REGULATION BY RETINOIC ACID SYNTHESIZED IN THE CHOROID PLEXUS

转录激活剂维甲酸是最重要的 已知的致畸物质，并通过意外接触人类 胚胎对痤疮药物阿卡坦(R)，小脑发育被发现 要特别脆弱。对系统性疾病的高度易感性 应用维甲酸可以表明发育中的小脑 天生对内源性合成的维甲酸有反应 而精确调控的时空分布 内源性化合物是正常发育所必需的。我们的预赛 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很少 小脑本身的合成，但密切相关的高水平 对置的脉络丛。此外，脉络丛中的酶水平 显示了小脑中似乎平行于两个突起的两个最大值 形态发生：胎儿晚期浦肯野细胞发育的第一阶段 颗粒细胞阶段和出生后第二阶段 发育；发育中的小脑培养显示出一种强大的 脉络丛分泌的促生长作用。在这里，我们建议 为了检验后脑脉络丛代表 影响神经元的小脑发育中的旁分泌器官 维甲酸在时间和空间上的分化 分泌物。 具体来说，我们计划解决以下几个问题：(1)我们将 表征维甲酸合成在体内的分布 后脑发育的功能测定和原位观察 与我们新近研制的脉络丛酶的探针杂交 为小鼠隔离。(2)我们将测定维甲酸的程度 酸是脉络丛神经突起诱导活性的原因，是什么 异构体是在体内合成的。(3)我们将测试甲状腺的影响 荷尔蒙，一种已知的影响小脑发育的因素 通过与维甲酸的直接合作 甲状腺激素受体和小脑维甲酸受体RXR。 (4)我们将尝试干扰维甲酸在体内的分布 单侧脉络膜损伤在体内发育小脑 神经丛和应用维甲酸浸泡的珠子。(5)我们会努力的 分离小鼠维甲酸产生的人类同源物 酶，以便于今后对小脑异常的研究 在人类身上。阿卡坦(R)诱导的小脑就是一个例证 类似于零星发生的Dandy-Walker畸形 综合征和Joubert综合征，其中共济失调和智力低下 观察到的。

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.