Code used in the manuscript Alcobia et al 2024.
Using the chick-quail chimera system, we tested whether non-canonical pouches could contribute to thymus formation and assessed the role of pharyngeal arch (PA) mesenchyme in this process. After testing several embryonic tissue associations, we identified thymus-forming potential in both non-canonical second PP (2PP) and canonical third/fourth PP (3/4PP) endoderm. We further identified the 3/4PA and the ventral region of the second PA (2PA) mesenchymes as capable of positively regulate this potential, while the dorsal region of 2PA exerts an inhibitory effect.
Transcriptomic analysis helped us revealing a shared genetic program linked to thymus potential in PP endoderm along with distinct signalling pathways driving cellular interactions with PA mesenchyme that modulate this potential. These findings offer insights into initial specification of thymus primordium and may help advance the development of thymus organoid systems.