Fig. 4

Pax1a and Pax1b have redundant function in regulating pharyngeal cartilage development. Mandibular pharyngeal arch 1 (Meckel's cartilage (m) and palatoquadrate (pq)), hyoid pharyngeal arch 2 (hyosymplectic (hs), interhyal (ih), ceratohyal (ch)) and five branchial arches (ceratobranchial (cb), hypobranchial (hb) and basibranchial (bb)) were identified in Alcian blue-stained wild types (A) and embryos injected with 0.75 ng each of 5 mm pax1a MO and 5 mm pax1b MO (B) at 96 hpf are shown. Mild pharyngeal cartilage defect (C, shortened cb 2–3, lack of cb 1 and 4 on one side and lack of cb1 on the other side) and two types of severe cartilage defects (D, straightened ch, shortened cb 2–3, lack of cb 1 and 4 on one side and lack of cb1–4 on the other side; E, reversed ch and lack of cb 1–4 on both sides) were detected in respective embryos injected with 1.5 ng pax1a MO (MOa), 10 ng pax1b MO (MOb), or 0.75 ng of both pax1a MO and pax1b MO. The majority of embryos injected with suboptimal dose (0.75 ng) of both pax1a MO and pax1b MO exhibited severe pharyngeal cartilage defects, while embryos injected with 1.5 ng pax1a MO or 10 ng pax1b MO showed less frequent severe phenotypes (F, G). Number of embryos for various treatment is shown under the x-axis. Brackets indicate lack of cb1–4. Scale bar represents 100 μm.