The polymorphism of the Knops blood group system among five Chinese ethnic groups.

This work aims to explain the complexity of the Knops blood group system in the Chinese population. The Knops blood group system consists of antigens encoded by CR1 gene exon 29. A total of 281 individuals from the Han, Uigur, Tu, Lisu and Dong ethnic groups were studied. The coding region of the CR1 gene of 11 Han donors was analysed using reverse transcription-polymerase chain reaction (PCR) and sequencing. CR1 gene exon 29 in the 39 samples was analysed through genomic DNA sequencing. According to the sequencing result, a PCR-sequence-specific primers system was designed to screen the A4646G and A4870G alleles in the Chinese population. Twelve single nucleotide polymorphisms (SNPs) were observed in the coding region of the CR1 gene in the Han population. Two SNPs (A4646G and A4870G) were detected in the CR1 gene exon 29. The 4646G allele was found only in the Uigur and Tu ethnic groups, in which the allele frequencies were 0·11 and 0·06, respectively. The frequencies of the 4870A allele in the Han, Uigur, Tu, Lisu and Dong ethnic groups were 0·82, 0·83, 0·82, 0·57 and 0·57, respectively. The CR1 gene in the Chinese people is more conservative than that in the Caucasian or African people. Different Chinese ethnic groups may have their own different CR1 gene characteristics. The existence of 4646G in the Uigur and Tu ethnic groups suggests that both may carry certain Caucasian characteristics in the CR1 gene. The frequency of 4870G in the Lisu and Dong ethnic groups implies possible incidence of evolutionary pressure similar to what the Africans had experienced.