Excess Retinoic Acid Induces Fusion of Centra by Degenerating Intervertebral Ligament Cells in Japanese flounder, Paralichthys olivaceus. Issue 8 (18th January 2017)

• Record Type: Journal Article
• Authors: Wu, Xiaoming; Chen, Qiran; Washio, Youhei; Yokoi, Hayato; Suzuki, Tohru
• Is Part Of: Journal of experimental zoology. Volume 326:Issue 8(2016)
• Page Start: 464
• Page End: 473
• Publication Date: 2017-01-18
• Subjects: Developmental biology -- Periodicals; Evolution (Biology) -- Periodicals; Molecular evolution -- Periodicals; Zoology -- Periodicals; Evolution, Molecular -- Periodicals; Developmental Biology -- Periodicals; Zoology -- Periodicals; 591
• DOI: 10.1002/jez.b.22717
• Languages: English
• ISSNs: 1552-5007

Abstract

GRAPHICAL ABSTRACT: In large‐sized teleost fish possessing highly calcified centra, intervertebral ligaments derived from embryonic sclerotome build intervertebral joints in combination with the notochord segmented by growing centra during larval to adult development. We show using flounder, Paralichthys olivaceus, that intervertebral ligaments, which can be visualized by RNA in situ using shh probe, degenerate when larvae are transiently exposed to retinoic acid (RA) at early stage of centra ossification, and the intervertebral region is instead ossified, causing fusion of bone elements of centra. Then, during development to adult, the growth of centra in RA‐treated fish is severely suppressed in anterior‐posterior direction, and the notochord tissues degenerate in the fused centra, resulting in loss of intervertebral joints, complete fusion of centra and body truncation. ABSTRACT: In marine aquaculture fish, excessive supplement of vitamin A (VA) to zooplanktons for larval culture and experimental exposure of larvae to retinoic acid (RA: active form of VA) have been known to cause vertebral deformity. However, the tissues in the developing vertebral column that are affected by RA and the progression of vertebral deformity remain undetermined. To examine these questions, we histologically traced the progress of vertebral deformity induced by RA in Japanese flounder ( Paralichthys olivaceus ). Larvae were exposed to RA for 3 days at mid‐metamorphosis (G‐stage), a critical stage for vertebral deformity. Intervertebral ligament, which is known to form intervertebral joints in cooperation with the notochord, was severely degenerated by RA, leading to fusion of centra. During further development to adult, growth of centra was severely suppressed in an anterior–posterior direction in RA‐treated fish and the notochord tissue was lost from fused centra, resulting in complete loss of intervertebral joints and fusion of centra. We conclude that RA initially damages the intervertebral ligaments, and these defects lead to fusion, narrowing of centra, and loss of intervertebral joints in the vertebral column. The cumulative effect of these modifications is a truncated body form.