# Maternal expression of the novel centrosome assembly factor Wdr8 is required for vertebrate embryonic mitosis and development

## TL;DR

This study identifies Wdr8 as a crucial protein for centrosome assembly in vertebrate embryos, impacting early development and genome stability.

## Contribution

The study reveals Wdr8 as a novel maternal factor essential for PCM assembly and genome stability in early vertebrate embryos.

## Key findings

- Wdr8 is maternally essential for PCM assembly during embryonic mitoses in medaka.
- Wdr8 interacts with SSX2IP via its WD40 domains to ensure proper centrosome function.
- Exogenous Wdr8 rescues Wdr8−/− embryos to adulthood, except when WD40 domains are mutated.

## Abstract

The assembly of the first centrosome occurs upon fertilisation when the male centrioles recruit pericentriolar material (PCM) from the egg cytoplasm. While inaccuracy in the assembly of centrosomes leads to infertility and abnormal embryogenesis, the mechanism that ensures accurate assembly in vertebrate embryos remains obscure. Here we applied a CRISPR-Cas9-mediated gene knockout to show that Wdr8, a novel centrosomal protein, is maternally essential for PCM assembly during embryonic mitoses of medaka (Oryzias latipes). Maternal/zygotic Wdr8-null (Wdr8−/−) blastomeres exhibit severe defects in PCM assembly that cause them to divide asymmetrically and develop multipolar mitotic spindles and aneuploidy. We demonstrate that Wdr8 interacts via its WD40 domains with the centriolar satellite protein SSX2IP. Strikingly, exogenously provided Wdr8 fully rescues Wdr8−/− embryos to adulthood, except in variants with mutations in the WD40 domains. This combination of targeted gene inactivation and in vivo reconstitution of the maternally essential Wdr8-SSX2IP complex reveals an essential link between maternal PCM and the stability of the zygotic genome in the early vertebrate embryo.