Bao-An Chen

Simultaneous detection of platelet-specific antibodies based on a photonic crystal-encoded suspension array.

BACKGROUNDnThe appearance of antibodies to platelets in the blood is an important cause of immune thrombocytopenia (ITP), and platelet glycoprotein (GP)-specific antibody detection may be helpful to diagnose this condition.nnnMETHODSnPhotonic crystal microspheres with different distinct reflection spectra were coated with anti-GPIIb, -GPIIIa, -GPIb and -GPIX monoclonal antibodies (MoAbs) to create a photonic crystal-encoded suspension array (PCSA). Fluorescein isothiocyanate-labelled goat anti-human IgG was added to detect human IgG simultaneously. The detection results were analysed by fluorescence microscopy. Parallel MoAb immobilization of platelet antigen (MAIPA) was used as a reference test. Both methods were used to analyse 63 clinical samples including serum from 32 ITP patients and 31 healthy humans.nnnRESULTSnThe PCSA showed greater sensitivity than MAIPA in detecting anti-GPIIb (75.0% vs 31.1%) and GPIIIa (84.4% vs 40.6%) antibodies and similar sensitivity as MAIPA in detecting anti-GPIb (37.5% vs 34.4%) and GPIX (50.0% vs 40.8%) antibodies. The MAIPA and PCSA tests had similar specificity. The PCSA detected higher dilutions of serum containing anti-GPIIIa antibody or anti-GPIIb antibody than did MAIPA. The entire testing process was controlled within 3.5h.nnnCONCLUSIONSnThe PCSA assay described has comparable or better sensitivity and specificity compared to the MAIPA and is more rapid.

CTCF boundary remodels chromatin domain and drives aberrant HOX gene transcription in acute myeloid leukemia

HOX gene dysregulation is a common feature of acute myeloid leukemia (AML). The molecular mechanisms underlying aberrant HOX gene expression and associated AML pathogenesis remain unclear. The nuclear protein CCCTC-binding factor (CTCF), when bound to insulator sequences, constrains temporal HOX gene-expression patterns within confined chromatin domains for normal development. Here, we used targeted pooled CRISPR-Cas9-knockout library screening to interrogate the function of CTCF boundaries in the HOX gene loci. We discovered that the CTCF binding site located between HOXA7 and HOXA9 genes (CBS7/9) is critical for establishing and maintaining aberrant HOXA9-HOXA13 gene expression in AML. Disruption of the CBS7/9 boundary resulted in spreading of repressive H3K27me3 into the posterior active HOXA chromatin domain that subsequently impaired enhancer/promoter chromatin accessibility and disrupted ectopic long-range interactions among the posterior HOXA genes. Consistent with the role of the CBS7/9 boundary in HOXA locus chromatin organization, attenuation of the CBS7/9 boundary function reduced posterior HOXA gene expression and altered myeloid-specific transcriptome profiles important for pathogenesis of myeloid malignancies. Furthermore, heterozygous deletion of the CBS7/9 chromatin boundary in the HOXA locus reduced human leukemic blast burden and enhanced survival of transplanted AML cell xenograft and patient-derived xenograft mouse models. Thus, the CTCF boundary constrains the normal gene-expression program, as well as plays a role in maintaining the oncogenic transcription program for leukemic transformation. The CTCF boundaries may serve as novel therapeutic targets for the treatment of myeloid malignancies.