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.

12q14 microdeletion syndrome: A family with short stature and Silver-Russell syndrome (SRS)-like phenotype and review of the literature.

We report here on the first family with short stature and Silver-Russell-like phenotype due to a microdeletion in 12q14.3. The Netchine-Harbison clinical scoring system was used for the clinical diagnosis of Silver-Russell syndrome (SRS). The three affected first-degree relatives (index patient, mother and brother) presented with prenatal and postnatal growth retardation, feeding difficulties, a prominent forehead and a failure to thrive, but did not show relative macrocephaly. In addition, our index patient showed dysmorphic facial features, periodically increased sweating, and scoliosis. Learning problems and cardiac arrhythmia presented as additional features of her brother. Using high-resolution array-CGH, heterozygosity for a 1.67 Mb deletion in 12q14.3 was detected in the index patient. The heterozygous loss was confirmed by MLPA in the index patient and the other two affected family members. The deletion includes the genes HMGA2, LLPH, TMBIM4, IRAK3, HELB, GRIP1, and the pseudogene RPSAP52. We conclude from these results and from the data of other patients reported in the literature that haploinsufficiency of HMGA2 leads to the short stature in this family.