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

Female heterozygotes for the hypomorphic R40H mutation can have ornithine transcarbamylase deficiency and present in early adolescence: a case report and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Ornithine transcarbamylase deficiency is the most common hereditary urea cycle defect. It is inherited in an X-linked manner and classically presents in neonates with encephalopathy and hyperammonemia in males. Females and males with hypomorphic mutations present later, sometimes in adulthood, with episodes that are frequently fatal.</p> <p>Case presentation</p> <p>A 13-year-old Caucasian girl presented with progressive encephalopathy, hyperammonemic coma and lactic acidosis. She had a history of intermittent regular episodes of nausea and vomiting from seven years of age, previously diagnosed as abdominal migraines. At presentation she was hyperammonemic (ammonia 477 μmol/L) with no other biochemical indicators of hepatic dysfunction or damage and had grossly elevated urinary orotate (orotate/creatinine ratio 1.866 μmol/mmol creatinine, reference range <500 μmol/mmol creatinine) highly suggestive of ornithine transcarbamylase deficiency. She was treated with intravenous sodium benzoate and arginine and made a rapid full recovery. She was discharged on a protein-restricted diet. She has not required ongoing treatment with arginine, and baseline ammonia and serum amino acid concentrations are within normal ranges. She has had one further episode of hyperammonemia associated with intercurrent infection after one year of follow up. An R40H (c.119G>A) mutation was identified in the ornithine transcarbamylase gene (<it>OTC</it>) in our patient confirming the first symptomatic female shown heterozygous for the R40H mutation. A review of the literature and correspondence with authors of patients with the R40H mutation identified one other symptomatic female patient who died of hyperammonemic coma in her late teens.</p> <p>Conclusions</p> <p>This report expands the clinical spectrum of presentation of ornithine transcarbamylase deficiency to female heterozygotes for the hypomorphic R40H <it>OTC </it>mutation. Although this mutation is usually associated with a mild phenotype, females with this mutation can present with acute decompensation, which can be fatal. Ornithine transcarbamylase deficiency should be considered in the differential diagnosis of unexplained acute confusion, even without a suggestive family history.</p

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

<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

Variant non ketotic hyperglycinemia is caused by mutations in <i>LIAS</i>, <i>BOLA3</i> and the novel gene <i>GLRX5</i>

Patients with nonketotic hyperglycinemia and deficient glycine cleavage enzyme activity, but without mutations in AMT, GLDC or GCSH, the genes encoding its constituent proteins, constitute a clinical group which we call ‘variant nonketotic hyperglycinemia’. We hypothesize that in some patients the aetiology involves genetic mutations that result in a deficiency of the cofactor lipoate, and sequenced genes involved in lipoate synthesis and iron-sulphur cluster biogenesis. Of 11 individuals identified with variant nonketotic hyperglycinemia, we were able to determine the genetic aetiology in eight patients and delineate the clinical and biochemical phenotypes. Mutations were identified in the genes for lipoate synthase (LIAS), BolA type 3 (BOLA3), and a novel gene glutaredoxin 5 (GLRX5). Patients with GLRX5-associated variant nonketotic hyperglycinemia had normal development with childhood-onset spastic paraplegia, spinal lesion, and optic atrophy. Clinical features of BOLA3-associated variant nonketotic hyperglycinemia include severe neurodegeneration after a period of normal development. Additional features include leukodystrophy, cardiomyopathy and optic atrophy. Patients with lipoate synthase-deficient variant nonketotic hyperglycinemia varied in severity from mild static encephalopathy to Leigh disease and cortical involvement. All patients had high serum and borderline elevated cerebrospinal fluid glycine and cerebrospinal fluid:plasma glycine ratio, and deficient glycine cleavage enzyme activity. They had low pyruvate dehydrogenase enzyme activity but most did not have lactic acidosis. Patients were deficient in lipoylation of mitochondrial proteins. There were minimal and inconsistent changes in cellular iron handling, and respiratory chain activity was unaffected. Identified mutations were phylogenetically conserved, and transfection with native genes corrected the biochemical deficiency proving pathogenicity. Treatments of cells with lipoate and with mitochondrially-targeted lipoate were unsuccessful at correcting the deficiency. The recognition of variant nonketotic hyperglycinemia is important for physicians evaluating patients with abnormalities in glycine as this will affect the genetic causation and genetic counselling, and provide prognostic information on the expected phenotypic course