Mechanisms of germ cell specification across the metazoans: epigenesis and preformation.
Germ cells play a unique role in gamete production, heredity and evolution. Therefore, to understand the mechanisms that specify germ cells is a central challenge in developmental and evolutionary biology. Data from model organisms show that germ cells can be specified either by maternally inherited determinants (preformation) or by inductive signals (epigenesis). Here we review existing data on 28 metazoan phyla, which indicate that although preformation is seen in most model organisms, it is actually the less prevalent mode of germ cell specification, and that epigenetic germ cell specification may be ancestral to the Metazoa.
Laboratory for Development and Evolution, University Museum of Zoology, Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK. cgme2@hermes.cam.ac.uk
Cassandra G
CG
Extavour
Michael
M
Akam
D000818:Animals; D005075:Biological Evolution; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000502:physiology; D044127:Epigenesis, Genetic; D005854:Germ Cells / Q000502:physiology*; D009024:Morphogenesis; D010802:Phylogeny