Roles of the unfolded protein response transduces IRE1alpha and IRE1beta and their downstream transcription factor XBP1 in medaka development

IRE1alpha and IRE1beta are transmembrane proteins in the endoplasmic reticulum (ER). When activated in response to ER stress, they cleave XBP1 mRNA to initiate unconventional splicing, resulting in translation of the spliced XBP1 mRNA and production of the active transcription factor pXBP1(S), which leads to the maintenance of the homeostasis of the ER. Double knockout (KO) of IRE1alpha and IRE1beta causes severe developmental defects in medaka fish, a vertebrate model. To understand physiological functions of medaka IRE1alpha, IRE1beta and XBP1, we have compared the transcriptome of embryos at 5 day post fertilization derived from IRE1beta single KO medaka, IRE1alpha/beta double KO medaka, and IRE1alpha/beta double KO medaka constitutively expressing pXBP1(S).