SUMMARY Growing evidence indicates that non-neuronal mutant huntingtin toxicity plays an important role in Huntington’s disease (HD); however, whether and how mutant huntingtin affects oligodendrocytes, which are vitally important for neural function and axonal integrity, remain unclear. We first verified the presence of mutant huntingtin in oligodendrocytes in HD140Q knock-in mice. We then established transgenic mice (PLP-150Q) that selectively express mutant huntingtin in oligodendrocytes. PLP-150Q mice show progressive neurological symptoms and early death, as well as age-dependent demyelination and reduced expression of myelin genes that are downstream of myelin regulatory factor (MYRF or MRF), a transcriptional regulator that specifically activates and maintains the expression of myelin genes in mature oligodendrocytes. Consistently, mutant huntingtin binds abnormally to MYRF and affects its transcription activity. Our findings suggest that dysfunction of mature oligodendrocytes is involved in HD pathogenesis and may also make a good therapeutic target.

Bisphenol A (BPA) is a known reproductive toxicant in rodents. However, the effects of in utero BPA exposure on early ovarian development and the consequences of such exposure on female reproduction in later reproductive life are unclear. Thus, we determined the effects of in utero BPA exposure during a critical developmental window on germ cell nest breakdown, a critical process for establishment of the finite primordial follicle pool, and on female reproduction. Pregnant FVB mice (F0) were orally dosed daily with tocopherol-striped corn oil (vehicle), diethylstilbestrol (DES; 0.05 μg/kg, positive control), or BPA (0.5, 20, and 50μg/kg) from gestational day 11 until birth. Ovarian morphology and gene expression profiles then were examined in F1 female offspring on postnatal day (PND) 4 and estrous cyclicity was examined daily after weaning for 30 days. F1 females were also subjected to breeding studies with untreated males at three to nine months. The results indicate that BPA inhibits germ cell nest breakdown via altering expression of selected apoptotic factors. BPA also significantly advances the age of first estrus, shortens the time that the females remain in estrus, and increases the time the females remain in metestrus and diestrus compared to controls. Further, F1 females exposed to low doses of BPA exhibit various fertility problems and have a significantly higher percentage of dead pups compared to controls. These results indicate that in utero exposure to low doses of BPA during a critical ovarian developmental window interferes with early ovarian development and reduces fertility with age.

Di(2-ethylhexyl) phthalate (DEHP) is a ubiquitous environmental toxicant found in consumer products that causes ovarian toxicity. Antral follicles are the functional ovarian units and must undergo growth, survival from atresia, and proper regulation of steroidogenesis to ovulate and produce hormones. Previous studies have determined that DEHP inhibits antral follicle growth and decreases estradiol levels in vitro; however, the mechanism by which DEHP elicits these effects is unknown. The present study tested the hypothesis that DEHP directly alters regulators of the cell cycle, apoptosis, and steroidogenesis to inhibit antral follicle functionality. Antral follicles from adult CD-1 mice were cultured with vehicle control or DEHP (1-100μg/ml) for 24-96 hr to establish the temporal effects of DEHP on the follicle. Following 24-96 hr of culture, antral follicles were subjected to gene expression analysis, and media were subjected to measurements of hormone levels. DEHP increased the mRNA levels of cyclin D2, cyclin dependent kinase 4, cyclin E1, cyclin A2, and cyclin B1 and decreased the levels of cyclin-dependent kinase inhibitor 1A prior to growth inhibition. Additionally, DEHP increased the mRNA levels of BCL2-associated agonist of cell death, BCL2-associated X protein, BCL2-related ovarian killer protein, B-cell leukemia/lymphoma 2, and Bcl2-like 10, leading to an increase in atresia. Further, DEHP decreased the levels of progesterone, androstenedione, and testosterone prior to the decrease in estradiol levels, with decreased mRNA levels of side-chain cleavage, 17α-hydorxylase-17,20-desmolase, 17β-hydroxysteroid dehydrogenase, and aromatase. Collectively, DEHP directly alters antral follicle functionality by inhibiting growth, inducing atresia, and inhibiting steroidogenesis.

