Molecular Studies of Bone Marrow Failure

描述（由申请人提供）：我们的实验室对再生障碍性贫血和其他形式的骨髓衰竭（BMF）的分子发病机制有着长期的兴趣。在儿童中，大约25%的BMF病例是遗传性的，而在成人中，这一比例更低；大多数儿童和成人的BMF病例被归类为特发性。患有遗传性BMF的患者易患骨髓增生异常综合征（MDS）、白血病、鳞状细胞癌和其他形式的癌症。我们的实验室参与了最近的一项发现，常染色体显性先天性角化不良症（DKC）是一种与癌症易感性相关的BMF遗传形式，其编码端粒酶RNA亚基（hTERC）的基因发生突变。常染色体显性DKC患者的临床症状通常很轻微，很容易被忽视。基于这一观察，我们假设hTERC的突变可能是导致大量BMF病例的原因，包括目前被归类为特发性的病例。此外，由于已经观察到来自各种形式BMF患者的骨髓细胞具有相对较短的端粒，我们假设造血干细胞中过度的端粒缩短可能在BMF的发病机制中起核心作用，并导致基因组不稳定性增加，从而易导致癌症的发展。为了验证这些假设，将邀请在华盛顿大学或确定的合作机构诊断或治疗BMF的儿童和成人的未选择队列参加拟议的研究。同样，将从国际再生障碍性贫血和骨髓增生异常协会和其他国际骨髓衰竭登记处入选一个选定的患者队列。在获得知情同意后，将对从外周血或皮肤活检中分离的DNA进行hTERC基因突变和端粒长度/完整性研究。将使用标准化表格和程序获取每位参与者的详细临床和家族史信息。本研究有几个目的：1)确定hTERC基因突变的频率；2)描述hTERC基因突变的遗传力、外显率和表达性；3)研究BMF的发病和严重程度是否与端粒长度和完整性相关。所提出的研究将有助于阐明hTERC基因突变的临床后果，并为BMF的发病机制提供新的革命性见解。结果可能表明，hTERC基因的遗传分析应成为所有诊断为BMF的患者的常规预后检测。hTERC基因突变临床后果的表征，可能对hTERC基因突变BMF患者及其家族成员的临床管理产生直接影响。拟议的研究还将增加对功能失调端粒在人类疾病中的作用的认识，包括肿瘤发生和进展的分子遗传途径，它们在退行性疾病和衰老中的作用。

DESCRIPTION (provided by applicant): Our laboratory has a longstanding interest in the molecular pathogenesis of aplastic anemia and other forms of bone marrow failure (BMF). In children about 25% of cases of BMF are inherited, while in adults the percentage is even lower; most cases of BMF in children and adults are classified as idiopathic. Patients with inherited forms of BMF have a predisposition to develop myelodysplastic syndrome (MDS), leukemia, squamous cell carcinoma, and other forms of cancer. Our laboratory was involved in the recent discovery that individuals with autosomal dominant dyskeratosis congenita (DKC), an inherited form of BMF associated with cancer susceptibility, have mutations in the gene encoding the telomerase RNA subunit (hTERC). Clinical signs in patients with autosomal dominant DKC are often mild and are easily missed. Based on this observation we postulate that mutations in hTERC may be responsible for a significant number of cases of BMF, including cases currently classified as idiopathic. Moreover, because bone marrow cells from patients with various forms of BMF have been observed to have relatively short telomeres, we hypothesize that excessive telomere shortening in hematopoietic stem cells may play a central role in the pathogenesis of BMF and cause increased genomic instability that predisposes to the development of cancer. To test these hypotheses, an unselected cohort of children and adults diagnosed or treated for BMF at Washington University or at identified collaborating institutions will be invited to participate in the proposed study. Similarly, a selected patient cohort will be enrolled from the International Aplastic Anemia and Myelodysplasia Society and other international bone marrow failure registries. After obtaining informed consent, DNA isolated from peripheral blood cells or from a skin biopsy will be examined for mutations in the hTERC gene and for telomere length/integrity studies. Detailed clinical and family history information will be obtained for each participant using standardized forms and procedures. There are several goals of this study: 1) to determine the frequency of hTERC gene mutations; 2) to delineate the heritability, penetrance and expressivity of hTERC gene mutations; and 3) to investigate whether the onset and severity of BMF correlates with telomere length and integrity. The proposed studies will help to elucidate the clinical consequences of mutations in the hTERC gene and provide new revolutionary insights into the pathogenesis of BMF. The results may indicate genetic analysis of the hTERC gene should become a routine prognostic test for all patients diagnosed with BMF. The characterization of the clinical consequences of hTERC gene mutations is likely to have a direct impact on the clinical management of patients with BMF due to hTERC gene mutations and their family members. The proposed studies will also increase the knowledge of the role of dysfunctional telomeres in human disease, including the molecular genetic pathways in tumor initiation and progression, their role in degenerative diseases, and in aging.