Counted absence: AFF1/AF4 - the partner in the commonest infant fusion - has no phase-separation literature under any alias, and the two hits that look like it are token collisions
also called AFF1 condensate absence · AF4 phase separation zero · MLLT2 droplet search
The protein fused to MLL in the commonest infant leukemia has never been shown to form liquid droplets by anyone. Searching every name it has ever published under returns two papers, and one is about plants while the other is about a lab technique that happens to have 'droplet' in its name.
The same thing, for a scientist
This graph carries a hypothesis that AFF1 condensates are dispensable for KMT2A-fusion function, and an experiment designed to test it. Both are built on a literature that does not exist. Run on 2026-09-20 over four alias spellings: `AFF1 AND (phase separation OR condensate OR droplet OR liquid-liquid)` returns **2**; `MLLT2 AND (phase separation OR condensate OR droplet)` returns **0**; `FEL AND leukemia AND (phase separation OR condensate)` returns **0**; `(AF4 AND leukemia) AND (phase separation OR condensate OR droplet)` returns **2** [E1]. Every query translation was read and none contains an injected `[UID]` term. All four returned records were title-checked and none is about AFF1 phase separation: the AFF1 pair are a 2026 bioRxiv preprint on an acetylation circuit and a plant paper on AUXIN RESPONSE FACTOR condensation (the **ARF/AF4 token family** at work), and the AF4 pair are a droplet-digital-PCR assay paper for KMT2A fusion detection and a review of the MLLT3/MLLT1 intrinsically disordered proteins. **The word 'droplet' in a PCR method title is the exact failure mode this project's alias-precision rule was written for.** The graph's condensate position for KMT2A::AFF1 therefore rests entirely on the *partner-symbol* literature for ENL and on the SEC, not on AFF1 at all.
The queries, verbatim, with counts
| query | count | verdict on the hits |
|---|---|---|
AFF1 AND (phase separation OR condensate OR droplet OR liquid-liquid) | 2 | neither about AFF1: a 2026 acetylation-circuit preprint, and a plant AUXIN RESPONSE FACTOR paper |
MLLT2 AND (phase separation OR condensate OR droplet) | 0 | true zero |
FEL AND leukemia AND (phase separation OR condensate) | 0 | true zero |
(AF4 AND leukemia) AND (phase separation OR condensate OR droplet) | 2 | neither about AFF1: droplet digital PCR for KMT2A fusion detection, and an MLLT3/MLLT1 IDR review |
All four translations were read; none contains a [UID] term the query did not ask for, so none is the silent-rewrite failure this project has logged. Checked count for AFF1 phase separation across all four spellings: zero.
Why the ENL literature does not fill the gap
The condensate framing applied to KMT2A fusions in this graph comes from one paper, in which ENL initiates multivalent phase separation of the super elongation complex; its single fusion-context panel is that transfecting MLL-ENL into HeLa increases the number of nuclear puncta containing AFF4 with ENL, with CDK9 and with ELL2 2. That is a KMT2A::MLLT1 observation in an overexpressing heterologous cell. It says nothing about AFF1, and AFF1 and AFF4 are different proteins with different expression and different fusion status.
The transferable lesson, which this beat confirms independently, is the one the previous beat found: search the partner symbol with the mechanism term, not the fusion name. MLL-ENL AND condensate misses the ENL paper entirely because its abstract says 'the fusion of ENL with MLL'. Here the same discipline applied to AFF1 produces a genuine zero rather than a retrieval artefact, which is the outcome that makes the zero worth recording.
What this does to two existing entries
hyp-aff1-condensates-dispensable-for-kmt2a-fusion-function and exp-aff1-idr-condensate-separation-of-function should be read with this count attached. The hypothesis is not refuted - a hypothesis about an unmeasured property cannot be - but its framing as a dispute with an existing positive claim is not supportable, because there is no positive claim about AFF1 to dispute.
The experiment is strengthened rather than weakened: a separation-of-function test on the AFF1 IDR would be the first measurement of AFF1 phase behaviour of any kind, which raises its value and lowers the prior that the answer is already known.
And the general caution applies whichever way the experiment comes out: 1,6-hexanediol and classical FRAP both fail to distinguish phase separation from binding to spatially clustered sites 3, and 1,6-hexanediol independently immobilises and condenses chromatin in living cells 4, so a chromatin-associated droplet claim built on either reagent is uninterpretable before it is run.
| script | not applicable - live PubMed esearch, queries recorded verbatim |
|---|---|
| status | run |
| result summary | zero primary records report phase separation of AFF1 under AFF1, MLLT2, FEL or AF4-plus-leukemia spellings |
| date run | 2026-09-20 |
queries — the numbers behind the chart
[
{
"q": "AFF1 AND (phase separation OR condensate OR droplet OR liquid-liquid)",
"raw": 2,
"checked_on_topic": 0
},
{
"q": "MLLT2 AND (phase separation OR condensate OR droplet)",
"raw": 0,
"checked_on_topic": 0
},
{
"q": "FEL AND leukemia AND (phase separation OR condensate)",
"raw": 0,
"checked_on_topic": 0
},
{
"q": "(AF4 AND leukemia) AND (phase separation OR condensate OR droplet)",
"raw": 2,
"checked_on_topic": 0
}
]token collisions found
[ "AUXIN RESPONSE FACTOR (ARF/AF4 family)", "droplet digital PCR" ]
- Designing a condensate-disrupting therapeutic against AFF1 would mean drugging a property that has never been measured for the protein, in a fusion whose partner contribution is the pSER and AF4-integrating regions rather than a characterised IDR.
