[Show abstract][Hide abstract] ABSTRACT: Citrullinemia type I (CTLN1, OMIM# 215700) is an inherited urea cycle disorder that is caused by an argininosuccinate synthetase (ASS) enzyme deficiency. In this report, we describe two spontaneous hypomorphic alleles of the mouse Ass1 gene that serve as an animal model of CTLN1. These two independent mouse mutant alleles, also described in patients affected with CTLN1, interact to produce a range of phenotypes. While some mutant mice died within the first week after birth, others survived but showed severe retardation during postnatal development as well as alopecia, lethargy, and ataxia. Notable pathological findings were similar to findings in human CTLN1 patients and included citrullinemia and hyperammonemia along with delayed cerebellar development, epidermal hyperkeratosis, and follicular dystrophy. Standard treatments for CTLN1 were effective in rescuing the phenotype of these mutant mice. Based on our studies, we propose that defective cerebellar granule cell migration secondary to disorganization of Bergmann glial cell fibers cause cerebellar developmental delay in the hyperammonemic and citrullinemic brain, pointing to a possible role for nitric oxide in these processes. These mouse mutations constitute a suitable model for both mechanistic and preclinical studies of CTLN1 and other hyperammonemic encephalopathies and, at the same time, underscore the importance of complementing knockout mutations with hypomorphic mutations for the generation of animal models of human genetic diseases.
Full-text · Article · Oct 2010 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: The recessive mutation oligotriche (olt) affects the coat and male fertility in the mouse. In homozygous (olt/olt) mutants, the coat is sparse, most notably in the inguinal and medial femoral region. In these regions, almost all hair shafts are bent and distorted in their course through the dermis and rarely penetrate the epidermis because the hair cortex is not fully keratinized. During hair follicle morphogenesis, mutant hair follicles exit from anagen one day before those of normal littermates and show a prolongation of the catagen stage. The oligotriche (olt) locus was mapped to distal chromosome 9 within a 5-Mbp interval distal to D9Mit279. Analysis of candidate gene expression revealed that olt/olt mutant mice do not express functional phospholipase C delta 1 (Plcd1) mRNA. This deficiency is the consequence of a 234-kbp deletion involving not only the Plcd1 locus but also the chromosomal segment harboring the genes Vill (villin-like), Dlec1 (deleted in lung and esophageal cancer 1), Acaa1b (acetyl-Coenzyme A acyltransferase 1B, synonym thiolase B), and parts of the genes Ctdspl (carboxy-terminal domain RNA polymerase II polypeptide A small phosphatase-like) and Slc22a14 (solute carrier family 22 member 14). Offspring of olt/olt females, mated with Plcd1
knockout males, exhibit coat defects similar to those observed in homozygous olt/olt mutant mice but the spermiogenesis in male offspring is normal. We conclude that the 234-kbp deletion from chromosome 9 harbors a gene involved in spermiogenesis and we propose that the oligotriche mutant be used as a model for the study of the putative tumor suppressor genes Dlec1, Ctdspl, and Vill. We also suggest that the oligotriche locus be named Del(9Ctdspl-Slc22a14)1Pas.
[Show abstract][Hide abstract] ABSTRACT: e have identified (by chemical analysis) and mapped (at the ultrastructural level) the phospholipids present in enamel and dentin. Analysis of the data obtained suggests that, as matrix extracellular (MEC) components, phospholipids play important functions not only during the formation of dental tissues, but also in mineralization processes (Goldberg et al., 1983; Goldberg and Boskey, 1996; Goldberg and Septier, 2002). Nevertheless, we were still looking to substantiate what was perhaps a matter of faith regarding the role of lipids, when finally we met the fro/fro mouse. Lipids play major biological roles as components of cell membranes. As components of the extracellular matrix (ECM) of mineralized tissues, lipids have been infrequently studied. Their presence is now well-recognized, but their role in biological and pathological mineralization is far from clear. In dental tissues, the total lipid content is 0.26-0.36% in dentin, 0.014% of which is phospholipids, and 0.60% in enamel, among which 12.5% is phospholipids (0.075% of total enamel) (Goldberg and Boskey, 1996). Compared with the major dentin ECM components, namely, the phosphorylated proteins of the SIBLING family, lipids appear as minor components. Due to the low ratio between lipids and the total ECM molecules, and because of the fact that the major part of the lipid fraction is lost after routine fixation and processing for light and electron microscopy, lipids have been investigated less than have other matrix components easier to preserve and analyze.
No preview · Article · Jan 2008 · Journal of Dental Research
[Show abstract][Hide abstract] ABSTRACT: The mouse mutation fragilitas ossium (fro) leads to a syndrome of severe osteogenesis and dentinogenesis imperfecta with no detectable collagen defect. Positional cloning of the locus identified a deletion in the gene encoding neutral sphingomyelin phosphodiesterase 3 (Smpd3) that led to complete loss of enzymatic activity. Our knowledge of SMPD3 function is consistent with the pathology observed in mutant mice and provides new insight into human pathologies.
[Show abstract][Hide abstract] ABSTRACT: Our objective was to study the teeth of a mutant mice fro/fro that display severe forms of osteogenesis imperfecta. One day and 8 week-old fro/fro and +/fro heterozygote mice (wild type, WT) were processed for light and scanning electron microscopy. The genetic defect, shown to be located on chromosome 8, induced alveolar bone and teeth hypomineralisation. Due to defective cell proliferation in the fro/fro, the distal growth of the mandibular incisors was impaired. Immunolabelling revealed an increase of chondroitin/dermatan sulphate, whereas no difference was detected in dental tissues for decorin and biglycan. Amelogenin expression was decreased in the incisor and enhanced in the molar. Dentin sialoprotein was below the level of detection in the fro/fro, whereas osteonectin and osteopontin were unchanged. The main target of the mutation was seen in the lingual part of the incisor near the apex where dentine formation was delayed. In the molars, bulbous roots with obliteration of the pulp chamber were seen. In the TGFbeta1 overexpressing mice, the lingual root-analogue part of the incisor was missing. In the molar, short roots, circumpulpal dentine of the osteodentine type and pulp obliteration were seen. It may be noted that, although the mutant and transgenic strains mutations are two different genetic alterations not related to the same defective gene, in both cases the expression of the dentin sialoprotein is altered. Altogether, the present data suggest that the lingual forming part of the incisor seems to be an anatomical entity bearing its own biological specificities.
No preview · Article · Mar 2005 · Archives of Oral Biology