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Development 2006 Oct 01;13320:4109-18. doi: 10.1242/dev.02563.
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Shroom2 (APXL) regulates melanosome biogenesis and localization in the retinal pigment epithelium.

Fairbank PD , Lee C , Ellis A , Hildebrand JD , Gross JM , Wallingford JB .

Shroom family proteins have been implicated in the control of the actin cytoskeleton, but so far only a single family member has been studied in the context of developing embryos. Here, we show that the Shroom-family protein, Shroom2 (previously known as APXL) is both necessary and sufficient to govern the localization of pigment granules at the apical surface of epithelial cells. In Xenopus embryos that lack Shroom2 function, we observed defects in pigmentation of the eye that stem from failure of melanosomes to mature and to associate with the apical cell surface. Ectopic expression of Shroom2 in naïve epithelial cells facilitates apical pigment accumulation, and this activity specifically requires the Rab27a GTPase. Most interestingly, we find that Shroom2, like Shroom3 (previously called Shroom), is sufficient to induce a dramatic apical accumulation of the microtubule-nucleating protein gamma-tubulin at the apical surfaces of naïve epithelial cells. Together, our data identify Shroom2 as a central regulator of RPE pigmentation, and suggest that, despite their diverse biological roles, Shroom family proteins share a common activity. Finally, because the locus encoding human SHROOM2 lies within the critical region for two distinct forms of ocular albinism, it is possible that SHROOM2 mutations may be a contributing factor in these human visual system disorders.

PubMed ID: 16987870
Article link: Development
Grant support: [+]

Species referenced: Xenopus
Genes referenced: actl6a rab27a rap1b rap1gap rpe shroom2 shroom3 tubg1
Morpholinos: shroom2 MO1

Article Images: [+] show captions