Humans are ubiquitously exposed to di(2-ethylhexyl) phthalate (DEHP), which is an environmental toxicant present in common consumer products. DEHP potentially targets the ovary through its metabolite mono(2-ethylhexyl) phthalate (MEHP). However, the direct effects of MEHP on ovarian folliculogenesis and steroidogenesis, two processes essential for reproductive and nonreproductive health, are unknown. The present study tested the hypotheses that MEHP directly accelerates early folliculogenesis via overactivation of phosphatidylinositol 3-kinase (PI3K) signaling, a pathway that regulates primordial follicle quiescence and activation, and inhibits the synthesis of steroid hormones by decreasing steroidogenic enzyme levels. Neonatal ovaries from CD-1 mice were cultured for 6 days with vehicle control, DEHP, or MEHP (0.2-20 lg/ml) to assess the direct effects on folliculogenesis and PI3K signaling. Further, antral follicles from adult CD-1 mice were cultured with vehicle control or MEHP (0.1-10 lg/ml) for 24-96 h to establish the temporal effects of MEHP on steroid hormones and steroidogenic enzymes. In the neonatal ovaries, MEHP, but not DEHP, decreased phosphatase and tensin homolog levels and increased phosphorylated protein kinase B levels, leading to a decrease in the percentage of germ cells and an increase in the percentage of primary follicles. In the antral follicles, MEHP decreased the mRNA levels of 17alpha-hydroxylase-17,20-desmolase, 17beta-hydroxysteroid dehydrogenase, and aromatase leading to a decrease in testosterone, estrone, and estradiol levels. Collectively, MEHP mediates the effect of DEHP on accelerated folliculogenesis via overactivating PI3K signaling and inhibits steroidogenesis by decreasing steroidogenic enzyme levels.

Di-n-butyl phthalate (DBP) is present in many consumer products, such as infant, beauty, and medical products. Several studies have shown that DBP causes reproductive toxicity in rodents, but no studies have evaluated its effects on ovarian follicles. Therefore, we used a follicle culture system to evaluate the effects of DBP on antral follicle growth, cell cycle and apoptosis gene expression, cell cycle staging, atresia, and 17β-estradiol (E(2)) production. Antral follicles were isolated from adult CD-1 mice and exposed to DBP at 1, 10, 100, and 1000 μg/ml for 24 or 168 h. Follicles treated with vehicle or DBP at 1-100 μg/ml grew over time, but DBP at 1000 μg/ml significantly suppressed follicle growth. Regardless of effect on follicle growth, DBP-treated follicles had decreased mRNA for cyclins D2, E1, A2, and B1 and increased p21. Levels of the proapoptotic genes Bax, Bad, and Bok were not altered by DBP treatment, but DBP 1000 μg/ml increased levels of Bid and decreased levels of the antiapoptotic gene Bcl2. DBP-treated follicles contained significantly more cells in G(1) phase, significantly less cells in S, and exhibited a trend for fewer cells in G(2). Although DBP did not affect E(2) production and atresia at 24 h, follicles treated with DBP had reduced levels of E(2) at 96 h and underwent atresia at 168 h. These data suggest that DBP targets antral follicles and alters the expression of cell cycle and apoptosis factors, causes cell cycle arrest, decreases E(2), and triggers atresia, depending on dose.

Bisphenol A (BPA) is an endocrine disruptor that inhibits growth of mouse ovarian follicles and disrupts steroidogenesis at a dose of 438 μM. However, the effects of lower doses of BPA and its mechanism of action in ovarian follicles are unknown. We hypothesized that low doses of BPA inhibit follicular growth and decrease estradiol levels through the aryl hydrocarbon receptor (AHR) pathway. Antral follicles from wild-type and Ahr knock-out (AhrKO) mice were cultured for 96 hours. Follicle diameters and estradiol levels then were compared in wild-type and AhrKO follicles ± BPA (0.004 - 438 μM). BPA inhibited follicle growth (110 - 438 μM) and decreased estradiol levels (43.8 - 438 μM) in wild-type and AhrKO follicles. However, at BPA 110 μM, inhibition of growth in AhrKO follicles was attenuated compared to wild-type follicles. These data suggest that BPA may inhibit follicle growth partially via the AHR pathway, whereas its effects on estradiol synthesis likely involve other mechanisms.

