Genetic and Biochemical Dissection of Prolactin Actions

描述（由申请人提供）：使用多种方法，包括基因破坏小鼠，表达谱和体外和体内药理学，我们最近惊人地发现色氨酸羟化酶（TPH）基因是乳腺功能的重要调节因子。TPH催化l -色氨酸转化为5-羟色氨酸，这是合成5-羟色胺（5-HT）的限速底物。我们发现TPH是由乳瘀引起的，5-羟色胺参与了抑制泌乳的自分泌/旁分泌反馈回路。这些发现表明生物单胺（尤其是5-羟色胺）是重要的乳源性信号分子。

DESCRIPTION (provided by applicant): Using a combination of approaches, including gene-disrupted mice, expression profiling, and pharmacology in vitro and in vivo, we recently made the surprising discovery that the tryptophan hydroxylase (TPH) gene is an important regulator of mammary gland function. TPH catalyzes the conversion of L-tryptophan to 5-hydroxytryptophan, which is the rate-limiting substrate for serotonin (5-HT) synthesis. We showed that TPH is induced by milk stasis, and that 5-HT participates in an autocrine/paracrine feedback loop that inhibits lactation. These discoveries imply that biogenic monoamines (esp. 5-HT) are important mammary-derived signaling molecules. The central objective of our plan is to explore critical details of the mechanisms by which 5-HT acts within the mammary gland (aims 1-3). A subsidiary objective (aim 4) is to determine whether 5-HT is exported from the mammary gland into the maternal circulation and/or milk. The situation we now confront is that we know neither what specific aspects of mammary physiology and development are influenced by 5-HT, nor do we know the pharmacological profile (receptor types) for the 5-HT regulated functions in the mammary glands. To fill these knowledge gaps we will make use of the wealth of available serotonergic agents to examine mammary gene regulation, proliferation, and apoptosis in organotypic cultures and primary cultures of dissociated cells. The means to do in vivo studies of mammary TPH functions are very limited because of the confounding effects that pharmacological agents have on tissues other than the mammary gland (esp. the brain). To circumvent these problems we need genetic models in which to do the physiological and developmental studies, but useful models, such as TPH gene knockouts, have not been made by other labs. Consequently, we propose to make mice in which the TPH gene is disrupted in the mammary glands, and transgenic mice expressing the human serotonin transporter (hSERT) in the mammary glands. These models will allow us to examine the role of mammary-expressed TPH in development and physiology in animals that have interruptions in their autocrine/paracrine 5-HT exposure.