Enables RS domain binding activity. Predicted to be involved in several processes, including mRNA processing; mitotic cytokinesis; and regulation of mRNA splicing, via spliceosome. Predicted to act upstream of or within RNA splicing. Predicted to be located in nuclear speck. Is expressed in several structures, including alimentary system; central nervous system; genitourinary system; respiratory system; and sensory organ. Orthologous to human SON (SON DNA and RNA binding protein). [provided by Alliance of Genome Resources, Apr 2022]