Flow cytometry has become a highly valuable method to monitor minimal residual disease (MRD) and evaluate the depth of complete response (CR) in bone marrow (BM) of multiple myeloma (MM) after therapy. However, current flow-MRD has lower sensitivity than molecular methods and lacks standardization. Here we report on a novel next generation flow (NGF) approach for highly sensitive and standardized MRD detection in MM. An optimized 2-tube 8-color antibody panel was constructed in five cycles of design-evaluation-redesign. In addition, a bulk-lysis procedure was established for acquisition of ⩾107 cells/sample, and novel software tools were constructed for automatic plasma cell gating. Multicenter evaluation of 110 follow-up BM from MM patients in very good partial response (VGPR) or CR showed a higher sensitivity for NGF-MRD vs conventional 8-color flow-MRD -MRD-positive rate of 47 vs 34% (P=0.003)-. Thus, 25% of patients classified as MRD-negative by conventional 8-color flow were MRD-positive by NGF, translating into a significantly longer progression-free survival for MRD-negative vs MRD-positive CR patients by NGF (75% progression-free survival not reached vs 7 months; P=0.02). This study establishes EuroFlow-based NGF as a highly sensitive, fully standardized approach for MRD detection in MM which overcomes the major limitations of conventional flow-MRD methods and is ready for implementation in routine diagnostics.

Determining the genetic bases of age-related disease remains a major challenge requiring a spectrum of approaches from human and clinical genetics to the utilization of model organism studies. Here we report a large-scale genetic screen in mice employing a phenotype-driven discovery platform to identify mutations resulting in age-related disease, both late-onset and progressive. We have utilized N-ethyl-N-nitrosourea mutagenesis to generate pedigrees of mutagenized mice that were subject to recurrent screens for mutant phenotypes as the mice aged. In total, we identify 105 distinct mutant lines from 157 pedigrees analysed, out of which 27 are late-onset phenotypes across a range of physiological systems. Using whole-genome sequencing we uncover the underlying genes for 44 of these mutant phenotypes, including 12 late-onset phenotypes. These genes reveal a number of novel pathways involved with age-related disease. We illustrate our findings by the recovery and characterization of a novel mouse model of age-related hearing loss.

BackgroundNuclease-based technologies have been developed that enable targeting of specific DNA sequences directly in the zygote. These approaches provide an opportunity to modify the genomes of inbred mice, and allow the removal of strain-specific mutations that confound phenotypic assessment. One such mutation is the Cdh23ahl allele, present in several commonly used inbred mouse strains, which predisposes to age-related progressive hearing loss.ResultsWe have used targeted CRISPR/Cas9-mediated homology directed repair (HDR) to correct the Cdh23ahl allele directly in C57BL/6NTac zygotes. Employing offset-nicking Cas9 (D10A) nickase with paired RNA guides and a single-stranded oligonucleotide donor template we show that allele repair was successfully achieved. To investigate potential Cas9-mediated ‘off-target’ mutations in our corrected mouse, we undertook whole-genome sequencing and assessed the ‘off-target’ sites predicted for the guide RNAs (≤4 nucleotide mis-matches). No induced sequence changes were identified at any of these sites.Correction of the progressive hearing loss phenotype was demonstrated using auditory-evoked brainstem response testing of mice at 24 and 36 weeks of age, and rescue of the progressive loss of sensory hair cell stereocilia bundles was confirmed using scanning electron microscopy of dissected cochleae from 36-week-old mice.ConclusionsCRISPR/Cas9-mediated HDR has been successfully utilised to efficiently correct the Cdh23ahl allele in C57BL/6NTac mice, and rescue the associated auditory phenotype. The corrected mice described in this report will allow age-related auditory phenotyping studies to be undertaken using C57BL/6NTac-derived models, such as those generated by the International Mouse Phenotyping Consortium (IMPC) programme.Electronic supplementary materialThe online version of this article (doi:10.1186/s13073-016-0273-4) contains supplementary material, which is available to authorized users.

