Housekeeping Genes

What is a housekeeping gene?  Theoretically, these are genes that are constantly expressed in cells, whose expression is not altered by treatment with any chemical.  By choosing an appropriate housekeeping gene, one hopes to find a baseline upon which the expression of other genes can be tested.  In other words, a housekeeping gene is an internal loading control for cDNA added to the PCR reaction. 

Of course, even the best housekeeping genes are affected by some treatments.  Therefore, it is important to use multiple housekeeping genes to examine your changes in gene expression.  Choosing a combination of ribosomal RNA and genomic transcripts can provide the best results.  For example, I often use actin, GAPDH, and 18S-rRNA. 

See this guide for an in-depth analysis of the expression of various housekeeping genes in mouse brain tissue.