Publications by authors named "Peixin Amy Chen"

2 Publications

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Constrained chromatin accessibility in PU.1-mutated agammaglobulinemia patients.

J Exp Med 2021 Jul 5;218(7). Epub 2021 May 5.

Department of Genetics, University of Alabama at Birmingham, Birmingham, AL.

The pioneer transcription factor (TF) PU.1 controls hematopoietic cell fate by decompacting stem cell heterochromatin and allowing nonpioneer TFs to enter otherwise inaccessible genomic sites. PU.1 deficiency fatally arrests lymphopoiesis and myelopoiesis in mice, but human congenital PU.1 disorders have not previously been described. We studied six unrelated agammaglobulinemic patients, each harboring a heterozygous mutation (four de novo, two unphased) of SPI1, the gene encoding PU.1. Affected patients lacked circulating B cells and possessed few conventional dendritic cells. Introducing disease-similar SPI1 mutations into human hematopoietic stem and progenitor cells impaired early in vitro B cell and myeloid cell differentiation. Patient SPI1 mutations encoded destabilized PU.1 proteins unable to nuclear localize or bind target DNA. In PU.1-haploinsufficient pro-B cell lines, euchromatin was less accessible to nonpioneer TFs critical for B cell development, and gene expression patterns associated with the pro- to pre-B cell transition were undermined. Our findings molecularly describe a novel form of agammaglobulinemia and underscore PU.1's critical, dose-dependent role as a hematopoietic euchromatin gatekeeper.
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http://dx.doi.org/10.1084/jem.20201750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8105723PMC
July 2021

Polymer-stabilized Cas9 nanoparticles and modified repair templates increase genome editing efficiency.

Nat Biotechnol 2020 01 9;38(1):44-49. Epub 2019 Dec 9.

Department of Medicine, University of California, San Francisco, San Francisco, CA, USA.

Versatile and precise genome modifications are needed to create a wider range of adoptive cellular therapies. Here we report two improvements that increase the efficiency of CRISPR-Cas9-based genome editing in clinically relevant primary cell types. Truncated Cas9 target sequences (tCTSs) added at the ends of the homology-directed repair (HDR) template interact with Cas9 ribonucleoproteins (RNPs) to shuttle the template to the nucleus, enhancing HDR efficiency approximately two- to fourfold. Furthermore, stabilizing Cas9 RNPs into nanoparticles with polyglutamic acid further improves editing efficiency by approximately twofold, reduces toxicity, and enables lyophilized storage without loss of activity. Combining the two improvements increases gene targeting efficiency even at reduced HDR template doses, yielding approximately two to six times as many viable edited cells across multiple genomic loci in diverse cell types, such as bulk (CD3) T cells, CD8 T cells, CD4 T cells, regulatory T cells (Tregs), γδ T cells, B cells, natural killer cells, and primary and induced pluripotent stem cell-derived hematopoietic stem progenitor cells (HSPCs).
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http://dx.doi.org/10.1038/s41587-019-0325-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954310PMC
January 2020