The molecular pathophysiology of the congenital dyserythropoietic anemias

项目摘要 红细胞生成缺陷引起的贫血是死亡的主要来源， 世界范围内的发病率。先天性红细胞生成性贫血(CDA)是一组终末期疾病 红系成熟缺陷的特征是无效的红细胞生成和独特的骨髓(BM)发现- 英格斯。CDAII是最常见的CDA亚型，其次是CDAI。CDAII是一种常染色体隐性遗传病 由编码外壳蛋白复合体-2核心成分的SEC23B功能缺失突变引起 (COPII)小泡，将分泌蛋白从内质网(ER)运输到高尔基体-APPA- 拉特斯。CDAI也是一种常染色体隐性遗传病，由编码CDAN1的功能缺失突变引起 CODANIN1，它被认为在染色质组装中发挥作用。尽管对基因进行了鉴定 CDAI和CDAII的缺陷，这些疾病的病理生理学仍不清楚。CODANIN1有 与SEC23B在细胞内共定位，表明CDAI和CDAII可能共享COM- MON或相关分子发病机制。我们先前建立了造血性SEC23B缺陷小鼠； 这些小鼠没有表现出红细胞缺陷。接下来，我们通过对酵母、斑马鱼、小鼠和人的研究展示了 SEC23B与其密切相关的Paralog SEC23A在功能上重叠的MAN细胞，并且表达 SEC23Paralog的模式在进化中发生了变化(SEC23B是主要在 人骨髓，与小鼠骨髓中SEC23A和SEC23B水平相当)。这项提案的总体目标是 目的是研究CDA的分子发病机制。在早期的初步结果中，i)我们培育了小鼠 具有红系特异性的Sec23a/Sec23b联合缺失，这些小鼠表现出深刻的红系表型； Ii)我们还产生了造血细胞CDAn1缺失的小鼠，这表明了一种严重的血液学破坏。 完美无瑕。在这项建议中，我们的目标是表征CODANIN1和SEC23在红细胞生成和释放中的关键作用。 确定由CDAN1或Sec23a/Sec23b联合缺失引起的造血缺陷的程度。我们 还旨在确定Sec23b和CDan1在体内的遗传相互作用，并确定细胞内 CODANIN1在SEC23B缺陷型与野生型红系细胞中的转运此外，基于ER- CDAII的TO-Golgi转运缺陷和某些酸化的人血清中CDAII RBC的裂解 一种红细胞膜的异常，我们假设CDAII是由于一个或多个 红细胞膜上的关键货运蛋白。在初步结果中，我们显示出显著的耗竭 CDAII中仅有5种蛋白质与对照红细胞质膜相比。我们将通过定义以下内容来扩展我们的研究- 在额外的CDAII患者样本中检测这些货物的分泌物，我们将确定这些CAR的作用- GOS在CDAII病理生理学中的作用我们建议的研究对理解 CDA的病理生理学，有望为开发新的治疗方法奠定基础 这些疾病可能与其他由红系终末成熟缺陷引起的贫血有关。

Project Summary Anemia due to defects in erythropoiesis (red blood cell [RBC] production) is a major source of mortality and morbidity worldwide. The Congenital Dyserythropoietic Anemias (CDAs) are a group of disorders of terminal erythroid maturation defects characterized by ineffective erythropoiesis and distinctive bone marrow (BM) find- ings. CDAII is the most common CDA subtype, followed by CDAI. CDAII is an autosomal recessive disease resulting from loss-of-function mutations in SEC23B, encoding a core component of coat protein complex-2 (COPII) vesicles, which transport secretory proteins from the Endoplasmic reticulum (ER) to the Golgi appa- ratus. CDAI, also an autosomal recessive disease, results from loss-of-function mutations in CDAN1, encoding CODANIN1, which is proposed to play a role in chromatin assembly. Despite the identification of the genetic defects underlying CDAI and CDAII, the pathophysiology of these disorders remains unknown. CODANIN1 has been shown to co-localize intracellularly with SEC23B, suggesting that CDAI and CDAII might share a com- mon or related molecular pathogenesis. We previously generated mice with hematopoietic SEC23B deficiency; these mice did not exhibit a RBC defect. We next showed through studies in yeast, zebrafish, mice, and hu- man cells that SEC23B overlaps in function with its closely related paralog, SEC23A, and that the expression pattern of the SEC23 paralogs has shifted in evolution (SEC23B is the predominantly expressed paralog in human BM, with comparable SEC23A and SEC23B levels in mouse BM). The overall objective of this proposal is to characterize the molecular pathogenesis of the CDAs. In early preliminary results, i) we generated mice with erythroid-specific combined Sec23a/Sec23b deletion; these mice exhibit a profound erythroid phenotype; ii) we also generated mice with hematopoietic Cdan1 deletion, which demonstrate a profound hematologic de- fect. In this proposal, we aim to characterize the critical roles of CODANIN1 and SEC23 in erythropoiesis and define the extent of the hematopoietic defect resulting from Cdan1 or combined Sec23a/Sec23b deletion. We also aim to define the genetic interaction between Sec23b and Cdan1 in vivo and determine the intracellular trafficking of CODANIN1 in SEC23B-deficient versus wild-type erythroid cells. Furthermore, based on the ER- to-Golgi transport defect in CDAII and on the lysis of CDAII RBC in some acidified human sera, which suggests an RBC membrane abnormality, we hypothesize that CDAII results from impaired trafficking of one or more key cargo proteins to the RBC plasma membrane. In preliminary results we demonstrate significant depletion of only 5 proteins in CDAII compared to control RBC plasma membranes. We will expand our studies by defin- ing the secretion of these cargos in additional CDAII patient samples and we will identify the roles of these car- gos in the pathophysiology of CDAII. Our proposed studies have important implications for understanding the pathophysiology of the CDAs and are expected to lay the foundation for the development of novel therapies for these disorders, which may be relevant to other anemias resulting from defective terminal erythroid maturation.