Schlafen regulates gastrulation in Xenopus laevis early embryonic development and exhibits immune tissue-specific expression in adult frogs.

Schlafen genes are conserved regulators of cell proliferation and play a pivotal role in immunity and host defence, yet their function during vertebrate development remains poorly understood. Here, we characterize the expression, phosphorylation dynamics, and function of the single Schlafen ortholog in Xenopus laevis (slfn13) during embryogenesis and in adult tissues. Slfn13 protein levels increase markedly around the mid-blastula transition/late blastula, with unphosphorylated Slfn13 predominating during gastrulation and neurulation, while phosphorylated Slfn13 (p-Slfn13) is more abundant during early cleavage stages. We found that Morpholino-mediated knockdown of Slfn13 in Xenopus laevis causes delayed blastopore lip formation, impaired blastopore closure, and severe gastrulation defects in a dose-dependent manner, indicating a non-redundant requirement for Slfn13 in early morphogenesis. We further analysed Slfn13 expression in adult Xenopus laevis. Slfn13 is enriched in immune tissues and thymic tumour cell lines, with p-Slfn13 specifically detected in proliferative tumour-derived cells. Collectively, our findings reveal a previously unrecognized role for slfn13 in gastrulation and support a conserved immuneassociated expression pattern in adult frogs, expanding the functional landscape of Schlafen proteins across vertebrates.