Delivery of sry1, but not sry2, to the kidney increases blood pressure and sns indices in normotensive wky rats

Chronic intermittent hypoxia-induced hypertension: the impact of sex hormones

Obstructive sleep apnea, a common form of sleep-disordered breathing, is characterized by intermittent cessations of breathing that reduce blood oxygen levels and contribute to the development of hypertension. Hypertension is a major complication of obstructive sleep apnea that elevates the risk of end-organ damage. Premenopausal women have a lower prevalence of obstructive sleep apnea and cardiovascular disease than men and postmenopausal women, suggesting that sex hormones play a role in the pathophysiology of sleep apnea-related hypertension. The lack of protection in men and postmenopausal women implicates estrogen and progesterone as protective agents but testosterone as a permissive agent in sleep apnea-induced hypertension. A better understanding of how sex hormones contribute to the pathophysiology of sleep apnea-induced hypertension is important for future research and possible hormone-based interventions. The effect of sex on the pathophysiology of sleep apnea and associated intermittent hypoxia-induced hypertension is of important consideration in the screening, diagnosis, and treatment of the disease and its cardiovascular complications. This review summarizes our current understanding of the impact of sex hormones on blood pressure regulation in sleep apnea with a focus on sex differences.

Sex-limited chromosomes and non-reproductive traits

Sex chromosomes are typically viewed as having originated from a pair of autosomes, and differentiated as the sex-limited chromosome (e.g. Y) has degenerated by losing most genes through cessation of recombination. While often thought that degenerated sex-limited chromosomes primarily affect traits involved in sex determination and sex cell production, accumulating evidence suggests they also influence traits not sex-limited or directly involved in reproduction. Here, we provide an overview of the effects of sex-limited chromosomes on non-reproductive traits in XY, ZW or UV sex determination systems, and discuss evolutionary processes maintaining variation at sex-limited chromosomes and molecular mechanisms affecting non-reproductive traits.

Rat models of human diseases and related phenotypes: a systematic inventory of the causative genes

The laboratory rat has been used for a long time as the model of choice in several biomedical disciplines. Numerous inbred strains have been isolated, displaying a wide range of phenotypes and providing many models of human traits and diseases. Rat genome mapping and genomics was considerably developed in the last decades. The availability of these resources has stimulated numerous studies aimed at discovering causal disease genes by positional identification. Numerous rat genes have now been identified that underlie monogenic or complex diseases and remarkably, these results have been translated to the human in a significant proportion of cases, leading to the identification of novel human disease susceptibility genes, helping in studying the mechanisms underlying the pathological abnormalities and also suggesting new therapeutic approaches. In addition, reverse genetic tools have been developed. Several genome-editing methods were introduced to generate targeted mutations in genes the function of which could be clarified in this manner [generally these are knockout mutations]. Furthermore, even when the human gene causing a disease had been identified without resorting to a rat model, mutated rat strains (in particular KO strains) were created to analyze the gene function and the disease pathogenesis. Today, over 350 rat genes have been identified as underlying diseases or playing a key role in critical biological processes that are altered in diseases, thereby providing a rich resource of disease models. This article is an update of the progress made in this research and provides the reader with an inventory of these disease genes, a significant number of which have similar effects in rat and humans.

Y Chromosome, Hypertension and Cardiovascular Disease: Is Inflammation the Answer?

It is now becomingly increasingly evident that the functions of the mammalian Y chromosome are not circumscribed to the induction of male sex. While animal studies have shown variations in the Y are strongly accountable for blood pressure (BP), this is yet to be confirmed in humans. We have recently shown modulation of adaptive immunity to be a significant mechanism underpinning Y-chromosome-dependent differences in BP in consomic strains. This is paralleled by studies in man showing Y chromosome haplogroup is a significant predictor for coronary artery disease through influencing pathways of immunity. Furthermore, recent studies in mice and humans have shown that Y chromosome lineage determines susceptibility to autoimmune disease. Here we review the evidence in animals and humans that Y chromosome lineage influences hypertension and cardiovascular disease risk, with a novel focus on pathways of immunity as a significant pathway involved.

Sex differences in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.

