnt4 allele, or mice that over-express Wnt4 from a transgene, reportedly are not sex-reversed. Because genetic background plays a critical role in testis differentiation, particularly in C57BL/6J (B6) mice, we tested the hypothesis that Wt1, Sf1, and Wnt4 are dosage sensitive in B6 XY mice. We found that reduced Wt1 or Sf1 dosage in B6 XY(B6) mice impaired testis differentiation, but no ovarian tissue developed. If, however, a Y(AKR) chromosome replaced the Y(B6) chromosome, these otherwise genetically identical B6 XY mice developed ovarian tissue. In contrast, reduced Wnt4 dosage increased the amount of testicular tissue present in Sf1+/- B6 XY(AKR), Wt1+/- B6 XY(AKR), B6 XY(POS), and B6 XY(AKR) fetuses. We propose that Wt1(B6) and Sf1(B6) are hypomorphic alleles of testis-determining pathway genes and that Wnt4(B6) is a hypermorphic allele of an ovary-determining pathway gene. The latter hypothesis is supported by the finding that expression of Wnt4 and four other genes in the ovary-determining pathway are elevated in normal B6 XX E12.5 ovaries. We propose that B6 mice are sensitive to XY sex reversal, at least in part, because they carry Wt1(B6) and/or Sf1(B6) alleles that compromise testis differentiation and a Wnt4(B6) allele that promotes ovary differentiation and thereby antagonizes testis differentiation. Addition of a "weak" Sry allele, such as the one on the Y(POS) chromosome, to the sensitized B6 background results in inappropriate development of ovarian tissue. We conclude that Wt1, Sf1, and Wnt4 are dosage-sensitive in mice, this dosage-sensitivity is genetic background-dependant, and the mouse strains described here are good models for the investigation of human dosage-sensitive XY sex reversal.

Calmodulin-dependent nuclear import of HMG-box family nuclear factors: importance of the role of SRY in sex reversal

The HMG (high-mobility group)-box-containing chromatin-remodelling factor SRY (sex-determining region on the Y chromosome) plays a key role in sex determination. Its role in the nucleus is critically dependent on two NLSs (nuclear localization signals) that flank its HMG domain: the C-terminally located 'beta-NLS' that mediates nuclear transport through Impbeta1 (importin beta1) and the N-terminally located 'CaM-NLS' which is known to recognize the calcium-binding protein CaM (calmodulin). In the present study, we examined a number of missense mutations in the SRY CaM-NLS from human XY sex-reversed females for the first time, showing that they result in significantly reduced nuclear localization of GFP (green fluorescent protein)-SRY fusion proteins in transfected cells compared with wild-type. The CaM antagonist CDZ (calmidazolium chloride) was found to significantly reduce wild-type SRY nuclear accumulation, indicating dependence of SRY nuclear import on CaM. Intriguingly, the CaM-NLS mutants were all resistant to CDZ's effects, implying a loss of interaction with CaM, which was confirmed by direct binding experiments. CaM-binding/resultant nuclear accumulation was the only property of SRY found to be impaired by two of the CaM-NLS mutations, implying that inhibition of CaM-dependent nuclear import is the basis of sex reversal in these cases. Importantly, the CaM-NLS is conserved in other HMG-box-domain-containing proteins such as SOX-2, -9, -10 and HMGN1, all of which were found for the first time to rely on CaM for optimal nuclear localization. CaM-dependent nuclear translocation is thus a common mechanism for this family of important transcription factors.

FOXL2 versus SOX9: a lifelong "battle of the sexes"

Testis determination in most mammals is regulated by a genetic hierarchy initiated by the SRY gene. Early ovarian development has long been thought of as a default pathway switched on passively by the absence of SRY. Recent studies challenge this view and show that the ovary constantly represses male-specific genes, from embryonic stages to adulthood. Notably, the absence of the crucial ovarian transcription factor FOXL2 (alone or in combination with other factors) induces a derepression of male-specific genes during development, postnatally and, even more interestingly, during adulthood. Strikingly, in the adult, targeted ablation of Foxl2 leads to a molecular transdifferentiation of the supporting cells of the ovary, which acquire cytological and transcriptomic characteristics of the supporting cells of the testes. These studies bring many answers to the field of gonadal determination, differentiation and maintenance, but also open many questions.

