Sequence variations in equine candidate genes For XX and XY inherited disorders of sexual development.

Inherited disorders of sexual development (DSD) cause sterility and infertility in horses. Mutations causing such disorders have been identified in other mammals, but there is little information on the molecular causes in horses. While the equine genome sequence has made it possible to identify candidate genes, additional tools are needed to routinely screen them for causative mutations. In this study, we designed a screening panel of polymerase chain reaction primer pairs for 15 equine genes. These are the candidate genes for testicular or ovotesticular XX DSD and XY DSD, the latter of which includes gonadal dysgenesis, androgen insensitivity syndrome (AIS), persistent Mullerian duct syndrome and isolated cryptorchidism. Six horses with testicular or ovotesticular XX DSD and controls were screened. In addition, candidate genes for androgen insensitivity syndrome, persistent Mullerian duct syndrome and isolated cryptorchidism were screened in normal horses. While no sequence variants were uniquely associated with XX DSD, the 38 sequence variants identified can serve as intragenic markers in genome-wide association studies or linkage studies to hasten mutation identification in equine XX DSD and XY DSD.

Male rats with the testicular feminization mutation of the androgen receptor display elevated anxiety-related behavior and corticosterone response to mild stress.

Testosterone influences the hypothalamic-pituitary-adrenal axis, anxiety-related behavior, and sensorimotor gating in rodents, but little is known about the role of the androgen receptor (AR) in mediating these influences. We compared levels of the stress hormone corticosterone at baseline and following exposure to a novel object in an open field in wild type (wt) male and female rats, and male rats with the testicular feminization mutation (Tfm) of the AR, which disables its function. Basal corticosterone was equivalent in all groups, but exposure to a novel object in an open field elicited a greater increase in corticosterone in Tfm males and wt females than in wt males. Tfm males also showed increased behavioral indices of anxiety compared to wt males and females in the test. Analysis of the immediate early gene c-Fos expression after exposure to a novel object revealed greater activation in Tfm males than wt males in some regions (medial preoptic area) and lesser activation in others (dentate gyrus, posterodorsal medial amygdala). No differences were found in a measure of sensorimotor gating (prepulse inhibition of the acoustic startle response), although Tfm males had an increased acoustic startle response compared to wt males and females. These findings demonstrate that ARs play a role in regulating anxiety-related behaviors, as well as corticosterone responses and neural activation following exposure to a mild stressor in rats.

Androgen Receptor Gene Variants in New Cases of Equine Androgen Insensitivity Syndrome.

In the domestic horse; failure of normal masculinization and virilization due to deficiency of androgenic action leads to a specific disorder of sexual development known as equine androgen insensitivity syndrome (AIS). Affected individuals appear to demonstrate an incoherency between their genetic sex and sexual phenotype; i.e., XY-sex chromosome constitution and female phenotypic appearance. AIS is well documented in humans. Here we report the finding of two novel genetic variants for the AR-gene identified in a Tennessee Walking Horse and a Thoroughbred horse mare; each in individual clinical cases of horse AIS syndrome.

DDT-induced feminization of gull embryos.

Injection of DDT [1, 1, 1-trichloro-2,2-bis(p-chlorophenyl)ethane] into gull eggs at concentrations comparable to those found in contaminated seabird eggs in 1970 induces abnormal development of ovarian tissue and oviducts in male embryos. Developmental feminization of males is associated with inability to breed as adults and may explain the highly skewed sex ratio and reduced number of male gulls breeding on Santa Barbara Island in southern California.

Mice with the testicular feminization mutation demonstrate a role for androgen receptors in the regulation of anxiety-related behaviors and the hypothalamic-pituitary-adrenal axis.

Testosterone (T) appears to play a role in anxiety and sensorimotor gating in rodents, but whether T acts through the androgen receptor (AR) to influence these behaviors is less clear. We compared adult genetic male mice with the testicular feminization mutation (Tfm), which lack functional ARs, to wild type male littermates (wt males) on an assay of sensorimotor gating (prepulse inhibition of the acoustic startle response; PPI) and several tests thought to reflect anxiety: open field exposure, novel object exposure, elevated plus maze (EPM), and light/dark (LD) box. PPI was similar between groups, but indices of anxiety in the novel object and LD box tests were increased in Tfm males with no significant differences found in the open field or EPM. Since Tfm male mice have decreased circulating T, the same tests were conducted in mice that were gonadectomized (wt males) or sham-operated (Tfm males) as adults and supplemented with T or nothing (B). While T treatment reduced indices of anxiety in the novel object and LD box tests in wt males, it was ineffective in Tfm males. Increased indices of anxiety in Tfm males appear to be related to hyper-activation of the hypothalamic-pituitary-adrenal axis since levels of the stress hormone corticosterone were elevated in Tfm males compared to wt males at baseline and at several time points after exposure to a novel object. These findings demonstrate that ARs influence anxiety and stress responses in mice.

Studies on the pathogenesis of the pseudohermaphroditism in the mouse with testicular feminization.

