Anti-Müllerian hormone produces endocrine sex reversal of fetal ovaries.

Abstract

We have previously reported that antiMullerian hormone (AMH), also known as Mfillerianinhibiting substance, the testicular glycoprotein involved in regression of the Mullerian ducts of the mnale fetus, induces the formation of seminiferous cord-like structures in fetal ovaries exposed to it in organ culture. We have now investigated the effect of bovine AMH, purified to homogeneity, on ovarian endocrine differentiation. Ovine fetal ovaries exposed to AMH release testosterone instead of estradiol, an endocrine sex reversal due to suppression of aromatase activity. AMH dramatically decreases the conversion rate of testosterone to estradiol and also decreases total aromatase activity, as measured by the tritiated water technique. AMH acts by decreasing aromatase biosynthesis rather than by blocking enzyme activity, as suggested by the relatively long period of AMH exposure required to produce an effect. In the rabbit fetal ovary, aromatase activity is AMH-responsive during the whole gestational period. The basal steroidogenic activity of rat fetal ovaries is extremely low but can be markedly increased by cAMP. AMH completely blocks the effect of cAMP. Taken together, our results suggest that AMH plays a pivotal role in both morphological and endocrine gonadal sex differentiation. New Zealand rabbits were sacrificed between day 16 and 28 of gestation. Prior to day 20, fetal sex was determined by a sex chromatin test performed on a fragment of the amniotic membrane (12); in older fetuses, sex was easily identified under the dissecting microscope. Wistar rat fetuses were used at 15 days postcoitum; sex was recognized macroscopically. Fetal age was counted from the day of mating, which was considered day 0.Reagents. Bovine AMH was purified by immunochromatography on a monoclonal antibody-conjugated matrix (3) and quantified by radioimmunoassay (13). Other unlabeled reagents were purchased from Sigma; [7-3H]testosterone (24.5 Ci/mmol; 1 Ci = 37 GBq) and [1,3,213-3H] Leshin et al. (14) to a specific activity of 23.2 Ci/mmol.Organ Culture. Fetal gonads were explanted in organ culture (7); they were separated from the mesonephros except in 29-day-old ovine fetal gonads, half of which were cultured together with the mesonephros. No difference was seen between gonads explanted with or without mesonephros, and the results were pooled. Culture medium was CMRL 1066 containing bovine serum albumin at 0.5 mg/ml and, for rat fetal gonads, 0.1 mM 3-isobutyl-1-methylxanthine; 1 mM N6,02'-dibutyryladenosine 3',5'-cyclic monophosphate (Bt2-cAMP) was added to culture medium in some cases. One gonad was placed in control medium, and the other one was placed in medium containing purified bovine AMH (2.25-3 Abbreviations: AMH, anti-Mullerian hormone; Bt2cAMP, N6,02'-dibutyryladenosine 3',5'-cyclic monophosphate. 3684The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Expression of Sox9 in granulosa cells lacking the estrogen receptors, ERα and ERβ

“…It is noteworthy that, similarly, only a fraction of the granulosa cells in ER␣␤KO mice express Sox9 and exhibit morphologic features of Sertoli cells. Thus, another event that is distinct from the block in estrogen signalling and could be the loss of an oocyte-secreted factor (Vigier et al, 1989;Behringer et al, 1990;Taketo et al, 1993;Vainio et al, 1999) appears to be required to induce the transformation of granulosa cells into Sertoli cells. In this respect, it is noteworthy that oocytes in prepubertal ER␣␤KO ovaries appear histologically healthy and do not display DNA fragmentation, as assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL; data not shown).…”

Aromatase expression in the ovary: Hormonal and molecular regulation

“…In many species, ovaries acquire the enzymatic capacity to produce estrogen during embryonic life as determined by the capacity of fetal ovaries to convert radiolabeled androgen to estrone and estradiol [6][7][8] or by the amplification of aromatase cDNA by PCR [9]. Aromatase expression in fetal ovaries is extremely low; although it can be increased by treatment with an analog of cAMP but not by follicle stimulating hormone (FSH) [8,10].…”

“…Aromatase expression in fetal ovaries is extremely low; although it can be increased by treatment with an analog of cAMP but not by follicle stimulating hormone (FSH) [8,10]. Whether this minute expression of aromatase in fetal ovaries plays any role in the regulation of ovarian development is not clear since estrogens do not appear to be critical for the normal development of the ovary.…”

Sex determination: insights from the chicken

“…(Studies in mammals have shown that AMH can negatively regulate the aromatase gene, Ref. 45.) This would be a delicate balancing act, given that AMH is also expressed in females, at lower levels, where aromatase repression must not occur.…”