Whole-transcriptome analysis in acute lymphoblastic leukemia: a report from the DFCI ALL Consortium Protocol 16-001.

The molecular hallmark of childhood acute lymphoblastic leukemia (ALL) is characterized by recurrent, prognostic genetic alterations, many of which are cryptic by conventional cytogenetics. RNA sequencing (RNA-seq) is a powerful next-generation sequencing technology that can simultaneously identify cryptic gene rearrangements, sequence mutations and gene expression profiles in a single assay. We examined the feasibility and utility of incorporating RNA-seq into a prospective multicenter phase 3 clinical trial for children with newly diagnosed ALL. The Dana-Farber Cancer Institute ALL Consortium Protocol 16-001 enrolled 173 patients with ALL who consented to optional studies and had samples available for RNA-seq. RNA-seq identified at least 1 alteration in 157 patients (91%). Fusion detection was 100% concordant with results obtained from conventional cytogenetic analyses. An additional 56 gene fusions were identified by RNA-seq, many of which confer prognostic or therapeutic significance. Gene expression profiling enabled further molecular classification into the following B-cell ALL (B-ALL) subgroups: high hyperdiploid (n = 36), ETV6-RUNX1/-like (n = 31), TCF3-PBX1 (n = 7), KMT2A-rearranged (KMT2A-R; n = 5), intrachromosomal amplification of chromosome 21 (iAMP21) (n = 1), hypodiploid (n = 1), Philadelphia chromosome (Ph)-positive/Ph-like (n = 16), DUX4-R (n = 11), PAX5 alterations (PAX5 alt; n = 11), PAX5 P80R (n = 1), ZNF384-R (n = 4), NUTM1-R (n = 1), MEF2D-R (n = 1), and others (n = 10). RNA-seq identified 141 nonsynonymous mutations in 93 patients (54%); the most frequent were RAS-MAPK pathway mutations. Among 79 patients with both low-density array and RNA-seq data for the Philadelphia chromosome-like gene signature prediction, results were concordant in 74 patients (94%). In conclusion, RNA-seq identified several clinically relevant genetic alterations not detected by conventional methods, which supports the integration of this technology into front-line pediatric ALL trials. This trial was registered at www.clinicaltrials.gov as #NCT03020030.

Genome-wide detection and characterization of mating asymmetry in human populations.

The study of the genetic component of early-onset diseases requires investigation into parental genetic effects, particularly those mediated by the mother who can influence the offspring's risk of disease through the effects of her genes acting directly on the intrauterine milieu or indirectly through maternal-gene child-gene interaction effects. An important source of bias that can arise in feto-maternal association testing is the possibility of confounding due to mating asymmetry (MA). However, there is little information on the levels of MA present in human populations and the impact on maternal association testing. In this study, we developed a novel approach to measuring MA and, using HapMap mate-pairs of European and African descent, carried out a genome-wide investigation and characterization of MA. We further investigated the impact of observed levels of MA on maternal association tests through simulation experiments. For the first time, we showed that non-negligible levels of MA are detected in human populations, such that subtle genotype frequency differences between individuals mating in the population are sufficient to induce spurious maternal genotype associations. Though the underlying mechanisms driving the asymmetry within these populations remain elusive, our findings provide consequential evidence for the occurrence of MA in humans and highlight the importance of controlling for MA in maternal association testing.