We propose to extend the classic Jost hypothesis of sexual differentiation by showing that female sexual differentiation is not simply a default pathway secondary to a lack of androgen but an active process dependent upon estrogen. Furthermore, male external genitalia (ExG) differentiation may not be solely a function of androgens but also influenced by estrogens. Thus, the overall hypothesis of this proposal is that normal male and female development of the external genitalia is dependent upon the correct balance of androgen and estrogen that signal through their respective receptors. Our recent studies on a variety of mutant mice (?ERKO, NERKI, ER? null, ?ERKO, and AROM+) demonstrate profound effects of these "estrogen mutants" on clitoral development, and subtle effects on development of the penis. Given the wealth of our Preliminary Data, we are in an excellent position (a) to establish an important role of estrogen in normal clitoral (a new concept) and possibly normal penile development, (b) to identify specific morphogenetic events in the developing external genitalia that are dependent upon estrogen (especially in the epithelium), and (c) to demonstrate that female sex differentiation of the external genitalia is in fact a unique active process requiring ER? signaling and not simply a default pathway associated with the absence of androgen. To validate the hypothesis that normal female and male development of the mouse external genitalia are dependent upon signaling through ER?, the following Specific Aims will be pursued: 1. Define ontogeny of sex differentiation of male and female ExG and hormonal parameters of sex differentiation of the ExG. 2. Identify morphological features within the male and female external genitalia that are directly or indirectly dependent upon estrogens through analysis of mutant mice. 3. Define the role of proliferation and apoptosis in development of sexual dimorphism. 4. High resolution localization of AR and ER? in the developing male and female external genitalia. 5. Define the role of epithelial ER? in the development of the external genitalia. This proposal will extend the classic Jost hypothesis adding estrogen along with androgen as a critical hormone for normal development. The concepts emerging from this investigation will also have translational relevance to a variety of disorders of sexual differentiation in humans including hypospadias. For example, abnormalities such as hypospadias might be explained by a disruption in the normal balance between androgens and estrogens. If this is the case then prevention strategies could be designed for at risk populations to prevent abnormal prenatal exposure to estrogenic compounds.

Public Health Relevance

We propose to validate the paradigm that estrogen, in addition to the classic male hormone testosterone, is critical for normal feminine development of the clitoris and possibly masculine development of the penis by demonstrating actual morphogenetic/cell differentiation events attributable to either estrogen or androgen action. Understanding this new role for estrogen in sexual differentiation is germane to understanding the etiology of hypospadias and other disorders of sex development.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Special Emphasis Panel (ZRG1-DKUS-A (03))
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Rankin, Tracy L
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University of California San Francisco
Schools of Medicine
San Francisco
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Ching, Saunders T; Cunha, Gerald R; Baskin, Laurence S et al. (2014) Coordinated activity of Spry1 and Spry2 is required for normal development of the external genitalia. Dev Biol 386:1-11
Mahawong, Phitsanu; Sinclair, Adriane; Li, Yi et al. (2014) Prenatal diethylstilbestrol induces malformation of the external genitalia of male and female mice and persistent second-generation developmental abnormalities of the external genitalia in two mouse strains. Differentiation 88:51-69
Mahawong, Phitsanu; Sinclair, Adriane; Li, Yi et al. (2014) Comparative effects of neonatal diethylstilbestrol on external genitalia development in adult males of two mouse strains with differential estrogen sensitivity. Differentiation 88:70-83
Cunha, Gerald R; Risbridger, Gail; Wang, Hong et al. (2014) Development of the external genitalia: perspectives from the spotted hyena (Crocuta crocuta). Differentiation 87:4-22
Blaschko, Sarah D; Mahawong, Phitsanu; Ferretti, Max et al. (2013) Analysis of the effect of estrogen/androgen perturbation on penile development in transgenic and diethylstilbestrol-treated mice. Anat Rec (Hoboken) 296:1127-41
Qiao, Liang; Tasian, Gregory E; Zhang, Haiyang et al. (2012) Androgen receptor is overexpressed in boys with severe hypospadias, and ZEB1 regulates androgen receptor expression in human foreskin cells. Pediatr Res 71:393-8
Kalfa, Nicolas; Sultan, Charles; Baskin, Laurence S (2010) Hypospadias: etiology and current research. Urol Clin North Am 37:159-66
Kalfa, Nicolas; Liu, Benchun; Klein, Ophir et al. (2008) Genomic variants of ATF3 in patients with hypospadias. J Urol 180:2183-8;discussion 2188
Wang, Ming-Hsien; Baskin, Laurence S (2008) Endocrine disruptors, genital development, and hypospadias. J Androl 29:499-505
Agras, Koray; Shiroyanagi, Yoshiyuki; Baskin, Laurence S (2007) Progesterone receptors in the developing genital tubercle: implications for the endocrine disruptor hypothesis as the etiology of hypospadias. J Urol 178:722-7

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