Foxi3^GFP and Foxi3^CreER mice allow identification and lineage labeling of pharyngeal arch ectoderm and endoderm, and tooth and hair placodes

Abstract

BackgroundFOXI3 is a forkhead family transcription factor that is expressed in the progenitors of craniofacial placodes, epidermal placodes, and the ectoderm and endoderm of the pharyngeal arch region. Loss of Foxi3 in mice and pathogenic Foxi3 variants in dogs and humans cause a variety of craniofacial defects including absence of the inner ear, severe truncations of the jaw, loss or reduction in external and middle ear structures, and defects in teeth and hair.ResultsTo allow for the identification, isolation, and lineage tracing of Foxi3‐expressing cells in developing mice, we targeted the Foxi3 locus to create Foxi3GFP and Foxi3CreER mice. We show that Foxi3GFP mice faithfully recapitulate the expression pattern of Foxi3 mRNA at all ages examined, and Foxi3CreER mice can trace the derivatives of pharyngeal arch ectoderm and endoderm, the pharyngeal pouches and clefts that separate each arch, and the derivatives of hair and tooth placodes.ConclusionsFoxi3GFP and Foxi3CreER mice are new tools that will be of use in identifying and manipulating pharyngeal arch ectoderm and endoderm and hair and tooth placodes.

Sensory cells in tunicates: insights into mechanoreceptor evolution

“…A n alternative explanation for this paradox is that the posterior region of the tunicate larval head that expresses Six and FoxI genes does not give rise to sensory structures at all. Vertebrate Six and Foxi1/3 genes are also expressed in the developing pharyngeal arch region of vertebrates at a slightly later stage than their expression in the pre-placodal domain ( Ohyama and Groves, 2004 ; Khatri and Groves, 2013 ; Edlund et al, 2014 ; Birol et al, 2016 ; Ankamreddy et al, 2023 ), and they are required for correct formation of the pharyngeal arch structures ( Solomon et al, 2003a ; Nissen et al, 2003 ; Edlund et al, 2014 ). Interestingly, FoxI and Six orthologues are also expressed in the branchial fissures (stigmata) of the tunicate atrium where peribranchial and branchial epithelium contact each other and fuse ( Gasparini et al, 2013b ).…”