Nguyen Matthew, Singhal Pankhuri, Piet Judith W, Shefelbine Sandra J, Maden Malcolm, Voss S Randal, Monaghan James R
Department of Biology, Northeastern University, Boston, MA 02115, USA.
Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
Development. 2017 Feb 15;144(4):601-611. doi: 10.1242/dev.139873. Epub 2017 Jan 13.
Salamanders are capable of regenerating amputated limbs by generating a mass of lineage-restricted cells called a blastema. Blastemas only generate structures distal to their origin unless treated with retinoic acid (RA), which results in proximodistal (PD) limb duplications. Little is known about the transcriptional network that regulates PD duplication. In this study, we target specific retinoic acid receptors (RARs) to either PD duplicate (RA treatment or RARγ agonist) or truncate (RARβ antagonist) regenerating limbs. RARE-EGFP reporter axolotls showed divergent reporter activity in limbs undergoing PD duplication versus truncation, suggesting differences in patterning and skeletal regeneration. Transcriptomics identified expression patterns that explain PD duplication, including upregulation of proximal homeobox gene expression and silencing of distal-associated genes, whereas limb truncation was associated with disrupted skeletal differentiation. RARβ antagonism in uninjured limbs induced a loss of skeletal integrity leading to long bone regression and loss of skeletal turnover. Overall, mechanisms were identified that regulate the multifaceted roles of RARs in the salamander limb including regulation of skeletal patterning during epimorphic regeneration, skeletal tissue differentiation during regeneration, and homeostatic regeneration of intact limbs.
蝾螈能够通过生成一团称为芽基的谱系受限细胞来再生被截断的肢体。芽基仅生成其起源部位远端的结构，除非用视黄酸（RA）处理，这会导致肢体出现近远轴（PD）重复。关于调节PD重复的转录网络，人们了解甚少。在本研究中，我们将特定的视黄酸受体（RARs）作用于正在再生的肢体，使其要么发生PD重复（RA处理或RARγ激动剂），要么被截断（RARβ拮抗剂）。携带RARE - EGFP报告基因的美西螈在经历PD重复与截断的肢体中显示出不同的报告基因活性，这表明在模式形成和骨骼再生方面存在差异。转录组学确定了解释PD重复的表达模式，包括近端同源框基因表达上调和远端相关基因沉默，而肢体截断与骨骼分化破坏有关。在未受伤的肢体中使用RARβ拮抗剂会导致骨骼完整性丧失，从而导致长骨退化和骨骼更新丧失。总体而言，我们确定了调节RARs在蝾螈肢体中多方面作用的机制，包括在形态再生过程中对骨骼模式形成的调节、再生过程中骨骼组织分化的调节以及完整肢体的稳态再生。
