Oncofusion

start / graph / ana-unstated-system-osteolineage-cre-resolved

Analysisstrong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.Q18b-unstated-systems

The unnamed osteolineage Cre is Prx1-Cre, which is not osteoblast-restricted - and that changes what the negative result means

also called GSE189928 provenance · Prx1-Cre Cxcl12 niche · osteolineage cre identity

An entry on osteoblasts rests on a negative result whose validity depends on which genetic tool the authors used, and the abstract never names it. The deposited data and full text name it: Prx1-Cre, which switches genes off in a broad mesenchymal population rather than in mature bone-forming cells - so the negative result is about the wrong cells to be read as an osteoblast result.

The same thing, for a scientist

`cell-type-osteoblast` carries the caveat *"the negative osteolineage result depends on the specificity of the osteolineage cre used, which the abstract does not name"* [E1]. That is a caveat whose resolution changes the entry's meaning rather than merely annotating it. GEO series **GSE189928** holds 18 *Mus musculus* samples, strain **C57BL/6JRj**, `tissue: Bone marrow`, `cell type: Leukemia stem cells (LSCs)`, split by `genotype: Prx1-Cxcl12-mutant` (10) and `genotype: Prx1-Cxcl12-wild type` (8) [E2]. The full text, recovered through NCBI `efetch db=pmc` for PMC7614282 after Europe PMC returned HTTP 500, names **Prx1-cre** five times and cites the Prx1-enhancer Cre founding report [E3]. The leukaemia is MLL::AF9, named 22 times in the same text and in the series title [E2][E3]. **Prx1-Cre is a limb-bud mesenchymal driver, not an osteoblast driver.** It recombines in skeletal stem and progenitor cells of the limb-bud lineage, from which osteoblasts, chondrocytes and marrow stromal cells all descend, and it is active long before osteoblast commitment. A `Prx1-Cre; Cxcl12^fl` mouse therefore deletes CXCL12 from a broad mesenchymal compartment, and a null result in it is **not** evidence that mature osteoblasts do not matter - it is evidence about the mesenchymal compartment as a whole, in which an osteoblast-specific contribution could be present and masked, or absent and untested.

Go deeper
What the entry can now say, and what it must stop saying

Can say: deleting Cxcl12 with Prx1-Cre, in a broad limb-bud-derived mesenchymal population, in C57BL/6JRj mice bearing MLL::AF9 leukaemia, gave the reported result across 18 deposited bone-marrow LSC samples (10 mutant, 8 wild type) 2.

Must stop saying: that this is an osteolineage negative. Prx1-Cre marks skeletal stem and progenitor cells; the osteoblast-restricted drivers are Col1a1-Cre, Osx/Sp7-Cre and Ocn/Bglap-Cre, and none of them appears in this deposition. The entry's own caveat anticipated that the answer would be decisive and it is - in the unfavourable direction for reading the result as an osteoblast finding.

The standing brief's rule applies exactly: a mutation-centric analysis cannot detect deletion; a targeted panel returns negative for every partner it was not designed around. A Prx1-driven deletion cannot return an osteoblast-specific answer because it was never asking an osteoblast-specific question.

The leukaemia is also an import, and the entry does not say so

Separately from the Cre question, the deposition fixes the disease model: MLL::AF9, mouse, myeloid, with leukaemia stem cells sorted from bone marrow 23. So a niche result that cell-type-osteoblast carries into a project about infant KMT2A::AFF1 B-ALL carries three imports of its own - fusion, species and lineage - on top of the Cre problem. The marrow niche a pro-B blast occupies is not obviously the niche an MLL-AF9 myeloid LSC occupies, and CXCL12 gradients are among the things known to differ between them.

Facts and figures
scriptnone - GEO accession-display text endpoint plus NCBI efetch db=pmc full text
statusrun
result summaryThe unnamed osteolineage Cre is Prx1-Cre, a limb-bud mesenchymal driver, not an osteoblast-restricted one. 18 murine MLL::AF9 bone-marrow LSC samples, 10 Prx1-Cxcl12-mutant against 8 wild type, C57BL/6JRj. No Col1a1-, Osx- or Ocn-Cre arm exists in the deposition, so the negative result cannot be read as an osteoblast-specific negative.
counts
osteoblast_restricted_dri…0.000osteoblast_restricted_driver_arms: 0samples_wildtype8.000samples_wildtype: 8samples_mutant10.0samples_mutant: 10samples_total18.0samples_total: 18samples_mouse18.0samples_mouse: 18
inputs
[
  "PMID 35618797",
  "GSE189928",
  "PMC7614282",
  "PMID 12112875"
]
counts — the numbers behind the chart
{
  "samples_total": 18,
  "samples_mouse": 18,
  "samples_mutant": 10,
  "samples_wildtype": 8,
  "osteoblast_restricted_driver_arms": 0
}
entries affected
[
  "cell-type-osteoblast"
]
import axes
[
  "cell type: limb-bud mesenchymal progenitors, not osteoblasts",
  "fusion: KMT2A::MLLT3",
  "species: mouse",
  "lineage: myeloid"
]
How this could bite us back
  • A niche-directed intervention chosen because osteoblasts appeared irrelevant would be chosen from an experiment that never isolated osteoblasts, so the negative that justified deprioritising them does not support the decision.
  • CXCL12 signalling is required for normal B-lymphopoiesis and HSC retention, so disrupting it therapeutically in an infant carries a developmental haematopoietic cost that a murine myeloid LSC transcriptome cannot bound.
  • If the mesenchymal compartment as a whole matters but no single restricted driver reproduces the effect, then the niche dependency is distributed and not druggable through any one cell type - a possibility this deposition is consistent with and cannot exclude.
Still open
  1. Does CXCL12 deletion with an osteoblast-restricted driver (Col1a1-, Osx- or Ocn-Cre) give the same result? The question the entry thought it had answered is untested.
  2. Does any of this niche biology hold for a B-lymphoid KMT2A::AFF1 blast? The deposition is myeloid LSCs throughout, and pro-B cells depend on CXCL12 differently.
Every source behind this entry (3)
  1. E1established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.paper

