Development of the lamprey velum and implications for the evolution of the vertebrate jaw

Background The vertebrate jaw is thought to have evolved through developmental modification of the mandibular arch. An extant jawless vertebrate, the lamprey, possesses a structure called “velum”—a mandibular arch derivative—in addition to the oral apparatus. This leads us to assess the velum's...

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Bibliographic Details
Published in:Developmental dynamics 2021-01, Vol.250 (1), p.88-98
Main Authors: Yokoyama, Hiromasa, Yoshimura, Miho, Suzuki, Daichi G., Higashiyama, Hiroki, Wada, Hiroshi
Format: Article
Language:English
Subjects:
Animals
Arches
Biological Evolution
Cell Movement
Cells (biology)
Evolution
Female
Gene Expression
Hindbrain
Homology
Jaw
Jaw - embryology
lamprey
Lampreys - embryology
Lampreys - metabolism
Mandible
mandibular arch
Mesencephalon
Muscles
Musculoskeletal Development
Musculoskeletal system
Neural crest
Neural Crest - physiology
Neural stem cells
Oral apparatus
Pattern formation
Progenitor cells
Structural members
velum
Vertebrates
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Summary:Background The vertebrate jaw is thought to have evolved through developmental modification of the mandibular arch. An extant jawless vertebrate, the lamprey, possesses a structure called “velum”—a mandibular arch derivative—in addition to the oral apparatus. This leads us to assess the velum's possible contribution to the evolution of jaws. Results The velar muscles develop from progenitor cells distinct from those from which the oral muscles develop. In addition, the oral and velar regions originate from the different sub‐population of the trigeminal neural crest cells (NCCs): the former region receives NCCs from the midbrain, whereas the latter region receives NCCs from the anterior hindbrain. The expression of patterning genes (eg, DlxA and MsxA) is activated at a later developmental stage in the velum compared to the oral region, and more importantly, in different cells from those in the oral region. Conclusion The lamprey mandibular arch consists of two developmental units: the anterior oral unit and the posterior velar unit. Because structural elements of the lamprey velum may be homologous to the jaw, the evolution of vertebrate jaws may have occurred by the velum being released from its functional roles in feeding or respiration in jawless vertebrates. Key Findings Lamprey velum receive neural crest from hindbrain Velar muscle develop from a distinct cell population from that for oral muscle Velum is likely to contribute jaw evolution
ISSN:1058-8388
1097-0177
DOI:10.1002/dvdy.243