Bilateral gonadoblastoma with dysgerminoma and pilocytic astrocytoma with WT1 GT-IVS9 mutation: A 46 XY phenotypic female with Frasier syndrome

Frasier syndrome is characterized by a 46 XY disorder of sex development, nephropathy, and increased risk for gonadoblastoma due to Wilms tumor 1(WT1) mutation in the donor splice site of intron-9, resulting in the splice form +KTS. Germ cell tumors and gonadoblastomas have been reported previously in Frasier syndrome. We present the clinical, radiological, and genetic (WT1 mutation analysis) of a 46 XY phenotypic female with Frasier syndrome with bilateral gonadoblastoma with dysgerminoma who developed pilocytic astrocytoma.

Two cases of bovine male pseudohermaphrodites with different endocrinological and pathological findings

Two cases of bovine male pseudohermaphrodites (PH) were subjected for clinical investigation with transrectal ultrasonography, endocrinology with adoption of hCG-stimulation test, cytogenetics with analysis of sex chromosome and Y-specific DNA, and finally histological examination. Results were compared with normal calves. Case 1 was a 10-month-old calf with XX/XY chimeras, showing elevation of testosterone (T) levels, but no change in progesterone (P(4)) after hCG test, and possessed atrophied testes in the cavitas pelvis. Case 2 was an 18-month-old calf with SRY positive-XY chromosome, showing lower level of plasma T and P(4) after hCG test, and possessed atrophied testes and undifferentiated genital ducts. Both cases possessed female-like external genitalia with similar pathological findings, however endocrinological and cytogenetical aspects were different each other.

Sex determination in the Squalius alburnoides complex: an initial characterization of sex cascade elements in the context of a hybrid polyploid genome

Background

Sex determination processes vary widely among different vertebrate taxa, but no group offers as much diversity for the study of the evolution of sex determination as teleost fish. However, the knowledge about sex determination gene cascades is scarce in this species-rich group and further difficulties arise when considering hybrid fish taxa, in which mechanisms exhibited by parental species are often disrupted. Even though hybridisation is frequent among teleosts, gene based approaches on sex determination have seldom been conducted in hybrid fish. The hybrid polyploid complex of Squalius alburnoides was used as a model to address this question.

Methodology/Principal Findings

We have initiated the isolation and characterization of regulatory elements (dmrt1, wt1, dax1 and figla) potentially involved in sex determination in S. alburnoides and in the parental species S. pyrenaicus and analysed their expression patterns by in situ hybridisation. In adults, an overall conservation in the cellular localization of the gene transcripts was observed between the hybrids and parental species. Some novel features emerged, such as dmrt1 expression in adult ovaries, and the non-dimorphic expression of figla, an ovarian marker in other species, in gonads of both sexes in S. alburnoides and S. pyrenaicus. The potential contribution of each gene to the sex determination process was assessed based on the timing and location of expression. Dmrt1 and wt1 transcripts were found at early stages of male development in S. alburnoides and are most likely implicated in the process of gonad development.

Conclusions/Significance

For the first time in the study of this hybrid complex, it was possible to directly compare the gene expression patterns between the bisexual parental species and the various hybrid forms, for an extended set of genes. The contribution of these genes to gonad integrity maintenance and functionality is apparently unaltered in the hybrids, suggesting that no abrupt shifts in gene expression occurred as a result of hybridisation.