Inherited platelet disorders are a heterogeneous group of rare diseases, caused by inherited defects in platelet production and/or function. Their genetic diagnosis would benefit clinical care, prognosis and preventative treatments. Until recently, this diagnosis has usually been performed via Sanger sequencing of a limited number of candidate genes. High-throughput sequencing is revolutionizing the genetic diagnosis of diseases, including bleeding disorders. We have designed a novel high-throughput sequencing platform to investigate the unknown molecular pathology in a cohort of 82 patients with inherited platelet disorders. Thirty-four (41.5%) patients presented with a phenotype strongly indicative of a particular type of platelet disorder. The other patients had clinical bleeding indicative of platelet dysfunction, but with no identifiable features. The high-throughput sequencing test enabled a molecular diagnosis in 70% of these patients. This sensitivity increased to 90% among patients suspected of having a defined platelet disorder. We found 57 different candidate variants in 28 genes, of which 70% had not previously been described. Following consensus guidelines, we qualified 68.4% and 26.3% of the candidate variants as being pathogenic and likely pathogenic, respectively. In addition to establishing definitive diagnoses of well-known inherited platelet disorders, high-throughput sequencing also identified rarer disorders such as sitosterolemia, filamin and actinin deficiencies, and G protein-coupled receptor defects. This included disease-causing variants in DIAPH1 (n=2) and RASGRP2 (n=3). Our study reinforces the feasibility of introducing high-throughput sequencing technology into the mainstream laboratory for the genetic diagnostic practice in inherited platelet disorders.

Background: Eltrombopag is effective and safe for treating chronic immune thrombocytopenia (ITP) patients who have not responded to previous therapy. Interestingly, some patients in whom hemostatic platelet counts are achieved with eltrombopag may sustain the platelet response when eltrombopag ceases to be administered. However, the frequency of sustained responses after discontinuing eltrombopag without additional therapy for ITP is largely unknown. Methods: A total of 260 adult patients (aged 18 years or more) with primary ITP treated with eltrombopag included in the Spanish Eltrombopag Registry were retrospectively evaluated. The study was performed in accordance with the standards of the Helsinki declaration and approved by the Hospital Universitario de Burgos Ethics Committee. Results: The median age was 62 [range, 18–93] years. There were 165 women and 95 men. According to the standard definition, patients were allocated to newly diagnosed (n=29), persistent (n=36) and chronic (n=195) ITP groups. The median time from diagnosis to eltrombopag initiation was 24 [range, 1–480] months. The median number of previous therapies was 3 [range, 0–10], including splenectomy (22%), rituximab (23%) and romiplostim (19%). The initial response rate to eltrombopag was 231/260 (89%), including 77% (n=201) cases of complete remission (platelet count ≥100 x 109/L). The median duration of eltrombopag treatment was 6 [range, 1–54] months. Eltrombopag was discontinued in 80 out of 201 (39.8%) patients who achieved CR. Reasons for eltrombopag discontinuation were: persistent response despite a reduction in dose over time (n=33), platelet count >400x109/L (n=29), patient’s request (n=5), aspartate aminotransferase elevation (n=3), diarrhea (n=3), thrombosis (n=3) and other reasons (n=4). For analysis of discontinuation, patients with follow-up < 6 months (n=15), newly diagnosed ITP (n=11) or patients who received concomitant or previous (6 months before) treatments at the start of eltrombopag use (n=5) were excluded. Of the 49 evaluable patients, 22 (45%) had an immediate relapse after stopping eltrombopag. One patient with sustained response after stopping treatment relapsed at 10 months. A total of 26 patients (53%) showed sustained response after discontinuing eltrombopag without additional ITP therapy, with a median follow-up of 9 [range, 6–25] months. These patients were characterized by a median time since ITP diagnosis of 46.5±114.1 months, with 4/26 having ITP <1 year. Eleven patients (42%) were male and their median age was 59 [range, 18-88] years. They had received a median of four previous treatment lines [range: 0–9 lines] and 11 (42%) were splenectomized. The median platelet count before starting eltrombopag was 22 x 109/L and that before eltrombopag withdrawal was 269 x 109/L. The main characteristics (age, gender, duration of ITP, prior anti-ITP lines, prior splenectomy, prior rituximab, prior romiplostim, platelet count before starting eltrombopag, duration of eltrombopag treatment, and platelet count before eltrombopag withdrawal) of the 26 patients with sustained response after stopping eltrombopag were compared with those of the 23 patients relapsing after eltrombopag withdrawal. No predictive factors of sustained response after eltrombopag withdrawal could be identified. Conclusion: Platelet response following eltrombopag cessation may be sustained in nearly half of adult patients with primary ITP after CR with eltrombopag. However, reliable markers for predicting which patients will have this response are lacking. Disclosures No relevant conflicts of interest to declare.