EXPRESSION AND LOCALIZATION OF BRAIN ANKYRIN ISOFORMS AND RELATED PROTEINS DURING EARLY DEVELOPMENTAL STAGES OF RAT NERVOUS-SYSTEM

Expression and localization of two isoforms of brain ankyrin, 440- and 220-kDa ankyrin,, were studied in the developing nervous system of th e rat fetus. The 440-kDa ankyrin, appeared on as early as embryonic da y 13, and its level increased progressively toward the day of birth, w hich was similar to the expression pattern of growth-associated protei n (GAP)-43, a well-established axonal protein. On the other hand, 220- kDa ankyrin, was expressed at a low level but constitutively throughou t the latter prenatal period and was a major isoform even before embry onic day 14. Whereas the localization of 440-kDa ankyrin, was essentia lly confined to the axons, judging from the similarity with that of GA P-43, 220-kDa ankyrin, showed a rather general distribution in neural tissue. The localization of L1, known as an ankyrin(B)-binding protein , was similar to that of 440-kDa ankyrin, in the brain tissue, whereas it was similar to that of 220-kDa ankyrin, in cultured neurons, sugge sting that the interaction of L1 with brain ankyrins in neurons is aff ected by their environment.