A Genetic Model of Perinatal Hippocampal Iron Deficiency

描述（由申请人提供）：铁缺乏症（ID）仍然是影响胎儿和儿童大脑发育的最重要的世界性营养缺乏症之一。ID影响早期大脑发育的至少3个主要方面：能量代谢（特别是在海马（HC）），单胺神经递质稳态和髓鞘形成，进而可能影响行为，如识别记忆，程序记忆和处理速度。在人类和饮食ID动物模型中，尚不清楚发育中的大脑中的结构和行为效应是否直接归因于缺乏与重要的转录、翻译或翻译后过程相互作用的铁，或间接效应，例如缺氧（由于贫血）或对大脑发育中重要的其他二价阳离子（例如Zn、Cu或Mn）的稳态的扰动。为了规避这些潜在的混杂因素，并直接评估铁在HC发展中的作用，我们通过有条件地改变HC CA-1区两种铁摄取转运蛋白的表达，产生了两种非贫血遗传小鼠模型。CA-1是识别记忆功能所必需的，并且在饮食ID中在代谢、结构和功能上发生改变。模型1依赖于CaM激酶II α-Cre-lox系统来敲除（KO）二价金属转运蛋白-1（DMT-1），DMT-1是在CA-1分化之前胚胎第18天（E）的主要细胞内亚铁卸载蛋白。该动物已繁殖，无贫血，需要从基因型和铁表型的角度进行表征。模型2使用多西环素诱导的（四环素反式激活因子）显性负性（DN）方法来功能性地降低GA-1锥体神经元中主要的神经元跨膜铁摄取蛋白转铁蛋白受体-1（TfR-1）的活性。该动物的亲本谱系已经产生，并准备进行繁殖。后代将需要进行基因型和表型表征。该R-21的具体目的是1）确认不存在DMT-1蛋白和mRNA，确定海马铁状态并评估条件性DMT-1 KO动物的行为表型，以及2）繁殖，确认HC中TfR-1的突变，确定CA-1铁状态并评估TfR-1 DN动物的行为表型。这种高风险，高收益的建议的潜在回报是模型，定义是否，具体来说，铁是必要的正常HC发展在分子，蛋白质和系统水平。这些模型将用于确定缺乏铁本身是否是饮食ID的人类和动物模型中认知缺陷的原因，而没有饮食模型中发现的众多混杂变量。

DESCRIPTION (provided by applicant): Iron deficiency (ID) remains one of the foremost world-wide nutrient deficiencies that affect brain development in the fetus and in children. ID affects at least 3 major aspects of early brain development: energy metabolism (especially in hippocampus (HC)), monoamine neurotransmitter homeostasis, and myelination, in turn potentially affecting behaviors such as recognition memory, procedural memory and speed of processing. In humans and dietary ID animal models, it is unclear whether structural and behavioral effects in the developing brain are due directly to a lack of iron interacting with important transcriptional, translational or post-translational processes or to indirect effects such as hypoxia (due to anemia) or perturbation of the homeostasis of other divalent cations important in brain development such as Zn, Cu or Mn. To circumvent these potential confounders and to directly assess iron's role in the development of the HC, we have generated two non-anemic genetic mouse models by conditionally altering the expression of two iron uptake transport proteins in area CA-1 of the HC. CA-1 is essential to recognition memory function and is altered metabolically, structurally and functionally in dietary ID. Model 1 relies on a CaMKinase II alpha-Cre-lox system to knock-out (KO) divalent metal transporter-1 (DMT-1), the major intracellular ferrous off-loading protein at embryonic day (E) 18 prior to CA-1 differentiation. This animal has been bred, is non-anemic and needs to be characterized from genotypic and iron phenotypic perspective. Model 2 uses a doxycycline induced (tetracycline transactivator) dominant-negative (DN) approach to functionally reduce the activity of transferrin receptor-1 (TfR-1), the major neuronal transmembrane iron uptake protein, in GA-1 pyramidal neurons. The parent lineages for this animal have been generated and are ready to be bred. The offspring will need to be genotypically and phenotypically characterized. The Specific Aims of this R-21 are to 1) confirm the absence of DMT-1 protein and mRNA, establish the hippocampal iron status and assess the behavioral phenotype of the conditional DMT-1 KO animal, and 2) to breed, confirm the mutation of TfR-1 in HC, establish the CA-1 iron status and assess the behavioral phenotype of the TfR-1 DN animal. The potential pay-offs of this high-risk, high gain proposal are models that define whether and, specifically, how iron is necessary for normal HC development at the molecular, protein and systems level. The models will be used to determine whether the lack of iron, per se, is responsible for the cognitive deficits in humans and animal models with dietary ID without the numerous confounding variables found in dietary models.