CRISPR-Cas9 globin editing can induce megabase-scale copy-neutral losses of heterozygosity in hematopoietic cells.

CRISPR-Cas9 is a promising technology for gene therapy. However, the ON-target genotoxicity of CRISPR-Cas9 nuclease due to DNA double-strand breaks has received little attention and is probably underestimated. Here we report that genome editing targeting globin genes induces megabase-scale losses of heterozygosity (LOH) from the globin CRISPR-Cas9 cut-site to the telomere (5.2 Mb). In established lines, CRISPR-Cas9 nuclease induces frequent terminal chromosome 11p truncations and rare copy-neutral LOH. In primary hematopoietic progenitor/stem cells, we detect 1.1% of clones (7/648) with acquired megabase LOH induced by CRISPR-Cas9. In-depth analysis by SNP-array reveals the presence of copy-neutral LOH. This leads to 11p15.5 partial uniparental disomy, comprising two Chr11p15.5 imprinting centers (H19/IGF2:IG-DMR/IC1 and KCNQ1OT1:TSS-DMR/IC2) and impacting H19 and IGF2 expression. While this genotoxicity is a safety concern for CRISPR clinical trials, it is also an opportunity to model copy-neutral-LOH for genetic diseases and cancers.

Fetal phenotypes in otopalatodigital spectrum disorders.

Otopalatodigital spectrum disorders (OPDSD) include OPD syndromes types 1 and type 2 (OPD1, OPD2), Melnick-Needles syndrome (MNS), and frontometaphyseal dysplasia (FMD). These conditions are clinically characterized by variable skeletal dysplasia associated in males, with extra-skeletal features including brain malformations, cleft palate, cardiac anomalies, omphalocele and obstructive uropathy. Mutations in the FLNA gene have been reported in most FMD and OPD2 cases and in all instances of typical OPD1 and MNS. Here, we report a series of 10 fetuses and a neonatally deceased newborn displaying a multiple congenital anomalies syndrome suggestive of OPDSD and in whom we performed FLNA analysis. We found a global mutation rate of 44%. This series allows expanding the clinical and FLNA mutational spectrum in OPDSD. However, we emphasize difficulties to correctly discriminate OPDSD based on clinical criteria in fetuses due to the major overlap between these conditions. Molecular analyses may help pathologists to refine clinical diagnosis according to the type and the location of FLNA mutations. Discriminating the type of OPDSD is of importance in order to improve the genetic counseling to provide to families.

Influence of FCGR3A-V212F and TNFRSF1B-M196R genotypes in patients with rheumatoid arthritis treated with infliximab therapy.

OBJECTIVE: Anti-TNF-alpha therapies are widely used in rheumatoid arthritis (RA) patients. Despite their clearly proven efficacy, some discrepancies were observed in the treatment response with 40% of non-responder patients. The aim of this study is to determine whether two functional single-nucleotide polymorphisms, V212F in the FCGR3A, and M196R in the TNFRSF1B genes correlate with rheumatoid arthritis susceptibility and response to anti-TNF-alpha therapy. METHODS: The population study was composed of a French cohort of 78 RA patients and 70 healthy controls. Allele and genotype frequencies were compared between patients and controls, according to their response to infliximab therapy, using the American College of Rheumatology (ACR) response criteria. RESULTS: No association was found between these two SNPs and RA susceptibility. A significant correlation was found between 196R allele carriers and low response to infliximab therapy. CONCLUSION: This is the first report of a statistically significant association between the TNFRSF1B-M196R SNP and response to infliximab in a French cohort. Larger studies are needed to confirm the relevance of this association.