Biology

Dr. Chaitanya Dingare
Institute of Cell Biology and Neuroscience, Goethe University, Frankfurt-am-Main, Germany

In aquatic species such as fishes, the process of fertilization is external and is mediated by binding of a sperm to a funnel shaped opening on the vitelline membrane of an egg, named ‘Micropyle’. Very little information is available on how this Micropyle is formed and the signaling pathways involved in its formation. Our recent findings in the lab show that a hippo pathway component, the transcriptional co-activator Taz (wwtr1) plays a major role in the formation of a functional Micropyle in zebrafish. The Micropyle in zebrafish is formed by the Micropylar Cell (MC) a specialized follicular cell present at the animal pole of the oocyte. The MC blocks the formation of the vitelline membrane at the contact point between itself and the oocyte, leaving an opening. In the maternal zygotic taz mutants there is no functional Micropyle formed leading to infertility. The absence of the functional Micropyle alludes to either a complete absence of or a defective MC. Interestingly Taz protein is restricted to the MC, supporting its cell-autonomous role. Accordingly, Taz also marks the ectopic MCs in the buckyball (buc) mutant, which shows animal-vegetal polarity defects. These results altogether corroborate the role of Taz in the MC fate specification. Here, we identified the first known marker for the MC. Moreover, our study represents a unique case of how the hippo-signaling component brings about the interaction between the somatic and the germ cells, which further influences the fertility in a vertebrate system.