缺乏pycr1降低斑馬稚魚進食量並促進早衰症狀之產生

Abstract

早衰症是一種基因表現失調造成之罕見遺傳疾病。到目前為止，已發現許多不同類型的早衰症，而Cutis Laxa是其中之一，其常見症狀包含掉髮、視力下降、多餘和鬆垮的肌膚。在2009年發現Cutis Laxa患者pycr1基因常有突變，但其致病機制仍不清楚 。本論文乃研究pycr1突變斑馬魚老化相關表徵已確立其可為Cutis Laxa實驗動物模型，並嘗試探討pycr1突變導致Cutis Laxa 的致病機轉。實驗中發現pycr1基因高量表現於成魚及幼魚腸道，且其雄性pycr1突變斑馬成魚體重較對照組低。測試幼魚，發現pycr1突變魚攝食量低於對照組。另一方面pycr1突變幼魚細胞凋亡和衰老現象亦增加。因過去已知pycr1在粒腺體大量表現，我進一步發現在早期發育階段，pycr1突變幼魚粒Cutis Laxa體DNA拷貝數顯著較低，卻在發育晚期恢復到正常水平，其可能藉由pycr2的補償作用造成，因我觀察到在這之前pycr2基因表現增高。總體而言，藉由剔除pycr1，斑馬魚可成為很好的早衰症模式動物以探討其致病機轉。

Progeria also known as premature aging is an extremely rare genetic disorder. Up to now, there are several types of progeria described. Cutis Laxa is one of progeria diseases and patients have common aging symptoms such as hair loss, deterioration of eyesight, redundant and inelastic skin. In 2009, mutations in pycr1 gene had been found in Cutis Laxa patients. The paper is, however, one of few mechanistic studies about pycr1-dependent progeria due to the rareness and lack of animal models. Therefore, I aimed to characterize the aging-related phenotypes of pycr1-/- zebrafish and use them to understand how pycr1 causes Cutis Laxa. I first showed spatial and temporal expression of pycr1 gene in zebrafish. In particular, the pycr1 gene is highly expressed in guts of both larvae and adult fish. Pycr1-/-males exhibited lower body weight. Therefore, I first measured food intake and found that pycr1-/- larvae indeed ate less than that of controls. Apoptosis and cellular senescence were also increased in pycr1-/- zebrafish. Pycr1 is a mitochondria-enriched enzyme, so I examined mitochondrial DNA copy number and found it is significantly decreased in early pycr1-/- larvae, but is restored by 5 day post fertilization which might be due to compensatory effect of Pycr2. Overall, this study shows molecular and physiological defects in the absence of pycr1 that could possibly contribute to our understanding the mechanisms of premature aging.