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Nashchekin et al 2021 Figure 4 Diagram of cyst polarisation

Oocyte identity is established inside a cyst of interconnected germ cells but how this occurs is not well understood. Using Drosophila as a model, the St Johnston lab reveal a molecular mechanism underlying the oocyte specification process. Initial asymmetry in the cyst results from unequal divisions during cyst formation. The microtubule minus end-binding protein Patronin/CAMSAP translates the asymmetry into a polarised microtubule network that directs transport of oocyte fate determinants into a single germ cell to establish the oocyte.

 

Symmetry breaking in the female germline cyst

Nashchekin D et al. (2021) Science 374: 874-879. DOI: 10.1126/science.abj3125

 

Summary from the paper

In mammals and flies, only one cell in a multicellular female germline cyst becomes an oocyte, but how symmetry is broken to select the oocyte is unknown.

Here, we show that the microtubule (MT) minus end-stabilizing protein Patronin/CAMSAP marks the future Drosophila oocyte and is required for oocyte specification. The spectraplakin Shot recruits Patronin to the fusome, a branched structure extending into all cyst cells. Patronin stabilizes more MTs in the cells with the most fusome material.

Our data suggest that this weak asymmetry is amplified by Dynein-dependent transport of Patronin-stabilized MTs. This forms a polarized MT network, along which Dynein transports oocyte determinants into the presumptive oocyte. Thus, Patronin amplifies a weak fusome anisotropy to break symmetry and select one cell to become the oocyte.

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Studying development to understand disease

The Gurdon Institute is funded by Wellcome and Cancer Research UK to study the biology of development, and how normal growth and maintenance go wrong in cancer and other diseases.
 

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