REGULATION BY RETINOIC ACID SYNTHESIZED IN THE CHOROID PLEXUS

转录激活因子视黄酸是最重要的 已知的致畸物质，并通过意外接触人类 胚胎对痤疮药物Acutane（R），小脑发育被发现， 特别脆弱。 对全身性 应用视黄酸可能表明，发育中的小脑是 天然倾向于对内源性合成的视黄酸产生反应 而且，一个精确调节的空间和时间分布， 内源性化合物是正常发育所必需的。 我们的初步 观察结果与这一概念一致：使用一种新的技术， 维甲酸合成酶的检测发现很少 合成在小脑适当的，但高水平的密切 并置脉络丛 此外，脉络丛中的酶水平 显示两个极大值似乎平行于小脑中的两个过程 形态发生：第一个在浦肯野细胞发育在晚期胎儿 生后第2、3、4、6、8、10、12、14、16、18、19、 发展;发展中的小脑文化揭示了一个强大的 脉络丛分泌的生长促进作用。 在这里我们建议 为了验证后脑脉络丛代表 发育中小脑的旁分泌器官，影响神经元 通过空间和时间调节的视黄酸分化 分泌物 具体而言，我们计划解决以下问题：（1）我们将 表征视黄酸合成的分布， 通过功能分析和原位分析开发后脑 与我们最近发现的脉络丛酶探针杂交， 隔离老鼠。 (2)我们将分析维甲酸 酸解释了脉络丛神经突诱导活性， 异构体在体内合成。 (3)我们将测试甲状腺的影响 激素，一种已知影响小脑发育的因素， 与视黄酸相互作用，通过直接合作， 甲状腺激素受体和小脑视黄酸受体RXR。 (4)我们将试图扰乱维甲酸在细胞中的分布， 通过单侧脉络膜损伤在体内发育小脑 丛和应用视黄酸浸泡珠。 (5)我们将尝试 为了分离小鼠维甲酸生成蛋白的人类同源物， 酶，以促进未来的工作小脑异常 在人类身上。 这是通过Acutane（R）诱导的小脑 类似于偶尔发生的Dandy-Walker畸形 综合征和Joubert综合征，其中共济失调和精神发育迟滞是 观察

The transcriptional activator retinoic acid is one of the most teratogenic substances known, and through accidental exposure of human embryos to the acne drug Acutane(R), cerebellar development was found to be particularly vulnerable. A high susceptibility to systemically applied retinoic acid could indicate that the developing cerebellum is naturally disposed to respond to endogenously synthesized retinoic acid and that a precisely regulated spatial and temporal distribution of the endogenous compound is essential for normal development. Our preliminary observations are consistent with this notion: with a novel technique for the detection of retinoic-acid synthesizing enzymes we find very little synthesis in the cerebellum proper, but high levels in the closely apposed choroid plexus. Moreover, enzyme levels in the choroid plexus shown two maxima that seem to parallel two processes in cerebellar morphogenesis: the first during Purkinje cell development at late fetal stages and the second during the postnatal stage of granule cell development; cultures of the developing cerebellum reveal a potent growth-promoting effect secreted by the choroid plexus. Here we propose to test the hypothesis that the metencephalic choroid plexus represents a paracrine organ for the developing cerebellum, influencing neuronal differentiation through spatially and temporally regulated retinoic acid secretion. In detail, we plan to address to following topics: (1) We will characterize the distribution of retinoic acid synthesis in the developing metencephalon by functional assay, and by in situ hybridization with a probe to the choroid plexus enzyme that we recently isolated for the mouse. (2) We will assay the extent to which retinoic acid accounts for the choroid-plexus neurite inducing activity, and what isomer is synthesized in vivo. (3) We will test for effects of thyroid hormone, a factor known to influence cerebellar development and which interacts with retinoic acid through the direct cooperation between the thyroid hormone receptor and the cerebellar retinoic acid receptor RXR. (4) We will attempt to perturb the distribution of retinoic acid in the developing cerebellum in vivo by unilateral lesioning of the choroid plexus and by application of retinoic-acid soaked beads. (5) We will try to isolate the human homolog of the murine retinoic-acid generating enzyme, in order to facilitate future work on cerebellar abnormalities in humans. This is exemplified by the Acutane(R)-induced cerebellar malformation which resembles the sporadically occurring Dandy-Walker syndrome and Joubert syndrome, in which ataxia and mental retardation are observed.