Low maternal levels detected at the 4-cell stage. At gastrulation, uniformly expressed in the animal cap and marginal zone. During neurulation, expressed in the notochord, underlying gastrocoel roof plate and ventral epidermis. In tailbud embryos, expression is maintained in the notochord and is also found in the anterior brain, eye and head mesenchyme and in the heart, dermomyotome, pronephros, lateral blood islands and proctodeum. Expression persists in head tissues, heart and notochord in late tailbud stages. Belongs to the GASK family.