Guichard A, Roark M, Ronshaugen M, Bier E
Section of Cell and Developmental Biology, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0349, USA.
Dev Biol. 2000 Oct 15;226(2):255-66. doi: 10.1006/dbio.2000.9851.
The Drosophila rhomboid (rho) gene participates in localized activation of EGF-receptor signaling in various developmental settings. The Rhomboid protein has been proposed to promote presentation and/or processing of the membrane-bound Spitz (mSpi) EGF-related ligand to generate an active diffusible form of the ligand. Here, we report on a new rhomboid-related gene identified by sequence similarity searching that we have named brother of rhomboid (brho). In contrast to rho, which is expressed in complex patterns during many stages of development, brho appears to be expressed only during oogenesis. brho transcripts are present in early oocytes and abut posterior follicle cells which exhibit high levels of MAPK activation. brho, like rho, collaborates with Star to promote signaling through the EGF-R/MAPK pathway, and genetic evidence indicates that Brho can activate both the mSpi and the Grk precursor EGF ligands in the wing. We propose that endogenous brho may activate the oocyte-specific Gurken ligand and thereby participate in defining posterior cell fates in the early follicular epithelium.
果蝇类菱形基因（rho）在多种发育环境中参与表皮生长因子受体（EGF-receptor）信号的局部激活。有人提出，类菱形蛋白可促进膜结合型斯皮茨蛋白（mSpi）这种与EGF相关的配体的呈递和/或加工，以生成一种有活性的可扩散形式的配体。在此，我们报告通过序列相似性搜索鉴定出的一个新的类菱形相关基因，我们将其命名为类菱形之弟（brho）。与rho在发育的许多阶段以复杂模式表达不同，brho似乎仅在卵子发生过程中表达。brho转录本存在于早期卵母细胞中，并紧邻显示高水平丝裂原活化蛋白激酶（MAPK）激活的后部卵泡细胞。与rho一样，brho与星状蛋白（Star）协同作用，促进通过EGF-R/ MAPK途径的信号传导，并且遗传学证据表明，Brho可在翅膀中激活mSpi和葛氏激酶（Grk）前体EGF配体。我们提出，内源性brho可能激活卵母细胞特异性的gurken配体，从而参与确定早期卵泡上皮中的后部细胞命运。
