Brown fat starts in the aorta
Against a backdrop of rising global obesity, researchers trace brown fat to an unexpected embryonic source
18 Mar 2026
Prof. Sigmar Stricker, Karl Landsteiner University (KL Krems)
A team of scientists has identified an unexpected embryonic 'starting point' for several brown-fat depots: a small cell niche around the dorsal aorta1.
Brown adipose tissue helps mammals to regulate their body temperature, and it is drawing growing attention as obesity rises worldwide. Using a combination of time-controlled genetic lineage tracing and single-cell RNA sequencing in early mouse embryos, the researchers show that progenitor cells from this aorta-adjacent region later contribute to brown fat in multiple body locations – while the best-known depot between the shoulder blades (interscapular region) is only minimally derived from this source.
The work was carried out primarily at several top research facilities in Berlin and parts of it are now brought to Karl Landsteiner University (KL Krems) through the senior scientist Prof. Sigmar Stricker.
Brown adipose tissue, often called ‘brown fat’, is not uniform across the body: it appears in distinct anatomical depots, and these depots differ in cellular composition and gene activity. This matters because researchers often use one depot as a model for 'brown fat' in general. If depots do not share the same developmental origin, they may also differ in how they are regulated, and in how reliably findings from one region translate to another.
The new study tackles this uncertainty by mapping exactly which embryonic progenitor pools feed into which depots, and when those fate decisions are made.
Hidden location
“Previous studies suggested that brown fat depots might not all develop in the same way,” says Prof. Sigmar Stricker, Head of the Department of Cell Biology at KL Krems. “We now used lineage tracing and single-cell data to check this idea in more detail – and, indeed, we found strong evidence for a yet unknown location of progenitor cells of brown adipose tissue near the dorsal aorta.”
The team around Prof. Stricker focused on cells expressing the gene Osr1 (a transcription factor) and followed the development and migration of these cells over time. By labelling Osr1-positive cells at defined embryonic stages, they uncovered clear depot-specific patterns: Osr1-lineage cells contributed strongly to brown fat beneath the shoulder blade (subscapular) and in the neck (cervical) regions, but only minimally to the large depot between the shoulder blades (interscapular), a widely used reference tissue in mouse studies.
An even earlier labeling time point still revealed substantial contributions to the subscapular and cervical depots, indicating that relevant Osr1-positive progenitors are present very early in development.
Single-cell RNA sequencing added the molecular context. At a later embryonic stage, Osr1-positive cells showed a clearer 'pre–brown fat' signature. At an earlier stage, however, a subset displayed a broader, multipotent profile, with gene-expression features linked to vascular- and muscle-related programs. Consistent with this, lineage tracing indicated that early Osr1-positive cells can contribute not only to adipose tissue, but also to other mesoderm-derived tissues in defined embryonic regions.
From aorta to adipose
The anatomical clue to the origin and route of the progenitor cells emerged when the researchers examined embryos at the earlier stage using immunofluorescence: Osr1-positive cells were enriched in the dorsal aortic compartment, a narrow zone around the embryonic aorta.
Over subsequent days, time-resolved tracing suggested that Osr1-lineage cells disperse from this area toward more back-and-side regions of the embryo (dorso-lateral territories). This pattern is consistent with ideas about mesoangioblasts – vessel-associated, multipotent progenitors.
The authors therefore propose that dorsal aorta–associated, Osr1-positive cells represent an in vivo source of progenitors that can later form several brown-fat depots.
A substantial part of the experimental work and infrastructure for this study was based at Freie Universität Berlin, with additional expertise coming from the Max Delbrück Center Berlin, the Max Planck Institute for Molecular Genetics in Berlin, the Charité University Medicine Berlin, and the German Institute of Human Nutrition (DIfE).
References
1. Heider, S., Fischer, C., Secener, A.K. et al. The dorsal aortic compartment is a developmental source of brown adipose tissue in mice. Nat Communications 17, 286 (2026). https://doi.org/10.1038/s41467-025-68147-9.