Ectopic Transcript Analysis in Human Antithrombin Deficiency

A number of reports have demonstrated that it is possible to identify correctly spliced low-level transcripts for tissue-specific genes in a number of non-specific tissues (1 –3 ). The number of transcripts is low (approx 1 copy every 500–1000 cells) (2 ), but as they are initiated at the normal mRNA start site this suggests that the normal promoters are used. Although ectopic transcript analysis has been used primarily in the study of large and complex genes, e.g., factor VIII, or for the study of splice-site mutations, the relative ease with which the technique can be adapted to the study of a variety of smaller genes and their mutations makes its use attractive for the study of a variety of inherited disorders. A limitation of the described method is that it will not detect mutations in the 3′ and 5′ untranslated regions of the gene and these areas will require analysis by conventional DNA-based techniques.