CDC-like kinase 2 (CLK2) belongs to a family of autophosphorylating kinases termed CLK (CDC2/CDC28-like kinases), which have been shown to phosphorylate serine- and arginine-rich (SR) proteins of the spliceosomal complex, and to influence alternative splicing in overexpression systems. Recent findings demonstrated that the CLK kinases activate PTP-1B family members, and this phosphatase may be an important cellular target for CLK action. Mutations in the CLK2 proteins affect organismal featu