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Background Therapies targeting certain CFTR mutants have been approved, yet variations in clinical response highlight the need for in-vitro and genetic tools that predict patient-specific clinical outcomes. Toward this goal, the CF Canada-Sick Kids Program in Individual CF Therapy (CFIT) is generating a "first of its kind", comprehensive resource containing patient-specific cell cultures and data from 100 CF individuals that will enable modeling of therapeutic responses. Methods The CFIT program is generating: 1) nasal cells from drug naive patients suitable for culture and the study of drug responses in vitro , 2) matched gene expression data obtained by sequencing the RNA from the primary nasal tissue, 3) whole genome sequencing of blood derived DNA from each of the 100 participants, 4) induced pluripotent stem cells (iPSCs) generated from each participant's blood sample, 5) CRISPR-edited isogenic control iPSC lines and 6) prospective clinical data from patients treated with CF modulators. Results To date, we have recruited 57 of 100 individuals to CFIT, most of whom are homozygous for F508del (to assess in-vitro: in-vivo correlations with respect to ORKAMBI response) or heterozygous for F508del and a minimal function mutation. In addition, several donors are homozygous for rare nonsense and missense mutations. Nasal epithelial cell cultures and matched iPSC lines are available for many of these donors. Conclusions This accessible resource will enable development of tools that predict individual outcomes to current and emerging modulators targeting F508del-CFTR and facilitate therapy discovery for rare CF causing mutations.

Summary: Human pluripotent stem cells (hPSCs) provide an invaluable tool for modeling diseases and hold promise for regenerative medicine. For understanding pluripotency and lineage differentiation mechanisms, a critical first step involves systematically cataloging essential genes (EGs) that are indispensable for hPSC fitness, defined as cell reproduction in this study. To map essential genetic determinants of hPSC fitness, we performed genome-scale loss-of-function screens in an inducible Cas9 H1 hPSC line cultured on feeder cells and laminin to identify EGs. Among these, we found FOXH1 and VENTX, genes that encode transcription factors previously implicated in stem cell biology, as well as an uncharacterized gene, C22orf43/DRICH1. hPSC EGs are substantially different from other human model cell lines, and EGs in hPSCs are highly context dependent with respect to different growth substrates. Our CRISPR screens establish parameters for genome-wide screens in hPSCs, which will facilitate the characterization of unappreciated genetic regulators of hPSC biology. : Mair et al. establish a robust, inducible CRISPR screening platform for forward genetics in human pluripotent stem cells (hPSCs). Genome-wide proliferation screens identified core essential genes for hPSCs and revealed context-dependent genetic requirements on different substrates. This underlines hPSC plasticity and helps us to understand the genetic wiring of hPSCs. Keywords: human pluripotent stem cells, genome-wide CRISPR screen, functional genomics, essential genes, DRICH1

After the successful cloning of the first gene for a polyglutamine disease in 1991, the expanded polyglutamine tract in the nine polyglutamine disease proteins became an obvious therapeutic target. Early hypotheses were that misfolded, precipitated protein could be a universal pathogenic mechanism. However, new data are accumulating on Huntington's disease and other polyglutamine diseases that appear to contradict the toxic aggregate hypothesis. Recent data suggest that the toxic species of protein in these diseases may be soluble mutant conformers, and that the protein context of expanded polyglutamine is critical to understanding disease specificity. Here we discuss recent publications that define other important therapeutic targets for polyglutamine-mediated neurodegeneration related to the context of the expanded polyglutamine tract in the disease protein.