|Ph.D Student||Lugassy Yevgenia|
|Subject||Genetic Basis of Cornification Disorders|
|Department||Department of Medicine||Supervisors||Mr. Eli Sprecher|
|Professor Reuven Bergman|
|Full Thesis text|
Cornification disorders are classified as non-syndromic and syndromic diseases and are including ARCI, NFJS/DPR and CEDNIK syndromes.
ARCI represents a non - syndromic cornification disorder. We ascertained four ACRI families of Iranian, Druze and Mouslim origins. Exploiting the high degree of consanguinity, we typed all family members for microsatellite markers spanning the major ACRI chromosomal loci and used homozygosity mapping to identify candidate genes for subsequent mutational analysis. This strategy led to the rapid identification of three novel homozygous CRI-causing mutations in TGM1, FLJ39501 and ALOX12B.
NFJS/DPR are two closely related autosomal dominant ectodermal dysplasia syndromes. Combined multipoint of six families affected with NFJS/DPR syndromes analysis generated a maximal LOD score of 8.3 at marker D17S800 at a recombination fraction of 0 on 17q11.2-q21. We identified a total of 4 different heterozygous nonsense or frameshift mutations (Q7X, 17delG, 26delC, C18X) affecting the nonhelical head (E1/V1) domain of KRT14, which were predicted to result in very early termination of translation. Performing a modified quantitative fluorescent PCR-RFLP assay, Western analysis and cell culture experiments we demonstrated that the new mutations result in haploinsufficiency of keratin 14. Basal cell layer of the patients was characterized with increased apoptotic activity. Reduction of KRT14 expression by 50% and exposure to 2 ng/ml recombinant TNF-alpha, the number of TUNEL-positive cells increased from 32% to 96%. Therefore, decreased KRT14 expression is associated with increased susceptibility of keratinocytes to pro-apoptotic signals which may be involved in the pathogenesis of this ectodermal dysplasia syndrome.
CEDNIK syndrome is caused by mutations in SNAP29, which expression was decreased in the skin of the patients, resulting in abnormal maturation of lamellar granules and mislocation of epidermal lipids and proteases. We demonstrated that SNAP29 is co-localizing with glucosyltransferase, a marker for trans-golgi, and Cathepsin D, a marker for lamellar granules. Our results suggest that SNAP29 is upregulated by PPAR- γ, PPAR-β/δ and RXR pathways. Activation of PPARs has been shown to stimulate keratinocyte differentiation, formation of the cornified envelope, stimulation of LB secretion, epidermal lipid synthesis, and lipid processing in the stratum corneum. This data is accentuating the essential role of SNAP29 in the cornification process and in vesicle trafficking regulatory mechanisms.
Our data provide a paradigm illustrating the power of a combined genetic and functional cell biological approach for the deciphering of the mechanisms underlying physiological and pathological epidermal cornification.