Chromosome Y genetic variants: impact in animal models and on human disease

Chromosome Y (chrY) variation has been associated with many complex diseases ranging from cancer to cardiovascular disorders. Functional roles of chrY genes outside of testes are suggested by the fact that they are broadly expressed in many other tissues and correspond to regulators of basic cellular functions (such as transcription, translation, and protein stability). However, the unique genetic properties of chrY (including the lack of meiotic crossover and the presence of numerous highly repetitive sequences) have made the identification of causal variants very difficult. Despite the prior lack of reliable sequences and/or data on genetic polymorphisms, earlier studies with animal chrY consomic strains have made it possible to narrow down the phenotypic contributions of chrY. Some of the evidence so far indicates that chrY gene variants associate with regulatory changes in the expression of other autosomal genes, in part via epigenetic effects. In humans, a limited number of studies have shown associations between chrY haplotypes and disease traits. However, recent sequencing efforts have made it possible to greatly increase the identification of genetic variants on chrY, which promises that future association of chrY with disease traits will be further refined. Continuing studies (both in humans and in animal models) will be critical to help explain the many sex-biased disease states in human that are contributed to not only by the classical sex steroid hormones, but also by chrY genetics.

Biological factors underlying sex differences in neurological disorders

The prevalence, age of onset, pathophysiology, and symptomatology of many neurological and neuropsychiatric conditions differ significantly between males and females. Females suffer more from mood disorders such as depression and anxiety, whereas males are more susceptible to deficits in the dopamine system including Parkinson's disease (PD), attention-deficit hyperactivity disorder (ADHD), schizophrenia, and autism spectrum disorders (ASD). Until recently, these sex differences have been explained solely by the neuroprotective actions of sex hormones in females. Emerging evidence however indicates that the sex chromosome genes (i.e. X- and Y-linked genes) also contribute to brain sex differences. In particular, the Y-chromosome gene, SRY (Sex-determining Region on the Y chromosome) is an interesting candidate as it is expressed in dopamine-abundant brain regions, where it regulates dopamine biosynthesis and dopamine-mediated functions such as voluntary movement in males. Furthermore, SRY expression is dysregulated in a toxin-induced model of PD, suggesting a role for SRY in the pathogenesis of dopamine cells. Taken together, these studies highlight the importance of understanding the interplay between sex-specific hormones and sex-specific genes in healthy and diseased brain. In particular, better understanding of regulation and function of SRY in the male brain could provide entirely novel and important insights into genetic factors involved in the susceptibility of men to neurological disorders, as well as development of novel sex-specific therapies.

SRY gene transferred by extracellular vesicles accelerates atherosclerosis by promotion of leucocyte adherence to endothelial cells

We set out to investigate whether and how SRY (sex-determining region, Y) DNAs in plasma EVs (extracellular vesicles) is involved in the pathogenesis of atherosclerosis. PCR and gene sequencing found the SRY gene fragment in plasma EVs from male, but not female, patients; EVs from male patients with CAD (coronary artery disease) had a higher SRY GCN (gene copy number) than healthy subjects. Additional studies found that leucocytes, the major source of plasma EVs, had higher SRY GCN and mRNA and protein expression in male CAD patients than controls. After incubation with EVs from SRY-transfected HEK (human embryonic kidney)-293 cells, monocytes (THP-1) and HUVECs (human umbilical vein endothelial cells), which do not endogenously express SRY protein, were found to express newly synthesized SRY protein. This resulted in an increase in the adherence factors CD11-a in THP-1 cells and ICAM-1 (intercellular adhesion molecule 1) in HUVECs. EMSA showed that SRY protein increased the promoter activity of CD11-a in THP-1 cells and ICAM-1 in HUVECs. There was an increase in THP-1 cells adherent to HUVECs after incubation with SRY-EVs. SRY DNAs transferred from EVs have pathophysiological significance in vivo; injection of SRY EVs into ApoE−/− (apolipoprotein-knockout) mice accelerated atherosclerosis. The SRY gene in plasma EVs transferred to vascular endothelial cells may play an important role in the pathogenesis of atherosclerosis; this mechanism provides a new approach to the understanding of inheritable CAD in men.

