Alix is a cytoplasmic protein involved in both programmed cell death and endocytosis (Oncogene 21 (2002) 6801). These activities of Alix may be related to its demonstrated capacity to bind ALG-2 (Apoptosis Linked Gene-2), CIN85/SETA and endophilins (J. Biol. Chem. 275 (2000) 19275; Science 271 (1996) 521; Cell Death Differ. 6 (1999) 124; J. Biol. Chem. 274 (1999) 1533; J. Biol. Chem. 28 (2002) 29108). Here we report for the first time the developmental expression pattern of Alix protein during chick development. We show by immunochemistry that the protein appears first in the ventral part of the rostral neural tube (stage 16 HH) and then in more caudal parts, thereby following the rostro-caudal maturation of the neural tube. Later on, the protein is found in the distal part of axons as well as in the dermomyotome where it becomes restricted to the muscle progenitors. This first demonstration of Alix modulation during development suggests a role for the protein in early phases of motoneuron and muscle growth and differentiation.