Peripheral neuropathy and 46XY gonadal dysgenesis: a heterogeneous entity

Gonadal dysgenesis with normal male karyotype (46XY) is a sexual differentiation disorder. So far three patients have been reported presenting the association of 46XY gonadal dysgenesis with peripheral neuropathy. Examination of sural nerves revealed minifascicle formation in two of them. In one patient, a mutation was found in desert hedgehog homolog (Drosophila), a gene important in gonadal differentiation and peripheral nerve development. We studied neuropathological and molecular genetic aspects of a patient with 46XY gonadal dysgenesis and peripheral neuropathy. Examination of a sural nerve biopsy specimen revealed an axonal neuropathy with pronounced axonal loss, limited signs of axonal regeneration and no minifascicle formation. A normal male karyotype was found (46XY) without micro-deletions in the Y chromosome. No mutations were found in the sex determining region Y gene, peripheral myelin protein 22, Myelin Protein Zero, Gap-Junction protein Beta 1, Mitofusin 2 or desert hedgehog homolog. The absence of minifascicle formation and the absence of a mutation in desert hedgehog homolog in this patient with gonadal dysgenesis and peripheral neuropathy expand the clinical and genetic heterogeneity of this rare entity.

New insights into type II germ cell tumor pathogenesis based on studies of patients with various forms of disorders of sex development (DSD)

Disorders of sex development (DSD), previously known as intersex, refer to congenital conditions in which development of chromosomal, gonadal, or anatomical sex is atypical. Patients with specific variants of this disorder have an elevated risk for the development of so-called type II germ cell cancers, i.e., the seminomatous and nonseminatous tumors, referred to as germ cell tumors (GCTs). Specifically DSD patients with gonadal dysgenesis or hypovirilization are at risk. A prerequisite for type II GCT formation is the presence of a specific part of the Y chromosome (referred to as the GBY region), with the TSPY gene being the most likely candidate. Also the octamer binding transcription factor OCT3/4 is consistently expressed in all type II GCTs with pluripotent potential, as well as in the precursor lesions carcinoma in situ (CIS) in case of a testis and gonadoblastoma (GB) in the DSD gonad. The actual risk for malignant transformation in individual DSD patients is hard to predict, because of confusing terminology referring to the different forms of DSD, and unclear criteria for identification of the presence of malignant germ cells, especially in young patients. This is specifically due to the phenomenon of delay of germ cell maturation, which might result in over diagnosis. This review will give novel insight into the pathogenesis of the type II GCTs through the study of patients with various forms of DSD for which the underlying molecular defect is known. To allow optimal understanding of the pathogenesis of this type of cancers, first normal gonadal development, especially regarding the germ cell lineage, will be discussed, after which type II GCTs will be introduced. Subsequently, the relationship between type II GCTs and DSD will be described, resulting in a number of new insights into the development of the precursor lesions of these tumors.

Sexual dimorphic expression of DMRT1 and Sox9a during gonadal differentiation and hormone-induced sex reversal in the teleost fish Nile tilapia (Oreochromis niloticus)

We examined the expression profiles of tDMRT1 and Sox9a during gonadal sex differentiation and hormone-induced sex reversal. tDMRT1 was detected in the gonial germ-cell-surrounding cells in XY fry specifically before the appearance of any signs of morphological sex differentiation, that is, sex differences in germ cell number and histogenesis, such as differentiation into intratesticular efferent duct or ovarian cavity. The signals became localized in the Sertoli and epithelial cells comprising the efferent duct during gonadal differentiation. After the induction of XY sex reversal with estrogen, tDMRT1 decreased and then disappeared completely. In contrast, tDMRT1 was expressed in the germ-cell-surrounding cells in XX sex reversal with androgen. On the other hand, Sox9a did not show sexual dimorphism before the appearance of sex differences in histogenesis and was not expressed in the efferent duct in the testis. These results suggest that tDMRT1 is a superior testicular differentiation marker in tilapia.