MAS promoter regulation: a role for Sry and tyrosine nitration of the KRAB domain of ZNF274 as a feedback mechanism

The ACE2 (angiotensin-converting enzyme 2)/Ang-(1-7) [angiotensin-(1-7)]/MAS axis of the RAS (renin-angiotensin system) has emerged as a pathway of interest in treating both cardiovascular disorders and cancer. The MAS protein is known to bind to and be activated by Ang-(1-7); however, the mechanisms of this activation are just starting to be understood. Although there are strong biochemical data regarding the regulation and activation of the AT1R (angiotensin II type 1 receptor) and the AT2R (angiotensin II type 2 receptor), with models of how AngII (angiotensin II) binds each receptor, fewer studies have characterized MAS. In the present study, we characterize the MAS promoter and provide a potential feedback mechanism that could compensate for MAS degradation following activation by Ang-(1-7). Analysis of ENCODE data for the MAS promoter revealed potential epigenetic control by KRAB (Krüppel-associated box)/KAP-1 (KRAB-associated protein-1). A proximal promoter construct for the MAS gene was repressed by the SOX [SRY (sex-determining region on the Y chromosome) box] proteins SRY, SOX2, SOX3 and SOX14, of which SRY is known to interact with the KRAB domain. The KRAB-KAP-1 complex can be tyrosine-nitrated, causing the dissociation of the KAP-1 protein and thus a potential loss of epigenetic control. Activation of MAS can lead to an increase in nitric oxide, suggesting a feedback mechanism for MAS on its own promoter. The results of the present study provide a more complete view of MAS regulation and, for the first time, suggest biochemical outcomes for nitration of the KRAB domain.

Why are sex and gender important to basic physiology and translational and individualized medicine?

Sex refers to biological differences between men and women. Although sex is a fundamental aspect of human physiology that splits the population in two approximately equal halves, this essential biological variable is rarely considered in the design of basic physiological studies, in translating findings from basic science to clinical research, or in developing personalized medical strategies. Contrary to sex, gender refers to social and cultural factors related to being a man or a woman in a particular historical and cultural context. Unfortunately, gender is often used incorrectly by scientists and clinical investigators as synonymous with sex. This article clarifies the definition of sex and gender and reviews evidence showing how sex and gender interact with each other to influence etiology, presentation of disease, and treatment outcomes. In addition, strategies to improve the inclusion of female and male human beings in preclinical and clinical studies will be presented, and the importance of embedding concepts of sex and gender into postgraduate and medical curricula will be discussed. Also, provided is a list of resources for educators. In the history of medical concepts, physiologists have provided pivotal contributions to understanding health and disease processes. In the future, physiologists should provide the evidence for advancing personalized medicine and for reducing sex and gender disparities in health care.

Analysis of Sry duplications on the Rattus norvegicus Y-chromosome

Background

Gene copy number variation plays a large role in the evolution of genomes. In Rattus norvegicus and other rodent species, the Y-chromosome has accumulated multiple copies of Sry loci. These copy number variations have been previously linked with changes in phenotype of animal models such as the spontaneously hypertensive rat (SHR). This study characterizes the Y-chromosome in the Sry region of Rattus norvegicus, while addressing functional variations seen in the Sry protein products.

Results

Eleven Sry loci have been identified in the SHR with one (nonHMG Sry) containing a frame shift mutation. The nonHMGSry is found and conserved in the related WKY and SD rat strains. Three new, previously unidentified, Sry loci were identified in this study (Sry3BII, Sry4 and Sry4A) in both SHR and WKY. Repetitive element analysis revealed numerous LINE-L1 elements at regions where conservation is lost among the Sry copies. In addition we have identified a retrotransposed copy of Med14 originating from spliced mRNA, two autosomal genes (Ccdc110 and HMGB1) and a normal mammalian Y-chromosome gene (Zfy) in the Sry region of the rat Y-chromosome. Translation of the sequences of each Sry gene reveals eight proteins with amino acid differences leading to changes in nuclear localization and promoter activation of a Sry-responsive gene. Sry-β (coded by the Sry2 locus) has an increased cytoplasmic fraction due to alterations at amino acid 21. Sry-γ has altered gene regulation of the Sry1 promoter due to changes at amino acid 76.

