Early Mitochondrial Pathology Conferred By Gtpbp3Depletion Affects Zebrafish(Danio Rerio) Further Development

The GTPBP3protein family is an evolutionarily conserved, multidomain protein involved in mitochondrial tRNA modification which plays a vital role in the fidelity of translational process. GTPBP3mutations in humans lead to defects in tRNA modification and manipulate penetrance of deafness associated with the mitochondrial12S rRNA mutation. Yeast mssl cells carrying15S rRNA PR454mutation manifest a respiratory-deficient phenotype, indicating that MSS1is essential for mitochondrial function.Zebrafish is an attractive model for studying human diseases because of its high conservation of genetic information, low cost of maintenance and optical clarity facilitating observation and manipulation. Its mitochondrial genome is sequenced and zebrafish is emerging as a model for studying mitochondria-linked disorders. The zebrafish gtpbp3has three isoforms and is expressed throughout zebrafish development and ubiquitously in adult zebrafish tissue, but extremely abundantly in ovary. Functional conservation of Gtpbp3is supported by the observation that zebrafish Gtpbp3localizes in mitochondrion and the isolated zebrafish gtpbp3cDNA can rescue the respiratory-deficient phenotype of yeast mss1cells carrying PR454mutation. In this study, Gtpbp3was successfully abrogated in zebrafish embryos using antisense morpholinos, which resulted in mitochondrial disorder. In response to mitochondrial dysfunction, upregulation of the mitochondria-coding genes and nuclear-coding genes involved in mitochondrial function and biogenesis were observed. In addition, Gtpbp3depletion induced increased levels of apoptosis and reactive oxygen species. Furthermore, Gtpbp3depletion caused bioenergetic defects, with a marked decrease of mitochondrial ATP generation. Phenotypically, these Gtpbp3-deficient zebrafish exhibited melanin, oedema and skeletal abnormalities which include lordosis, kyphosis and curved tail. Additionally, Gtpbp3-deficient zebrafish exhibited impaired organ development, especially those of high metabolic activity like brain and liver. Finally, most of the Gtpbp3-deficient zebrafish died within 5days after fertilization. These results not only elucidate the absolute requirement of Gtpbp3for successful zebrafish development, but also manifest that zebrafish is a promising vertebrate model for human mitochondria-linked disorders.