The "his and hers" of the renin-angiotensin system.

Sex differences exist in the regulation of arterial pressure and renal function by the renin-angiotensin system (RAS). This may in part stem from a differential balance in the pressor and depressor arms of the RAS. In males, the ACE/AngII/AT(1)R pathways are enhanced, whereas, in females, the balance is shifted towards the ACE2/Ang(1-7)/MasR and AT(2)R pathways. Evidence clearly demonstrates that premenopausal women, as compared to aged-matched men, are protected from renal and cardiovascular disease, and this differential balance of the RAS between the sexes likely contributes. With aging, this cardiovascular protection in women is lost and this may be related to loss of estrogen postmenopause but the possible contribution of other sex hormones needs to be further examined. Restoration of these RAS depressor pathways in older women, or up-regulation of these in males, represents a therapeutic target that is worth pursuing.

Genitales ambiguos / Ambiguous genitalia

El nacimiento de un niño con genitales ambiguos representa un choque emocional para la familia y un reto para los médicos, cuando no una verdadera situación de urgencia en etapa neonatal. Los trastornos congénitos que dan lugar a una discrepancia entre genitales externos, gónadas y sexo cromosómico son clasificados como anomalías o trastornos de la diferenciación sexual (ADS). En el año 2006 se decidió consensuar la terminología a emplear, desechando aquellos términos que resultaban peyorativos, tales como intersexo, hermafroditismo o pseudohermafroditismo, etc. Desde entonces hablamos de ADS. Presentan una incidencia anual de 1/4500 nacidos vivos, aproximadamente, siendo la hiperplasia suprarrenal congénita (HSC) la causa más frecuente. Esta incidencia aumenta al incluir los casos de criptorquidia, micropene e hipospadias neonatales. La evaluación de estos niños debe realizarse de forma precoz, debido a que la forma más frecuente de estas alteraciones es la HSC, que puede poner en riesgo la vida del neonato. La valoración inicial debe incluir exploración física, determinación de iones, 17-hidroxiprogesterona, cortisol, 11-desoxicortisol, 17-hidroxipregnenolona, dehidroepiandrosterona y hormona adrenocorticotropa para valorar la posibilidad de HSC. También debe solicitarse cariotipo, gen SRY y ecografía abdominal. En función de los resultados se clasificarán estos trastornos en ADS 46XX, ADS 46XY y ADS por alteraciones cromosómicas. El manejo de dicha situación debe ser realizado por un equipo multidisciplinario (neonatólogos, genetistas, endocrinólogos pediátricos, cirujanos pediátricos y psicólogos) en hospitales con experiencia (AU)

The birth of an infant with ambiguous genitalia represents an emotional shock for the family, a challenge for the medical doctors and a critical situation in neonatal stage. Individuals with a congenital discrepancy between external genitalia, gonadal and chromosomal sex, are classified as a disorder of sex development (DSD). In 2006 a new consensus about the terminology was reached, so pejorative terms like intersex, hermaphroditism and pseudohermaphroditism were abandoned. From then on, DSD is used. DSD presents an annual incidence of 1/4500 alive newborn and the adrenal hyperplasia is the most common cause. The incidence is increased if cryptorquidia, microphallus and hypospadias are included. The evaluation of newborns with ambiguous genitalia should be carried out as soon as possible, because the most common cause, congenital adrenal hyperplasia, can be life threatening. The initial assessment should include physical examinations, serum electrolytes, 17-hydroxyprogesterone, cortisol, 11-deoxycortisol, 17-hydroxypregnenolone, dehydroepiandrosterone and adrenocorticotropic hormone in order to evaluate for the possibility of congenital adrenal hyperplasia. Furthermore, karyotype, SRY gen and abdominal ultrasonography must be requested. These disorders will be classified depending on karyotype as 46XX DSD, 46XY DSD or DSD due to chromosome disorders. The management of this situation must be performed by a multidisciplinary team (neonatologist, genetics, paediatric endocrinologist, paediatric surgeon and psychologist) in hospitals with documented experience (AU)

Sex differences in prenatal epigenetic programming of stress pathways.

Maternal stress experience is associated with neurodevelopmental disorders including schizophrenia and autism. Recent studies have examined mechanisms by which changes in the maternal milieu may be transmitted to the developing embryo and potentially translated into programming of the epigenome. Animal models of prenatal stress have identified important sex- and temporal-specific effects on offspring stress responsivity. As dysregulation of stress pathways is a common feature in most neuropsychiatric diseases, molecular and epigenetic analyses at the maternal-embryo interface, especially in the placenta, may provide unique insight into identifying much-needed predictive biomarkers. In addition, as most neurodevelopmental disorders present with a sex bias, examination of sex differences in the inheritance of phenotypic outcomes may pinpoint gene targets and specific windows of vulnerability in neurodevelopment, which have been disrupted. This review discusses the association and possible contributing mechanisms of prenatal stress in programming offspring stress pathway dysregulation and the importance of sex.

