Two type XVII collagen (BP180) mRNA transcripts in human keratinocytes:a long and a short form

We have analysed BP180 mRNA expression in normal human keratinocytes. Here we report the presence in normal keratinocytes of two COL17A1 transcripts which differ by 0.6 kb in length. Both mRNAs hybridized on Northern blot with probes directed to sequences encoding intracellular and extracellular fragments of BP180. By blast homology search alignments we extended the 3' untranslated region (3'UTR) of the known BP180 mRNA sequence by 877 bases to completion. Three of 20 cDNAs identified by blast searches contained a 610 bp deletion in this new 3'UTR sequence. Northern blot analysis with a probe complementary to this deleted sequence showed binding only to the larger mRNA. The deletion of 610 nucleotides in the smaller mRNA was verified by reverse transcription-PCR and sequencing. Genomic PCR showed the new sequence to be an extension of exon 56 of the COL17A1 gene which suggests that the second mRNA is generated by differential splicing. In normal keratinocytes the level of the smaller transcript was 5-15% of that of the larger transcript whereas in a squamous cell carcinoma cell line this ratio was reversed, the smaller mRNA being three times more abundant than the larger mRNA. The biological significance of this newly identified transcript in protein synthesis and tissue expression or in cell differentiation, proliferation or adhesion is as yet unknown

Two type XVII collagen (BP180) mRNA transcripts in human keratinocytes:a long and a short form

We have analysed BP180 mRNA expression in normal human keratinocytes. Here we report the presence in normal keratinocytes of two COL17A1 transcripts which differ by 0.6 kb in length. Both mRNAs hybridized on Northern blot with probes directed to sequences encoding intracellular and extracellular fragments of BP180. By blast homology search alignments we extended the 3' untranslated region (3'UTR) of the known BP180 mRNA sequence by 877 bases to completion. Three of 20 cDNAs identified by blast searches contained a 610 bp deletion in this new 3'UTR sequence. Northern blot analysis with a probe complementary to this deleted sequence showed binding only to the larger mRNA. The deletion of 610 nucleotides in the smaller mRNA was verified by reverse transcription-PCR and sequencing. Genomic PCR showed the new sequence to be an extension of exon 56 of the COL17A1 gene which suggests that the second mRNA is generated by differential splicing. In normal keratinocytes the level of the smaller transcript was 5-15% of that of the larger transcript whereas in a squamous cell carcinoma cell line this ratio was reversed, the smaller mRNA being three times more abundant than the larger mRNA. The biological significance of this newly identified transcript in protein synthesis and tissue expression or in cell differentiation, proliferation or adhesion is as yet unknown

The use of skin substrates deficient in basement membrane molecules for the diagnosis of subepidermal autoimmune bullous disease

A case is presented of subepidermal, autoimmune bullous disease in which the initial examinations suggested the combination of epidermolysis bullosa acquisita and bullous pemphigoid. The diagnosis of epidermolysis bullosa acquisita was made by indirect immunofluorescence microscopy: the patient's serum bound to normal skin substrate but not to type VII collagen-deficient skin substrate derived from a patient with mutilating dystrophic epidermolysis bullosa. The use of skin substrates deficient in basement membrane molecules also excluded the presence of concomitant, circulating bullous pemphigoid autoantibodies in our patient. The diagnosis of epidermolysis bullosa acquisita was confirmed by split mapping, fluorescence overlay antigen mapping and Western blot