MECHANISMS OF CHIEF CELL DEDIFFERENTIATION

 描述（由申请人提供）：在过去的两年中，消化器官中的许多成熟细胞系可以去分化并重新进入细胞周期以修复组织损伤已经变得很清楚。我们和其他人已经表明，有丝分裂后的细胞可以重新诱导祖细胞标记，重新进入细胞周期，甚至可以作为其他谱系的祖细胞。然而，去分化过程具有风险，因为祖细胞基因的重新表达是细胞化生的一种形式。在慢性损伤状态下，如H。幽门螺杆菌感染在环胃，化生继续无限期，并增加发展为癌症的风险。总的来说，细胞去分化为理解组织修复、“干性”和癌症起始提供了新的范例。我们的首要目标是了解去分化的细胞和分子机制。 在这里，我们将集中在胃消化酶分泌酶原主细胞（ZCs）的最早阶段的去分化。我们的初步和已发表的数据将表明，第一阶段是分泌颗粒被溶酶体吞噬，并且消化酶分泌颗粒的溶酶体周转（分泌装置“缩小”）必须在进展到下一阶段之前发生：祖细胞基因的化生再表达和细胞周期再进入。我们将表明，在去分化ZCs的最早的分子变化是显着降低表达的bHLH转录因子MIST 1（BHLHA 15）和Mist 1的删除，即使在健康的ZCs是足以诱导分泌颗粒的溶酶体周转。最后，我们将表明，唯一已知的转录目标的MIST 1，交通溶酶体，因此是最可能的原因，分泌颗粒上的溶酶体攻击时，MIST 1是在去分化过程中丢失的是小的GT3，RAB 26。 我们的目标是：2）确定RAB 26是否通过自噬/mTOR信号传导影响流量，以及它是否调节溶酶体和/或自体溶酶体的颗粒破坏; 3）a）通过在成熟ZC中缺失关键自噬基因Atg 5和Atg 7后诱导化生来确定自噬机制是否是缩小比例所必需的，和B）定量自噬/自噬。溶酶体与分泌颗粒的相互作用，其中存在经历去分化/化生的ZC病灶的人类样本数据库中。这些实验将首次揭示新描述的细胞去分化过程的分子机制，并将对人类健康产生影响，因为我们需要了解化生前体病变是如何从成熟细胞的去分化中形成的，以便能够了解如何逆转它们并降低患者发展为癌症的风险。

 DESCRIPTION (provided by applicant): It has become clear in just the past two years that many mature cell lineages in digestive organs can dedifferentiate and re-enter the cell cycle to repair tissue damage. We and others have shown that post-mitotic cells can re-induce progenitor cell markers, re-enter the cell cycle, and can even serve as progenitors for other lineages. The dedifferentiation process carries a risk, however, as re-expressing progenitor cell genes is a form of cellular metaplasia. In states of chronic injury, like H. pylori infection in huan stomach, metaplasia continues indefinitely and increases risk for progression to cancer. Overall, cellular dedifferentiation presents a new paradigm for understanding tissue repair, "stemness", and cancer initiation. Our overarching goal is to understand the cellular and molecular mechanisms governing dedifferentiation. Here, we will focus on the earliest stages of dedifferentiation in gastric digestive-enzyme secreting zymogenic chief cells (ZCs). Our preliminary and published data will show that the first stage is engulfment of secretory granules by lysosomes and that lysosomal turnover of the digestive enzyme secretory granules (secretory apparatus "downscaling") must occur before progression to the next stages: metaplastic re- expression of progenitor cell genes and cell cycle re-entry. We will show the earliest molecular change in dedifferentiating ZCs is dramatically decreased expression of the bHLH transcription factor MIST1 (BHLHA15) and that deletion of Mist1 even in healthy ZCs is sufficient to induce lysosomal turnover of secretory granules. Finally, we will show that the only known transcriptional target of MIST1 that traffics lysosomes and is hence the most likely reason for the lysosomal attack on secretory granules when MIST1 is lost during dedifferentiation is the small GTPase, RAB26. Our aims are to: 1) determine the requirement/sufficiency for MIST1 in metaplasia downscaling; 2) determine if RAB26 affects flux through autophagy/mTOR signaling and whether it modulates granule destruction by lysosomes and/or autolysosomes; 3) a) determine if autophagic machinery is required for downscaling by inducing metaplasia following deletion in mature ZCs of the key autophagy genes Atg5 and Atg7 and b) to quantify autophagy/lysosome interaction with secretory granules in a database of human specimens where there are foci of ZCs undergoing dedifferentiation/metaplasia. Together the experiments will uncover for the first time the molecular mechanisms underlying the newly described cellular process of dedifferentiation and will have impact on human health because we will need to understand how metaplastic precursor lesions form from dedifferentiation of mature cells to be able to understand how to revert them and decrease risk for patients to progress to cancer.