Mice lacking cyclin D1 are small and show defects in eye and mammary gland development.
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Using homologous recombination, mice lacking cyclin D1 were generated by replacing most of the first exon of the Cyl-1 gene with sequences encoding neomycin resistance. Cyl-1(-1-) mice were viable and fertile but consistently smaller than their heterozygous or wild-type littermates. The nullizygous animals also showed two distinctive abnormalities: a severe retinopathy caused by impaired development of all layers of the retina and, in the mammary gland during pregnancy, a marked reduction in acinar development accompanied by a failure to lactate. Approximately 50% of animals also had a malformation of the jaw that manifested itself as a misalignment of the incisor teeth. Mouse embryo fibroblasts isolated from 14 day nullizygous, heterozygous, or wild-type embryos and grown under standard conditions showed similar cell-cycle and growth characteristics. Thus although cyclin D1 kinase activity may facilitate G1 progression, it is not essential for the development of most tissues and organs, and only a few specialized cell lineages are demonstrably sensitive to its absence. (+info)
Mouse Otx2 functions in the formation and patterning of rostral head.
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The anterior part of the vertebrate head expresses a group of homeo box genes in segmentally restricted patterns during embryogenesis. Among these, Otx2 expression covers the entire fore- and midbrains and takes place earliest. To examine its role in development of the rostral head, a mutation was introduced into this locus. The homozygous mutants did not develop structures anterior to rhombomere 3, indicating an essential role of Otx2 in the formation of the rostral head. In contrast, heterozygous mutants displayed craniofacial malformations designated as otocephaly; affected structures appeared to correspond to the most posterior and most anterior domains of Otx expression where Otx1 is not expressed. The homo- and heterozygous mutant phenotypes suggest Otx2 functions as a gap-like gene in the rostral head where Hox code is not present. The evolutionary significance of Otx2 mutant phenotypes was discussed for the innovation of the neurocranium and the jaw. (+info)
Congenital abnormalities in newborn lambs after infection of pregnant sheep with Akabane virus.
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Akabane virus (a Bunyavirus) has been associated with epizootics of congenital deformities in cattle, sheep, and goats. Experimental studies using mouse-adapted virus inoculated intravenously into pregnant sheep gave an inapparent infection. Neutralizing antibodies were detected on day 5, and peaks in the titer were seen at days 10 and 48. Ewes infected at day 30 to 36 of pregnancy produced five (31% incidence) deformed lambs. Sera from four of these possessed neutralizing antibodies to Akabane virus before ingesting colostrum. Two lambs had arthrogryposis, hydranencephaly, kyphosis, scoliosis, and brachygnathia; one had micrencephaly; and the other two had porencephaly. The two lambs with arthrogryposis and hydranencephaly also had extensive lesions in other tissues. In the spinal cord there was a marked decrease in the number of ventral horn neurones and a depletion of myelin. Skeletal muscles showed marked atrophy. The medulla of the thymus possessed large Hassall's corpuscles and a reduced number of thymocytes in the cortex. It would appear that the pathogenic effects of Akabane virus are related to the gestational age (30 to 36 days) at which the fetus is infected. Akabane virus can now be included in the growing list of teratogenic viruses and provides an interesting system for studying such congenital diseases. (+info)
Two sibs with cleft palate, ankyloblepharon, alveolar synechiae, and ectodermal defects: a new recessive syndrome?
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Hay and Wells in 1976 reported seven patients from four families who had an inherited condition of which the main features were ankyloblepharon, ectodermal defects, and cleft lip and palate. The inheritance pattern was determined to be autosomal dominant. This condition is known as AEC syndrome or Hay-Wells syndrome. We report a family with two sibs showing some of these features and congenital adhesions between the upper and lower jaws (alveolar synechiae). There seems to be a recessive pattern of inheritance as neither of the parents has any features of the syndrome. This could be described as a recessive form of Hay-Wells syndrome with additional features or be named as a new syndrome. (+info)
Craniofacial morphology in young patients with Turner syndrome.
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The craniofacial morphology of 33 Turner syndrome patients, aged 7-16.7 years, was evaluated by standard cephalometric methods. The sample was subdivided according to karyotype and 72 normal girls aged 7.1-16.1 years served as controls. The size of the calvarium and face was generally smaller in the Turner group than in the controls. The morphology was characterized by a flattened cranial base angle, a marked reduction in posterior cranial base length, facial retrognathism and short and posteriorly rotated jaws. The same morphological pattern was found in all the karyotypes, but the deviations were most pronounced in monosomy X (45X) patients. The results indicate that a deviating pattern of craniofacial size and morphology has already been established in childhood. It is suggested that the deviations originate in the fetal period, when the primary cartilages form the craniofacial skeleton. (+info)
Anesthesia for maxillary and mandibular osteotomies in osteogenesis imperfecta.
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A 21-yr-old female suffering from osteogenesis imperfecta was anesthetized for correction of maxillary and mandibular deformities that had restricted her chewing. Preoperative assessment revealed a difficult intubation, restrictive lung disease secondary to bony deformities, and multiple repairs of fractures. Management of anesthesia for this operation--which is very rarely carried out in this disorder--is described along with a review of the problems of anesthesia associated with osteogenesis imperfecta. (+info)
Mutations affecting development of the zebrafish inner ear and lateral line.
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Mutations giving rise to anatomical defects in the inner ear have been isolated in a large scale screen for mutations causing visible abnormalities in the zebrafish embryo (Haffter, P., Granato, M., Brand, M. et al. (1996) Development 123, 1-36). 58 mutants have been classified as having a primary ear phenotype; these fall into several phenotypic classes, affecting presence or size of the otoliths, size and shape of the otic vesicle and formation of the semicircular canals, and define at least 20 complementation groups. Mutations in seven genes cause loss of one or both otoliths, but do not appear to affect development of other structures within the ear. Mutations in seven genes affect morphology and patterning of the inner ear epithelium, including formation of the semicircular canals and, in some, development of sensory patches (maculae and cristae). Within this class, dog-eared mutants show abnormal development of semicircular canals and lack cristae within the ear, while in van gogh, semicircular canals fail to form altogether, resulting in a tiny otic vesicle containing a single sensory patch. Both these mutants show defects in the expression of homeobox genes within the otic vesicle. In a further class of mutants, ear size is affected while patterning appears to be relatively normal; mutations in three genes cause expansion of the otic vesicle, while in little ears and microtic, the ear is abnormally small, but still contains all five sensory patches, as in the wild type. Many of the ear and otolith mutants show an expected behavioural phenotype: embryos fail to balance correctly, and may swim on their sides, upside down, or in circles. Several mutants with similar balance defects have also been isolated that have no obvious structural ear defect, but that may include mutants with vestibular dysfunction of the inner ear (Granato, M., van Eeden, F. J. M., Schach, U. et al. (1996) Development, 123, 399-413,). Mutations in 19 genes causing primary defects in other structures also show an ear defect. In particular, ear phenotypes are often found in conjunction with defects of neural crest derivatives (pigment cells and/or cartilaginous elements of the jaw). At least one mutant, dog-eared, shows defects in both the ear and another placodally derived sensory system, the lateral line, while hypersensitive mutants have additional trunk lateral line organs. (+info)