Identification of Genes Involved in FHLH

描述(申请人提供)：家族性噬血细胞性淋巴组织细胞增多症(FHLH)几乎普遍是致命的，除非在确诊后立即积极治疗，并通过异基因骨髓移植纠正。所有形式的FHLH都可能是由于免疫/炎症反应的自然下调机制中的遗传缺陷造成的。在全球40%-50%的原发(家族性)病例中，有三种常染色体隐性基因缺陷：主要的免疫细胞毒蛋白穿孔素(20-30%)，参与细胞毒颗粒在细胞凋亡过程中胞吐的MUNC 13-4(20%)，以及可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体(SNARE)的成员STX11。因此，在超过一半的FHLH病例中，受影响的个体有其他未知的基因改变。通过连锁分析来识别这些基因的经典遗传方法有局限性，因为连锁分析需要从单个家庭中相对较多的受影响和未受影响的成员中提取DNA。这样的家庭在北美并不常见。我们估计至少有六到七个基因可能与FHLH的各种遗传形式有关。在这项研究中，我们提出了新的程序，以寻找与剩余50%-60%的FHLH病例有关的候选基因。据估计，人类30%的遗传性遗传疾病是由过早终止密码子突变引起的。基因的无义突变激活了无义介导的衰变(NMD)途径，导致突变的mRNA降解。我们将识别基因表达谱，将FHLH2、FHLH3和FHLH4与其他遗传形式的FHLH区分开来。我们认为，NMD途径可以通过表达芯片杂交的方式来筛选FHLH候选基因。此外，可以通过抑制人类免疫缺陷病毒永生化的CD8+T细胞中的无意义介导的衰退(NMD)机制来确定候选基因，这些细胞来自不明遗传原因的FHLH患者。或者，我们将使用RNA干扰策略在9q21.3-22和11q25的淋巴组织细胞增生症敏感区以及编码SNARE蛋白的基因中确定候选基因，这些基因对于磷脂膜的直接、可控和非常快速的融合是必不可少的。

DESCRIPTION (provided by applicant): Familial Hemophagocytic Lymphohistiocytosis (FHLH) is almost universally fatal unless aggressively treated soon after diagnosis, and corrected with allogeneic bone marrow transplantation. All forms of FHLH likely result from genetic defects in the natural down regulating mechanisms of immune/inflammatory responses. Three autosomal recessive gene defects underlie 40-50% of primary (familial) cases worldwide: perforin (20-30%), the major immune cytotoxic protein, MUNC 13-4 (20%), a protein involved in exocytosis of perforin-bearing cytotoxic granules during apoptosis and STX11, member of soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNARE). Thus in more than half of the FHLH cases, the affected individuals have other as yet unknown genetic alterations. The classic genetic approach to identify these genes, through linkage analysis, has limitations because linkage analysis requires DNA from relatively large numbers of affected and unaffected members of a single family. Such families are unusual in North America. We estimate at least six or seven genes could be responsible to the various genetic forms of FHLH. In this study we propose novel procedures, to search for candidate genes responsible for the remaining 50-60% of FHLH cases. It is estimated that 30% of inherited genetic disorders in humans result from premature termination codon mutations. Nonsense mutations in mRNA activate the nonsense-mediated decay (NMD) pathway, which results in the degradation the mutant mRNA. We will identify gene expression profiles that will distinguish FHLH2, FHLH3 and FHLH4 from other genetic forms of FHLH. We propose that NMD pathway could be utilized to identify FHLH candidate genes through expression microarray hybridization. In addition, candidate genes could be identified through inhibition of the nonsense-mediated decay (NMD) mechanism in HVS immortalized CD8+T cells from patients with FHLH of yet unknown genetic cause. Alternatively, we will use RNAinterference strategy to identify candidate genes in lymphohistiocytosis susceptibility regions of chromosome 9q21.3-22 and 11q25 and among genes coding for SNARE proteins essential for direct, controlled and very rapid fusion of phospholipids membranes.