Hypospadias is the abnormal opening of the urethra on the underside of the penis and occurs in approximately 1/125 live male births worldwide. The incidence rate of hypospadias has dramatically increased over the past few decades. This is now attributed, at least in part, to our exposure to endocrine-disrupting chemicals (EDCs) which alter the hormonal signals required for development of the penis. In humans androgens are the main drivers of fusion of the urethral folds to form the urethra within the shaft of the penis, a process required for termination of the urethra in its normal location at the tip of the penis. However, recent research has suggested that estrogen also plays a role in this process. To better understand how EDCs impact urethral development it is essential that we understand the normal function of hormones during development of the penis. To define the role of estrogen in urethral development we examined development of the penis in the aromatase (Cyp19a1) Knockout (ArKO) mouse strain in which endogenous estrogen production is completely ablated. We found that the ArKO penis had a mild hypospadias phenotype. The developing ArKO postnatal penis displayed an early disruption in preputial development, which likely causes the mild hypospadias observed in adults. Using qPCR, we found altered expression of keratin genes and key urethral patterning genes in response to the disrupted estrogen signaling. The hypospadias phenotype was almost identical to that reported for the estrogen receptor α (ERα) knockout confirming that ERα is the predominant receptor for mediating estrogen action during development of the mouse penis. Our results show that estrogen is required for normal prepucial development and placement of the mature urethral opening at the distal aspect of the penis. We also identified several genes which are potential downstream targets of estrogen during normal urethral closure. With this knowledge, we can now better understand how anti-estrogenic as well as estrogenic EDCs disrupt urethral closure to cause mild hypospadias in both mice and humans.

尿道下裂是阴茎下侧尿道的异常开口，在全世界约有1/125的活产婴儿中发生。在过去的几十年中，尿道下裂的发生率急剧增加。现在，这至少部分归因于我们接触破坏内分泌的化学物质（EDC），而这些物质会改变阴茎发育所需的激素信号。在人类中，雄激素是尿道皱褶融合形成阴茎杆内尿道的主要驱动力，这是终止尿道在阴茎尖端的正常位置所需要的过程。但是，最近的研究表明，雌激素在这一过程中也起作用。为了更好地了解EDC如何影响尿道发育，我们必须了解在阴茎发育过程中激素的正常功能。为了确定雌激素在尿道发育中的作用，我们检查了芳香酶中阴茎的发育（Cyp19a1）完全消除内源性雌激素产生的基因敲除（ArKO）小鼠品系。我们发现ArKO阴茎具有轻度尿道下裂表型。发育中的ArKO产后阴茎显示出较早的前牙发育紊乱，这可能导致成年人观察到轻度尿道下裂。使用qPCR，我们发现响应于破坏的雌激素信号转导的角蛋白基因和关键尿道模式基因的表达改变。尿道下裂的表型与报道的雌激素受体α（ERα）敲除几乎相同，这证实了ERα是在小鼠阴茎发育过程中介导雌激素作用的主要受体。我们的结果表明，雌激素是正常的癌前发育和在阴茎远端放置成熟的尿道开口所必需的。我们还确定了几个基因，它们是正常尿道关闭过程中雌激素的潜在下游靶标。有了这些知识，我们现在可以更好地了解抗雌激素和雌激素EDC如何干扰尿道闭合，从而在小鼠和人类中引起轻度尿道下裂。