Regulation of monoamine oxidase A by the SRY gene on the Y chromosome.

Monoamine oxidase A (MAO A), encoded by the X chromosome, catalyzes the oxidative deamination of monoamine neurotransmitters, such as serotonin, and plays a critically important role in brain development and functions. Abnormal MAO A activity has been implicated in several neuropsychiatric disorders, such as depression, autism, and attention deficit hyperactivity disorder, which show sexual dimorphism. However, the molecular basis for these disease processes is unclear. Recently, we found that MAO A was a putative target gene directly regulated by a transcription factor encoded by the sex-determining region Y (SRY) gene located on the Y chromosome. We demonstrated that SRY activates both MAO A-promoter and catalytic activities in a human male neuroblastoma BE(2)C cell line. A functional SRY-binding site in the MAO A core promoter was identified and validated by electrophoretic mobility shift and chromatin immunoprecipitation (ChIP) analyses. Coimmunoprecipitation and ChIP assays showed that SRY and Sp1 form a transcriptional complex and synergistically activate MAO A transcription. This is the first study demonstrating that the Y-encoded transcription factor SRY is capable of regulating an X-located gene, suggesting a novel molecular mechanism for sexual dimorphism in neural development, brain functions, and initiation/progression of neural disorders associated with MAO A dysfunction.

[Recent advances on sex determining mechanisms of Microtus mandarinus].

Most mammalian sex determination belongs to male heterogametic type of genetic sex determination. Sex determination of most mammals depends on the Y chromosome. SRY gene is the testis-determining factor on Y chromosome of most mammals, which is thought to be the most important gene in sex determination by far. Recent studies on Microtus mandarinus mandarinus demonstrated that the subspecies has Y chromosome, but there is no SRY gene on Y chromosome. Sex determination of Microtus mandarinus mandarinus is independent of SRY gene. R-spondin1 has also been excluded as the sex determination gene of Microtus mandarinus mandarinus. This paper reviews recent advances on sex determining mechanisms of Microtus mandarinus mandarinus. Possible sex determining mechanisms of Microtus mandarinus mandarinus in the absence of SRY gene are also discussed.

Sex chromosome complement affects social interactions in mice.

Sex differences in behavior can be attributed to differences in steroid hormones. Sex chromosome complement can also influence behavior, independent of gonadal differentiation. The mice used for this work combined a spontaneous mutation of the Sry gene with a transgene for Sry that is incorporated into an autosome thus disassociating gonad differentiation from sex chromosome complement. The resulting genotypes are XX and XY(-) females (ovary-bearing) along with XXSry and XY(-)Sry males (testes-bearing). Here we report results of basic behavioral phenotyping conducted with these mice. Motor coordination, use of olfactory cues to find a food item, general activity, foot shock threshold, and behavior in an elevated plus maze were not affected by gonadal sex or sex chromosome complement. In a one-way active avoidance learning task females were faster to escape an electric shock than males. In addition, sex chromosome complement differences were noted during social interactions with submissive intruders. Female XY(-) mice were faster to follow an intruder than XX female mice. All XY(-) mice spent more time sniffing and grooming the intruder than the XX mice, with XY(-) females spending the most amount of time in this activity. Finally, XX females were faster to display an asocial behavior, digging, and engaged in more digging than XXSry male mice. All of these behaviors were tested in gonadectomized adults, thus, differences in circulating levels of gonadal steroids cannot account for these effects. Taken together, these data show that sex chromosome complement affects social interaction style in mice.

Sex chromosome complement regulates habit formation.

Sex differences in brain function and behavior are regularly attributed to gonadal hormones. Some brain sexual dimorphisms, however, are direct actions of sex chromosome genes that are not mediated by gonadal hormones. We used mice in which sex chromosome complement (XX versus XY) and gonadal sex (ovaries versus testes) were independent, and found that XX mice showed faster food-reinforced instrumental habit formation than XY mice, regardless of gonadal phenotype.

Sex chromosome complement and gonadal sex influence aggressive and parental behaviors in mice.

