Fig. 7. A putative model for ApoB function in regulating differentiation of planarian stem cell progeny.

a Our data support a working model in which ApoB is expressed by phagocytes in the intestine, a primary site of LP production and secretion. b ApoB mediates secretion of neutral lipids in LPs from intestinal phagocytes to neoblasts and their progeny. c In the absence of ApoB, lipids accumulate in the intestine, and LP delivery to neoblasts and their progeny is disrupted, reducing their neutral lipid content. Neoblast proliferation and renewal are largely unaffected by reduced ApoB function. Instead, differentiation and later maturation of most, if not all, planarian cell lineages are slowed, causing an accumulation of differentiating progeny and a delay in regeneration of multiple organs. Box in a represents region magnified in b wild type and c apob knockdown conditions. Nuclei, blue. Lipid droplets, light green. LPs, magenta. Apical/lumenal phagocyte surface is to the left and basal/mesenchymal phagocyte surface is to the right in b and c. Image in a reproduced from Forsthoefel et al.¹¹⁷ under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). No changes were made to the original image.