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Housekeeping genes are genes assumed to be expressed stably in every cell type and condition because they support basic cellular maintenance. In the lab they serve mainly as normalization controls for gene-expression measurements such as RT-qPCR. The assumption is a working hypothesis, not a guarantee: published analyses show that stable expression and essential function are separate properties, and that commonly used controls such as GAPDH can vary a lot between datasets.
Definition and scope
The classical definition, restated by Joshi et al. (2022), describes housekeeping genes as genes that are stably expressed irrespective of tissue type, developmental stage, cell cycle state or external signal, and that are essential for cellular existence regardless of their specific function in the tissue or organism. The same paper points out that this definition is axiomatic: it was assumed rather than tested, and there is no known biological basis for choosing a numerical threshold for how stable is stable enough. The authors propose that “housekeepingness” may be better treated as a continuous metric, and they use the Gini coefficient of expression across samples as a stability measure, where a low value marks a candidate housekeeping gene.
What is the function of housekeeping genes?
Housekeeping genes are defined by a maintenance role: they are involved in basic cell maintenance, which is why constant expression is expected (Eisenberg and Levanon, 2013). In practice, the working function for a bench scientist is different: a gene that behaves as a stable internal reference lets you benchmark and normalize expression results from qRT-PCR or transcriptomics (Joshi et al., 2022). For how those controls are chosen and validated in a qPCR workflow, see qPCR reference gene selection and validation.
Why use housekeeping genes in qPCR?
Expression of a gene of interest is only interpretable relative to something that did not change. A reference gene that is stable across your samples absorbs differences in input amount and sample quality, so remaining differences are more likely to be biology. The gene is useful only if it is actually stable in your tissue and treatment, which is why validation matters more than reputation. Related reading: the RT-qPCR guide, delta-delta Ct analysis and the MIQE reporting checklist. For the same logic in protein work, see Western blot loading controls.
What is an example of a housekeeping gene?
GAPDH and beta-actin (see b-actin) are the genes most often called housekeeping controls, but the primary literature is more cautious than the textbook label. Joshi et al. (2022) report that GAPDH has a high Gini coefficient, meaning unstable expression, in most of the datasets they examined. Eisenberg and Levanon publish a separate, small set of highly uniform and strongly expressed genes intended for experimental calibration, for example as PCR control genes: C1orf43, CHMP2A, EMC7, GPI, PSMB2, PSMB4, RAB7A, REEP5, SNRPD3, VCP and VPS29. GAPDH and ACTB are not on that list.
Housekeeping genes vs constitutive genes vs regulatory genes
She et al. (2009) describe housekeeping genes as constitutively expressed in all tissues, with comparatively constant expression levels across cell types. In that usage, “constitutive” describes the expression pattern (steady rather than signal-dependent), while “housekeeping” describes a functional category with an expected expression pattern attached. The two sets overlap heavily; they are not formally identical. A regulatory gene is defined by a different criterion, controlling other genes, rather than by stable expression.
Where it matters for lab work: a definition-versus-practice comparison
| Question | Classical assumption | What the sources report |
|---|---|---|
| Is expression the same everywhere? | Stable across tissues and conditions | She et al. (2009): expression of some commonly used control genes varies by more than an order of magnitude across tissues, and they do not necessarily show high expression with low variance. |
| Is GAPDH a safe default? | Yes, widely used | Joshi et al. (2022): high Gini coefficient (unstable) in most datasets examined; varied widely between datasets. |
| Are housekeeping genes essential? | Essential for cell existence | Joshi et al. (2022): stably expressed genes are not necessarily essential; most housekeeping genes are expressed at relatively low levels. |
| Is there one universal list? | One set for all samples | Joshi et al. (2022): stability depends on the samples included, and housekeeping genes differ between cancer cell lines and tissues. Eisenberg and Levanon’s RNA-seq list replaces an older microarray-based list. |
Checklist before you trust a reference gene
- Confirm the gene is stable in your tissue, cell line and treatment, not only in published panels.
- Do not rely on a single gene by default; test candidates against each other (see the validation guide linked above).
- Remember that RNA quality affects any reference gene; see RNA integrity number.
- Report which reference genes you used and how you validated them.
Common misunderstandings
- “Housekeeping means constant.” Constant expression is the expectation, not a measured property of every housekeeping gene.
- “Housekeeping means highly expressed.” Joshi et al. note that most housekeeping genes are expressed at relatively low levels.
- “Stable means essential.” The two properties are separate in the 2022 analysis.
- “One list fits every sample.” Lists depend on the samples and method used to build them.
FAQ
What is an example of a housekeeping gene?
GAPDH and ACTB are the usual examples, though recent analyses question their stability. Eisenberg and Levanon list PSMB2, VCP and RAB7A among uniformly expressed calibration genes.
What is the function of housekeeping genes?
They are involved in basic cell maintenance, and in the lab they act as stable references for normalizing expression data.
What is the difference between constitutive genes and housekeeping genes?
Constitutive describes steady expression; housekeeping describes maintenance function with expected constant expression. They overlap heavily without being identical.
Why use housekeeping genes in qPCR?
To normalize results to a reference that should not change between samples, provided it has been validated for your samples.
Sources
- Joshi CJ, Ke W, Drangowska-Way A, O’Rourke EJ, Lewis NE. What are housekeeping genes? PLoS Comput Biol 2022;18(7):e1010295. pmc.ncbi.nlm.nih.gov/articles/PMC9312424 (read 2026-11-07).
- Eisenberg E, Levanon EY. Human housekeeping genes, revisited. Trends Genet 2013;29. Gene list: tau.ac.il/~elieis/HKG (read 2026-11-07).
- She X, Rohl CA, Castle JC, et al. Definition, conservation and epigenetics of housekeeping and tissue-enriched genes. BMC Genomics 2009;10:269. PMC2706266 (read 2026-11-07).
