Xenopus Dead end mRNA is a localized maternal determinant that serves a conserved function in germ cell development

Abstract

Germ plasm formation is considered to define the first step in germ cell development. Xenopus Dead end represents a germ plasm specific transcript that is homologous to the previously characterized zebrafish dead end, which is required for germ cell migration and survival. XDead end mRNA localizes to the vegetal pole of Xenopus oocytes; in contrast to all other known germ plasm associated transcripts in Xenopus, XDead end is transported via the late transport pathway, suggesting a different mode of germ plasm restriction. Vegetal localization in the oocyte is achieved via a localization element mapping to a 251 nucleotide element in the 3'-UTR. This RNA sequence binds to a set of proteins characteristic for the late localization pathway and to one additional protein of 38 kDa. Inhibition of XDead end translation in Xenopus embryos results in a loss of primordial germ cells at tadpole stages of development. Early specification events do not seem to be affected, but the primordial germ cells fail to migrate dorsally and eventually disappear. This phenotype is very similar to what has been observed in the zebrafish, indicating that the role of XDead end in germ cell development has been conserved in evolution.

Identification of a germ cell marker gene, the dead end homologue, in Chinese sturgeon Acipenser sinensis

“…Dead end (dnd) is a germ plasm component in vertebrates that is crucial for zebrafish PGC migration and survival (Weidinger et al, 2003). The gene has been subsequently isolated in diverse vertebrates, including mouse, Xenopus, chicken, and medaka (Youngren et al, 2005;Horvay et al, 2006;Aramaki et al, 2007;Liu et al, 2009). In mouse, mutations of the dnd gene were shown to cause germ cell loss and increase the incidence of testicular germ cell tumor (Youngren et al, 2005).…”

Germ cell-specific expression of dead end (dnd) in rare minnow (Gobiocypris rarus)

“…In one study, the knockdown of Dnd resulted in loss of germ cells without effects on the somatic cells in zebrafish (Weidinger et al 2003). The homologous genes of dnd have been identified in medaka (Oryzias latipes) (Liu et al 2009), loach (Misgurnus anguillicaudatus) (Fujimoto et al 2010), African clawed frog (Xenopus laevis) (Weidinger et al 2003;Horvay et al 2006), chicken (Gallus gallus) (Weidinger et al 2003;Aramaki et al 2009) and mouse (Mus musculus) (Weidinger et al 2003;Youngren et al 2005;Bhattacharya et al 2007). Loss of dnd also resulted in loss of germ cells in loach (Fujimoto et al 2010), frog (Horvay et al 2006) and mouse (Youngren et al 2005;Bhattacharya et al 2007).…”

Molecular characterization and expression pattern of a germ cell marker gene dnd in gibel carp (Carassius gibelio)

“…In some species, however, the dnd expression in adults appears to be different with sex. In Xenopus, dnd expression is restricted in ovary (Horvay et al, 2006), whereas in mouse, dnd1α is specifically expressed in testis (Bhattacharya et al, 2007). Similarly, a differential expression pattern of dnd between testis and ovary was also observed in turbot (Lin et al, 2013) and Pacific bluefin tuna (Yazawa et al, 2013).…”

“…Dnd has been cloned and identified in many vertebrates, including mouse (Youngren et al, 2005), zebrafish (Weidinger et al, 2003), chicken (Aramaki et al, 2009), Xenopus (Horvay et al, 2006), medaka (Liu et al, 2009;Hong et al, 2016), loach (Fujimoto et al, 2010), goldfish (Goto et al, 2012), sterlet sturgeon (Linhartova et al, 2015), and Atlantic salmon (Wargelius et al, 2016). In most of examined teleost fishes, such as zebrafish, medaka, loach, goldfish, sterlet sturgeon, and Atlantic salmon, dnd is specifically expressed in PGCs, and the dnd translation block or depletion completely abolishes PGCs during early embryogenesis (Weidinger et al, 2003;Fujimoto et al, 2010;Goto et al, 2012;Hong et al, 2016;Wargelius et al, 2016).…”