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Hoxa2 knockdown in Xenopus results in hyoid to mandibular homeosis
Author(s) -
Baltzinger Mireille,
Ori Michela,
Pasqualetti Massimo,
Nardi Irma,
Rijli Filippo M.
Publication year - 2005
Publication title -
developmental dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.634
H-Index - 141
eISSN - 1097-0177
pISSN - 1058-8388
DOI - 10.1002/dvdy.20567
Subject(s) - hox gene , biology , zebrafish , xenopus , morpholino , anatomy , gene knockdown , branchial arch , homeotic gene , cranial neural crest , neural crest , vertebrate , embryo , microbiology and biotechnology , gene , genetics , phenotype , transcription factor
The skeletal structures of the face and throat are derived from cranial neural crest cells (NCCs) that migrate from the embryonic neural tube into a series of branchial arches (BAs). The first arch (BA1) gives rise to the upper and lower jaw cartilages, whereas hyoid structures are generated from the second arch (BA2). The Hox paralogue group 2 (PG2) genes, Hoxa2 and Hoxb2 , show distinct roles for hyoid patterning in tetrapods and fishes. In the mouse, Hoxa2 acts as a selector of hyoid identity, while its paralogue Hoxb2 is not required. On the contrary, in zebrafish Hoxa2 and Hoxb2 are functionally redundant for hyoid arch patterning. Here, we show that in Xenopus embryos morpholino‐induced functional knockdown of Hoxa2 is sufficient to induce homeotic changes of the second arch cartilage. Moreover, Hoxb2 is downregulated in the BA2 of Xenopus embryos, even though initially expressed in second arch NCCs, similar to mouse and unlike in zebrafish. Finally, Xbap , a gene involved in jaw joint formation, is selectively upregulated in the BA2 of Hoxa2 knocked‐down frog embryos, supporting a hyoid to mandibular change of NCC identity. Thus, in Xenopus Hoxa2 does not act redundantly with Hoxb2 for BA2 patterning, similar to mouse and unlike in fish. These data bring novel insights into the regulation of Hox PG2 genes and hyoid patterning in vertebrate evolution and suggest that Hoxa2 function is required at late stages of BA2 development. Developmental Dynamics 234:858–867, 2005. © 2005 Wiley‐Liss, Inc.