Choosing nuclear factor antibodies that survive the protocol: why an oct4 antibody, the oct-4 antibody spelling beside it, a nanog antibody, a sox2 antibody and a sox11 antibody need a nuclear extraction and a retrieval optimised per reagent before any of them report anything, what an hmga2 antibody, a bmi1 antibody, a dlk1 antibody, a prox1 antibody, an olfm4 antibody and an sca1 antibody mark in progenitor populations, how a foxa1 antibody, a foxa2 antibody, a foxp1 antibody, a gata1 antibody, a gata6 antibody, a cebpa antibody, a cebpb antibody, a runx1 antibody, a myod1 antibody, a pax5 antibody and a tcf4 antibody assign lineage rather than state, where an egr2 antibody, a mafb antibody, a nur77 antibody, an nr4a1 antibody, an atf3 antibody, a fosb antibody, a jun antibody, a fra1 antibody, the fra-1 antibody spelling beside it and a creb antibody read immediate early activity instead, what an sp1 antibody, a yy1 antibody and a tbp antibody are as general factors rather than markers, and how a cytokeratin antibody, a cytokeratin 7 antibody, a filaggrin antibody, an involucrin antibody, an sftpc antibody and a muc5ac antibody name differentiated products

Getting nuclear stains to work

1. Extract the nucleus, do not lyse the cell. A standard whole cell buffer leaves much of a chromatin bound factor in the pellet. A nuclear extraction protocol, with the pellet checked, is what puts these targets on a blot.
2. Optimise retrieval per reagent in tissue. Nuclear epitopes in cross linked tissue almost always need retrieval, and the optimal buffer and duration differ between reagents. Optimise on tissue known to be positive.
3. Separate identity from immediate early activity. Several factors here are induced within minutes of any stimulus, including handling. Treating them as lineage markers produces conclusions about identity from what is actually a stress response.
4. Score nuclear localisation, not intensity alone. For factors that shuttle, the informative measurement is the proportion in the nucleus per cell. Whole field intensity mixes that with expression level.
5. Include a known positive population. A tissue or cell line known to express the factor, on the same slide or blot, is what makes a negative result credible and a weak result interpretable.

Low abundance and tightly bound

Transcription factors are present at a small fraction of the abundance of structural proteins and are held in complexes on DNA. Both properties work against detection, and both are addressed by extraction rather than by a more sensitive reagent.

Check the pellet once, on a positive control, and the extraction question is settled for every subsequent experiment in that cell type.

Handling induces some of these markers

Dissociation, medium change and even a few minutes at room temperature induce immediate early factors. In any experiment where one arm is processed differently from another, that becomes a group difference.

Randomise processing across groups, keep the interval fixed, and record it. It is the same discipline that protects phosphorylation work, applied to transcription.

Common questions

Why is my nuclear factor absent from the lysate?

Because it is bound to chromatin and stayed in the pellet. Use a nuclear extraction protocol and blot the pellet as well as the supernatant to confirm where the target went.

Are immediate early genes useful as markers?

As activity readouts, yes; as identity markers, no. They respond within minutes to handling, dissociation and medium change, so a difference between groups can be a difference in processing.

How much does retrieval matter?

More than the antibody, for most nuclear targets in fixed tissue. A weak nuclear stain is far more often under-retrieved than under-sensitive.

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