Expression pattern and functions of autophagy-related gene atg5 in zebrafish organogenesis

The implications of autophagy related genes in serious neural degenerative diseases have been well documented. However, the functions and regulation of the family genes in embryonic development remain to be rigorously studied. Here, we make the first report on the important role of atg5 gene in zebrafish neurogenesis and organogenesis as evidenced by the spatiotemporal expression pattern and functional analysis. Using morpholino oligo knockdown and mRNA overexpression, we demonstrate that zebrafish atg5 is required for normal morphogenesis of brain regionalization and body plan as well as for expression regulation of neural gene markers: gli1, huC, nkx2.2, pink1, β-synuclein, xb51 and zic1. We further demonstrate that ATG5 protein is involved in autophagy by LC3-II/LC3I ratio and rapamycin induction experiments, and that ATG5 is capable of regulating expression of itself gene in the manner of a feedback inhibition loop. In addition, we find that expression of another autophagy related gene atg12 is maintained at a higher constant level like a housekeeping gene. This indicates that the formation of the ATG5-ATG12 conjugate may be dependent on ATG5 protein generation and its splicing, rather than on ATG12 protein in zebrafish. Importantly, in the present study, we provide a mechanistic insight into the regulation and functional roles of atg5 in development of zebrafish nervous system.