中文题名 / Chinese title: 龟类定义性骨骼结构腹甲的发育
英文题名 / English title: Development of the turtle plastron, the order-defining skeletal structure.
作者 / Authors: Rice R, Kallonen A, Cebra-Thomas J, Gilbert SF.
期刊 / Journal: PNAS
年份 / Year: 2016
DOI: 10.1073/pnas.1600958113
论文链接 / Article: https://doi.org/10.1073/pnas.1600958113
摘要来源 / Abstract source: https://europepmc.org/article/MED/27114549

英文摘要原文 / Original English abstract
The dorsal and ventral aspects of the turtle shell, the carapace and the plastron, are developmentally different entities. The carapace contains axial endochondral skeletal elements and exoskeletal dermal bones. The exoskeletal plastron is found in all extant and extinct species of crown turtles found to date and is synaptomorphic of the order Testudines. However, paleontological reconstructed transition forms lack a fully developed carapace and show a progression of bony elements ancestral to the plastron. To understand the evolutionary development of the plastron, it is essential to know how it has formed. Here we studied the molecular development and patterning of plastron bones in a cryptodire turtle Trachemys scripta We show that plastron development begins at developmental stage 15 when osteochondrogenic mesenchyme forms condensates for each plastron bone at the lateral edges of the ventral mesenchyme. These condensations commit to an osteogenic identity and suppress chondrogenesis. Their development overlaps with that of sternal cartilage development in chicks and mice. Thus, we suggest that in turtles, the sternal morphogenesis is prevented in the ventral mesenchyme by the concomitant induction of osteogenesis and the suppression of chondrogenesis. The osteogenic subroutines later direct the growth and patterning of plastron bones in an autonomous manner. The initiation of plastron bone development coincides with that of carapacial ridge formation, suggesting that the development of dorsal and ventral shells are coordinated from the start and that adopting an osteogenesis-inducing and chondrogenesis-suppressing cell fate in the ventral mesenchyme has permitted turtles to develop their order-specific ventral morphology.

摘要依据的主要发现 / Findings based on the abstract
巴西龟腹甲骨凝聚区选择成骨命运并抑制软骨形成，其发生时间与鸡、小鼠胸骨软骨发育及龟类背甲嵴形成相重叠。
Plastron-bone condensations in Trachemys scripta adopt an osteogenic fate while suppressing cartilage formation. Their timing overlaps development of sternal cartilage in chicks and mice and carapacial-ridge formation in turtles.

摘要依据的结论 / Conclusions based on the abstract
背腹甲协调发育及骨与软骨细胞命运改变，有助于解释龟类特有的腹侧身体构型。
Coordinated dorsal and ventral shell development and altered bone-versus-cartilage cell fate help explain the turtle-specific ventral body plan.

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