LAMELLAR ICHTHYOSIS IS GENETICALLY HETEROGENEOUS - CASES WITH NORMAL KERATINOCYTE TRANSGLUTAMINASE

We recently identified mutations of the keratinocyte transglutaminase gene as a cause of lamellar ichthyosis, In this study we analyzed two sporadic: cases of lamellar ichthyosis. Transglutaminase activity meas ured in membrane extracts from cultured differentiating keratinocytes was within the range observed in normal individuals. Western blot and Northern blot analysis revealed normal size and quantities of keratino cyte transglutaminase protein and mRNA. Sequencing of the 15 exons and their flanking regions demonstrated no deviation from the published s equence except for two silent polymorphisms. These results exclude mut ations of keratinocyte transglutaminase as a cause for lamellar ichthy osis in these patients, indicating that lamellar ichthyosis is a genet ically heterogeneous disorder.