Plays a role in planar mitotic spindle orientation in retinal progenitor cells (RPCs) and promotes the production of symmetric terminal divisions (By similarity). Negatively regulates the mitotic apical cortex localization of GPSM2 (PubMed:26766442). Involved also in positive regulation of cell proliferation and tumor cell growth (PubMed:23576022, PubMed:23704824). Interacts with a spindle orientation complex at least composed of GNAI1, GPSM2 and NUMA1 (PubMed:26766442). Interacts with GPSM2 (via TPR motifs); this interaction is required to prevent GPSM2 anchoring at the mitotic apical cortex and is inhibited in presence of NUMA1 in a dose dependent manner (PubMed:26766442). Interacts with PARD3 (PubMed:26766442). Localized at the apical cortical region during the M phase. In horizontally retinal progenitor dividing cells, localized at the pole cortical region from prophase to telophase cells. In vertically retinal progenitor dividing cells, not detected at the pole cortical region at any stage of mitosis. Expressed in 5-month-old fetal tissues, including stomach, intestine, colon, liver, brain, lung, heart, spleen and kidney (PubMed:17525738). Undetectable in non-cancerous adult tissues (PubMed:17525738). Expressed in many primary gastric carcinoma, but almost not in adjacent normal mucosa (PubMed:17525738). Expressed preferentially in M and G1 phases, compared to S and G2 phases (PubMed:17525738). Expression is up-regulated in hepatocellular carcinoma (HCC) and colorectal cancer (CRC) tissues (at protein level) (PubMed:23704824). Truncated N-terminus. Truncated N-terminus.