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bioRxiv · 10.1101/2023.01.18.524359

The Shot CH1 domain recognises a distinct form of F-actin during Drosophila oocyte determination

Nashchekin, D.·Squires, I.·Prokop, A.·St Johnston, D.
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Abstract

As in mammals, only one cell in a Drosophila multicellular female germline cyst is specified as an oocyte. The symmetry-breaking cue for oocyte selection is provided by the fusome, a tubular structure connecting all cells in the cyst. The Drosophila spectraplakin Shot localises to the fusome and translates its asymmetry into a polarised microtubule network that is essential for oocyte specification, but how Shot recognises the fusome is unclear. Here we demonstrate that Shots actin-binding domain (ABD) is necessary and sufficient to localise Shot to the fusome and mediates Shot function in oocyte specification together with the microtubule-binding domains. The calponin homology domain 1 (CH1) of Shots ABD recognises fusomal F-actin and requires CH2 to distinguish it from other forms of F-actin in the cyst. By contrast, the ABDs of Utrophin, Fimbrin, Filamin, Lifeact and F-tractin do not recognise fusomal F-actin. We therefore propose that Shot propagates fusome asymmetry by recognising a specific conformational state of F-actin on the fusome.

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Nashchekin, D., Squires, I., Prokop, A., St Johnston, D.. 2023-01-19. The Shot CH1 domain recognises a distinct form of F-actin during Drosophila oocyte determination. https://doi.org/10.1101/2023.01.18.524359

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