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- Title
Measuring potential effects of the developmental burden associated with the vertebrate notochord.
- Authors
Fujimoto, Satoko; Yamanaka, Kaori; Tanegashima, Chiharu; Nishimura, Osamu; Kuraku, Shigehiro; Kuratani, Shigeru; Irie, Naoki
- Abstract
The notochord functions primarily as a supporting tissue to maintain the anteroposterior axis of primitive chordates, a function that is replaced entirely by the vertebral column in many vertebrates. The notochord still appears during vertebrate embryogenesis and plays a crucial role in the developmental pattern formation of surrounding structures, such as the somites and neural tube, providing the basis for the vertebrate body plan. The indispensable role of the notochord has often been referred to as the developmental burden and used to explain the evolutionary conservation of notochord; however, the existence of this burden has not been successfully exemplified so far. Since the adaptive value of target tissues appears to result in the evolutionary conservation of upstream structures through the developmental burden, we performed comparative gene expression profiling of the notochord, somites, and neural tube during the mid‐embryonic stages in turtles and chicken to measure their evolutionary conservation. When compared with the somites and neural tube, overall gene expression profiles in the notochord showed significantly lower or merely comparable levels of conservation. However, genes involved in inductive signalings, such as the sonic hedgehog (Shh) cascade and the formation of functional primary cilia, showed relatively higher levels of conservation in all the three structures analyzed. Collectively, these results suggest that shh signals are critical as the inductive source and receiving structures, possibly constituting the inter‐dependencies of developmental burden. Research Highlights: Potential evolutionary effects toward notochord by developmental burden was evaluated by Laser Micro Dissection RNAseq (LMDseq). Notochord was less conserved than neural tube and somites; however, genes in sonic hedgehog (shh) signaling cascade was found to be evolutionarily conserved (not only in notochord but also in somites and neural tube). These results suggest that Shh signals are critical as the inductive source and receiving structures, possibly constituting the inter‐dependencies of developmental burden. Further studies that directly measure the burden required to verify the hypothesis are awaited.
- Subjects
NOTOCHORD; NEURAL tube; GENE expression profiling; SPINE; VERTEBRATES; CHORDATA
- Publication
Journal of Experimental Zoology Part B: Molecular & Developmental Evolution, 2022, Vol 338, Issue 1, p129
- ISSN
1552-5007
- Publication type
Article
- DOI
10.1002/jez.b.23032