A complex intersex condition in a Holstein calf

A case of disrupted embryonic development of the genital tract in a newborn Holstein calf is described. The physical examination of the calf evidenced several abnormalities, like atresia ani, rudimentary external genitalia and caudal vertebral agenesis. On necropsy, the excised genitalia consisted of bilateral streak gonads, apparently normal uterine tubes, a fluid-filled uterus, a long vagina and a very narrow clitoris-like structure covered with a discrete skin-fold. The urinary tract seemed normal and the urethra's opening was at the vestibule-vaginal junction. A cytogenetic analysis was requested. Karyotype revealed the existence of Y chromosome material in the two X chromosomes. However, the search for the sex-determining region Y (SRY) showed that this was an apparently absent gene. The histological examination of the gonads revealed the existence of ovarian dysplasia. Uterine sections evidenced the absence of the uterine epithelium, with only sporadic caruncles. Under microscopic examination, the uterine tubes and vagina structure was normal. The external genitalia sections revealed the existence of a skin-fold covering an erectile structure surrounding the urethra, a structure more similar to a penis than to a clitoris. This is an unusual situation of gonadal dysplasia combined with genital tract anomalies in cattle, probably associated to a genetic defect.

Correct dosage of Fog2 and Gata4 transcription factors is critical for fetal testis development in mice

Previous reports suggested that humans and mice differ in their sensitivity to the genetic dosage of transcription factors that play a role in early testicular development. This difference implies that testis determination might be somewhat different in these two species. We report that the Fog2 and Gata4 transcription factors are haploinsufficient for testis determination in mice. Whether gonadal sex reversal occurs depends on genetic background (i.e., modifier genes). For example, C57BL/6J (B6) XY mice develop testes if they are heterozygous for a mutant Fog2 (Fog2-) or Gata4 (Gata4(ki)) allele. However, if the B6 Y chromosome (Y(B6)) is replaced by the AKR Y chromosome (Y(AKR)), B6 Fog2-/+ XY(AKR) mice develop ovaries, and B6 Gata4(ki)/+ XY(AKR) mice develop ovaries and ovotestes (gonads containing both ovarian and testicular tissue). Furthermore, DBA/2J (D2) Fog2-/+ XY(AKR) mice and (B6 x D2)F1 hybrid Gata4(ki)/+ XY(AKR) mice develop testes. Sry is expressed in the mutant XY gonads, indicating that the lack of Sry expression is not the cause of ovarian tissue development in B6 Fog2-/+ or Gata4(ki)/+ XY(AKR) mice. However, up-regulation of Sox9 expression, which is critical for normal testicular development, does not occur in mutant XY gonads that develop as ovaries. We conclude that under certain genetic conditions, Sox9 up-regulation depends on the proper dosage of Fog2 and Gata4. We propose that in humans the FOG2 and/or GATA4 genes might be haploinsufficient for normal testis determination and thus could be the cause of some previously unassigned cases of XY gonadal sex reversal.

Impact of the Y-containing cell line on histological differentiation patterns in dysgenetic gonads

OBJECTIVE

Gonadal karyotyping is considered a tool for increasing our knowledge of disturbed gonadal development in patients with gonadal dysgenesis and for estimating more accurately the risk for gonadoblastoma formation. The objective was to gain insight into the role of Y chromosome distribution in the histological heterogeneity of gonads of patients with gonadal dysgenesis.

DESIGN

Investigation of the possible relationship between peripheral blood karyotype, gonadal karyotype, morphological differentiation patterns of dysgenetic gonads and tumour formation.

PATIENTS

In total 22 gonadal samples from 19 patients with gonadal dysgenesis (45,X/46,XY and variants n = 14; 46,XY: n = 3; 46,XX: n = 2) were examined.

MEASUREMENTS

Morphological examination and immunohistochemical staining for testis specific protein, Y encoded (TSPY) and fluorescent and nonfluorescent in situ hybridization directly on gonadal tissue.

RESULTS

No correlation was observed between peripheral blood karyotype and gonadal karyotype or between gonadal karyotype and the corresponding differentiation pattern. A Y-containing cell line in Sertoli cells was encountered no more frequently than were other cell types.