Conclusions

The duplication of Sry on the Rattus norvegicus Y-chromosome has led to proteins with altered functional ability that may have been selected for functions in addition to testis determination. Additionally, several other genes not normally found on the Y-chromosome have duplicated new copies into the region around the Sry genes. These suggest a role of active transposable elements in the evolution of the mammalian Y-chromosome in species such as Rattus norvegicus.

Should there be sex-specific criteria for the diagnosis and treatment of heart failure?

All-cause mortality from cardiovascular disease is declining in the USA. However, there remains a significant difference in risk factors for disease and in mortality between men and women. For example, prevalence and outcomes for heart failure with preserved ejection fraction differ between men and women. The reasons for these differences are multifactorial, but reflect, in part, an incomplete understanding of sex differences in the etiology of cardiovascular diseases and a failure to account for sex differences in pre-clinical studies including those designed to develop new diagnostic and treatment modalities. This review focuses on the underlying physiology of these sex differences and provides evidence that inclusion of female animals in pre-clinical studies of heart failure and in development of imaging modalities to assess cardiac function might provide new information from which one could develop sex-specific diagnostic criteria and approaches to treatment.

Genetic polymorphism of human Y chromosome and risk factors for cardiovascular diseases: a study in WOBASZ cohort

Genetic variants of Y chromosome predispose to hypertension in rodents, whereas in humans the evidence is conflicting. Our purpose was to study the distribution of a panel of Y chromosome markers in a cohort from a cross-sectional population-based study on the prevalence of cardiovascular risk factors in Poland (WOBASZ study). The HindIII, YAP Y chromosome variants, previously shown to influence blood pressure, lipid traits or height, as well as SNPs defining main Y chromosome haplogroups, were typed in 3026, 2783 and 2652 samples, respectively. In addition, 4 subgroups (N∼100 each) representing extremes of LDL concentration or blood pressure (BP) were typed for a panel of 17 STRs. The HindIII and YAP polymorphism were not associated with any of the studied traits. Analysis of the haplogroup distribution showed an association between higher HDL level and hg I-M170 (P = 0.02), higher LDL level and hg F*(xI-M170, J2-M172, K-M9) (P = 0.03) and lower BMI and hg N3-Tat (P = 0.04). Analysis of STRs did not show statistically significant differences. Since all these associations lost statistical significance after Bonferroni correction, we conclude that a major role of Y chromosome genetic variation (defined by HindIII, YAP or main Y chromosome haplogroups) in determining cardiovascular risk in Poles is unlikely.

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.

The human testis-determining factor SRY localizes in midbrain dopamine neurons and regulates multiple components of catecholamine synthesis and metabolism

The male gender is determined by the sex-determining region on the Y chromosome (SRY) transcription factor. The unexpected action of SRY in the control of voluntary movement in male rodents suggests a role in the regulation of dopamine transmission and dopamine-related disorders with gender bias, such as Parkinson's disease. We investigated SRY expression in the human brain and function in vitro. SRY immunoreactivity was detected in the human male, but not female substantia nigra pars compacta, within a sub-population of tyrosine hydroxylase (TH) positive neurons. SRY protein also co-localized with TH positive neurons in the ventral tegmental area, and with GAD-positive neurons in the substantia nigra pars reticulata. Retinoic acid-induced differentiation of human precursor NT2 cells into dopaminergic cells increased expression of TH, NURR1, D2 R and SRY. In the human neuroblastoma cell line, M17, SRY knockdown resulted in a reduction in TH, DDC, DBH and MAO-A expression; enzymes which control dopamine synthesis and metabolism. Conversely, SRY over-expression increased TH, DDC, DBH, D2 R and MAO-A levels, accompanied by increased extracellular dopamine levels. A luciferase assay demonstrated that SRY activated a 4.6 kb 5' upstream regulatory region of the human TH promoter/nigral enhancer. Combined, these results suggest that SRY plays a role as a positive regulator of catecholamine synthesis and metabolism in the human male midbrain. This ancillary genetic mechanism might contribute to gender bias in fight-flight behaviours in men or their increased susceptibility to dopamine disorders, such as Parkinson's disease and schizophrenia.

