Involved in pre-mRNA splicing as a component of the spliceosome (By similarity). Regulates alternative splicing of the HSPG2 pre-mRNA (By similarity). Required for normal accumulation of IK (By similarity). Required for normal mitotic spindle assembly and normal progress through mitosis (By similarity). Component of the spliceosome B complex. Interacts with IK. Colocalizes with SRSF1 in nuclear speckles. Highly expressed in cerebellum, midbrain and heart. Moderately expressed in brain stem, cerebral cortex and liver. Detected in dentate gyrus, pyramidal layer of the hippocampus and Purkinje and granule neurons of cerebellum. The WD repeats assemble into a seven-bladed WD propeller. Belongs to the WD repeat SMU1 family.