CONCLUSIONS

The distribution of the Y-containing cell line in peripheral blood is not a suitable indicator for predicting the histological differentiation pattern found in the gonads of patients with gonadal dysgenesis. The analysis of Y-containing cell lines in the gonads of such patients could be informative with regard to the specific characteristics of gonadal development in humans as compared to chimeric mouse models. Moreover, it is essential to understand the mechanisms underlying disturbed gonadogenesis in these patients. As the gonadal karyotype is not related to the encountered gonadal differentiation pattern, it does not allow prediction of the risk for gonadoblastoma formation.

Characterization and distribution of hyaluronan and the proteoglycans decorin, biglycan and perlecan in the developing embryonic mouse gonad

The morphogenesis of tissues and organs requires dynamic changes in cells and in extracellular matrix components. It is known that various extracellular matrix molecules are of fundamental importance for gonad differentiation and growth. In the adult testis, the extracellular matrix represents an important component of the interstitium, participating in the transport of biologically active substances needed for the communication between different cellular components, as well as for the regulation of spermatogenesis and hormone production. The present study was designed in order to identify the proteoglycans biglycan, decorin and perlecan, as well as the glycosaminoglycan hyaluronan, during testis development in mouse embryos. Our data profile the chronology of testis differentiation, as well as the distribution of these extracellular matrix components during testis development in mice. We show that these extracellular matrix molecules are present early in the development of the gonads, suggesting that they play a role in gonad development. In addition, we found no decorin in the testicular cords. Furthermore, of the proteoglycans analysed, only biglycan was seen surrounding immature Sertoli cells and Leydig cell precursors in the testicular cords. This indicates that specific sets of extracellular matrix molecules are required in the various compartments of the developing gonad.

Ovotestes and XY sex reversal in a female with an interstitial9q33.3-q34.1 deletion encompassingNR5A1 andLMX1B causing features of genitopatellar syndrome

We describe our findings in a 46,XY female with a clinical features of Genitopatellar syndrome (GPS) and confirmed hermaphroditism with ovotestes, and five additional patients with GPS. GPS is a genetic disorder characterized by renal and genital anomalies, joint dislocation, aplastic or hypoplastic and often displaced patellae, minor facial anomalies, and mental retardation. The genital anomalies clearly distinguish GPS from nail-patella syndrome (NPS) that has similar features, but additionally shows hypoplastic finger- and toenails as found in the 46,XY female. In our patients no mutation was found in the coding regions of WNT4, WNT7A, TBX4, and LMX1B. Fluorescent in situ hybridization (FISH) and array-based comparative genome hybridization (aCGH) analysis showed a 3 Mb deletion of LMX1B, NR6A1, and NR5A1 (SF1) in the 46,XY female. This is the first report of a microdeletion causing haploinsuffiency of LMX1B and NR5A1. The deletion of LMX1B is responsible for the knee anomalies and the deletion of NR5A1 likely causes the sex reversal. Cytogenetic analysis of the five additional patients with diagnosed GPS failed to identify a similar microdeletion, or inversion of a potentially regulatory element between the two genes. This suggests that the locus 9q33-9q34 can be excluded for GPS and that the presented case is unique in its combination of GPS and NPS features caused by a microdeletion associated with loss of function of LMX1B and NR5A1.

Germ cell tumors in the intersex gonad: old paths, new directions, moving frontiers

The risk for the development of germ cell tumors is an important factor to deal with in the management of patients with disorders of sex development (DSD). However, this risk is often hard to predict. Recently, major progress has been made in identifying gene-products related to germ cell tumor development (testis-specific protein-Y encoded and octamer binding transcription factor 3/4) and in recognizing early changes of germ cells (maturation delay, preneoplastic lesions, and in situ neoplasia). The newly recognized "undifferentiated gonadal tissue" has been identified as a gonadal differentiation pattern bearing a high risk for the development of gonadoblastoma. It is expected that the combination of these findings will allow for estimation of the risk for tumor development in the individual patient (high risk/intermediate risk/low risk). This article reviews the recent literature regarding the prevalence of germ cell tumors in patients with DSD. Some major limitations regarding this topic, including a confusing terminology referring to the different forms of intersex disorders and unclear criteria for the diagnosis of malignant germ cells at an early age (maturation delay vs. early steps in malignant transformation) are discussed. Thereafter, an overview of the recent advances that have been made in our knowledge of germ cell tumor development and the correct diagnosis of early neoplastic lesions in this patient population is provided. A new classification system for patients with DSD is proposed as a tool to refine our insight in the prevalence of germ cell tumors in specific diagnostic groups.

