Primordial germ cell development in fishes: Genes and morphology

Primordial Germ Cell (PGC) determination is one of the most important feats of vertebrate embryonic development because it allows the continuation of life among future generations. In vertebrates, at least two different mechanisms exist that allow species to develop cells that later form the eggs and sperm. In the predetermined mechanism of PGC development, cells are specified by maternal determinants that are located within the germ plasm. In the induced mechanism, cells must be induced by external regulating factors that initiate germ cell development. Preliminary evidence suggests that different groups of fish may use different mechanisms of PGC development.;This thesis seeks to investigate the mechanism of germ cell development in several fish species using conserved sequences of the germ cell-specific gene, POU5f1. Currently, POU5f1 has been identified only in the induced mechanism of PGC development based on morphology of a primitive body plan in the induced mode. Therefore, using phylogenetic analysis of the gene family can determine if a correlation exists between the mode of germ cell development and the presence of a POU5f1 ortholog. This will help to investigate the hypothesis that germ cell determination can be correlated with morphology patterns, specifically an anteriorization of the pelvic fin. It can also test the hypothesis that some genes associated with germ cell development, especially POU5f1, evolve through a mechanism relationship and not a species phylogeny. This can lead to a better understanding of embryonic development processes and its implication for species evolution.