Hydroxyurea therapy has proven laboratory and clinical efficacies for children with sickle cell anemia (SCA

Caspase-2 is an initiator caspase, activated in response to heat shock and other stressors that induce apoptosis. Activation of caspase-2 requires induced proximity resulting after recruitment to caspase-2 activation complexes, such as the PIDDosome. We have adapted bimolecular fluorescence complementation (BiFC) to measure caspase-2 induced proximity in real time, in single cells. Non-fluorescent fragments of the fluorescent protein Venus that can associate to reform the fluorescent complex were fused to caspase-2 allowing visualization and kinetic measurements of caspase-2 induced proximity after heat shock and other stresses. This revealed that the caspase-2 activation platform occurred in the cytosol and not in the nucleus in response to heat shock, DNA damage, cytoskeletal disruption and other treatments. Activation, as measured by this approach, in response to heat shock, was RAIDD-dependent and upstream of mitochondrial outer membrane permeabilization. Furthermore we identify Hsp90α as a key negative regulator of heat shock-induced caspase-2 activation.

Stroke is a devastating complication of sickle cell anemia (SCA), affecting 5% to 10% of patients before adulthood. Several candidate genetic polymorphisms have been proposed to affect stroke risk, but few have been validated, mainly because previous studies were hampered by relatively small sample sizes and the absence of additional patient cohorts for validation testing. To verify the accuracy of proposed genetic modifiers influencing stroke risk in SCA, we performed genotyping for 38 published single nucleotide polymorphisms (SNPs), as well as ␣-thalassemia, G6PD A ؊ variant deficiency, and ␤-globin haplotype in 2 cohorts of children with well-defined stroke phenotypes (130 stroke, 103 nonstroke). Five polymorphisms had significant influence (P < .05): SNPs in the ANXA2, TGFBR3, and TEK genes were associated with increased stroke risk, whereas ␣-thalassemia and a SNP in the ADCY9 gene were linked with decreased stroke risk. Further investigation at these genetic regions may help define mutations that confer stroke risk or protection in children with SCA. (Blood. 2011;117(24): 6681-6684)

Key Points• WES can be applied for precise RH genotyping, detection of new or uncommon variants, and determination of RHD zygosity.• An altered RH genotype is a risk factor for Rh alloimmunization in patients with sickle cell anemia.RH genes are highly polymorphic and encode the most complex of the 35 human blood group systems. This genetic diversity contributes to Rh alloimmunization in patients with sickle cell anemia (SCA) and is not avoided by serologic Rh-matched red cell transfusions.

• The complication of stroke is common in patients with SCA, and there is a genetic component.• We have performed a largeassociation study to identify 2 genetic variants that protect patients with SCA from stroke.Stroke is a devastating complication of sickle cell anemia (SCA), occurring in 11% of patients before age 20 years. Previous studies of sibling pairs have demonstrated a genetic component to the development of cerebrovascular disease in SCA, but few candidate genetic modifiers have been validated as having a substantial effect on stroke risk. We performed an unbiased whole-genome search for genetic modifiers of stroke risk in SCA. Genome-wide association studies were performed using genotype data from single-nucleotide polymorphism arrays, whereas a pooled DNA approach was used to perform whole-exome sequencing. In combination, 22 nonsynonymous variants were identified and represent key candidates for further in-depth study. To validate the association of these mutations with the risk for stroke, the 22 candidate variants were genotyped in an independent cohort of control patients (n 5 231) and patients with stroke (n 5 57) with SCA. One mutation in GOLGB1 (Y1212C) and another mutation in ENPP1 (K173Q) were confirmed as having significant associations with a decreased risk for stroke. These mutations were discovered and validated by an unbiased whole-genome approach, and future studies will focus on how these functional mutations may lead to protection from stroke in the context of SCA. (Blood. 2013;121(16):3237-3245)