Fig. 1

Morphogenesis and polarity of pharyngeal cartilages.

(A–B): First (A) and last (B) time points of an 8 hour time-lapse movie of the first pharyngeal arch in a sox10:lyn-tdTomato transgenic, lateral view, anterior to the left. These frames show changes in cell shape and organization in presumptive palatoquadrate (pq) (A′ and B′) and Meckels (Mc) (A′′ and B′′) between 48 and 56 hpf. Arrowheads point to presumptive joint. (C). Color tracking of selected pq and Mc cells in the time lapse shown at 2 hour intervals. Asterisks denote medio-laterally intercalating cells. (D–G): Polarity dynamics during cartilage morphogenesis. Embryos stained for cortical actin with phalloidin (red) to reveal cell outlines, and anti-acetylated tubulin (white). (D) sox10:eGFP fluorescence first appears in differentiating chondrocytes of presumptive pq by 48 hpf, and in Mc by 54 hpf (E). (D′, D′′, E′, E′′) MTOCs of intercalating cells localize towards the center of the condensation. (F, F2₁, F′′₁, F′₂, F′′₂) Stable cell arrangement and polarity patterns are achieved by 66 hpf. (G) Polarity map of cartilages in pharyngeal arches 1–3 at 66 hpf, illustrated in lateral view, anterior to the left. (H–J) Polarity pattern in the e13.5 mouse Mc. (H) Alcian Blue stained e13.5 mouse head showing regions of Mc assayed for polarity. (I) proximal Mc is polarized ventrally, while distal Mc is polarized dorsally (J). Scale bar = 21µl;m. Mc: Meckel′s; pq: palatoquadrate; PA: pharyngeal arch. Hm: hyosymplectic; ih: interhyal; ch: ceratohyal; bh: basihyal; cb1: ceratobranchial1; hb1: hypobranchial1; bb1: basibranchial.