ALBERT

Description: Abstract 1013 More than 3% of Chinese in Hong Kong are heterozygous carriers of β-thalassemia. Homozygotes or compound heterozygotes for β-thalassemia are usually severely ill and require monthly transfusions. Increased production of fetal hemoglobin (HbF) can modulate the disease severity by compensating for the shortfall of HbA caused by the β-thalassemia mutations. HbF level in adults varies and is regulated as a multigenic trait. Three major HbF quantitative trait loci (QTL) have been identified: the C/T SNP also known as the Xmn I site at the Gγ-globin gene promoter, the BCL11A polymorphism on chromosome 2p16, and the HBS1L-MYB intergenic polymorphism (HMIP) on chromosome 6q23. The functional motif for each of these 3 QTLs responsible for their effects upon HbF is not known. We undertook a genome-wide association study (GWAS), using Illumina Human 610-Quad BeadChip array, on 619 Chinese β-thalassemia heterozygotes from Hong Kong. In this population, the variance in HbF due to HMIP is 13.5%, significantly higher than that due to BCL11A polymorphism (6.4%). We used 1,000 Genomes Project data, SNP imputation, comparisons of association results across populations, predicted binding of transcription factors, and phylogenetic conservation to identify the functional variant in HMIP. Based on these lines of evidence, a hitherto unreported association between HbF expression and a 3-bp deletion on chromosome 6q23 was found. In 335 Chinese β-thalassemia heterozygotes, the 3-bp deletion polymorphism is in complete linkage disequilibrium with rs9399137, the SNP found in multiple GWAS to be most significantly associated with HbF (P=1.4E-24 in the Chinese cohort GWAS). Flanking this deletion are conserved binding sites for TAL1/SCL1, E47, GATA, and RUNX1/AML1, which are essential erythropoiesis-related transcription factors. The 3-bp deletion changes the normal DNA binding configuration of these transcription factors and spatial configuration for DNA-protein binding and/or protein-protein interactions. Furthermore, this 3-bp deletion polymorphism resides within a likely erythroid distal regulatory region manifested by DNase I hypersensitivity and GATA-1 binding (Wahlberg et al, Blood 114:1254, 2009). We hypothesized that a 61-bp fragment of DNA that encompasses the site of the 3-bp deletion polymorphism might have enhancer-like activity. When ligated to the Gγ-globin gene 1.4 kb proximal promoter linked to a luciferase reporter gene, the 61-bp fragment of DNA enhances the Gγ-globin gene promoter activity by more than 3-fold after transient transfection into K562 cells. A 58-bp fragment of DNA that includes the 3-bp deletion has 60% more enhancer-like activity than the 61-bp fragment without the deletion. These findings suggest that this 3-bp deletion polymorphism is most likely the functional motif accounting for HMIP modulation of HbF. Further studies are needed to identify target genes for this enhancer-like activity mediated by the DNA sequences encompassing the 3-bp deletion polymorphism in HMIP. These studies also suggest that this experimental approach could be used to identify functional motifs in other genotype-phenotype association studies. Disclosures: No relevant conflicts of interest to declare.

Description: Fetal hemoglobin (HbF) is regulated as a multigenic trait. By genome-wide association study, we confirmed that HBS1L-MYB intergenic polymorphisms (HMIP) and BCL11A polymorphisms are highly associated with HbF in Chinese β-thalassemia heterozygotes. In this population, the variance in HbF resulting from the HMIP is 13.5%; that resulting from the BCL11A polymorphism is 6.4%. To identify the functional variant in HMIP, we used 1000 Genomes Project data, single nucleotide polymorphism imputation, comparisons of association results across populations, potential transcription factor binding sites, and analysis of phylogenetic conservation. Based on these studies, a hitherto unreported association between HbF expression and a 3-bp deletion, between 135 460 326 and 135 460 328 bp on chromosome 6q23 was found. This 3-bp deletion is in complete linkage disequilibrium with rs9399137, which is the single nucleotide polymorphism in HMIP most significantly associated with HbF among Chinese, Europeans, and Africans. Chromatin immunoprecipitation assays confirmed erythropoiesis-related transcription factors binding to this region in K562 cells. Based on transient expression of a luciferase reporter plasmid, the DNA fragment encompassing the 3-bp deletion polymorphism has enhancer-like activity that is further augmented by the introduction of the 3-bp deletion. This 3-bp deletion polymorphism is probably the most significant functional motif accounting for HMIP modulation of HbF in all 3 populations.

Description: We observe experimentally the spectral and spatial reshaping of fluorescence emission in dye-doped dielectric-metal core-shell resonators that support multipolar electric and magnetic-based cavity plasmon resonances. By comparing the experimental fluorescence spectra with analytical calculations based on Mie theory, we are able to demonstrate that the strong reshaping effects are the results of the coupling of dye molecules to those narrow-band cavity plasmon resonances. In addition, we show that the polarization of the fluorescence emission can also be modified by selectively coupling the molecules to the magnetic or electric based cavity plasmons.

Description: 30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the presence of the intermediate Pt film. The YIG surface shows atomic steps with the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear in-plane uniaxial magnetic anisotropy with a well-defined easy axis along 〈001〉 and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz, similar to YIG epitaxially grown on GGG. Both spin Hall magnetoresistance and longitudinal spin Seebeck effects in the inverted bilayers indicate excellent Pt/YIG interface quality.