PgmNr Z543: Functional conservation of the zebrafish germ plasm organizer Bucky ball and Drosophila Oskar.

Authors:
P. Krishnakumar 1 ; S. Riemer 1 ; T. Lingner 1 ; F. Bontems 2 ; R. Dosch 1


Institutes
1) University Of Goettingen, Goettingen, Niedersachsen, DE; 2) University of Geneva Genève, GE, Switzerland.


Abstract:

The germline is vital for the continuation of a species. Many animals specify their germ cells by deposition of a maternal RNA granule termed germ plasm. The inheritance of germ plasm by an embryonic cell initiates its development into a primordial germ cell. To this end, two proteins are known in animals which program germ cell development in vivo: Oskar, which is specific to insects and Bucky ball (Buc), which we discovered in vertebrates. These two proteins are termed germ plasm organizers because their loss of function results in the failure to form germ plasm.

We discovered in the zebrafish embryo that both germ plasm organizers possess the fascinating ability to transform a somatic cell into a primordial germ cell. This result indicates that both proteins act through a conserved biochemical network to specify the germ cell fate. Comparing the amino acid sequence of the two organizers, we found that Drosophila Oskar and Zebrafish Bucky Ball showed no conserved domains to explain their similar function. To shed light on the biochemical interaction network of Bucky ball, we carried out co-immunoprecipitation experiments. We found that Buc interacts in-vivo with the canonical germ plasm factor Vasa as described for Oskar.

To explain the deviation from the traditional structure-function paradigm by the two proteins, we discovered that both encode intrinsically disordered proteins (IDP). As IDPs quickly change their sequence during evolution, we propose that Buc is an Oskar homolog, which exerts its conserved role through similar biophysical properties. In summary, these data describe the first example of proteins, which were previously classified as “novel” or “species-specific”, but which are indeed functional homologs from distant species.



ZFIN Genetics Index
1. buc
2. ddx4