UC Santa Cruz

Key PointsGerm cells generate an organism's gametes and progeny. To accomplish this, germ cells must be properly specified and protected during development.In some animals, specification of the germline is continuous and involves the segregation of cytoplasmic 'determinants' during embryogenesis (preformation). In other animals, the germline is newly formed and requires inductive signalling during embryogenesis (induction).Among the diverse mechanisms of germ cell specification are: transmission of maternally supplied germ plasm containing germ granules to primordial germ cells (PGCs); transmission of epigenetic memory from parent germ cells to PGCs in progeny; and expression of transcription factors that programme embryonic cells to develop as PGCs.Aberrant gene expression or misguided PGC migration can cause germ cells to exhibit somatic features and even contribute to somatic tissues. In the gonad, germ cells are prevented from expressing genes that would threaten germline health and development.The mechanisms that suppress aberrant gene expression and protect germline fate include global transcriptional repression in PGCs, maintenance of a germline chromatin state and translation of only germline-appropriate transcripts in germ cells.