Enables coreceptor activity. Predicted to be involved in negative regulation of activin receptor signaling pathway and regulation of transcription, DNA-templated. Predicted to be located in membrane. Human ortholog(s) of this gene implicated in IGSF1 deficiency syndrome. Orthologous to human IGSF1 (immunoglobulin superfamily member 1). [provided by Alliance of Genome Resources, Apr 2022]