Molecular Studies of Bone Marrow Failure

描述(由申请人提供)：我们实验室长期以来一直对再生障碍性贫血和其他形式的骨髓衰竭(BMF)的分子发病机制感兴趣。在儿童中，大约25%的BMF病例是遗传的，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。遗传性BMF患者容易患上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。我们实验室最近发现，常染色体显性遗传性先天性角化不良(DKC)患者的端粒酶RNA亚单位(HTERC)基因发生突变。DKC是一种与癌症易感性相关的BMF遗传形式。常染色体显性遗传性DKC患者的临床症状通常较轻，很容易被漏诊。根据这一观察结果，我们推测hTERC突变可能是相当数量的BMF病例的原因，包括目前被归类为特发性的病例。此外，由于已观察到来自不同形式BMF患者的骨髓细胞具有相对较短的端粒，我们推测，造血干细胞中端粒过度缩短可能在BMF的发病机制中发挥核心作用，并导致基因组不稳定性增加，从而易于癌症的发展。为了验证这些假设，华盛顿大学或已确定的合作机构将邀请一组未经选择的儿童和成人队列参与拟议的研究，这些儿童和成人被华盛顿大学或已确定的合作机构诊断或治疗为BMF。同样，选定的患者队列将从国际再生障碍性贫血和骨髓发育不良协会和其他国际骨髓衰竭登记机构登记。在获得知情同意后，从外周血细胞或皮肤活检中提取的DNA将被检测hTERC基因的突变，并进行端粒长度/完整性研究。将使用标准化表格和程序获取每个参与者的详细临床和家族史信息。本研究有几个目标：1)确定hTERC基因突变的频率；2)描述hTERC基因突变的遗传性、外显性和表达能力；3)研究BMF的发病和严重程度是否与端粒长度和完整性有关。拟议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。提示hTERC基因分析可作为诊断BMF患者的常规预后检测方法。HTERC基因突变的临床后果的表征可能会对hTERC基因突变引起的BMF患者及其家庭成员的临床治疗产生直接影响。拟议的研究还将增加对端粒功能障碍在人类疾病中作用的了解，包括肿瘤发生和发展的分子遗传途径，它们在退行性疾病中的作用，以及在衰老中的作用。

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.