Northern analysis of gene expression.

Northern analysis detects and quantitates full-length RNA transcripts by hybridizing a labeled sequence-specific probe to RNA fractionated by size and blotted onto a membrane. The first step in Northern analysis is RNA extraction from the tissue(s) of interest, followed by RNA denaturation and electrophoresis to separate all RNA transcripts in the tissue by size. The size-fractionated RNA is then transferred (blotted) onto a membrane. The membrane is incubated with a labeled probe complementary to the sequence of interest. Stringent washing removes nonspecifically bound probe and leaves labeled probe bound specifically to the transcript(s) of interest on the membrane. Northern analysis provides information on gene transcript sizes and abundance and the presence of alternative splice variants or transcription initiation sites. Northern analysis can also confirm the presence or absence of specific exons within a given transcript. The method is medium throughput, as multiple samples can be analyzed side by side with relatively little effort. Finally, any potential PCR amplification artifacts are completely avoided using this methodology. Northern analysis offers a unique view of a gene's transcripts and provides novel insight into gene expression.