CHRNB3 and Norrie disease: On the basis of the previous association results of a high-density study covering the complete family of 16 CHRN genes in a population of European ancestry, Saccone et al.30 extended their research to determine whether variants in the CHRNB3–CHRNA6 gene cluster also are associated with ND in African-Americans (AAs).33 They did not detect any associated SNP in their AA sample with a sample size of 710.