About the Chen lab
Unlike mammals, some vertebrates like salamanders and zebrafish, are able to regenerate complex tissues (e.g. lost appendages, injured heart muscle, and transected spinal cord). Understanding how and why natural regeneration occurs in these lower vertebrate species can ultimately transform medicine and human health.
The goal of my research program is to uncover the cellular, molecular, and genetic mechanisms by which zebrafish regenerate complex tissues as well as identify key factors and dynamic signals that instruct cell behaviors in regenerating tissues. The long-term goal of my lab is to translate these findings for enhancing regenerative capacity of human tissues and organs in vivo.
Morphogenesis and activation of the regeneration epidermis
Classical studies have revealed that the epidermis that forms quickly over an amputated limb stump is critical for initiating regenerative programs. Research in salamanders indicates that if the epidermis is removed, or replaced with flank skin, or disrupted by insertion of the limb into the abdominal cavity, limb regeneration does not proceed. Yet, little is understood about the molecular and cellular mechanisms by which a simple wound epithelium transforms into a key signaling source, a critical step necessary for the regeneration to occur. In contrast to amphibian limbs, zebrafish fins are an ideal model for applying cutting-edge imaging and genetic tools to dissect this dynamic process. For imaging, the fin structure is flat, thin (~200 μm), and optically translucent. Fluorescent proteins labeled cells can be assayed simultaneously in multiple structures over time within the same animal. Additionally, regulatory sequences that enable precise control of reporter proteins or gene expression in specific cells are available for most cell types in fin tissues. Thus, my laboratory aims to exploit the strengths of the zebrafish system (i.e. imaging and genetics) to reveal the cellular, molecular, and genetic mechanisms of regeneration with a focus on the signaling epidermis.
1. Define spatial and temporal regulation of epithelial cell behaviors and cell signaling during wound healing and tissue regeneration.
We have recently developed a multispectral live imaging strategy with the goal of barcoding entire cell populations in regenerating tissues for quantitative analyses (skinbow, Figure 1). Through large-scale, in vivo imaging analysis of superficial epithelial cell (SEC) populations covering zebrafish fins, we quantified individual and large-scale cell behaviors under homeostatic conditions, during repair of minor exfoliation injuries, and during regeneration of complex tissue after major amputation injuries. We discovered dynamic alterations in rates, principles, and patterns of epithelial cell behaviors that are determined by the mode and extent of tissue damage. Using a new reporter of basal keratinocyte cycle phase, we showed that SEC behaviors and the cell cycle activity of their progenitors can be simultaneously monitored in live tissue. These findings identify unexpected cell responses and behaviors that are inherent to skin regeneration in adult vertebrates.
We will apply this cutting-edge approach and other novel imaging tools to define mechanisms that instruct behaviors of epithelial cells as they participate in wound closure and regeneration. We hypothesize that injuries activate a complex network of diffusive, dynamic signals to regulate behaviors of epithelial cells and their signaling competence during tissue regeneration. We propose 3 specific aims to test this hypothesis:
Aim 1: Define basal cell dynamics during wound healing and tissue regeneration.
Aim 2: Identify dynamic signals that instruct epithelial cell behaviors in regenerating tissues.
Aim 3: Determine molecular mechanisms that underlie activation of the regeneration epidermis.
2. Characterize novel regeneration mutants recovered from a forward genetic screen.
We recently recovered a panel of novel mutants detective in regeneration of complex tissues awaits further characterization (Figure 2). We are in the process of refining the map position and generating independent genetic lesions using the CRISPR/Cas9 system for complementation assays. To date, zebrafish remain the only vertebrate model available that is both highly regenerative and amenable to forward genetic screens. The study of these mutants will provide novel, mechanistic insights into the fundamental features of tissue regeneration. We have three general aims to characterize each mutant:
Aim 1: Identify causative mutations underlying the phenotype.
Aim 2: Determine why candidate genes are essential to regeneration, where they are expressed, and how they are regulated in regenerating tissues.
Aim 3: Determine whether candidate genes and their mutations unveil new concepts and mechanisms of regeneration in a broader context.
跟哺乳類動物不同, 某些脊椎動物像是蠑螈和斑馬魚有很強的再生能力, 這些動物可以再生被截斷的身體肢體, 受傷的心肌, 和受損的脊髓神經. 研究了解再生過程是如何發生? 為什麼這些動物有很強的再生能力? 相關的發現可以帶來醫學上的應用和治療的突破.
我的實驗室利用斑馬魚研究再生過程的細胞機制, 尋找和了解調控細胞行為的重要基因和分子訊號. 實驗室的長期目標是應用發展我們發現的成果, 增強人類組織和器官再生的能力.
早期在蠑螈再生能力的研究已經發現: 當截肢後, 覆蓋肢體切面的表皮組織對再生過程的啟動有很重要的影響. 如果這層表皮被重複移除, 或是用一般的表皮組織替代, 又或是將截肢插入腹腔阻止其形成, 再生過程將無法繼續完成. 目前對這層表皮組織的了解仍是相當有限, 為什麼簡單的表皮組織在傷口癒合後會進一步活化, 形成分泌再生訊號的來源? 進一步探討這個動態過程的發生需要發展新的研究工具. 相對於蠑螈的截肢實驗模型, 斑馬魚的尾鰭提供一個理想的實驗系統來研究複雜組織的再生過程, 特別是應用新發展的細胞標記和基因調控技術來了解細胞行為及其分子層級的作用機制. 我們實驗室利用斑馬魚作為發育生物學, 遺傳學模型生物的優勢, 來探索表皮組織如何癒合傷口, 活化和調控再生過程.
1. 探索傷口修復和複雜組織再生過程中, 表皮細胞行為和訊號的動態調控.
2. 利用失去再生能力的斑馬魚 (經由基因突變篩檢出), 來了解再生過程的分子機制.
Chen-Hui Chen, Ph.D. Assistant Research Fellow
IInstitute of Cellular and Organismic Biology, Academia Sinica
128 Sec.2, Academia Rd, Nankang, Taipei 115, Taiwan