Cryptic TCF3 fusions in childhood leukemia: Detection by RNA sequencing.

Acute lymphoblastic leukemia (ALL) is the most frequent malignancy in childhood and adolescence. In more than 60% of cases of this heterogeneous disease, a genetic marker is identified via cytogenetic or molecular analyses. TCF3 gene fusions occur in 5%-11% of ALL patients. In < 1%, the TCF3 alteration in ALL leads to a TCF3-HLF fusion gene. Even though this is a very rare event, the detection of a TCF3-HLF fusion gene is associated with a very poor prognosis with incurable relapses in almost all patients. The frequent TCF3-PBX1 fusion gene, which is detectable in 5%-10% of childhood B-cell precursor ALLs and ~3.8% of adult B-cell precursor ALLs, is associated with a rather good prognosis, that is, an observed event-free 5-year survival of approximately 85%. Thus, the distinction of the different partner genes fused to TCF3 is essential for risk assessment. To verify RNA sequencing as a tool for detection of known and unknown fusion genes, we screened 200 cases of pediatric B-cell precursor ALL with "targeted" RNA sequencing in a pilot project in comparison to classical cytogenetic analyses (chromosome R-banding analysis), fluorescence in situ hybridization, and PCR. We observed a TCF3 fusion gene in 6.5% (13/200) of the patients. Ten (5%) patients displayed a TCF3-PBX1 fusion gene, two (1%) patients a TCF3-FLI1 fusion gene, and one (0.5%) patient a TCF3-HLF fusion gene. For the TCF3 fusions, we obtained discrepant results with the different methods, which are described in the article. Taken together, translocations leading to TCF3 fusion genes might appear cryptic and may remain undetected by a single method.

De novo missense variants in the RAP1B gene identified in two patients with syndromic thrombocytopenia.

We present two independent cases of syndromic thrombocytopenia with multiple malformations, microcephaly, learning difficulties, dysmorphism and other features. Exome sequencing identified two novel de novo heterozygous variants in these patients, c.35G>T p.(Gly12Val) and c.178G>C p.(Gly60Arg), in the RAP1B gene (NM_001010942.2). These variants have not been described previously as germline variants, however functional studies in literature strongly suggest a clinical implication of these two activating hot spot positions. We hypothesize that pathogenic missense variants in the RAP1B gene cause congenital syndromic thrombocytopenia with a spectrum of associated malformations and dysmorphism, possibly through a gain of function mechanism.

Serotonin 5-HT7 receptor is critically involved in acute and chronic inflammation of the gastrointestinal tract.

BACKGROUND: Intestinal inflammation is often associated with an increased level of serotonin (5-HT), an important gastrointestinal signaling molecule involved in gut homeostasis through stimulation of specific receptors. In this study, we investigated the role of 5-HT7 receptor (5-HT7R) in the induction and development of intestinal inflammation using a mouse model of acute and chronic colitis and human patients with Crohn's disease (CD). METHODS: Acute colitis was induced through administration of dextran sodium sulfate to wild-type, 5-HT7R-deficient mice and hematopoietic bone marrow chimera. Chronic colitis was induced in interleukin 10-deficient mice. The role of 5-HT7R in gut inflammation was assessed using agonist/antagonist treatment. We investigated expression and distribution of 5-HT7R, extent of gut inflammation with magnetic resonance imaging and histological analysis, survival rate, and disease activity index. Finally, biopsies from the large intestine of patients with CD were analyzed. RESULTS: Under basal conditions, 5-HT7R is expressed both in enteric neurons and CD11c cells of the large intestine. Expression of 5-HT7R significantly increased after induction of colitis in mice and in inflamed intestinal regions of patients with CD in CD11c/CD86 double-positive cells. Pharmacological blockade or genetic ablation of 5-HT7R resulted in increased severity of both acute and chronic dextran sodium sulfate-induced colitis, whereas receptor stimulation showed an anti-inflammatory effect. Analysis of bone marrow chimera indicated importance of 5-HT7R expressed by hematopoietic cells in intestinal inflammation. CONCLUSIONS: The 5-HT7R expressed on CD11c/CD86-positive myeloid cells modulates the severity of intestinal inflammation in an acute and chronic colitis and thus represents a potential therapeutic target for the treatment of inflammatory disorders such as CD.