Protein Z polymorphisms associated with vaso-occlusive crisis in young sickle cell disease patients

Abstract

We investigated the association of protein Z (PZ) promoter (rs3024718, rs3024719, and rs3024731) and intron (rs3024735; G79A) SNPs with sickle cell disease (SCD) vaso-occlusive crisis (VOC). Study subjects included 239 SCD patients with VOC and 138 pain-free SCD control patients. PZ genotyping was done by allelic discrimination (real-time PCR) assays. The minor allele frequency of rs3024718 (P=0.03), rs3024719 (P=0.02), rs3024731 (P<0.001), and rs3024735 (P<0.001) were higher in VOC patients than control SCD patients. Significant differences in the distribution of rs3024731 (P=0.028) and rs3024735 (P=0.045) genotypes were seen between VOC and steady-state SCD patients. This association remained significant after adjusting for gender, HbS, and HbF. Four-locus (rs3024718/rs3024719/rs3024731/rs3024735) PZ haplotypes analysis demonstrated increased frequency of GAAA (P=0.024), AGAA (P=0.011), and GGTG (P=0.002), and reduced frequency of AGTG haplotype (P=0.001) in VOC than in steady-state control patients, thereby conferring disease susceptibility and protective nature to these haplotypes, respectively. Of these, only AGTG (P(c)=0.001) and GGTG (P(c)=0.018) remained significant after applying the Bonferroni correction. In conclusion, specific PZ variants and haplotypes are significantly associated with SCD VOC.