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The Grooved Rodent Incisor Recapitulates Rudimentary Teeth Characteristics of Ancestral Mammals.

Authors
 L. Li  ;  Q. Tang  ;  H.-S. Jung 
Citation
 JOURNAL OF DENTAL RESEARCH, Vol.95(8) : 923-930, 2016 
Journal Title
JOURNAL OF DENTAL RESEARCH
ISSN
 0022-0345 
Issue Date
2016
MeSH
Animals ; Biological Evolution ; Embryonic Germ Cells/physiology ; Female ; Gerbillinae/anatomy & histology* ; Gerbillinae/embryology ; Incisor/anatomy & histology* ; Incisor/embryology ; Incisor/growth & development ; Mice, Nude/embryology ; X-Ray Microtomography
Keywords
Shh ; craniofacial biology ; dentition ; developmental biology ; gerbils ; morphogenesis
Abstract
It is known from the paleontology studies of eutherian mammals that incisor numbers were reduced during evolution. The evolutionary lost incisors may remain as vestigial structures at embryonic stages. The recapitulation of the incisor patterns among mammalian species will potentially uncover the mechanisms underlying the phenotypic transition of incisors during evolution. Here, we showed that a minute tooth formed in the presumptive groove region of the gerbil upper incisor at the early developmental stages, during which multiple epithelial swellings and Shh transcription domains spatiotemporally appeared in the dental epithelium, suggests the existence of vestigial dental primordia. Interestingly, when we trimmed the surrounding mesenchyme from incisor tooth germs at or before the bud stage prior to ex vivo culture, the explants developed different incisor phenotypes ranging from triplicated incisors, duplicated incisors, to Lagomorpha-like incisors, corresponding to the incisor patterns in the eutherian mammals. These results imply that the phenotypic transition of incisors during evolution, as well as the achievement of ultimate incisors in adults, arose from differential integrations of primordia. However, when the incisor tooth germ was trimmed at the cap stage, a grooved incisor developed similar to the normal condition. Furthermore, the incisor tooth germ developed a small but smooth incisor after the additional removal of the minute tooth and a lateral rudiment. These results suggest that multiple dental primordia integrated before the cap stage, with the labial primordia contributing to the labial face of the functional incisor. The minute tooth that occupied the boundary of the 2 labial primordia might be implicated in the groove formation. This study sheds light on how rudiments incorporate into functional organs and aids the understanding of incisor evolution.
Full Text
http://journals.sagepub.com/doi/abs/10.1177/0022034516633153
DOI
10.1177/0022034516633153
Appears in Collections:
2. College of Dentistry (치과대학) > Dept. of Oral Biology (구강생물학교실) > 1. Journal Papers
Yonsei Authors
Jung, Han Sung(정한성) ORCID logo https://orcid.org/0000-0003-2795-531X
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/151753
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