Plays a role in craniofacial and inner ear morphogenesis during embryonic development. Acts within the otic vesicle epithelium to control formation of the lateral semicircular canal in the inner ear, possibly by restricting the expression of NTN1. Interacts with EGFR, ERBB2 and ERBB4 (in vitro). Detected in cytoplasmic vesicles when coexpressed with ERBB4. Widely expressed. Detected in the lateral wall of the otic vesicle at 10.5 dpc. Enriched in lateral pouch epithelium at 12.5 dpc. Mice display circling and head tossing behavior, due to a defect in inner ear morphogenesis. In mutants, fusion of the canal pouches starts earlier than normal and involves an abnormally large region, leading to truncation of the lateral semicircular canal in the inner ear. Nevertheless, hearing seems to be normal. Mutant mice also display craniofacial deformities, and especially a dramatically shortened snout. Truncated N-terminus.