A critical role for <i>Xdazl</i>, a germ plasm-localized RNA, in the differentiation of primordial germ cells in <i>Xenopus</i>

TLDR

Xdazl is an RNA‑binding protein in Xenopus germ plasm homologous to Drosophila boule, a protein essential for meiotic entry in flies, and related to human and mouse DAZ/DAZL genes involved in gamete differentiation. The study demonstrates that Xdazl is essential for early primordial germ cell differentiation and indirectly required for their migration in Xenopus. Xdazl is expressed in the germ plasm from blastula to early tailbud stages and, as an RNA‑binding protein, likely regulates translation or expression of factors that mediate PGC migration. Maternal Xdazl depletion causes loss or severe deficiency of primordial germ cells, preventing their migration from ventral to dorsal endoderm and to the dorsal mesentery, while germ plasm aggregation and intracellular movements remain normal.

Abstract

ABSTRACT Xdazl is an RNA component of Xenopus germ plasm and encodes an RNA-binding protein that can act as a functional homologue of Drosophila boule. boule is required for entry into meiotic cell division during fly spermatogenesis. Both Xdazl and boule are related to the human DAZ and DAZL, and murine Dazl genes, which are also involved in gamete differentiation. As suggested from its germ plasm localization, we show here that Xdazl is critically involved in PGC development in Xenopus. Xdazl protein is expressed in the cytoplasm, specifically in the germ plasm, from blastula to early tailbud stages. Specific depletion of maternal Xdazl RNA results in tadpoles lacking, or severely deficient in, primordial germ cells (PGCs). In the absence of Xdazl, PGCs do not successfully migrate from the ventral to the dorsal endoderm and do not reach the dorsal mesentery. Germ plasm aggregation and intracellular movements are normal indicating that the defect occurs after PGC formation. We propose that Xdazl is required for early PGC differentiation and is indirectly necessary for the migration of PGCs through the endoderm. As an RNA-binding protein, Xdazl may regulate translation or expression of factors that mediate migration of PGCs.