RT Journal Article
T1 Thyroid and endostyle development in cyclostomes provides new insights into the evolutionary history of vertebrates.
A1 Takagi, Wataru
A1 Sugahara, Fumiaki
A1 Higuchi, Shinnosuke
A1 Kusakabe, Rie
A1 Pascual-Anaya, Juan
A1 Sato, Iori
A1 Oisi, Yasuhiro
A1 Ogawa, Nobuhiro
A1 Miyanishi, Hiroshi
A1 Adachi, Noritaka
A1 Hyodo, Susumu
A1 Kuratani, Shigeru
K1 Atavism
K1 Cyclostomes
K1 Development
K1 Endostyle
K1 Evolution
K1 Hagfish
K1 Lamprey
K1 Thyroid gland
AB The endostyle is an epithelial exocrine gland found in non-vertebrate chordates (amphioxi and tunicates) and the larvae of modern lampreys. It is generally considered to be an evolutionary precursor of the thyroid gland of vertebrates. Transformation of the endostyle into the thyroid gland during the metamorphosis of lampreys is thus deemed to be a recapitulation of a past event in vertebrate evolution. In 1906, Stockard reported that the thyroid gland in hagfish, the sister cyclostome group of lampreys, develops through an endostyle-like primordium, strongly supporting the plesiomorphy of the lamprey endostyle. However, the findings in hagfish thyroid development were solely based on this single study, and these have not been confirmed by modern molecular, genetic, and morphological data pertaining to hagfish thyroid development over the last century. Here, we showed that the thyroid gland of hagfish undergoes direct development from the ventrorostral pharyngeal endoderm, where the previously described endostyle-like primordium was not found. The developmental pattern of the hagfish thyroid, including histological features and regulatory gene expression profiles, closely resembles that found in modern jawed vertebrates (gnathostomes). Meanwhile, as opposed to gnathostomes but similar to non-vertebrate chordates, lamprey and hagfish share a broad expression domain of Nkx2-1/2-4, a key regulatory gene, in the pharyngeal epithelium during early developmental stages. Based on the direct development of the thyroid gland both in hagfish and gnathostomes, and the shared expression profile of thyroid-related transcription factors in the cyclostomes, we challenge the plesiomorphic status of the lamprey endostyle and propose an alternative hypothesis where the lamprey endostyle could be obtained secondarily in crown lampreys.
YR 2022
FD 2022-04-01
LK http://hdl.handle.net/10668/20305
UL http://hdl.handle.net/10668/20305
LA en
DS RISalud
RD Apr 13, 2025