Spatial control of mRNA translation underlies MKRN3-mediated delay of puberty.

Loss-of-function mutations in MKRN3 cause central precocious puberty, but the underlying mechanisms remain unclear, and findings from knockout mice are inconsistent. MKRN3 contains RNA-binding and ubiquitin-ligase domains, so we hypothesized that it regulates GnRH function through RNA and protein interactions. We performed transcriptomic, proteomic, and RNA/protein interactome analyses in GnRH neuronal cells overexpressing Mkrn3. Results indicated predominantly post-transcriptional effects, and the Mkrn3 interactome included the RNA-binding protein Igf2bp2, which is also linked to pubertal timing. Mkrn3 precipitated numerous mRNAs, notably Gnrh1 mRNA. Igf2bp2 also binds this mRNA but in an Mkrn3-dependent manner. Mkrn3 and Igf2bp2 share many mRNA targets, especially nuclear-encoded mitochondrial transcripts, suggesting roles in RNA transport and localized translation. Subcellular fractionation and reporter assays revealed that Mkrn3 alters the localization of proGnRH and Gnrh1 3'UTR-dependent translation and together support a model in which Mkrn3 spatially restricts Gnrh1 mRNA translation, limiting precursor processing and subsequent secretion of the mature peptide.