|Title||The Drosophila CPEB Protein Orb Specifies Oocyte Fate by a 3'UTR Dependent Autoregulatory Loop.|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Barr, J, Gilmutdinov, R, Wang, L, Shidlovskii, ii, Y, Schedl, P|
|Date Published||2019 Oct 08|
orb encodes one of the two fly CPEB proteins. These widely conserved proteins bind to the 3'UTRs of target mRNAs and activate or repress their translation. We show here that a positive autoregulatory loop driven by the orb gene propels the specification of oocyte identity in Drosophila egg chambers. Oocyte fate specification is mediated by a 3'UTR dependent mechanism that concentrates orb mRNAs and proteins in one of the two pro-oocytes in the 16 cell germline cyst. When the orb 3'UTR is deleted, orb mRNA and protein fail to localize and all sixteen cells become nurse cells. In WT, the oocyte is specified when orb and other gene products concentrate in a single cell in region 2b of the germarium. A partially functional orb 3'UTR replacement delays oocyte specification until the egg chambers reach stage 2 of oogenesis. Prior to this point, orb mRNA and protein are unlocalized, as are other markers of oocyte identity, and the oocyte is not specified. After stage 2, ∼50% of the chambers successfully localize orb in a single cell, and this cell assumes oocyte identity. In the remaining chambers, the orb autoregulatory loop is not activated and no oocyte is formed. Finally, maintenance of oocyte identity requires continuous orb activity.