CENTRIN IS SYNTHESIZED AND ASSEMBLED INTO BASAL BODIES DURING NAEGLERIA DIFFERENTIATION

During differentiation of Naegleria from vegetative amoebae to tempora ry flagellates, the microtubular cytoskeleton, including two basal bod ies and flagella, is assembled de novo. Centrin is an integral compone nt of these basal bodies [Levy et al., 1996, Cell Motil. Cytoskeleton 33: 298-323]. In many organisms, centrin appears to be a constitutive protein, but in Naegleria centrin gene expression occurs only during d ifferentiation. Cent-in mRNA, which has not been detected in amoebae: appears and disappears earlier in differentiation than a coordinately regulated set of differentiation-specific mRNAs encoding flagellar tub ulin and calmodulin. Centrin antigen accumulates during differentiatio n, and then decreases in abundance as the flagellates mature and rever t to amoebae. No localization of centrin has been detected in amoebae. During differentiation, centrin becomes localized to the basal bodies as soon as these structures are detected with anti-tubulin antibodies , first as a single dot and finally as two basal bodies. During revers ion of flagellates to amoebae, centrin remains localized to the basal bodies for as long as they are present. When assembly of tubulin-conta ining structures during differentiation is prevented using oryzalin, c entrin localization is prevented as well, yet inhibition of assembly d oes not affect accumulation of centrin antigen. Apparently in Naegleri a, the role of centrin is primarily for a differentiation- or flagella te-specific function. The temporary presence of centrin is concurrent with the presence of centriolar basal bodies, which supports the conje cture that in Naegleria centrin may be needed only when these organell es are present. Cell Motil. Cytoskeleton 40:249-260, 1998. (C) 1998 Wi ley-Liss, Inc.