Cauli: a mouse strain with an Ift140 mutation that results in a skeletal ciliopathy modelling jeune syndrome

Cilia are architecturally complex organelles that protrude from the cell membrane and have signalling, sensory and motility functions that are central to normal tissue development and homeostasis. There are two broad categories of cilia; motile and non-motile, or primary, cilia. The central role of primary cilia in health and disease has become prominent in the past decade with the recognition of a number of human syndromes that result from defects in the formation or function of primary cilia. This rapidly growing class of conditions, now known as ciliopathies, impact the development of a diverse range of tissues including the neural axis, craniofacial structures, skeleton, kidneys, eyes and lungs. The broad impact of cilia dysfunction on development reflects the pivotal position of the primary cilia within a signalling nexus involving a growing number of growth factor systems including Hedgehog, Pdgf, Fgf, Hippo, Notch and both canonical Wnt and planar cell polarity. We have identified a novel ENU mutant allele of Ift140, which causes a mid-gestation embryonic lethal phenotype in homozygous mutant mice. Mutant embryos exhibit a range of phenotypes including exencephaly and spina bifida, craniofacial dysmorphism, digit anomalies, cardiac anomalies and somite patterning defects. A number of these phenotypes can be attributed to alterations in Hedgehog signalling, although additional signalling systems are also likely to be involved. We also report the identification of a homozygous recessive mutation in IFT140 in a Jeune syndrome patient. This ENU-induced Jeune syndrome model will be useful in delineating the origins of dysmorphology in human ciliopathies

Cauli: a mouse strain with an Ift140 mutation that results in a skeletal ciliopathy modelling Jeune syndrome

Cilia are architecturally complex organelles that protrude from the cell membrane and have signalling, sensory and motility functions that are central to normal tissue development and homeostasis. There are two broad categories of cilia; motile and non-motile, or primary, cilia. The central role of primary cilia in health and disease has become prominent in the past decade with the recognition of a number of human syndromes that result from defects in the formation or function of primary cilia. This rapidly growing class of conditions, now known as ciliopathies, impact the development of a diverse range of tissues including the neural axis, craniofacial structures, skeleton, kidneys, eyes and lungs. The broad impact of cilia dysfunction on development reflects the pivotal position of the primary cilia within a signalling nexus involving a growing number of growth factor systems including Hedgehog, Pdgf, Fgf, Hippo, Notch and both canonical Wnt and planar cell polarity. We have identified a novel ENU mutant allele of Ift140, which causes a mid-gestation embryonic lethal phenotype in homozygous mutant mice. Mutant embryos exhibit a range of phenotypes including exencephaly and spina bifida, craniofacial dysmorphism, digit anomalies, cardiac anomalies and somite patterning defects. A number of these phenotypes can be attributed to alterations in Hedgehog signalling, although additional signalling systems are also likely to be involved. We also report the identification of a homozygous recessive mutation in IFT140 in a Jeune syndrome patient. This ENU-induced Jeune syndrome model will be useful in delineating the origins of dysmorphology in human ciliopathies

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

An <i>IFT140</i> mutation identified in a Jeune Syndrome patient.

<p>Family pedigree showing the relationship between JS1-1, JS 1-2, JS 1-3 and JS 1-4 (A; red arrow indicates the proband). Whole body (B), right (C) and left (D) upper limb and feet (E) radiographs from JS1-1. Note the short ribs, short long bones with bowed humeri and femora, “trident” appearance of the acetabular roofs and metaphyseal irregularity (B), short long bones with metaphyseal cupping and bowed humerus (C and D), and metaphyseal cupping and advanced tarsal bone ossification for age (E). A, acetabulum; F, femur; H, humerus; T, tarsus. Sequence chromatogram identifying the C&gt;T homozygous mutation in JS1-1 (F; arrow), and heterozygous mutation in immediate family members.</p

<i>Ift140^cauli/caul</i> mutants show palate defects, hydrops fetalis and malformation of the lungs and heart.

<p>Coronal sections of E13.5 <i>Ift140^+/+</i> (A) and <i>Ift140^cauli/cauli</i> (B) palates, highlighting hypoplastic palatal shelves in <i>Ift140^cauli/cauli</i> embryos. Transverse sections of E13.5 <i>Ift140^+/+</i> (C and E) and <i>Ift140^cauli/cauli</i> (D and F) embryos at the level of the kidneys (C and D) and heart (E and F). <i>Ift140^cauli/cauli</i> mutant embryos have grossly normal kidneys but show accumulation of fluid around the kidneys and lungs (asterisks in D and F), which is not evident in <i>Ift140^+/+</i> controls (C and E). The lungs of <i>Ift140^cauli/cauli</i> embryos are also abnormal in shape (F), unlike the cone-shaped lobes seen in <i>Ift140^+/+</i> controls (E). The atrioventricular valves of the heart are well formed in <i>Ift140^+/+</i> embryos (E), but both the tricuspid and mitral valves are abnormal in <i>Ift140^cauli/cauli</i> mutants (F). <i>Ift140^cauli/cauli</i> embryos appear to have ventricular hypotrophy and the interventricular septum is not well formed (depicted by dashed line in F). An irregular accumulation of blood can also be seen in the atria and ventricles of <i>Ift140^cauli/cauli</i> mutants (F). T, tongue; PS, palatal shelf; K, kidneys; L, lung; RA, right atrium; RV, right ventricle; TV, tricuspid valve; MV, mitral valve.</p

Oligonucleotide primers used in PCR.

<p>Oligonucleotide primers used in PCR.</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