Chromatin and transcriptional adaptation accompany monocyte engraftment in the injured retina

After retinal injury, donor-derived myeloid cells in bone marrow chimeras progressively acquire microglial markers P2RY12, TMEM119, and FCRLS, with distinct kinetics and heterogeneity over prolonged engraftment.

• Why it matters: Interpreting CNS inflammation depends on reliably distinguishing resident microglia from engrafted peripheral myeloid cells, yet marker performance after long-term engraftment is context dependent.
• What they did: Using bone marrow chimeras with single-cell and bulk RNA sequencing, ATAC-seq, flow cytometry, and immunostaining, the study tracked phenotypic and chromatin accessibility changes in donor-derived retinal monocytes.
• The result: At one year after injury, engrafted cells and injured host microglia share inflammatory transcriptional features, while engrafted cells show significantly lower Sall1 than naive microglia, supporting marker-plus-origin strategies.