Fig. 5. Pseudotime trajectory analysis identified the pathways by which breast milk epithelial cells differentiate into lactocytes.

(A) Pseudotime trajectory analysis determined the pathway of differentiation of progenitor-like epithelial cells (starting node is located in the dark purple region). (B) As pseudotime progressed, the expression of progenitor genes subsided as cells differentiated into mature phenotypes. (C) On the basis of the pseudotime trajectories and gene expression kinetics, milk cells differentiated along three pathways into chemotactic/secretory epithelial cells, fatty acid–synthesizing cells, and mature lactocytes. Each pathway was associated with the overexpression of key genes compared to the other cell types, including KRT15 (cluster 1), FDCSP (cluster 7), FASN (cluster 6), LALBA (cluster 2), and FGFBP1 (cluster 3).