Truncating variants in ASXL1 (Additional Sex Combs Like 1) are causal for Bohring-Opitz syndrome (BOS) and recurrent as somatic events in myeloid leukemia. ASXL1 is a chromatin-associated epigenetic regulator that forms the catalytic PR-DUB complex with BAP1. The source study reports a mechanistic connection between gain-of-function ASXL1 truncations and cellular metabolism mediated by repression of the mitochondrial pyruvate carrier (MPC).
The authors present evidence that truncated ASXL1 proteins alter chromatin occupancy at a regulatory element within MPC2 intron 1, leading to downstream effects on MPC expression, protein stability, and cellular metabolic state. The material summarized here is drawn from the preprint abstract; full experimental details and quantitative data are reported in the source but are beyond this summary.
Using patient-derived dermal fibroblasts, cells harboring truncating ASXL1 variants exhibited a Warburg-like metabolic phenotype. Specifically, the authors observed increased glycolytic flux together with accumulation of pyruvate and lactate. These changes indicate a shift toward cytosolic glycolysis and reduced mitochondrial pyruvate utilization.
The metabolic profile in ASXL1-truncated cells recapitulates features commonly associated with increased glycolysis and diminished mitochondrial oxidation of pyruvate, consistent with impaired import of pyruvate into mitochondria via the MPC.
Chromatin analyses revealed that truncated ASXL1 and BAP1 show co-occupancy at an intronic regulatory element in MPC2 intron 1 that bears H3K4me3 marks. Notably, ASXL1 occupancy in the truncated context was broadened beyond regulatory boundaries defined by BRD4, while BRD4 positioning itself remained unchanged.
This pattern is interpreted as aberrant spreading of the PR-DUB complex beyond its normally constrained chromatin territory when ASXL1 is truncated, implicating altered chromatin targeting or retention as an upstream event in altering gene regulation at the MPC2 locus.
The altered occupancy at the intronic regulatory element correlated with a modest but statistically significant reduction in MPC2 transcript abundance. Despite the moderate transcript decrease, there was a disproportionately larger reduction in MPC1 and MPC2 protein levels. The authors infer that transcriptional dysregulation at the intronic element is amplified post-transcriptionally.
Post-transcriptional mechanisms identified include impaired stability of the MPC1/MPC2 heterodimer. Because MPC function relies on a stable heterodimeric complex, disruption of protein stability can lead to marked loss of mitochondrial pyruvate transport even when transcript changes are modest.
Pharmacologic inhibition of the MPC in control cells reproduced both the metabolic phenotype (increased glycolysis, pyruvate and lactate accumulation) and the Wnt signaling alterations observed in BOS patient cells. This pharmacologic phenocopy supports the model that restricted mitochondrial pyruvate transport is sufficient to drive the observed metabolic and signaling consequences.
Conversely, direct activation of canonical Wnt signaling increased glycolytic flux but did not reduce MPC abundance, establishing that MPC repression is upstream of Wnt pathway dysregulation rather than a downstream consequence of Wnt activation. Thus, mitochondrial pyruvate restriction is positioned as a causal event leading to signaling and metabolic changes.
These results define a previously unrecognized axis linking ASXL1 truncation to mitochondrial pyruvate transport via repression of MPC. By connecting chromatin misregulation to metabolic reprogramming, the findings implicate MPC as a central mediator of epigenetic–metabolic crosstalk in both a rare developmental syndrome (BOS) and in ASXL1-mutant myeloid malignancy contexts.
The work suggests that altered chromatin occupancy by truncated ASXL1 and its catalytic partner BAP1 can produce downstream metabolic vulnerabilities related to mitochondrial pyruvate import. Pharmacologic modulation of MPC function recapitulates key phenotypes, highlighting the functional importance of the MPC axis in the observed biology.
This report is a preprint and has not undergone peer review. The abstract summarizes experimental observations but does not provide all methodological or quantitative details within the source text summarized here. Specific experimental conditions, sample sizes, and full datasets are available in the preprint but were not exhaustively detailed in the abstract. Competing interest disclosure notes that one author is a co-founder of a company developing MPC inhibitors.
Overall, the source describes a mechanistic link from ASXL1 truncating variants through aberrant PR-DUB occupancy to repression of MPC, resulting in mitochondrial pyruvate restriction that drives a Warburg-like metabolic state and alters Wnt signaling. These findings expand understanding of how epigenetic mutations can rewire cellular metabolism in developmental and malignant settings.