Identification of Genes Involved in FHLH

描述（由申请人提供）：家族性噬血细胞淋巴组织细胞病（FHLH）几乎是普遍致命的，除非在诊断后立即积极治疗，并通过同种异体骨髓移植纠正。所有形式的FHLH可能是由免疫/炎症反应自然下调机制中的遗传缺陷引起的。三种常染色体隐性基因缺陷是全世界40-50%的原发性（家族）病例的基础：穿孔素（20-30%），主要的免疫细胞毒性蛋白，MUNC 13-4(20%)，一种参与细胞凋亡过程中携带穿孔素的细胞毒性颗粒胞外分泌的蛋白，STX11，可溶性n-乙基male亚胺敏感因子附着蛋白受体（SNARE）的成员。因此，在一半以上的FHLH病例中，受影响的个体有其他未知的遗传改变。通过连锁分析来识别这些基因的经典遗传方法具有局限性，因为连锁分析需要来自单个家庭中相对大量的受影响和未受影响成员的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，以寻找负责剩余50-60%的FHLH病例的候选基因。据估计，30%的人类遗传疾病是由过早终止密码子突变引起的。mRNA的无义突变激活了无义介导的衰变（NMD）途径，导致突变mRNA的降解。我们将确定FHLH2、FHLH3和FHLH4与其他遗传形式的FHLH的基因表达谱。我们提出可以利用NMD途径通过表达微阵列杂交鉴定FHLH候选基因。此外，候选基因可以通过抑制来自遗传原因未知的FHLH患者的HVS永生化CD8+T细胞的无义介导的衰变（NMD）机制来鉴定。或者，我们将使用rnai干扰策略来鉴定染色体9q21.3-22和11q25淋巴组织细胞病易感区域的候选基因，以及编码直接、受控和非常快速的磷脂膜融合所必需的SNARE蛋白的基因。

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.