MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression that may act as buffering agents to stabilize gene-regulatory networks. Here, we identify two miRNAs that are maternally required for normal embryonic primordial germ cell development in Drosophila melanogaster. Embryos derived from miR-969 and miR-9c mutant mothers had, on average, reduced germ cell numbers. Intriguingly,...

Work in different organisms revealed that the vasa gene product is essential for germline specification. Here, we describe the asymmetric segregation of zebrafish vasa RNA, which distinguishes germ cell precursors from somatic cells in cleavage stage embryos. At the late blastula (sphere) stage, vasa mRNA segregation changes from asymmetric to symmetric, a process that precedes primordial germ ...

Developmental constraint and its converse constraint release are significant concepts in understanding pattern and process in macroevolution. The purpose of this paper is to propose a two-step method for identifying constraints and constraint release. The first step is a phylogenetic optimization procedure to identify which trait/process is primitive and which is derived. The primitive trait is...

Pediatric germ cell tumors (GCTs) commonly arise at extragonadal sites. It has been proposed that nongonadal GCTs arise from ectopic primordial germ cells that have aberrantly migrated during embryogenesis. During a time between their migration and development to mature gametes, primordial germ cells are characterized by their lack of imprinting, which can be assessed by the evaluation of allel...

Pediatric germ cell tumors (GCTs) commonly arise at extragonadal sites. It has been proposed that nongonadal GCTs arise from ectopic primordial germ cells that have aberrantly migrated during embryogenesis. During a time between their migration and development to mature gametes, primordial germ cells are characterized by their lack of imprinting, which can be assessed by the evaluation of allel...