In this study, we identified HERD-1, a component of germline-specific Z granules, as an essential factor for the selective degradation of these obsolete maternal membrane proteins. Normally, after fertilization, these proteins are transported via endosomes to lysosomes for degradation via the multivesicular body (MVB) pathway. However, we found that the loss of HERD-1 leads to a reduction in key regulators of the multivesicular body pathway that mediates this process. Interestingly, this degradation defect was suppressed by the loss of DEPS-1 or PRG-1, proteins involved in small RNA synthesis. These results suggest that maternal germ granule components actively trigger endosomal activation (“endosomal switching”) in the early embryo (the offspring) via small RNA pathways, thereby precisely controlling organelle remodeling.

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