Preliminary Study Of Redd1in Left-right Asymmetric Development Of Heart In Zebrafish

REDD1(Regulated in Development and DNA Damage response1) is a memberof the DNA Damage Inducible Transcript (DDIT) protein family. Proteins in thisfamily participate in DNA repair, inflammatory and stress responses, and have anti-tumor actions. In mammals, REDD1is up regulated by hypoxia, oxidative stress, andstarvation. The increased REDD1in turn inhibits mTOR signaling and therebymodulates growth and development. Up-regulation of REDD1expression isimplicated in several human diseases, such as Parkinson’s disease, tumor growth, andskeletal muscle atrophy. The majority of previous studies on REDD1have beenperformed using various mammalian cell lines in vitro. There is limited informationon their in vivo expression pattern.Recent studies suggest that Redd1is involved in Wnt signaling pathway and playscrucial role in dorsoventral pattern formation in zebrafish. During embryogenesis,zebrafish redd1mRNA was detected in germ ring at the shield stage. During thesegmentation stage and thereafter, redd1mRNA was detected mainly in theprechordal plate, posterior mesoderm and anterior ectoderm, Kupffer’s vesicle (KV),an essential organ that initiates left-right (LR) development in teleost fish. WhetherRedd1regulate left-right (LR) asymmetric development in zebrafish is unknown. Inthis study, we investigated the role of Redd1in left-right (LR) asymmetricdevelopment.In this study, we demonstrate that global knockdown of redd1by injectingantisense morpholino results in randomized expression of the early left-right (LR)asymmetric markers southpaw, lefty2and the later internal organic marker cmlc2but not foxa3in zebrafish embryos. Dorsal forerunner cells (DFCs) specific knockdownof redd1disrupts normal left-right (LR) asymmetries and impairs the formation of themidline molecular barrier in zebrafish embryos. Depletion of Redd1in DFCs/KVleads to reduce Kupffer’s vesicle size, as well as cilia length and number in Kupffer’svesicle, along with downregulation of foxj1a and sox17expression. Thus, redd1regulates asymmetric development through DFCs in a cell-autonomous fashion.Dorsal forerunner cells (DFCs) specific knockdown of redd1also disrupts the BMP4signals distribution in the cardiac field. Whether Redd1regulate heart laterality viaBMP4signals in cardiac field is unknown now.In summary, our results reveal a previously unexpected role of Redd1inregulation of left-right (LR) asymmetric development of heart in zebrafish.