Annexin XI co-localises with calcyclin in proliferating cells of the embryonic mouse testis

Mammalian sex determination relies on the expression of SRY, which triggers a tightly regulated cascade of gene expression leading to male differentiation. Many elements of this pathway remain to be identified. Here, we characterise Annexin XI (Anxa11), a gene whose major site of embryonic expression was within the undifferentiated and differentiating testis. Lower level expression was also observed in both sexes in the Müllerian and Wolffian ducts, the somitic dermamyotome, and the dorsal intermediate zone of the neural tube. Anxa11 transcripts were detected in the indifferent gonad from 10.5 days post coitum (dpc), becoming male specific as development proceeded. Expression was within the testis cords, initially in germ cells, and then in both Sertoli and germ cells. Annexin XI protein was seen in the testis cords from 12.5 dpc, localising to the cytoplasm of the Sertoli cells. Expression of calcyclin (S100a6), shown previously to interact with annexin XI in vitro, was also observed in proliferating cells of the embryonic testis, supporting a possible in vivo interaction.

Down-Regulation of Endogenous Wt1 Expression by Sry Transgene in the Murine Embryonic Mesonephros-Derived M15 Cell Line

Wt1 is one of numerous candidate genes comprising the hypothetical chain of gene expression essential for male sex differentiation of the bipotential indifferent gonads during embryogenesis. However, the evidence in the literature is ambivalent regarding the position of Wt1 relative to Sry in this scheme; Wt1 might act either upstream or downstream of Sry. In the present study, the effects of Sry expression upon Wt1 were investigated using M15 cells (XX karyotype), which are derived from murine embryonic mesonephros and express endogenous Wt1. In 3 stably-transformed Sry-expressing M15 cell lines, we showed that the expression levels of the mRNAs coding for all 4 isoforms of the WT1 proteins were down-regulated. Similarly, Wnt 4 expression was down-regulated in these cell lines. Silencing of Sry in the transformed cell lines using ribozymes or short hairpin RNAs (shRNAs) resulted in elevated levels of Wt1 and Wnt4 expression. These results strongly indicate that Wt1 might be under the control of Sry during gonadal differentiation in the mouse. In electrophoretic mobility shift assays (EMSA), we demonstrated that the 3.7 kb 5'-upstream DNA stretch of Wt1 containing potential Sry binding sites was capable of forming molecular complexes with nuclear protein(s) from Sry expressing cells but not with those from control non-Sry expressing cells. In summary, our present results support the notion that Wt1 is located downstream of Sry and down-regulated by the sex determining gene. Although the precise biological meaning of the present findings have yet to be clarified, it is possible that Wt1 plays a dual role during gonadal differentiation, i. e., turning on Sry expression on one hand, and being down-regulated by its product, Sry, on the other, possibly forming a type of negative feed-back mechanism. Further work is needed to substantiate this view.