Across human cultures and mammalian species, sex differences can be found in the expression of aggression and parental nurturing behaviors: males are typically more aggressive and less parental than females. These sex differences are primarily attributed to steroid hormone differences during development and/or adulthood, especially the higher levels of androgens experienced by males, which are caused ultimately by the presence of the testis-determining gene Sry on the Y chromosome. The potential for sex differences arising from the different complements of sex-linked genes in male and female cells has received little research attention. To directly test the hypothesis that social behaviors are influenced by differences in sex chromosome complement other than Sry, we used a transgenic mouse model in which gonadal sex and sex chromosome complement are uncoupled. We find that latency to exhibit aggression and one form of parental behavior, pup retrieval, can be influenced by both gonadal sex and sex chromosome complement. For both behaviors, females but not males with XX sex chromosomes differ from XY. We also measured vasopressin immunoreactivity in the lateral septum, which was higher in gonadal males than females, but also differed according to sex chromosome complement. These results imply that a gene(s) on the sex chromosomes (other than Sry) affects sex differences in brain and behavior. Identifying the specific X and/or Y genes involved will increase our understanding of normal and abnormal aggression and parental behavior, including behavioral abnormalities associated with mental illness.

Direct regulation of adult brain function by the male-specific factor SRY.

The central dogma of mammalian brain sexual differentiation has contended that sex steroids of gonadal origin organize the neural circuits of the developing brain. Recent evidence has begun to challenge this idea and has suggested that, independent of the masculinizing effects of gonadal secretions, XY and XX brain cells have different patterns of gene expression that influence their differentiation and function. We have previously shown that specific differences in gene expression exist between male and female developing brains and that these differences precede the influences of gonadal hormones. Here we demonstrate that the Y chromosome-linked, male-determining gene Sry is specifically expressed in the substantia nigra of the adult male rodent in tyrosine hydroxylase-expressing neurons. Furthermore, using antisense oligodeoxynucleotides, we show that Sry downregulation in the substantia nigra causes a statistically significant decrease in tyrosine hydroxylase expression with no overall effect on neuronal numbers and that this decrease leads to motor deficits in male rats. Our studies suggest that Sry directly affects the biochemical properties of the dopaminergic neurons of the nigrostriatal system and the specific motor behaviors they control. These results demonstrate a direct male-specific effect on the brain by a gene encoded only in the male genome, without any mediation by gonadal hormones.

Effective hepatocyte transplantation using rat hepatocytes with low asialoglycoprotein receptor expression.

Development of a reliable method of isolating highly proliferative potential hepatocytes provides information crucial to progress in the field of hepatocyte transplantation. The aim of this study was to develop reliable hepatocyte transplantation using highly proliferative, eg, progenitor-like hepatocytes, based on asialoglycoprotein receptor (ASGPR) expression levels for hepatocyte transplantation. We have previously reported that mouse hepatocytes with low ASGPR expression levels have highly proliferative potential and can be used as progenitor-like hepatocytes. We therefore fractionated F344 male rat hepatocytes expressing low and high levels of ASGPR and determined the liver repopulation capacity of hepatocytes according to low and high ASGPR expression in the liver. Next, 2 x 10(5) cells of each type were transplanted into female liver regenerative model dipeptidyl peptidase-deficient rats, and we estimated the rate of liver repopulation by the transplanted hepatocytes in the host liver, as determined by recognition of the Sry gene on the Y-chromosome. At 60 days after hepatocyte transplantation, the transplanted hepatocytes occupied approximately 76% of the total hepatocyte mass in the case of the transplantation of hepatocytes with low ASGPR expression, but accounted for approximately 12% and 17% of the mass in the case of the transplantation of hepatocytes with high ASGPR expression and unfractionated hepatocytes, respectively. In conclusion, these findings suggest that hepatocytes with low ASGPR expression can result in normal liver function and a high repopulation capacity in vivo. These results provide insight into development of a strategy for effective liver repopulation using transplanted hepatocytes.

[Advances in gonadal differentiation regulated by SRY].

Gondadal differentiation is genetically determined in humans. Sex is determined when the bipotential embryologic tissues differentiate into testes or ovary. SRY, a gene located on the Y chromosome, triggers a complex genetic cascade leading to testicular differentiation. However, only a minority of 46, XY sex reversal patients can be explained by SRY mutations, suggesting that other genes influencing sex determination are to be discovered. Recent studies show that testis differentiation requires insulin receptor family function in mice. SRY normally requires two distinct NLS-dependent nuclear import pathways to reach sufficient levels in the nucleus for gonadal differentiation.

[Sex differentiation and sex chromosomes].

The mechanisms for sex differentiation and the genes on the sex chromosomes are varied among different species. For human, SRY is the only testis-determining factor on the Y chromosome and triggers the cascade for male sex-determination. However, even if normal SRY exists, the haploinsufficienty of SOX9 or KTS+ splicing form of WT-1 can cause male-to-female sex reversal. Furthermore, the duplication of the partial region on the X chromosome including DAX-1 gene can also cause male-to-female sex reversal. The sex-determining system seems to be sensitive for the gene dosage or the gene expression level.

