Categories: Haematopoietic system phene

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Disease-related: yes

Key variant known: no

Species-specific name: Binucleated erythrocyte

Species-specific symbol: bn

Species-specific description: First reported by Buss (1965), this defect arises from nondisjunction in mitosis. Limited evidence (Searle and Bloom, 1979) suggests that the fault lies with anomalous function of the centrosome (a region of differentiated cytoplasm containing the centriole, which is an organelle involved in cell division - specifically in the formation of spindle fibres which play a central role in disjunction). Interestingly, only erythrocytes are affected - all other cells divide normally. Woods et al. (1995) identified a protein that occurs only in association with centrosomes in erythrocytes, that exists in two forms, p23 and p21, which are encoded at an autosomal locus. Despite initial hopes that the p23/p21 locus would be the locus for binucleated red cells, a segregation analysis by Wood et al. (1995) showed that the two loci are not linked.

Clinical features: Haemolytic anaemia due to abnormal erythrocytes.