title: ngs (notochord granular surface) gene encodes a novel type of intermediate filament family protein essential for notochord maintenance in zebrafish.
abstract: The notochord is an important organ involved in embryonic patterning and locomotion. In zebrafish, the mature notochord consists of a single stack of fully differentiated, large vacuolated cells called chordocytes, surrounded by a single layer of less differentiated notochordal epithelial cells called chordoblasts. Through genetic analysis of zebrafish lines carrying pseudo-typed retroviral insertions, a mutant exhibiting a defective notochord with a granular appearance was isolated, and the corresponding gene was identified as ngs (notochord granular surface), which was specifically expressed in the notochord. In the mutants, the notochord started to degenerate from 32 hours post-fertilization, and the chordocytes were then gradually replaced by smaller cells derived from chordoblasts. The granular notochord phenotype was alleviated by anesthetizing the mutant embryos with tricaine to prevent muscle contraction and locomotion. Phylogenetic analysis showed that ngs encodes a new type of intermediate filament (IF) family protein, which we named chordostatin based on its function. Under the transmission electron microcopy, bundles of 10-nm-thick IF-like filaments were enriched in the chordocytes of wild-type zebrafish embryos, whereas the chordocytes in ngs mutants lacked IF-like structures. Furthermore, chordostatin-enhanced GFP (EGFP) fusion protein assembled into a filamentous network specifically in chordocytes. Taken together, our work demonstrates that ngs encodes a novel type of IF protein and functions to maintain notochord integrity for larval development and locomotion. Our work sheds light on the mechanisms of notochord structural maintenance, as well as the evolution and biological function of IF family proteins.
authors.affiliation: Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, Center of Developmental Biology and Genetics, College of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Xiangjun
authors.initials: X
authors.lastname: Tong
authors.forename: Zhidan
authors.initials: Z
authors.lastname: Xia
authors.forename: Yao
authors.initials: Y
authors.lastname: Zu
authors.forename: Helena
authors.initials: H
authors.lastname: Telfer
authors.forename: Jing
authors.initials: J
authors.lastname: Hu
authors.forename: Jingyi
authors.initials: J
authors.lastname: Yu
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhang
authors.lastname: Sodmergen
authors.forename: Shuo
authors.initials: S
authors.lastname: Lin
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D049109:Cell Proliferation; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D007382:Intermediate Filaments / Q000378:metabolism*; D007814:Larva / Q000378:metabolism; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008954:Models, Biological; D009154:Mutation; D009672:Notochord / Q000196:embryology* / Q000378:metabolism; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D014018:Tissue Distribution; D014981:Xenopus; D015027:Zebrafish
chemical_list: D049452:Green Fluorescent Proteins