Mechanisms Leading to Adrenal Zonation

描述（由申请人提供）：背景：人肾上腺皮质作为一种复合内分泌腺，既分泌盐皮质激素又分泌糖皮质激素。这些类固醇产生于肾上腺皮质的不同区域，这些区域具有形态学和生物化学差异。无论是皮质区干细胞的起源，还是导致类固醇的区域特异性生产的机制都没有明确定义。肾上腺皮质的功能分区可以追溯到参与类固醇生物合成的酶的区域特异性表达。这对于醛固酮合酶（CYP 11B 2）、11 β-羟化酶（CYP 11B 1）和17 α-羟化酶（CYP 17）尤其如此。 目标：Specific Aim One中提出的实验将扩展申请人正在进行的合作项目，该项目已确定了（CYP 11 B2）和11 β-羟化酶（CYP 11 B1）基因5 '侧翼区的调控元件。这些研究将完成负责肾小球特异性表达和束状体抑制CYP 11B 2的反式作用因子的定义。重点将放在核受体的作用，NR 4A 2，它刺激CYP 11B 2启动子活性，这是由血管紧张素II上调，主要是在肾小球表达。 具体目标二将确定肾小球中缺乏CYP 17的机制。初步研究表明，这是多种机制的结果，包括血管紧张素II增加AP-1转录因子和WNT信号。WNT下游的因素负责CYP 17的抑制和AP-1的CYP 17转录抑制的机制将被定义。 具体目标Three将把我们正在进行的肾上腺细胞培养研究扩展到体内情况，使用细菌人工染色体（BAC）转基因以NURR 1抑制剂靶向球状带。鼠肾上腺，像人肾上腺，限制表达CYP 11B 2的肾小球，使其成为一个很好的模型，以确定调节醛固酮的生产因素。我们还将使用这种策略来产生肾小球-CRE小鼠，这将是进一步研究可能调节肾小球功能的基因的重要工具。 重要性：醛固酮增多症是由于结节性增生和醛固酮腺瘤中的分区破坏，特别是CYP 11B 2表达异常所致。拟议的研究将提供一个详细的了解的分子机制，调节CYP 11B 2在肾上腺内的表达，并应提供洞察与异常表达相关的疾病。

DESCRIPTION (provided by applicant): BACKGROUND: The human adrenal cortex acts as a compound endocrine gland that secretes both mineralocorticoids and glucocorticoids. These steroids arise from distinct zones of the adrenal cortex that have both morphologic and biochemical differences. Neither the origin of the stem cells of the cortical zones nor the mechanisms leading to the zone-specific production of steroids is clearly defined. The functional zonation of the adrenal cortex can be traced to the zone-specific expression of the enzymes involved in steroid biosynthesis. This is particularly true for aldosterone synthase (CYP11B2), 11 beta-hydroxylase (CYP11B1) and 17alpha-hydroxylase (CYP17). AIMS: The experiments proposed in Specific Aim One will extend the applicants ongoing collaborative project that has defined the regulatory elements in the 5'-flanking region of the (CYP11B2) and 11beta-hydroxylase (CYP11B1) genes. These studies will complete the definition of the transacting factors responsible for glomerulosa-specific expression and fasciculata repression of CYP11B2. Focus will be placed on the role of the nuclear receptor, NURR1 (NR4A2), which stimulates CYP11B2 promoter activity, which is up-regulated by angiotensin II and is expressed primarily in the zona glomerulosa. Specific Aim Two will determine the mechanisms responsible for the lack of CYP17 seen in the glomerulosa. Preliminary studies indicate that this results from multiple mechanisms including angiotensin II increased AP-1 transcription factors and WNT signaling. The WNT downstream factors responsible for CYP17 repression and the mechanisms of AP-1 repression of CYP17 transcription will be defined. Specific Aim Three will extend our ongoing adrenal cell culture studies to the in vivo situation using bacterial artificial chromosome (BAC) transgenesis to target the zona glomerulosa with an inhibitor of NURR1. The murine adrenal, like the human adrenal, limits expression of CYP11B2 to the zona glomerulosa making it an excellent model to define the factors regulating aldosterone production. We will also use this strategy to produce a glomerulosa-CRE mouse that will be an important tool for further study of genes that may regulate glomerulosa function. SIGNIFICANCE: Hyperaldosteronism results from the disruption of zonation, and particularly aberrant CYP11B2 expression, in nodular hyperplasia and aldosterone-producing adenomas. The proposed studies will provide a detailed understanding of the molecular mechanisms regulating CYP11B2 expression within the adrenal and should provide insight into the diseases associated with aberrant expression.