An intron capture strategy used to identify and map a lysyl oxidase-like gene on chromosome 9 in the mouse

Loss of lysyl oxidase-like 3 causes cleft palate and spinal deformity in mice

In mammals, embryonic development are highly regulated morphogenetic processes that are tightly controlled by genetic elements. Failure of any one of these processes can result in embryonic malformation. The lysyl oxidase (LOX) family genes are closely related to human diseases. In this study, we investigated the essential role of lysyl oxidase-like 3 (LOXL3), a member of the LOX family, in embryonic development. Mice lacking LOXL3 exhibited perinatal lethality, and the deletion of the Loxl3 gene led to impaired development of the palate shelves, abnormalities in the cartilage primordia of the thoracic vertebrae and mild alveolar shrinkage. We found that the obvious decrease of collagen cross-links in palate and spine that was induced by the lack of LOXL3 resulted in cleft palate and spinal deformity. Thus, we provide critical in vivo evidence that LOXL3 is indispensable for mouse palatogenesis and vertebral column development. The Loxl3 gene may be a candidate disease gene resulting in cleft palate and spinal deformity.

LOXL null mice demonstrate selective dentate structural changes but maintain dentate granule cell and CA1 pyramidal cell potentiation in the hippocampus

Lysyl oxidase-like protein (LOXL), part of the lysyl oxidase copper-dependent amine oxidase family, is expressed in the extracellular matrix and in the nucleus. It likely plays a role in cross-linking collagen and elastin, possibly modulating cellular functions. Immunohistochemical studies show the presence of LOXL in the pyramidal cell layer of the hippocampus; and in this study, we report that cells in the granule cell layer have significantly smaller somas in LOXL -/- compared to LOXL +/+ mice. In addition we tested the hypothesis that these structural alterations in the dentate granule layer were associated with synaptic efficacy and thus muted long-term potentiation in mice lacking the protein. Electrical recordings were obtained in 300-mum hippocampal slices in dentate and CA1 pyramidal cell layers in age-matched wild type and LOXL null mice. Potentiation in the CA1 cell layer of 10 LOXL -/- and 8 LOXL +/+ mice was 191.0+/-9.3% and 181.6+/-9.1%, respectively (mean+/-S.E.M.). Dentate potentiation was 120.8+/-7.0% and 121.0+/-3.4% in 11 LOXL -/- and 11 LOXL +/+ mice, respectively. No phenotypic difference in potentiation of population spike amplitude (or in EPSP slope) in either layer was observed. Thus, contrary to expectation, structural changes in the hippocampus of LOXL -/- mice did not affect synaptic remodeling in a manner that impaired the establishment of LTP.

Progressive hair loss and myocardial degeneration in rough coat mice: reduced lysyl oxidase-like (LOXL) in the skin and heart

The rough coat (rc) is a spontaneous recessive mutation in mice. To identify the mutated gene, we have characterized the rc phenotype and initiated linkage mapping. The rc mice show growth retardation, cyclic and progressive hair loss, hyperplastic epidermis, abnormal hair follicles, cardiac muscle degeneration, and reduced amount of collagen and elastin in the skin and heart. The rc locus was mapped at 32.0 cM on chromosome 9, close to the loxl gene. Lysyl oxidase-like (LOXL) protein is a novel copper-containing amine oxidase that is required for the cross-linking of elastin and collagen in vitro. LOXL is expressed at high levels in the skin and heart, where the rc mice show strong phenotype. The expression pattern and the genetic proximity to rc suggested loxl as a potential candidate gene. In rc mice, the loxl mRNA was reduced in the skin and the LOXL protein in the heart, dermis, atrophic hair follicles, and sebaceous glands. No mutations, however, were identified within the coding region of loxl, and offspring from rc/rc and loxl null mice crossing were phenotypically normal. Based on these results, loxl appears non-allelic to rc. Heart- and skin-specific downregulation of LOXL in rc mice, however, may contribute to the extracellular matrix alterations and the rc phenotype.

Lysyl oxidase is required for vascular and diaphragmatic development in mice

Lysyl oxidase (LOX) is an enzyme responsible for the cross-linking of collagen and elastin both in vitro and in vivo. The unique functions of the individual members of this multigene family have been difficult to ascertain because of highly conserved catalytic domains and overlapping tissue expression patterns. To address this problem of functional and structural redundancy and to determine the role of LOX in the development of tissue integrity, Lox gene expression was deleted by targeted mutagenesis in mice. Lox-targeted mice (LOX(-/-)) died soon after parturition, exhibiting cardiovascular instability with ruptured arterial aneurysms and diaphragmatic rupture. Microscopic analysis of the aorta demonstrated fragmented elastic fiber architecture in homozygous mutant null mice. LOX activity, as assessed by desmosine (elastin cross-link) analysis, was reduced by approximately 60% in the aorta and lungs of homozygous mutant animals compared with wild type mice. Immature collagen cross-links were decreased but to a lesser degree than elastin cross-links in LOX(-/-) mice. Thus, lysyl oxidase appears critical during embryogenesis for structural stability of the aorta and diaphragm and connective tissue development.