Fig 3. Modeling DS microglial phenotypes in human-mouse microglial chimeras.

(A) Representative images from sagittal brain sections showing the distribution of transplanted DS hiPSC-derived microglia at week 8 and 3 to 4 months. Scale bar: 1 mm and 500 μm.

(B) Representative images showing colocalization of hTMEM119⁺ and PSD95⁺ staining at 4, 8 weeks, and 3 months post-transplantation. Arrows indicate PSD95⁺ puncta. Scale bar: 5 μm and 1μm.

(C, D) Quantification of microglial volume, process length, endpoints, and PSD95⁺ puncta inside microglia (n=120–160 microglia from 3–5 mice/group).

(E) Representative images showing colocalization of hTMEM119⁺CD68⁺ PSD95⁺ staining of week 8 chimeras. Arrows indicate PSD95⁺ puncta in the CD68⁺ phagolysosome. Scale bar: 5 μm and 1 μm.

(F) Quantification of CD68⁺ phagolysosome volume and PSD95⁺ puncta inside CD68⁺ phagolysosomes (n=120 microglia from 4 mice/group).

(G) Representative images of hCD45 and synapsin I staining in week 8 of chimeras. Arrows indicate synapsin I⁺ puncta. Scale bar: 5 μm and 1 μm.

(H) Quantification of synapsin I⁺ puncta in hCD45⁺ microglia (n=120 microglia from 4 mice/group).

(I) A representative image of hTMEM119⁺ microglia and Neurobiotin⁺ recorded neurons in the hippocampus of DS microglia chimera. Arrows indicate Neurobiotin⁺ recorded neurons. Scale bar: 500 μm.

(J) Representative traces of mEPSCs in CA1 hippocampal pyramidal neurons.

(K) Quantification of the frequency and amplitude of mEPSCs (n=14–15 neurons from 4–5 mice/group).

Student’s t test, *P < 0.05 and **P < 0.01. Data are presented as mean ± SEM.