Institute of Cell Biology, Erez Raz Lab

In contrast with other organisms, the PGCs of zebrafish originate at random positions with respect to the dorsoventral axis. Yet, within 24 hours of development most of the cells arrive at distinct bilateral positions from which they coalesce into a gonad. We use zebrafish PGCs as model for cell fate specification, motility and directed migration in vivo 3D environment. Different research lines in each area are under investigation.


* Cell fate specification

To learn more about the molecular mechanisms of PGC specification in zebrafish we initiated screens for genes that are expressed in the germ cells at different time points during early embryogenesis. Results of In-Situ hybridization screens, Microarray analysis and next generation sequencing were combined to highlight the most crucial players in PGCs specification. Functional analysis of these genes are being investigated usisng forward (ZFNs and TALENs) and reverse genetic tools(morpholino knock-down).

For example, morphant embryos for Dead End (Dnd) function (maternally provided germ plasm component) will loose their PGCs through Apoptosis by the end of first day of development. We found that Dnd functions by protecting specific mRNAs from microRNA inhibitory effects. We set to find protein interaction partners of Dnd as well as protected mRNAs, to understand the molecular basis fate specification and maintenance in zebrafish PGCs.


* Motility

Zebrafish PGCs move by balloon like protrusions called Bleb. This behavior is intrinsic for PGCs and independent of external guiding cue. We would like to understand the basis for this type of motility.

Several projects are running in the lab which are using genetic and biophysical approaches including investigation of bleb formation mechanisms in PGCs,, characteristics of germ cells blebs and their actual contribution to cell motility.
Coordination of different forces inside and outside of motile germ cells including internal pressure, differential contractile forces and regulation of adhesiveness to neighboring cells are among other projects which are currently under investigation in our lab.



* Directed migration

We previously have identified the molecular nature of attractive signal for germ cell directed migration as chemokine SDF1a.
PGCs migrate up the gradient of SDF1a, which is dynamicly shaped by its receptor CXCR7, expressed in somatic cells, and sensed by its receptor in germ cells ,CXCR4b.
We currently investigate molecular machinery of chemokine signaling downstream of CXCR4b. Another line of researches in our lab are dealing with mechanisms of gradient sensing by germ cells.