Essential role of the posterior morphogen nanos for germline development in Drosophila

Abstract

In many animal groups, factors required for germline formation are localized in germ plasm, a region of the egg cytoplasm. In Drosophila embryos, germ plasm is located in the posterior pole region and is inherited in pole cells, the germline progenitors. Transplantation experiments have demonstrated that germ plasm contains factors that can form germline, and germ plasm also directs abdomen formation. Genetic analysis has shown that a common mechanism directs the localization of the abdomen and germline-forming factors to the posterior pole. The critical factor for abdomen formation is the nanos (nos) protein (nanos). Here we show that nos is also essential for germline formation in Drosophila; pole cells lacking nanos activity fail to migrate into the gonads, and so do not become functional germ cells. In such pole cells, gene expression, which normally initiates within the gonad, begins prematurely during pole-cell migration. Premature activation of genes in germline precursors may mean that these cells fail to develop normally. A function for nos protein in Drosophila germline formation is compatible with observations of its association with germ plasm in other animals.

Nanos suppresses somatic cell fate in Drosophila germ line

“…We have shown that transplanted nos pole cells never migrate into the host gonads (15). To our surprise, their ability to enter the gonads was restored by suppressing apoptosis.…”

“…Maternal nos mRNA is enriched in germ plasm, and its protein product is partitioned into pole cells when they are formed and remains detectable in these cells throughout embryogenesis (14). Nos is required in pole cells for their proper migration into the embryonic gonads (15,16). Within pole cells, Nos is involved in maintaining transcriptional quiescence (17) and is also required for maintenance of a germ-line-specific chromatin status that correlates with transcriptional inactivity (18).…”

The E-cadherin-repressed hNanos1 gene induces tumor cell invasion by upregulating MT1-MMP expression

“…Nanos proteins are involved in the regulation of various development processes. In Drosophila, nanos regulates differentiation of the anterior-posterior body axis, primordial germ cell migration, oogenesis and spermatogenesis (Wang and Lehmann, 1991;Wang et al, 1994;Kobayashi et al, 1996;Forbes and Lehmann, 1998;Bhat, 1999;Deshpande et al, 1999). hNanos1 is abundant in germ-line stem cells (Jaruzelska et al, 2003).…”

NANOS2 interacts with the CCR4-NOT deadenylation complex and leads to suppression of specific RNAs

“…Nanos is an evolutionarily conserved RNA-binding protein that is essential for germ cell development (7). In Drosophila, Nanos forms a complex with another RNA-binding protein, Pumilio, and represses the translation of the hunchback, cyclin B, and hid mRNAs thereby establishing embryonic polarity, mitotic quiescence, and suppression of apoptosis, respectively (8)(9)(10).…”