Gene Regulation in Spermatogenesis

Mammalian spermatogenesis is a complex hormone-dependent developmental program in which a myriad of events must take place to ensure that germ cells reach their proper stage of development at the proper time. Many of these events are controlled by cell type- and stage-specific transcription factors. The regulatory mechanisms involved provide an intriguing paradigm for the field of developmental biology and may lead to the development of new contraceptives an and innovative routs to treat male infertility. In this review, we address three aspects of the genetic regulatory mechanism that drive spermatogenesis. First, we detail what is known about how steroid hormones (both androgens and estrogens) and their cognate receptors initiate and maintain mammalian spermatogenesis. Steroids act through three mechanistic routes: (i) direct activation of genes through hormone-dependent promoter elements, (ii) secondary transcriptional responses through activation of hormone-dependent transcription factors, and (iii) rapid, transcription-independent (nonclassical) events induced by steroid hormones. Second, we provide a survey of transcription factors that function in mammalian spermatogenesis, including homeobox, zinc-finger, heat-shock, and cAMP-response family members. Our survey is not intended to cover all examples but to give a flavor for the gamut of biological roles conferred by transcription factors in the testis, particularly those defined in knockout mice. Third, we address how testis-specific transcription is achieved. In particular, we cover the evidence for and against the idea that some testis-specific genes are transcriptionally silent in somatic tissues as a result of DNA methylation.

The complete coding region sequence of river buffalo (Bubalus bubalis) SRY gene

The Y-linked SRY gene is responsible for testis determination in mammals. Mutations in this gene can lead to XY Gonadal Dysgenesis, an abnormal sexual phenotype described in humans, cattle, horses and river buffalo. We report here the complete river buffalo SRY sequence in order to enable the genetic diagnosis of this disease. The SRY sequence was also used to confirm the evolutionary divergence time between cattle and river buffalo 10 million years ago.

Mutations in the desert hedgehog (DHH) gene in patients with 46,XY complete pure gonadal dysgenesis

Mutations of SRY are the cause of complete pure gonadal dysgenesis (PGD) in 10-15% of patients. In the remaining individuals, it has been suggested that mutations in other genes involved in the testis-determining pathway could be causative. We describe the first report in which three cases of 46,XY complete PGD are attributed to mutations of the Desert hedgehog (DHH) gene. DHH was sequenced using genomic DNA from paraffin-embedded gonadal tissue from six patients with complete 46,XY PGD. Mutations were found in three patients: a homozygous mutation in exon 2, responsible for a L162P, and a homozygous 1086delG in exon 3. Mutated individuals displayed 46,XY complete PGD, differentiating from the only previously described patient with a homozygous DHH mutation, who exhibited a partial form of PGD with polyneuropathy, suggesting that localization of mutations influence phenotypic expression. This constitutes the first report where mutations of DHH are associated with the presence of 46,XY complete PGD, demonstrating that the genetic origin of this entity is heterogeneous and that disorders in other genes, different from SRY, involved in the testis-determining pathway are implicated in abnormal testicular differentiation in humans. These data extend previous reports demonstrating DHH is a key gene in gonadal differentiation.

Screening for mutations in the SRY gene in patients with mixed gonadal dysgenesis or with Turner syndrome and Y mosaicism

OBJECTIVE

To investigate the presence of mutations in the open reading frame (ORF), as well as on the 5' and 3', flanking regions of the SRY gene in patients with mixed gonadal dysgenesis (MGD) or with Turner syndrome (TS) and Y mosaicism.

STUDY DESIGN

We studied 13 patients with MGD and three patients with TS and Y mosaicism. DNA was isolated from blood leukocytes for subsequent polymerase chain reaction (PCR) and direct sequencing were performed in the ORF, as well as from the 5' and 3' flanking regions of the SRY gene.

RESULTS

No mutations were present in any of the patients studied.

CONCLUSION

The absence of mutations in these regions indicated that mutations were an unlikely cause of MGD or TS with Y mosaicism and suggested that there are others genes playing an important role in sex development.

Equilibrium binding assays reveal the elevated stoichiometry and salt dependence of the interaction between full-length human sex-determining region on the Y chromosome (SRY) and DNA