    The bone-marrow niche paper reports that the niche regulates redox and energy balance in MLL::AF9 leukaemia stem cells, and its abstract does not name the osteolineage Cre driver used for the conditional deletion.

    The bone marrow niche regulates redox and energy balance in MLL::AF9 leukemia stem cells. · Viñado AC, Calvo IA, Cenzano I, Olaverri D, Cocera M, San Martin-Uriz P, Romero JP, Vilas-Zornoza A, Vera L, Gomez-Cebrian N, Puchades-Carrasco L, Lisi-Vega LE, Apaolaza I, Valera P, Guruceaga E, Granero-Molto F, Ripalda-Cemborain P, Luck TJ, Bullinger L, Planes FJ, Rifon JJ, Méndez-Ferrer S, Yusuf RZ, Pardo-Saganta A, Prosper F, Saez B · Leukemia 2022
    PMID 35618797DOI
    What this evidence cannot show

    Identifiers taken from the NCBI esummary record fetched on 2026-09-19. The abstract-level claim is the one the graph's caveat was anchored to; the full text names the driver and is quoted in E3.

    Evidence that argues against this (1)
    • A niche result read as a negative for one cell type is only as good as the driver's specificity, and skeletal-stem-cell versus osteoblast attribution is an active and unsettled question in bone biology, so even a correctly named driver leaves the cell-of-origin attribution contestable. Logan M et al. 2002
  2. E2established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.dataset

    GEO series GSE189928 contains 18 Mus musculus samples, strain C57BL/6JRj, tissue bone marrow, cell type 'Leukemia stem cells (LSCs)', split 10 'Prx1-Cxcl12-mutant' against 8 'Prx1-Cxcl12-wild type', under a series titled for the bone-marrow niche regulating redox and energy balance in leukemia stem cells.

    What this evidence cannot show

    Read on 2026-09-19 from the GEO accession-display text endpoint and enumerated sample by sample. Submitter-entered. The genotype string names the driver only as 'Prx1', which this entry reads as the Prx1-Cre limb-bud enhancer line on the strength of the full text naming Prx1-cre explicitly (E3). The deposition contains no osteoblast-restricted driver arm, which is the substance of this entry's correction.

    Evidence that argues against this (1)
    • The deposition profiles leukaemia stem cells rather than the niche cells whose genotype was altered, so it reports the consequence of the deletion and not its extent; the actual recombination efficiency in any bone cell population is not recoverable from GEO. Rogic S et al. 2026
  3. E3established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.paper

    The paper's full text names Prx1-cre as the driver, cites the founding report of Cre expression in the developing mouse limb bud driven by a Prxl enhancer, and names MLL::AF9 as the leukaemia model.

    Expression of Cre Recombinase in the developing mouse limb bud driven by a Prxl enhancer. · Logan M, Martin JF, Nagy A, Lobe C, Olson EN, Tabin CJ · Genesis 2002
    PMID 12112875DOI
    What this evidence cannot show

    The driver identification was read from the NCBI efetch db=pmc full text for PMC7614282 on 2026-09-19, after Europe PMC fullTextXML returned HTTP 500; the recovered text contains 'Prx1-cre' 5 times, 'MLL::AF9' 22 times and 'C57BL/6JRj' once. The citation attached here is the Prx1-enhancer Cre founding report itself, fetched from PubMed on the same date, because that paper is what establishes the driver's expression domain - the limb bud - and therefore what the deletion actually covers.

    Evidence that argues against this (1)
    • Prx1-Cre is widely used and its limb-bud domain is not disputed, but recombination domains reported in a founding paper can be broader in practice than in the original characterisation, so the deletion could extend beyond the described compartment rather than being narrower than claimed. Viñado AC et al. 2022
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