RNA-Seq gene expression profile of the notochord composing the intervertebral joints in fugu, Takifugu rubripes

In the teleost vertebral column, the notochord consists of an outer notochord sheath, with basal cells and vacuolated cells enclosed by the notochord sheath, and forms intervertebral joints that connect the centra. To reveal the functions of teleost vertebral notochord, we here performed RNA-Seq of fugu vertebral notochord and revealed following three features of mRNA expression profile. First, the notochord exhibits high-level expression of cartilaginous collagens and enzymes for collagen maturation, as well as sox6 and sox9 that regulate the expression of cartilaginous collagens. Second, the expression levels of cytoskeletal keratins, krt13, krt8, and krt18 is markedly high. Third, the expression level of ntl is highest among transcription factors. The notochord basal cells maintained ntl expression even in an in vitro culture condition. These data, taken together with previous data, suggest that the notochord basal cells are specialized for the cartilaginous matrix production for the notochord sheath growth; the vacuolated cells give the notochord flexibility and physical strength using cytoskeletal keratins and vacuoles; ntl plays some crucial role in the maintenance of vertebral notochord in post-embryonic development.