In an effort to better define the molecular mechanism of the functional specificity of human sex-determining region on the Y chromosome (SRY), we have carried out equilibrium binding assays to study the interaction of the full-length bacterial-expressed protein with a DNA response element derived from the CD3epsilon gene enhancer. These assays are based on the observation of the fluorescence anisotropy of a fluorescein moiety covalently bound to the target oligonucleotide. The low anisotropy value due to the fast tumbling of the free oligonucleotide in solution increases substantially upon binding the protein to the labeled target DNA. Our results indicate that the full-length human wild-type SRY (SRY(WT)) forms a complex of high stoichiometry with its target DNA. Moreover, we have demonstrated a strong salt dependence of both the affinity and specificity of the interaction. We have also addressed the DNA bending properties of full-length human SRY(WT) in solution by fluorescence resonance energy transfer and revealed that maximal bending is achieved with a protein to DNA ratio significantly higher than the classical 1:1. Oligomerization thus appears, at least in vitro, to be tightly coupled to SRY-DNA interactions. Alteration of protein-protein interactions observed for the mutant protein SRY(Y129N), identified in a patient presenting with 46,XY sex reversal, suggests that oligomerization may play an important role in vivo as well.

Ontogenesis of female-to-male sex-reversal in XX polled goats

The association of polledness and intersexuality in domestic goats (PIS mutation) made them a practical genetic model for studying mammalian female-to-male sex reversal. In this study, gonads from XX sex-reversed goats (PIS-/-) were thoroughly characterized at the molecular and histologic level from the first steps of gonadal differentiation (36 days post coitum [dpc]) to birth. The first histologic signs of gonadal sex reversal were detectable between 36 and 40 dpc (4-5 days later than the XY male) and were mainly characterized by the reduction of the ovarian cortex and the organization of seminiferous cords. As early as 36 dpc, aromatase (CYP19) gene expression was decreased in XX (PIS-/-) gonads, whereas genes normally up-regulated in males, such as SOX9 and AMH, showed an increased expression level from 40 dpc. Thereafter, steroidogenic cell precursors were affected, and at 56 dpc, WNT4 and 3beta-HSD were expressed in a male-specific manner in sex-reversed gonads. Another noticeable feature was a progressive disappearance of germ cells, clearly visible in testicular cords around 70 dpc where 50-75% of germ cells were absent in XX (PIS-/-) gonads. These observations indicated that the causal mutation of PIS acts very early in the sex-determining cascade and affects primarily the supporting cells of the gonad.

Sex with two SOX on: SRY and SOX9 in testis development

Although gonads are not required for development or survival, defects in gonadal development undoubtedly have a profound influence on affected individuals. Recent complementary studies in the fields of cytology, biochemistry and molecular genetics have revealed that normal gonad development involves an exquisitely regulated network of gene expression and protein-protein interactions. The initial event of gonadogenesis, in both males and females, involves the formation of a bipotential primordium. A Y chromosome then activates the male-specific pathway. The demonstration that mutations in the SOX proteins, SRY and SOX9, are responsible for disorders associated with male-to-female sex reversal showed dramatically that SRY and SOX9 have an essential role in male sex differentiation. This was emphasized when it was shown that female mice carrying transgenes that encode these proteins developed as males. SRY and SOX9 proteins have been characterized extensively and aspects of their function and regulation are now known.

A case of intersexuality in pigs associated with a de novo paracentric inversion 9 (p1.2; p2.2)

In several mammalian species, genetic defects can be responsible for the interruption of and/or the deviation from the sequential steps of normal gonadal differentiation, leading to a sex-reversal syndrome. In pigs, female-to-male sex-reversal conditions are particularly frequent, but their aetiologies remain unclear. Chromosomal abnormalities that co-occur with sex-reversal disorders can be useful in the identification of loci containing responsible or susceptibility genes. This report describes a female-to-male SRY-negative intersex pig with a de novo paracentric inversion of the short arm of one chromosome 9 (p1.2; p2.2). We have fine mapped the proximal chromosomal breakpoint of this rearrangement because it corresponded to a region potentially involved in the pig intersexuality. Fluorescent in situ hybridization (FISH) experiments carried out with Bacterial Artificial Chromosome (BAC) clones located within the critical region defined by genetic linkage analysis and ordered on the porcine RH map allowed us to locate the proximal breakpoint between markers SW2571 and SW539. Further investigations are currently in progress to find new markers inside this interval, in order to determine the BAC in which the break occurred.