[Differentiation and development of internal sexual organs, and müllerian inhibiting substance].

Internal sexual organs are differentiated and developed by androgens and regressed by müllerian inhibiting substance(anti-müllerian hormone). The role of 5 alpha-dihydrotestosterone, reduced form of testosterone by 5 alpha-reductase, in terms of development of Wolffian duct is discussed with soluble mesenchymal factor responsible for the epithelial branching morphogenesis of mouse seminal vesicle on the basis of experimental results using organ culture assay of mouse new-born seminal vesicle. An update of müllerian inhibiting substance, a fetal regressor of female internal organs such as uterus, fallopian tubes and upper third vagina, is also discussed.

Are XX and XY brain cells intrinsically different?

In mammals and birds, the sex of the gonads is determined by genes on the sex chromosomes. For example, the mammalian Y-linked gene Sry causes testis differentiation. The testes then secrete testosterone, which acts on the brain (often after conversion to estradiol) to cause masculine patterns of development. If this were the only reason for sex differences in neural development, then XX and XY brain cells would have to be deemed otherwise equivalent. This equivalence is doubtful because of recent experimental results demonstrating that some XX and XY tissues, including the brain, are sexually dimorphic even when they develop in a similar endocrine environment. Although X and Y genes probably influence brain phenotype in a sex-specific manner, much more information is needed to identify the magnitude and character of these effects.

A model system for study of sex chromosome effects on sexually dimorphic neural and behavioral traits.

We tested the hypothesis that genes encoded on the sex chromosomes play a direct role in sexual differentiation of brain and behavior. We used mice in which the testis-determining gene (Sry) was moved from the Y chromosome to an autosome (by deletion of Sry from the Y and subsequent insertion of an Sry transgene onto an autosome), so that the determination of testis development occurred independently of the complement of X or Y chromosomes. We compared XX and XY mice with ovaries (females) and XX and XY mice with testes (males). These comparisons allowed us to assess the effect of sex chromosome complement (XX vs XY) independent of gonadal status (testes vs ovaries) on sexually dimorphic neural and behavioral phenotypes. The phenotypes included measures of male copulatory behavior, social exploration behavior, and sexually dimorphic neuroanatomical structures in the septum, hypothalamus, and lumbar spinal cord. Most of the sexually dimorphic phenotypes correlated with the presence of ovaries or testes and therefore reflect the hormonal output of the gonads. We found, however, that both male and female mice with XY sex chromosomes were more masculine than XX mice in the density of vasopressin-immunoreactive fibers in the lateral septum. Moreover, two male groups differing only in the form of their Sry gene showed differences in behavior. The results show that sex chromosome genes contribute directly to the development of a sex difference in the brain.

Familial occurrence of pig intersexes (38,XX; SRY-negative) on a commercial fattening farm.

Occurrence of sex-reversal (38,XX; SRY-negative) cases in the progeny of a single boar was observed. Altogether 11 intersexes, originating from nine litters, given by nine sows were found. The breeder classified the sex-reversal individuals as females with enlarged clitoris. In addition, it was noticed that the anus was joined with the vulva. Moreover, in the scrotum-like structure one or two gonads were present. Cytogenetic evaluation was carried out for the sire, five dams and seven intersexes. The study revealed the normal male karyotype (38,XY) in the sire and the normal female karyotype (38,XX) in the dams and the intersexes. Molecular detection of the presence of the SRY gene was carried out for the sire, five dams, 10 intersexes and 28 phenotypically normal siblings. The SRY gene was present in the genotype of the sire and the male siblings. Three intersexes were subjected to detailed anatomical and histological examinations, after slaughter in a local slaughterhouse. Gonads were classified as testes with well-developed epididymis, however, without spermatogenetic activity. The presence of a properly developed uterus and ducti deferens was observed, but oviducts were not found. The collected data indicate that the sex-reversal status was caused by an unknown autosome, recessive mutation. Genetic background of this type of intersexuality is discussed in this study.

[Genetic bases of human sex determination and differentiation]. / Genetyczne podstawy procesu determinacji i róznicowania plci.

Male and female sex determination depends on Y-linked SRY gene activity. This gene initiates the cascade of reactions which lead to the differentiation of bipotential, indifferent gonads to testes or ovaries, depending on the presence or absence of active from SRY. Since SRY discovery in 1990, several new genes playing important role in gonadal and in both internal and external genitalia development and differentiation have been identified. Detailed knowledge concerning above mentioned genes will enhance our understanding of etiology of sexual development abnormalities.