MOLECULAR GENETIC BASIS OF CYCLIC HEMATOPOIESIS

人类循环造血（也称为循环中性粒细胞减少症，MIM #162800）是一种常染色体显性遗传病，其中循环血细胞计数以21天不变的周期振荡，这是由骨髓细胞产生的周期性波动引起的。血液计数的循环在中性粒细胞和单核细胞中最为明显，在中性粒细胞减少的最低点引起机会性感染，单核细胞的循环与中性粒细胞的周期相反。在初步研究中，利用遗传连锁分析将循环造血的位点定位到染色体19p13.3（在theta = 0处最大2点LOD评分为13.1），并利用定位克隆策略在13个家族中的13个中发现了编码中性粒细胞弹性酶（中性粒细胞和单核细胞颗粒的凝血色氨酸蛋白酶）的基因中有7个不同的单碱基替换，并在一个散发性病例中发现了一个新的突变。中性粒细胞弹性蛋白酶是α -1抗胰蛋白酶抑制蛋白酶的靶标，其无对抗释放参与炎症部位的组织损伤。负责循环造血的突变聚集在涉及底物特异性和与α -1-抗胰蛋白酶相互作用的分子区域。我们假设中性粒细胞弹性蛋白酶与其抑制剂或其他生化异常之间的相互作用受到干扰可能会中断反馈回路，从而导致造血循环。我们提出了特定的目的来研究所观察到的突变的分子遗传效应，并计划通过转基因小鼠模型将生化缺陷与造血循环的生物学观察联系起来，该模型包含各种人类构建物，这些构建物交叉到修饰中性粒细胞弹性蛋白酶和α -1-抗胰蛋白酶相互作用的遗传背景中。广泛而长期的目标是了解骨髓的21天生物钟，其周期在这种疾病中很明显。

Human cyclic hematopoiesis (also known as cyclic neutropenia, MIM #162800) is an autosomal dominant disease in which circulating blood cell counts oscillate with an invariant 21 day period resulting from periodic fluctuations in the production of cells by the bone marrow. The cycling of blood counts is most pronounced for neutrophils, causing opportunistic infections to arise during the neutropenic nadir, and monocytes, which cycle in a phase opposite to that of neutrophils. In preliminary studies genetic linkage analysis has been used to map the locus for cyclic hematopoiesis to chromosome 19p13.3 (maximum 2-point LOD score of 13.1 at theta = 0) and with a positional cloning strategy 7 different single base substitutions have been identified in the gene encoding neutrophil elastase, a chymotryptic serine protease of neutrophil and monocyte granules, in 13 of 13 families as well as a new mutation in one sporadic case. Neutrophil elastase is the target for protease inhibition by alpha-1-antitrypsin, and its unopposed release is involved in tissue damage at sites of inflammation. The mutations responsible for cyclic hematopoiesis cluster in regions of the molecule implicated in substrate specificity and interaction with alpha-1- antitrypsin. We hypothesize that a perturbed interaction between neutrophil elastase and its inhibitors or other biochemical abnormality may interrupt a feedback circuit and thereby lead to hematopoietic cycling. We propose Specific Aims to investigate the molecular genetic effects of the observed mutations and plan to link the biochemical deficit to the biological observation of hematopoietic cycling through a transgenic mouse model containing various human constructs crossed into genetic backgrounds which modify neutrophil elastase and alpha-1-antitrypsin interactions. The broad, long-term objective is to understand the 21 day biological clock of the bone marrow, whose cycle is made evident in this disease.