The RNA-Binding Protein IGF2BP1 Marks Germ Cells but Is Dispensable for Mouse Fertility

Insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) is a key reader of N6-methyladenosine modifications that regulate target mRNA stability in eukaryotic cells; however, its role in germ cells has never been explored. Here, we analyzed the spatiotemporal expression of IGF2BP1 and revealed that it was present not only in oocytes of the mouse ovary but also in ZBTB16-positive undifferentiated spermatogonia in the mouse testis. Coimmunoprecipitation and fluorescence staining revealed that IGF2BP1 interacted with TRIM71, a regulator of spermatogonia differentiation, but that its expression was unaffected in the testes of Trim71 knockout mice. We also show that IGF2BP1 colocalized with components of the mRNA processing body (P-body), including DDX6 and EDC4. However, contrary to our expectations, using VASA (DDX4)-Cre-mediated conditional knockout mice, we found that germ cell-specific knockout of Igf2bp1 did not seem to affect the fertility of male or female mice. Further analysis revealed that spermatogenesis and ZBTB16-positive undifferentiated spermatogonia numbers in the testes of mutant mice remained unchanged and that there were no obvious changes in testicular morphology or cell subpopulations. In summary, although IGF2BP1 is preferentially expressed in germ cells, its function in germ cells may be dispensable.