Sex differences in primary hypertension

Men have higher blood pressure than women through much of life regardless of race and ethnicity. This is a robust and highly conserved sex difference that it is also observed across species including dogs, rats, mice and chickens and it is found in induced, genetic and transgenic animal models of hypertension. Not only do the differences between the ovarian and testicular hormonal milieu contribute to this sexual dimorphism in blood pressure, the sex chromosomes also play a role in and of themselves. This review primarily focuses on epidemiological studies of blood pressure in men and women and experimental models of hypertension in both sexes. Gaps in current knowledge regarding what underlie male-female differences in blood pressure control are discussed. Elucidating the mechanisms underlying sex differences in hypertension may lead to the development of anti-hypertensives tailored to one's sex and ultimately to improved therapeutic strategies for treating this disease and preventing its devastating consequences.

Amino acid function and docking site prediction through combining disease variants, structure alignments, sequence alignments, and molecular dynamics: a study of the HMG domain

Background

The DNA binding domain of HMG proteins is known to be important in many diseases, with the Sox sub-family of HMG proteins of particular significance. Numerous natural variants in HMG proteins are associated with disease phenotypes. Integrating these natural variants, molecular dynamic simulations of DNA interaction and sequence and structure alignments give detailed molecular knowledge of potential amino acid function such as DNA or protein interaction.

Results

A total of 33 amino acids in HMG proteins are known to have natural variants in diseases. Eight of these amino acids are normally conserved in human HMG proteins and 27 are conserved in the human Sox sub-family. Among the six non-Sox conserved amino acids, amino acids 16 and 45 are likely targets for interaction with other proteins. Docking studies between the androgen receptor and Sry/Sox9 reveals a stable amino acid specific interaction involving several Sox conserved residues.

Conclusion

The HMG box has structural conservation between the first two of the three helixes in the domain as well as some DNA contact points. Individual sub-groups of the HMG family have specificity in the location of the third helix, DNA specific contact points (such as amino acids 4 and 29), and conserved amino acids interacting with other proteins such as androgen receptor. Studies such as this help to distinguish individual members of a much larger family of proteins and can be applied to any protein family of interest.

From rat to human: regulation of Renin-Angiotensin system genes by sry

The testis determining protein, Sry, has functions outside of testis determination. Multiple Sry loci are found on the Y-chromosome. Proteins from these loci have differential activity on promoters of renin-angiotensin system genes, possibly contributing to elevation of blood pressure. Variation at amino acid 76 accounts for the majority of differential effects by rat proteins Sry1 and Sry3. Human SRY regulated rat promoters in the same manner as rat Sry, elevating Agt, Ren, and Ace promoter activity while downregulating Ace 2. Human SRY significantly regulated human promoters of AGT, REN, ACE2, AT2, and MAS compared to control levels, elevating AGT and REN promoter activity while decreasing ACE2, AT2, and MAS. While the effect of human SRY on individual genes is often modest, we show that many different genes participating in the renin-angiotensin system can be affected by SRY, apparently in coordinated fashion, to produce more Ang II and less Ang-(1-7).

The SHR Y chromosome increases cardiovascular, endocrine, and behavioral responses to stress compared to the WKY Y chromosome

The SHR Y chromosome has loci which are involved with behavioral, endocrine and brain phenotypes and respond to acute stress to a different degree than that of the WKY Y chromosome. The objectives were to determine if WKY males with an SHR Y chromosome (SHR/y) when compared to males with a WKY Y chromosome would have: 1. a greater increase in systolic and diastolic blood pressures (BP), heart rate (HR), and locomotor activity when placed in an open field environment and during an acute stress procedure; 2. enhanced stress hormone responses; 3. greater voluntary running; and 4. increased brain Sry expression. The SHR/y strain showed a significant rise in BP (32%) and HR (10%) during the open field test and exhibited higher BP (46% change) during air jet stress. SHR/y had higher locomotor activity and less immobility and had increased stress induced plasma norepinephrine and adrenocorticotrophic hormone and 3-4× more voluntary running compared to WKY. Differential Sry expression between WKY and SHR/y in amygdala and hippocampus was altered at rest and during acute stress more than that of WKY. Evidence suggests that this animal model allows novel functions of Y chromosome loci to be revealed. In conclusion, a transcription factor on the SHR Y chromosome, Sry, may be responsible for the cardiovascular, endocrine and behavioral phenotype differences between SHR/y and WKY males.

