The prevalence and spectrum of KLF1 mutations in the Chinese population. (A) Sampling design and study outcomes. Southern Chinese population: Three consecutive cohorts (A-C) of 3839 subjects from 2 thalassemia endemic regions (Guangxi and Guangdong provinces) were designed to investigate the incidence of KLF1 mutations; 79 phenotype-oriented subjects (cohort D) selected from the same region were recruited for enrichment of KLF1 mutation–positive subjects. The β-globin gene in all 79 subjects was completely analyzed; those patients positive for β-thalassemia mutations were excluded from analysis. All mutant alleles (n = 64) detected in these 2 approaches were used to assess the mutation spectrum of KLF1. ^#HBB genotype categories of 11 KLF1 mutation–positive subjects in cohort B were as follows: 1 β⁺/β^N, 1 β^E/β^N, 7 β⁰/β^N, and 2 β⁰/β^N coinherited with α-thalassemia. Northern Chinese population: 1190 nonthalassemics were recruited from a nonthalassemia endemic region (Shandong Province). (B) Exons, introns, and domains are shown with the untranslated regions (white), proline-rich regions (blue), and zinc fingers (ZFs; purple). The positions of the HRM primers are noted above the physical map, and 4 novel and 4 previously reported functional KLF1 mutations in south (red) and north (gray) China are shown below the map. Allelic distribution of KLF1 mutations in the southern Chinese population are indicated in parentheses.