The pathogenesis of the male pseudohermaphroditism in the mouse with X-linked testicular feminization (Tfm) has been investigated by comparing testosterone formation, the effects of androgen administration, and the metabolism of testosterone-1,2-(3)H in normal mice and Tfm mice of varying ages. First, it was established that the adult Tfm animal, in contrast to the human with testicular feminization, has both a low serum testosterone and a low rate of testosterone formation as assessed in slices of testes utilizing a variety of precursors. However, the formation of testosterone from pregnenolone-7alpha-(3)H was shown to be normal in newborn Tfm testes, suggesting that a defect in testosterone synthesis may not be primary to this mutation. Second, to establish that the pseudohermaphroditic state is due to androgen resistance rather than to diminished androgen biosynthesis during fetal life, the effect of the administration of dihydrotestosterone to pregnant animals was studied in male, female, and Tfm offspring. Whereas normal and carrier female littermates demonstrated striking virilization of the internal genital tract after such treatment, there was no sign of virilization in the Tfm animals. This finding provides direct experimental evidence in support of the view that male pseudohermaphroditism in testicular feminization is the result of resistance to androgen action during androgen-mediated sexual differentiation in embryos. Third, the metabolism of testosterone-1,2-(3)H was investigated both in tissue slices and in functionally hepatectomized animals. Dihydrotestosterone formation in tissue slices of the fetal anlage of the male organs of accessory reproduction is normal in the Tfm animal, suggesting that the primary defect in this disorder involves an intracellular event subsequent to this step and that the deficient dihydrotestosterone formation observed in the adult genital tract of the Tfm mouse is secondary to the failure of differentiation in these tissues. Finally, deficient binding of testosterone in the nuclei of the submandibular gland of adult Tfm animals, a known testosterone target tissue, was demonstrated in functionally hepatectomized mice. This finding could either be a manifestation of the primary genetic defect in this disorder or might reflect another acquired abnormality due to incomplete differentiation of adrogen-sensitive cell lines.

Testicular feminization syndrome in a mare.

Testicular feminization syndrome was diagnosed in a mare with aggressive, stallion like behavior and a history of infertility. She was found to have a high baseline testosterone concentration suggesting that testicular tissue was present, and ovarian-like structures examined by use of transrectal ultrasonography had the appearance typical of testicular tissue. Although her external female genitalia appeared normal, her vagina ended in a blind sac, and no cervix or uterus were identified. Surgery was performed, and structures removed from the abdominal cavity were determined to be hypoplastic testicles. Removal of the testicular tissue resulted in complete resolution of her aggressive behavior. Chromosomal evaluation revealed that the mare had 64X,Y (normal male) karyotype. Testicular feminization syndrome is a condition characterized by insensitivity of reproductive tissues to androgens during development because of an abnormality in androgen receptors. This androgen insensitivity results in development of normal external female genitalia, with high testosterone concentrations being released from developing testicles. Testicular feminization syndrome has not been commonly diagnosed in horses, but should be considered as a differential diagnosis for overly aggressive mares with a history of infertility.

Testicular feminization in a cat.

Testicular feminization, caused by an inherited defect of the androgen receptor, was diagnosed in a domestic cat. Individuals affected with this syndrome are genetic males that have testes but fail to undergo masculinization because the internal and external genitalia cannot respond to androgens. The affected cat had the external appearance of a sexually normal female, but during surgery for ovariohysterectomy, only 2 abdominal gonads were found. Müllerian (uterus) or wolffian (epididymides) derivatives were not present. Only testicular tissue was found in histologic sections of the gonad. A normal male chromosome constitution (38,XY) was found in karyotypes prepared from lymphocyte cultures. High affinity binding of dihydrotestosterone was undetectable in fibroblasts cultured from genital skin of the affected cat, indicating that the cytosolic androgen receptor was nonfunctional. Pedigree analysis indicates that this is an X-linked disorder in cats, as it is in other mammals. Accurate diagnosis and genetic counseling are advocated to reduce the prevalence of the disorder.

Androgen insensitivity syndrome in a thoroughbred mare (64, XY--testicular feminization).

A Thoroughbred mare was presented for stallion-like behavior. Reproductive and ultrasonographic evaluation, testosterone assays, and karyotyping confirmed a diagnosis of androgen insensitivity syndrome (64, XY--testicular feminization). Surgery to remove abdominal testicles was successful in alleviating the behavioral abnormality. This condition is discussed with reference to the current literature.

[Testicular tumors in dogs: a literature review]. / Testistumoren bij de hond: een literatuuroverzicht.

The incidence of testicular tumours in dogs is higher than in other species. The main three types are: Sertoli cell tumour, seminoma, and Leydig cell tumour. Metastases are rare. Sertoli cell tumours, and to a lesser extent Leydig cell tumours, are often associated with feminization, which occurs in 19% and 5% of cases, respectively. Seminomas are rarely associated with feminization. Feminization seems to be the result of an excessive oestrogen production by the tumour. In severe cases this may lead to bone marrow depression. Atrophy of the contralateral testis is a common finding. It is not clear whether this is a result of feminization or of age because most tumours occur in older dogs. By investigating the morphology of the testis, and the endocrinological and fertility status of the dog this phenomena is hopefully going to be explained. Extra attention is given to the pathogenesis of feminization.

Testicular feminization in the Finnish racoon dog (Nyctereutes procyonoides).

The clinical features of testicular feminization in the racoon dog (Nyctereutes procyonoides) are reported. The condition is characterized by a normal male karyotype, but a mixed phenotype consisting of vulva, enlarged clitoris and scrotal testes. Partial spermatogenesis with a relative arrest at the first meiotic division was observed. The likely underlying genetic defect and mode of inheritance are discussed, together with implications for breeding programmes.