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1 May 2006 Maintenance of Spermatogenesis by the Activated Human (Asp567Gly) FSH Receptor During Testicular Regression Due to Hormonal Withdrawal
Charles M. Allan, Alvaro Garcia, Jenny Spaliviero, Mark Jimenez, David J. Handelsman
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The first activating mutation of the FSH receptor (FSHR*D567G) was identified in a gonadotropin-deficient hypophysectomized man who exhibited persistent spermatogenesis and fertility with only androgen replacement. We have determined the ability of FSHR* activity to maintain spermatogenesis and/or steroidogenesis during gonadotropin and androgen deprivation in mature transgenic FSHR* mice (Tg(Abpa-FSHR*D567G)1Cmal), hereafter referred to as Tg-FSHR* mice. Testes of untreated adult Tg-FSHR* males were equivalent in weight to nontransgenic controls but exhibited increased total Sertoli cell (24%) and spermatogonia (34%) numbers and nonsignificantly elevated spermatocyte-spermatid numbers (13%–17%). During sustained GNRH1 agonist treatment that markedly reduced (96%–98%) serum LH and testosterone (T) and decreased serum FSH (68%–72%), the testes of GNRH1 agonist-treated Tg-FSHR* mice remained significantly larger than treated nontransgenic controls. After 4 wk of gonadotropin suppression, Sertoli cell numbers were reduced in Tg-FSHR* testes to levels comparable with nontransgenic testes, whereas spermatogonia numbers were maintained at higher levels relative to nontransgenic testes. However, after 8 wk of GNRH1 agonist treatment, the total spermatogonia, spermatocyte, or postmeiotic spermatid numbers were reduced to equivalent levels in Tg-FSHR* and nontransgenic mice. FSHR* effects were further examined in gonadotropin-deficient hypogonadal Gnrh1hpg/Gnrh1hpg (Gnrh1−/−) mice during testicular regression following withdrawal of T after maximal T-stimulated spermatogenesis. After 6 wk of T withdrawal, spermatogonia, spermatocyte, and postmeiotic spermatid numbers in Tg-FSHR* Gnrh1−/− testes decreased to levels found in untreated Tg-FSHR* Gnrh1−/− testes. Basal serum T levels in untreated Tg-FSHR* Gnrh1−/− males were 2-fold higher than Gnrh1−/− controls, but following T treatment/withdrawal, serum T and epididymal weights declined to basal levels found in nontransgenic Gnrh1−/− mice. Therefore, FSHR* was unable to sustain circulating T or androgen-dependent epididymal size or postmeiotic spermatogenic development. We conclude that FSHR* activity enhances Sertoli and spermatogenic development in normal testes but has limited ability to maintain spermatogenesis during gonadotropin deficiency, in which the testicular response provided by the FSHR*D567G mutation resembled typical FSH-mediated but not steroidogenic activity.

Charles M. Allan, Alvaro Garcia, Jenny Spaliviero, Mark Jimenez, and David J. Handelsman "Maintenance of Spermatogenesis by the Activated Human (Asp567Gly) FSH Receptor During Testicular Regression Due to Hormonal Withdrawal," Biology of Reproduction 74(5), 938-944, (1 May 2006).
Received: 10 October 2005; Accepted: 1 February 2006; Published: 1 May 2006

follicle-stimulating hormone receptor
Sertoli cells
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