- If AFF1 turns out not to phase-separate, a condensate strategy generalised from the ENL literature would fail specifically in the commonest infant fusion while working in a rarer one.
- Does an AFF1 droplet panel exist inside a paper framed at the level of the super elongation complex, invisible to a subunit-symbol query?
- Do the PBM1 and AF-4 spellings return anything the four queries here missed?
- If the AFF1 IDR were tested, would it be the first phase-behaviour measurement for this protein of any kind?
- E1moderate confidence 3 of 5: One strong study, or several smaller consistent ones.database
As of 2026-09-20, PubMed returns 2, 0, 0 and 2 records respectively for the four AFF1-alias phase-separation queries stated in this entry, every query translation is free of injected [UID] terms, and none of the four returned records reports phase separation of AFF1.
PubMed E-utilities esearch, db=pubmed: four AFF1/AF4/MLLT2/FEL alias queries crossed with phase-separation terms, run 2026-09-20 · Not applicable - database query · NCBI E-utilities 2026What this evidence cannot show
A counted absence is bounded by its symbol set. AFF1 also publishes as PBM1 and as AF-4 with a hyphen, neither of which was run, and the complex-name route (searching 'super elongation complex' as a phrase) returns 14 records that were not exhaustively title-checked for an AFF1-specific panel. Short aliases such as FEL inflate rather than deflate, so the zero there is the reliable direction.
Evidence that argues against this (1)
- Complex-level framing defeats subunit-symbol enumeration - the NSL and Mediator absences in this project were both produced that way - so an AFF1 droplet panel inside a paper framed at the level of the SEC would be invisible to every query in this table. Guo C et al. 2020
- E2moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
ENL initiates multivalent phase separation of the super elongation complex, and the only fusion-context observation in that work is that transfecting MLL-ENL into HeLa increases the number of nuclear puncta containing AFF4 with ENL, with CDK9 and with ELL2 relative to wild-type ENL.
ENL initiates multivalent phase separation of the super elongation complex (SEC) in controlling rapid transcriptional activation · Guo C, et al. · Science advances 2020What this evidence cannot show
HeLa transfection, an overexpressing heterologous system, and the fusion is KMT2A::MLLT1 rather than KMT2A::AFF1. The paper's condensate assays are in-vitro droplets, 1,6-hexanediol sensitivity and classical FRAP, all of which have documented interpretive limits.
Evidence that argues against this (1)
- Expression of an ENL variant beyond the endogenous level leads to non-functional condensates, so puncta counted in a transfected cell can be a consequence of the expression level rather than of the fusion. Song L et al. 2022
- E3strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
1,6-hexanediol sensitivity and classical FRAP recovery both fail to distinguish liquid-liquid phase separation from binding to spatially clustered sites; only model-free calibrated half-bleaching, which measures internal mixing, discriminates them.
Detecting and quantifying liquid-liquid phase separation in living cells by model-free calibrated half-bleaching · Muzzopappa F, et al. · Nature communications 2022What this evidence cannot show
A methods result in model systems; it constrains interpretation of existing assays rather than reporting on any leukaemia protein.
Evidence that argues against this (1)
- Binding to spatially clustered sites is a substantive rival model rather than an artefact, and in a chromatin context arguably the more informative one, so failing to exclude it is not the same as showing nothing is there. Chong S et al. 2018
- E4strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
1,6-hexanediol rapidly immobilises and condenses chromatin in living human cells, an action the authors state is distinct from melting a droplet and which they instruct readers to use in reinterpreting chromatin-associated droplet results.
1,6-hexanediol rapidly immobilizes and condenses chromatin in living human cells · Itoh Y, et al. · Life science alliance 2021What this evidence cannot show
Human cells but not leukaemia cells; the result bears on every chromatin-associated condensate claim including any future AFF1 one.
Evidence that argues against this (1)
- Hexanediol effects are concentration- and time-dependent, so a brief low-concentration treatment may still report on droplet material state; the authors' warning sets a design requirement rather than banning the reagent. Muzzopappa F et al. 2022
bounds the hypothesis: there is no positive AFF1 condensate claim for it to dispute
raises the value of the experiment: it would be the first AFF1 phase-behaviour measurement of any kind
no phase-separation literature under any alias searched
supplies the counted absence the standards entry needs for the commonest fusion's partner
the ENL literature is what the graph's condensate position actually rests on, and it is a different partner
the AFF-family droplet function is documented for AFF4 and for no other family member
the AFF1 condensate zero is one row of this beat's enumeration