An <i>Ift140</i> mutation is responsible for the ciliopathic phenotype observed in <i>cauli</i>.

<p>Representative E13.5 wildtype (A) and mutant (B) embryos showing exencephaly (black arrowhead), open mouth (white arrowhead), polydactyly (asterisks) and caudal neural tube closure defects (arrow) in mutants. Chromatogram of <i>cauli</i> mutant showing the homozygous missense mutation (c.2564T&gt;A) in the Intraflagellar Transport Protein 140 (<i>Ift140</i>) gene (C). IFT140 protein alignment showing the isoleucine to lysine substitution at position 855 of the protein in <i>cauli</i> and the corresponding amino acid across several species (D). Schematic of the IFT140 protein detailing protein domains, location of <i>Ift140^cauli/cauli</i> mutation and reported human mutations (E). Mainzer-Saldino (black), Jeune asphyxiating thoracic dystrophy (red), ⁺compound heterozygous, ^#homozygous ^∧no second mutation identified. Black box represents mutation reported in this paper. Primary cilia from E10.5 <i>Ift140^+/+</i> (F) and <i>Ift140^cauli/cauli</i> (G) limb buds show a severely altered cilia morphology in the mutant.</p

Molecular signalling is disturbed in <i>Ift140^cauli/cauli</i> embryos.

<p>WISH analysis of the forelimbs and hindlimbs of <i>Ift140^+/+</i> and <i>Ift140^cauli/cauli</i> embryos. Dorsal view of fore- and hindlimb buds (A–J′), where anterior is always to the top of the image. Distal view of forelimb buds (K′–M′), where dorsal side is facing to the right of the image. Arrowhead in (C) indicates ectopic <i>Shh</i> expression domain. Bars in (J,L and M′,N′) indicate anterior-posterior extent of <i>Grem1</i> expression. Arrowhead in (K) indicates disruption in <i>Grem1</i> expression in mutant forelimb. Asterisk in (W and X) indicates elevated anterior <i>Dusp6</i> expression. Arrow, arrowhead and asterisk in J′ indicate a single ectopic digit, bifid ectopic digit and proximal syndactyly respectively. A, anterior; P, posterior; D, dorsal; V, ventral; FL, forelimb; HL, hindlimb. All embryos are E11.5 except G′–J′ which are E13.5.</p

<i>Ift140^cauli/cauli</i> embryos exhibit skeletal, somite and neural tube defects.

<p>Morphological and expression analysis of <i>Ift140^+/+</i> and <i>Ift140^cauli/cauli</i> embryos. Lateral view of E16.5 skull in <i>Ift140^+/+</i> (A) and <i>Ift140^cauli/cauli</i> (B) embryos. <i>Ift140^cauli/cauli</i> embryos exhibit fusion of the exoccipital bone and C1/C2 vertebrae (arrow in B). Ventral view of skull base in <i>Ift140^+/+</i> (C) and <i>Ift140^cauli/cauli</i> (D) embryos. <i>Ift140^+/+</i> (E) and <i>Ift140^cauli/cauli</i> (F) mandibles. The normal organisation of the ribs seen in E16.5 <i>Ift140^+/+</i> embryos (G) is severely disrupted in <i>Ift140^cauli/cauli</i> (H) with lateral branching (asterisk), thickened ossified nodules (red arrow) and abnormal costovertebral articulations (red arrowhead). (I–P) <i>In situ</i> hybridisation of gene expression patterns of <i>myogenin</i> (I–L), <i>Msx1</i> (M,N) and <i>Sox9</i> (O,P). <i>Myogenin</i> staining at E11.5 reveals the highly ordered segmental structure of a <i>Ift140^+/+</i> embryo (I) while in the <i>Ift140^cauli/cauli</i> embryo (J) <i>myogenin</i> staining reveals the presence of disorganised and branched somite-derived structures (myotome; arrow). (K,L) Sections of wholemount embryos at the level indicated by the horizontal line in I and J, illustrating the loss of segmental <i>myogenin</i> staining and the accumulation of blood within distorted and irregular intersomitic vessels (arrowheads) in <i>Ift140^cauli/cauli</i> embryos. (M,N) <i>Msx1</i> expression delineates the dorsal margin of the neural tube in an E11.5 <i>Ift140^+/+</i> embryo (M) but highlights the disrupted neural tube structure in an <i>Ift140^cauli/cauli</i> embryo (arrowhead in N). In addition, the neural tube is convoluted and irregular in appearance, as shown in E12.5 embryos stained for <i>Sox9</i> (arrow in P). PMX, premaxilla; MD, mandible; MX, maxilla; P, palatine; PP, palatal process; AL, alisphenoid; BS, basisphenoid; TR, tympanic ring; BO, basioccipital; EX, exoccipital; C1/C2, fused 1^st and 2^nd cervical vertebrae.</p