NOVEL CENTROSOMAL PROTEIN REVEALS THE PRESENCE OF MULTIPLE CENTROSOMES IN TURKEY (MELEAGRIS-GALLOPAVO) BNBN BINUCLEATED ERYTHROCYTES

The phenotype of the bnbn hemolytic anemia mutation in the domestic tu rkey is manifested as binucleation specifically in the definitive eryt hrocyte lineage, most likely as the consequence of anomolous centrosom al activity (Bloom et al., 1970; Searle and Bloom, 1979). Here we have identified in turkey two variants of the novel, centrosomally-associa ted erythroid-specific protein p23, One variant is Ca2+-sensitive and is highly homologous to its chick counterpart (Zhu et al., 1995, accom panying paper). The other, p21, is a truncated form resulting from a 6 2 amino acid deletion from the 3' end and a 40 amino acid insertion at the 5' end, and appears to lack Ca2+-sensitivity. These proteins are localized at the marginal band, centrosomes and nuclear membrane of di fferentiated erythrocytes. Anti-p23/p21 immunofluorescence revealed th e presence of multiple centrosomes in bnbn eythrocytes. We therefore u ndertook a detailed genetic analysis to determine whether the p21 vari ant represented the bn mutation. Initial tests of normal BnBn and muta nt bnbn individuals suggested that the p23/p21 proteins might be encod ed by the Bu/bn genes. However. further genetic tests demonstrated ind ependent segregation for these two genetic loci. Thus, these proteins are encoded by the heretofore undescribed genes, p23/p21, mapping to a n autosomal locus in the turkey genome.