Abstract. The assembly of primordial follicles and subsequent development and transition of the primordial follicle to the primary follicle are critical processes in ovarian biology. In order to examine follicle formation and development in fetal and neonatal pigs, ovarian samples were obtained from a famous local breed of Chinese pigs, Erhualian pigs, ranging in age from 50 days postcoitum to 1 day postpartum in our current study. Morphological changes in the ovaries of the fetal and neonatal pigs indicated that egg nests were the earliest recognizable gamete cells. The proportion of egg nests decreased from 98.4 to 25.6% and the proportion of single follicles increased from 1.6 to 74.4% between 70 and 90 days postcoitum. The proportions of primordial follicles increased between 70 and 90 days postcoitum but decreased from 90 days postcoitum to 1 day postpartum. Our results suggested that the key stage of primordial follicle formation was between 70 and 90 days postcoitum and that the major stage of transition from primordial follicles into primary follicles was between 90 days postcoitum and 1 day postpartum. Experiments were also conducted to examine the localization of PTEN, PKB and FOXO3A proteins in the porcine ovaries by immunohistochemistry and immunoblotting. The results indicated that PTEN, PKB and FOXO3A were localized in the germ cells of egg nests, cytoplasm of oocytes and granulosa cells of follicles ranging from the primordial to secondary stages and that the staining intensity was weak in granulosa cells but strong in oocytes. The different staining patterns of PTEN, FOXO3A and PKB suggested that these proteins were expressed in a stage-and cell-specific manner during ovarian follicle formation and development in the fetal and neonatal pig. Key words: FOXO3A, Ovary, Pig, Primordial follicle, PTEN (J. Reprod. Dev. 56: [162][163][164][165][166][167][168] 2010) he mammalian ovary is a heterogeneous organ consisting of follicles and corpora lutea at various developmental stages. In the fetal ovaries, germ cells remain in clusters, which here will be referred to as egg nests [1][2][3]. Cells of a nest die, causing the nest to break into smaller nests. This process is repeated until a few individual eggs remain. At the time of birth, the mouse ovary is populated predominantly by primordial follicles, each composed of a meiotically-arrested primordial oocyte enclosed within several flattened pregranulosa cells [4][5][6]. Although many reports have indicated that primordial follicles mainly form in fetal porcine ovaries [7][8][9], the precise stage of egg nest breakdown to form primordial follicles is not clear.The oocytes in primordial follicles are thought to represent the entire pool of gametes available to a female throughout her reproductive life, although it has been suggested that there are postnatal germ line stem cells in the adult ovary [10]. Primordial follicle activation is irreversible, and is the metered process by which primordial follicles are removed from the long-lived reserve pool t...

The pituitary gland is composed of hormone-producing cells essential for homeostasis and reproduction. Pituitary cells are sensitive to endocrine feedback in the adult and can have altered hormonal secretion from exposure to the endocrine disruptor bisphenol A (BPA). BPA is a prevalent plasticizer used in food and beverage containers, leading to widespread human exposure. Although prenatal exposure to BPA can impact reproductive function in the adult, the effects of BPA on the developing pituitary are unknown. We hypothesized that prenatal exposure to low doses of BPA impacts gonadotroph cell number or parameters of hormone synthesis. To test this, pregnant mice were administered 0.5 μg/kg/day of BPA, 50 μg/kg/day of BPA, or vehicle beginning on Embryonic Day 10.5. At parturition, pituitaries from female offspring exposed in utero to either dose of BPA had increased proliferation, as assessed by mKi67 mRNA levels and immunohistochemistry. Coincidently, gonadotroph number also increased in treated females. However, we observed a dichotomy between mRNA levels of Lhb and Fshb. Female mice exposed to 0.5 μg/kg/day BPA had increased mRNA levels of gonadotropins and the gonadotropin-receptor hormone (GNRH) receptor (Gnrhr), which mediates GNRH regulation of gonadotropin production and release. In contrast, mice treated with 50 μg/kg/day of BPA had decreased gonadotropin mRNA levels, Gnrhr and Nr5a1, a transcription factor required for gonadotroph differentiation. No other pituitary hormones were altered on the day of birth in response to in utero BPA exposure, and male pituitaries showed no change in the parameters tested. Collectively, these results show that prenatal exposure to BPA affects pituitary gonadotroph development in females.