The Sry3 Y chromosome locus elevates blood pressure and renin-angiotensin system indexes

BACKGROUND

Sex-determining region Y (Sry) is a transcription factor. Our research group has shown that there are multiple copies of Sry in Wistar-Kyoto (WKY) and spontaneous hypertensive (SHR) rats, and that they have novel functions separate from testes determination.

OBJECTIVE

We hypothesized that exogenously delivered Sry3 to the normotensive WKY male kidney would activate the renin-angiotensin system (RAS) and raise blood pressure (BP), based on previous in vitro studies.

METHODS

Sry3 or control vector was electroporated to the left kidney of male WKY rats and the following measurements were taken: BP by telemetry, renin-angiotensin measures by radioimmunoassay, plasma and tissue catecholamines by HPLC with electrochemical detection, sodium by flame photometry, and inulin by ELISA.

RESULTS

Sry3 increased BP 10 to 20 mm Hg compared with controls (P < 0.01) and produced a significant 40% decrease in urine sodium compared with controls (P < 0.05). Sry3 increased renal angiotensin II and plasma renin activity by >100% compared with controls (P < 0.01 and P < 0.05, respectively).

CONCLUSION

The findings presented here confirm and extend the argument for Sry3 as one of the genes responsible for the SHR hypertensive Y chromosome phenotype and are consistent with increased tissue RAS activity due to Sry3 and increased sodium reabsorption.

Sex, hormones and neuroeffector mechanisms

Incidence and rate of cardiovascular disease differ between men and women across the life span. Although hypertension is more prominent in men than women, there is a group of vasomotor disorders [i.e. Raynaud's disease, postural orthostatic tachycardia syndrome and vasomotor symptoms (hot flashes) of menopause and migraine] with a female predominance. Both sex and hormones interact to modulate neuroeffector mechanisms including integrated regulation of the Sry gene and direct effect of sex steroid hormones on synthesis, release and disposition of monoamine neurotransmitters, and distribution and sensitivity of their receptors in brain areas associated with autonomic control. The interaction of the sex chromosomes and steroids also modulates these effector tissues, that is, the heart, vascular smooth muscle and endothelium. Although involvement of central serotonergic centres has been studied in regard to mood disorders such as depression, their contribution to cardiovascular risk is gaining attention. Studies are needed to further evaluate how hormonal treatments and drugs used to modulate adrenergic and serotonergic activity affect progression and risk for cardiovascular disease in men and women.

Sry, more than testis determination?

The Sry locus on the mammalian Y chromosome is the developmental switch responsible for testis determination. Inconsistent with this important function, the Sry locus is transcribed in adult males at times and in tissues not involved with testis determination. Sry is expressed in multiple tissues of the peripheral and central nervous system. Sry is derived from Sox3 and is similar to other SOXB family loci. The SOXB loci are responsible for nervous system development. Sry has been demonstrated to modulate the catecholamine pathway, so it should have functional consequences in the central and peripheral nervous system. The nervous system expression and potential function are consistent with Sry as a SOXB family member. In mammals, Sox3 is X-linked and undergoes dosage compensation in females. The expression of Sry in adult males allows for a type of sexual differentiation independent of circulating gonadal hormones. A quantitative difference in Sox3 plus Sry expression in males vs. females could drive changes in the transcriptome of these cells, differentiating male and female cells. Sry expression and its transcriptional effects should be considered when investigating sexual dimorphic phenotypes.

