The spectrum of mutations and possible function of the CHAC Gene

The gene responsible for autosomal-recessive chorea-acanthocytosis, CHAC, spans 250 kilobases on chromosome 9q21. It is a large gene, comprising 73 exons, and it seems to be ubiquitously expressed. So far, 71 different mutations have been reported in CHAC, the majority of which are predicted to lead to a null allele. Analysis of the CHAC product, chorein, reveals that it contains several tetratricopeptide repeats, which are believed to be involved in protein-protein interactions. Chorein is homologous to Vps13p, implicated in protein trafficking in yeast. However, until functional studies are carried out, the possible function of chorein, and how its absence leads to the erythrocyte abnormalities and neurodegeneration that are characteristic of chorea-acanthocytosis, is open to speculation.