Christina Ganster

Functional PMS2 hybrid alleles containing a pseudogene-specific missense variant trace back to a single ancient intrachromosomal recombination event.

Sequence exchange between PMS2 and its pseudogene PMS2CL, embedded in an inverted duplication on chromosome 7p22, has been reported to be an ongoing process that leads to functional PMS2 hybrid alleles containing PMS2‐ and PMS2CL‐specific sequence variants at the 5′‐and the 3′‐end, respectively. The frequency of PMS2 hybrid alleles, their biological significance, and the mechanisms underlying their formation are largely unknown. Here we show that overall hybrid alleles account for one‐third of 384 PMS2 alleles analyzed in individuals of different ethnic backgrounds. Depending on the population, 14–60% of hybrid alleles carry PMS2CL‐specific sequences in exons 13–15, the remainder only in exon 15. We show that exons 13–15 hybrid alleles, named H1 hybrid alleles, constitute different haplotypes but trace back to a single ancient intrachromosomal recombination event with crossover. Taking advantage of an ancestral sequence variant specific for all H1 alleles we developed a simple gDNA‐based polymerase chain reaction (PCR) assay that can be used to identify H1‐allele carriers with high sensitivity and specificity (100 and 99%, respectively). Because H1 hybrid alleles harbor missense variant p.N775S of so far unknown functional significance, we assessed the H1‐carrier frequency in 164 colorectal cancer patients. So far, we found no indication that the variant plays a major role with regard to cancer susceptibility. Hum Mutat 31:1–8, 2010.

New data shed light on Y-loss-related pathogenesis in myelodysplastic syndromes

Loss of the Y‐chromosome (LOY) is described as both a normal age‐related event and a marker of a neoplastic clone in hematologic diseases. To assess the significance of LOY in myelodysplastic syndromes (MDS), we determined the percentage of LOY in clonal CD34+ peripheral blood cells in comparison to normal CD3+ T‐cells of 27 MDS patients using fluorescence in situ hybridization (FISH) analysis. Results were compared with the percentage of LOY in CD34+ and CD3+ cells of 32 elderly men without hematologic diseases and in 25 young blood donors. While LOY could not be detected in CD3+ cells of young men, it was observed in CD3+ cells of elderly men without hematologic diseases (2.5% LOY) as well as in CD3+ cells of elderly MDS patients (5.8% LOY). The percentage of CD34+ cells affected by LOY was significantly higher in MDS patients compared to elderly men without hematologic diseases (43.3% vs. 13.2%, P = 0.005), indicating that LOY has an age‐related basis but is also associated with MDS. Furthermore, we aimed to define a threshold between age‐ and disease‐associated LOY in MDS. Statistical analysis revealed that a value of 21.5% LOY in CD34+ peripheral blood cells provided the best threshold to discriminate between these two conditions in MDS. We conclude that LOY is clonal in a substantial number of MDS based on an age‐related predisposition.

Molecular cytogenetic monitoring from CD34+ peripheral blood cells in myelodysplastic syndromes: First results from a prospective multicenter German diagnostic study

The gold standard of cytogenetic analysis in myelodysplastic syndromes (MDS) is conventional chromosome banding (CCB) analysis of bone marrow (BM) metaphases. Most aberrations can also be detected by fluorescence-in situ-hybridization (FISH). For this prospective multicenter German diagnostic study (www.clinicaltrials.gov: #NCT01355913) 360 patients, as yet, were followed up to 3 years by sequential FISH analyses of immunomagnetically enriched CD34+ peripheral blood (PB) cells using comprehensive FISH probe panels, resulting in a total number of 19,516 FISH analyses. We demonstrate that CD34+ PB FISH correlates significantly with CCB analysis and represents a feasible method for a reliable non-invasive cytogenetic monitoring from PB.

Uniparental Trisomy of a Mutated HRAS Proto-Oncogene in Embryonal Rhabdomyosarcoma of a Patient With Costello Syndrome

Introduction This single-patient research involves a girl with Costello syndrome who carries the heterozygous HRAS proto-oncogene mutation c.34G]T (p.G12C) on the paternal allele at 11p15.5. This rare genetic disorder allows for dysregulated Ras signaling, which enhances cell proliferation and predisposes to cancer. At the age of 3 years, the girl developed an embryonal rhabdomyosarcoma. This report presents details of the tumor genetics.

Influence of total genomic alteration and chromosomal fragmentation on response to a combination of azacitidine and lenalidomide in a cohort of patients with very high risk MDS

We genetically analyzed a group of high risk MDS/AML patients treated by a combination of azacitidine and lenalidomide. In our cohort, the extent of genetic rearrangements was associated with outcome and response to treatment. The size of total genomic aberrations as defined by molecular karyotyping (SNP-array analysis) was a predictive marker for overall survival. TP53 mutations were associated with therapy refractoriness only if accompanied by heavily rearranged chromosomes. This study suggests a potential value of molecular karyotyping as a method to objectivate comprehensively the extent of genetic alterations in high risk patients with complex karyotypes, especially if the clinical value of the size of total genomic aberrations and the fragmentation status of single chromosomes could be evaluated in larger therapy trials.

Targeted deep sequencing of CD34+ cells from peripheral blood can reproduce bone marrow molecular profile in myelodysplastic syndromes

of related donors for bone marrow transplantation in sickle cell anemia. Am J Pediatr Hematol Oncol. 1994;16:27–29. [5] Sorror ML, Maris MB, Storb R, et al. Hematopoietic cell transplantation (HCT)-specific comorbidity index: a new tool for risk assessment before allogeneic HCT. Blood. 2005;106(8):2912–2919. [6] Walters MC, De Castro LM, Sullivan KM, et al. Indications and results of HLA-identical sibling hematopoietic cell transplantation for sickle cell disease. Biol. Blood Marrow Transplant. 2016;22:207–211.

Cytogenetics of MDS

Cytogenetic aberrations are major markers in pathogenesis, diagnosis, and prognosis of patients with myelodysplastic syndromes (MDS). Their relevance for an individualized therapy in selected patients with MDS is increasing. Using conventional chromosomal banding analysis, aberrations are detectable in about 50% of patients. The application of additional methods like fluorescence in situ hybridization (FISH)-techniques improves the detection rate and diagnostic accuracy. In spite of the cytogenetic heterogeneity of MDS patients, the prognostic impact of the most frequent chromosomal changes is known and the understanding of rare abnormalities, independent clones, and double and complex aberrations is increasing. Future research will also focus on karyotype evolution, as it could give notice of disease progression and thus affect therapy decisions. International cooperations facilitate to unravel the remaining challenges for cytogenetics in MDS.