Recent advances in the understanding of germ cell-specific organelles and their functions

In sexually reproducing multicellular organisms, germ cell fate is specified in early embryogenesis, and the resulting germ cells differ structurally, mechanistically and functionally from the somatic cells. In the majority of animals, germ cells contain a subset of distinct organelles and molecules, which attributes and polar and/or asymmetrical distributions are fundamental for the proper function of the gamete, for fertilization and for the subsequent development and patterning of the embryo. Some of these organelles are shared among many different species, while some are unique and have been specifically acquired or adjusted to fit species-specific developmental requirements. In this review, we describe the current state of knowledge on the structures, dynamics and the role of germ cell-specific organelles, molecules, pathways and polarities, and we provide an overview on the most recent insights into their intraspecific uniqueness and interspecific similarities.