The formation of estrogens from C 19 steroids is catalyzed by aromatase cytochrome P450 (P450arom), the product of the cyp19 gene. The actions of estrogen include dimorphic anatomical, functional, and behavioral effects on the development of both males and females, considerations that prompted us to examine the consequences of deficiency of aromatase activity in mice. Mice lacking a functional aromatase enzyme (ArKO) were generated by targeted disruption of the cyp19 gene. Male and female ArKO mice were born with the expected Mendelian frequency from F 1 parents and grew to adulthood. Female ArKO mice at 9 weeks of age displayed underdeveloped external genitalia and uteri. Ovaries contained numerous follicles with abundant granulosa cells and evidence of antrum formation that appeared arrested before ovulation. No corpora lutea were present. Additionally the stroma were hyperplastic with structures that appeared to be atretic follicles. Development of the mammary glands approximated that of a prepubertal female. Examination of male ArKO mice of the same age revealed essentially normal internal anatomy but with enlargement of the male accessory sex glands because of increased content of secreted material. The testes appeared normal. Male ArKO mice are capable of breeding and produce litters of approximately average size. Whereas serum estradiol levels were at the limit of detection, testosterone levels were elevated, as were the levels of folliclestimulating hormone and luteinizing hormone. The phenotype of these animals differs markedly from that of the previously reported ERKO mice, in which the estrogen receptor ␣ is deleted by targeted disruption.The final step in the biosynthesis of estrogens from C 19 steroids is catalyzed by aromatase cytochrome P450 (P450arom) the product of the cyp19 gene (1). Aromatase activity is present in many human tissues, and the tissue-specific expression of this gene is regulated by means of tissue-specific promoters using alternative splicing, but the protein translated from the message is the same in all tissues (2).A number of cases of aromatase deficiency in humans caused by mutations in the cyp19 gene have been reported (3-9). In the case of the females this condition leads to an autosomal-recessive form of female pseudohermaphroditism and virilization of the mother during pregnancy, as a consequence of impaired or absent conversion of fetal and maternal androgens to estrogens by the placental syncytiotrophoblasts. Subsequently, the consequences of aromatase deficiency at puberty in affected females include pubertal failure, hypergonadotropic hypogonadism, virilization, cystic ovaries, delayed bone age, and the potential for tall stature.In the case of the males, childhood development appears unremarkable; however, there is continued linear bone growth throughout puberty, resulting in tall stature, delayed bone age, and osteopenia with failure of epiphysial closure in the affected young adult males. One of these individuals was placed on estrogen replacement with re...

Heat shock transcription factor 1 (HSF1) is a member of the vertebrate HSF family that regulates stress-inducible synthesis of heat shock proteins (HSPs). Although the synthesis of the constitutively expressed and inducible members of the heat shock family of stress proteins correlates with increased cellular protection, their relative contributions in acquired cellular resistance or "thermotolerance" in mammalian cells is presently unknown. We report here that constitutive expression of multiple HSPs in cultured embryonic cells was unaffected by disruption of the murine HSF1 gene. In contrast, thermotolerance was not attainable in hsf1 (؊/؊) cells, and this response was required for protection against heat-induced apoptosis. We conclude that 1) constitutive and inducibly expressed HSPs exhibit distinct physiological functions for cellular maintenance and adaptation, respectively, and 2) other mammalian HSFs or distinct evolutionarily conserved stress response pathways do not compensate for HSF1 in the physiological response to heat shock. Heat shock transcription factors (HSFs)1 regulate stressinducible synthesis of HSPs during development, growth, and adaptation (1-3). This response protects the ischemic heart (4 -6) and promotes tumor cell survival (7,8), thus indicating the clinical importance of this regulatory pathway. During unstressed conditions, constitutively expressed stress proteins may function as molecular chaperones to facilitate the synthesis, folding, or translocation of nascent polypeptides and the translocation or repair of existing polypeptides (9 -11). Similar chaperone functions have been proposed, but not established, for inducible HSPs during cellular adaptation such as thermotolerance (12, 13).Up-regulation of stress protein expression, within minutes after exposure to noxious stimuli, is accomplished through mechanisms that involve both transcriptional activation and preferential translation (2,14). Physiological stresses induce monomers of metazoan HSFs to: 1) oligomerize into trimers that bind DNA with high affinity, 2) translocate into the nucleus, and 3) activate transcription of target stress protein genes (reviewed in Ref.3). HSF1 is the major stress-inducible transactivator of the heat shock response (15); in contrast, HSF2 has been proposed to regulate "nonstress" HSP gene expression during early development stages and spermatogenesis (16 -19).To date, genetic studies indicate pleiotropic functions of the single copy HSF gene in Saccharomyces cerevisiae and Drosophila. Yeast HSF expression is essential for cell viability during unstressed conditions (20 -22), a property that may be related to regulation of basal HSP gene expression (23). Interestingly, the Drosophila HSF protein is not essential for general growth or viability, but is required for larvae development, oogenesis, and survival at extreme stress conditions (24). In vertebrates, multiple HSFs have been identified in chicks, plants, mice, and humans (16,(25)(26)(27). We hypothesize that members of the mammalian HSF fa...

It is well established that spermatogenesis is controlled by gonadotrophins and testosterone. However, a role for estrogens in male reproduction recently was suggested in adult mice deficient in estrogen receptor ␣. . Despite the demonstration of the aromatase enzyme, which converts androgens to estrogens, and estrogen receptors within the rodent seminiferous epithelium, the role of aromatase and estrogen in germ cell development is unknown. We have investigated spermatogenesis in mice that lack aromatase because of the targeted disruption of the cyp19 gene (ArKO). Male mice deficient in aromatase were initially fertile but developed progressive infertility, until their ability to sire pups was severely impaired. The mice deficient in aromatase developed disruptions to spermatogenesis between 4.5 months and 1 year, despite no decreases in gonadotrophins or androgens. Spermatogenesis primarily was arrested at early spermiogenic stages, as characterized by an increase in apoptosis and the appearance of multinucleated cells, and there was a significant reduction in round and elongated spermatids, but no changes in Sertoli cells and earlier germ cells. In addition, Leydig cell hyperplasia͞hypertrophy was evident, presumably as a consequence of increased circulating luteinizing hormone. Our findings indicate that local expression of aromatase is essential for spermatogenesis and provide evidence for a direct action of estrogen on male germ cell development and thus fertility.