Molecular functions of the shelterin component ACD/TPP1 in somatic stem cells and tissue homeostasis

 描述（由申请人提供）：六蛋白shelterin复合物与端粒酶合作以维持染色体末端的完整性。作为shelterin的一部分，蛋白ACD/TPP 1保护端粒末端免受DNA损伤反应机制的影响。此外，ACD/TPP 1独特地参与通过称为TEL补丁的专用蛋白质表面将端粒酶募集到端粒。末端保护和末端延长对于体干细胞在衰老组织中的维持和功能具有重要意义。我们发现ACD/TPP 1在造血干细胞和其他组织中具有重要的环境特异性功能。最近的工作确定了先天性角化不良患者的候选ACD/TPP 1突变，这是一种以骨髓和其他器官中的体干细胞功能受损为特征的人类疾病，具有早衰的特征。这是首次在人类疾病中发现ACD/TPP 1突变。我们的初步数据表明，这些突变可以破坏细胞系中端粒酶的募集和端粒的稳态。然而，由于ACD/TPP 1突变导致的细胞中的端粒维持缺陷如何转化为体内特定干细胞隔室的功能障碍以及它们如何导致组织衰老和疾病尚不清楚。我们推测ACD/TPP 1突变可能在先天性角化不良和相关的体干细胞疾病中起致病作用。此外，我们假设，点突变影响ACD/TPP 1与其蛋白质合作伙伴的接口可以揭示独特的功能时，在哺乳动物组织中建模的shelterin复合物。为了详细探索这一假设，我们将研究候选突变和其他影响ACD/TPP 1与端粒酶或其shelterin伴侣TIN 2结合的变体，使用现代基因组编辑技术评估它们在整个生物体中的体内效应。我们的具体目标是：2）确定ACD/TPP 1与TIN 2相互作用的结构要求和缺陷性TIN 2- ACD/TPP 1结合的功能后果; 3）研究组织稳态和寿命如何受到候选ACD/ACD的影响。TPP 1致病性变体破坏与关键蛋白质伴侣的相互作用。我们的多学科方法将确定ACD/TPP 1的不同功能表面，并确定它们对干细胞，组织稳态和衰老的影响。我们预计，我们将揭示如何突变失调的ACD/TPP 1和shelterin/端粒酶复合体可以最终导致人类疾病。

 DESCRIPTION (provided by applicant): The six-protein shelterin complex cooperates with telomerase to maintain the integrity of chromosomal ends. As part of shelterin, the protein ACD/TPP1 protects telomeric ends from the DNA damage response machinery. Additionally, ACD/TPP1 is uniquely involved in recruiting telomerase to telomeres through a dedicated protein surface known as the TEL patch. Both end-protection and end-elongation are important for the maintenance and function of somatic stem cells in aging tissues. We showed that ACD/TPP1 has essential context- specific functions in hematopoietic stem cells and in other tissues. Recent work identified candidate ACD/TPP1 mutations in patients with Dyskeratosis congenita, a human disorder characterized by impaired somatic stem cell function in the bone marrow and other organs, with features of premature aging. This is the first identification of ACD/TPP1 mutations in human disease. Our preliminary data show that these mutations can disrupt telomerase recruitment and telomere homeostasis in cell lines. However, how telomere maintenance defects in cells due to ACD/TPP1 mutations translate to dysfunction of specific stem cell compartments in vivo and how they contribute to tissue aging and disease is not understood. We hypothesize that ACD/TPP1 mutations can play a causative role in Dyskeratosis congenita and related somatic stem cell disorders. Furthermore, we postulate that point mutations affecting the interface of ACD/TPP1 with its protein partners can reveal unique functions of the shelterin complex when modeled in mammalian tissues. To explore this hypothesis in detail, we will study candidate mutations and other variants affecting binding of ACD/TPP1 with telomerase or with its shelterin partner TIN2, using modern genome-editing technology to assess their in vivo effects in the entire organism. Our Specific Aims are to: 1) Evaluate the impact of candidate human ACD/TPP1 TEL patch mutations on hematopoietic stem cells and bone marrow homeostasis; 2) Determine the structural requirements for the interaction of ACD/TPP1 with TIN2 and the functional consequences of defective TIN2- ACD/TPP1 binding; 3) Investigate how tissue homeostasis and longevity are affected by candidate ACD/TPP1 pathogenic variants that disrupt interaction with key protein partners. Our multidisciplinary approach will identify distinct functional surfaces of ACD/TPP1 and determine their impact on stem cells, tissue homeostasis and aging. We anticipate that we will uncover how mutational dysregulation of ACD/TPP1 and the shelterin/telomerase complex can ultimately result in human disease.