%0 Generic
%A Juanes, Silvia de
%D 2009
%F heidok:9425
%K Lipoxygenase , Skin differentation , Skin graft
%R 10.11588/heidok.00009425
%T 12R-Lipoxygenase deficient mouse skin models for autosomal recessive congenital ichthyosis
%U https://archiv.ub.uni-heidelberg.de/volltextserver/9425/
%X 12R-lipoxygenase (12R-LOX) and epidermal LOX-3 (eLOX-3) are part of a recently identified eicosanoid pathway critically involved in skin terminal differentiation. Inactivating mutations in the genes of 12R-LOX and eLOX-3 are causally linked to the development of autosomal recessive congenital ichthyosis (ARCI). ARCI is an inherited skin disease associated with hyperkeratosis and impaired barrier function. To analyse the impact of 12R-LOX in epidermal barrier function and to investigate its physiological role a Cre-LoxP based mouse model for the targeted inactivation of 12R-LOX was generated in a previous study. Constitutive ablation of 12R-LOX leads to early neonatal death due to a severely impaired permeability barrier function. Disruption of barrier function is associated with ultrastructural anomalies in the upper granular layers, disordered composition of ester-bound ceramide species and impairment of profilaggrin processing but does not result in the development of a typical ichthyosiform phenotype in the neonatal skin. The main focus of this thesis was to characterize the adult phenotype of 12RLOX deficient skin by establishing skin grafts and conditional knockout models. When transplanted onto the back of nude mice 12R-LOX-/- mouse skin developed a severe adult phenotype that closely resembles that seen in ichthyosis patients, with thickening of the epidermis, hyperproliferation, hypergranulosis, focal parakeratosis and marked hyperkeratosis. In contrast to the neonatal knockout phenotype, 12R-LOX deficiency did not affect profilaggrin processing in the adult transplanted skin but rather resulted in the over-expression of fully processed filaggrin monomers and other components of the cornified cell envelope such as involucrin and repetin. In order to study the adult phenotype in more detail we established a temporally-controlled site-specific 12R-LOX knockout model by using a transgenic mouse line expressing a tamoxifen-dependent Cre recombinase under the control of the Keratin 14 promoter. In these Alox12bfl/fl/K14-Cre-ERT2 (mutant) mice, Cre-mediated Alox12b inactivation was detected upon tamoxifen treatment but also spontaneously as early as day 17 after birth in K14-expressing tissues such as epidermis, tongue, cornea and thymus. 12R-LOX ablation resulted in the development of a severe phenotype associated with growth retardation, dramatic loss of body weight and premature death. Morphological changes observed in mutant mice included focal alopecia, scaling of the skin and palmoplantar keratoderma. Histological analyses of skin biopsies confirmed the development of an ichthyosiform phenotype mimicking that observed in ichthyosis patients. Comparative gene expression profiling to identify disease-related downstream targets of the 12R-LOX/eLOX-3 pathway showed that 12R-LOX ablation is associated with deregulation of members of the activating protein-1, small proline rich protein and keratin gene families, known to be important for the epidermal differentiation. This data documents a crucial role of 12R-LOX in the establishment and maintenance of the epidermal barrier function. Moreover, 12R-LOX knockout mice may be a suitable model to investigate molecular mechanisms of the LOX pathway related to diseased phenotype as well as for the development of novel strategies towards a therapy for ARCI forms associated with impaired LOX metabolism.