Whole rat DNA array survey for candidate genes related to hypertension in kidneys from three spontaneously hypertensive rat substrains at two stages of age and with hypotensive induction caused by hydralazine hydrochloride

Clarification of the genetic nature and more effective care for hypertension are required, given the high incidences of cardiovascular and cerebrovascular mortality. Thus, we surveyed candidate genes for hypertension with rat whole gene DNA microarrays using three novel methods. Gene expression analyses were conducted as follows: Method 1, three types of spontaneously hypertensive rat (SHR) substrains, SHR, stroke-prone SHR (SHRSP) and malignant type of SHRSP (M-SHRSP) were used and compared to normotensive Wistar Kyoto rats; Method 2, the expressed genes between rats of different ages were compared for different blood pressures; and Method 3, genes that were expressed in rats treated with or without an acute hypotensive stimulus, the antihypertensive hydralazine hydrochloride, were compared. This approach identified dozens of genes, including Dusp15, Cyp8b1, Armc 3, Gtpbp4, Mettl2, Mapk14, Prkar2b, frame 12, Anxa13, Ephx2, Myr8 and Pcdh9 by Method 1; Cyp2C and Atp12a by Method 2; and Kcnc3, Vnn1, TC560558 and Gabrq and a number of unknown genes by Methods 2 and 3, as probable candidate genes for hypertension in SHR substrains. Ephx2 was previously reported as a candidate gene in SHRs; however other genes were identified for the first time in this study. Since it was not always possible to completely demonstrate that these genes are responsible for hypertension in SHRs, further research into true candidate genes that participate in the genesis of hypertension in SHR substrains is warranted.

Review of the Y chromosome, Sry and hypertension

The following review examines the role of the SHR Y chromosome and specifically the Sry gene complex in hypertension and potential mechanisms that involve the sympathetic nervous system and renin-angiotensin system. There are consistent gender differences in hypertension, with a greater proportion of males affected than females in most mammalian populations. Our earlier studies demonstrated that a portion of the gender differences in blood pressure (BP) in the SHR rat mapped to the SHR Y chromosome. In rats, males with the SHR Y chromosome have higher BP than females, or males with a different Y chromosome. Consistent with these results, several human population studies have confirmed a Y chromosome effect on BP. Our more recent studies focus on a transcription factor, Sry, as the locus involved in not only BP modulation but effects on other phenotypes. The Sry locus is an evolutionarily conserved locus on the mammalian Y chromosome responsible for testis determination and is a transcription factor. The Sry locus contains a highly conserved High Mobility Group (HMG) box region responsible for DNA binding. Mutations in the HMG box result in sex reversal. We have found multiple functional copies of Sry in SHR and WKY male rats. There is abundant evidence that testes determination may not be Sry's only function as it is expressed in the brain, kidney and adrenal gland of adult males. These findings have potential implications for gender physiology research which involves, the sympathetic nervous system, renin-angiotensin system, androgen receptor regulation and prostate physiology.

Sex chromosome effects unmasked in angiotensin II-induced hypertension

Sex differences in mean arterial pressure (MAP) are reported in many experimental models of hypertension and are ascribed to gonadal sex based on studies showing that gonadectomy and gonadal hormone replacement affect MAP. The interpretation of these studies, however, has been confounded by differences in the sex chromosome complement (XX versus XY). To investigate the sex chromosome complement independent of gonadal sex, we used the 4 core genotype mouse model in which gonadal sex is separated from the sex chromosome complement enabling comparisons among XX and XY females and XX and XY males. We found that, in the gonadectomized (GDX) 4 core genotype, MAP after 2 weeks of angiotensin II infusion (200 ng/kg per minute) was greater in XX than XY (MAP [in millimeters of mercury]: GDX-XX-female, 148+/-4.5; GDX-XY-female, 133+/-4.4; GDX-XX-male, 149+/-9.4; GDX-XY-male, 138+/-5.5; P<0.03, XX versus XY; n=8 to 9 per group). In contrast, no sex chromosome effects were found on heart rate, body weight, or plasma angiotensin II 2 weeks after angiotensin II infusion. This study suggests that, in addition to effects of gonadal hormones on blood pressure, X- or Y-linked genes, parental imprinting, or X mosaicism contributes to sex differences in hypertension. Furthermore, the finding that MAP was greater in XX mice compared with XY mice in the GDX state suggests that adverse sex chromosome effects encoded within the XX sex chromosome complement could contribute to hypertension in women with ovarian hormone deficiency, such as postmenopausal women and women with premature ovarian failure.