E3 ubiquitin-protein ligase component of the CTLH complex. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Identified in the CTLH complex that contains at least RANBP9, MKLN1, MAEA, RMND5A, GID8 and ARMC8. Detected at constant levels throughout embryonic development (at protein level). Detected at high levels at the four cell stage of embryogenesis, followed by a steady decline until gastrulation. Detected at low levels throughout further stages of embryo development. Primarily expressed in the head region during gastrulation, and in the neuroectoderm during neurulation. Morpholino knockdown of the protein disrupts normal development of the mesencephalon, the prosencephalon and the eyes.