Allelic imbalance in CALR somatic mutagenesis

Harutyunyan, Ashot S.; Jäger, Roland; Chen, Doris; Berg, Tiina; Rumi, Elisa; Gisslinger, Bettina; Pietra, Daniela; Gisslinger, Heinz; Cazzola, Mario; Královics, Róbert

doi:10.1038/leu.2015.3

Cited by 6 publications

(7 citation statements)

References 16 publications

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“…Cases such as this support the possibility that a minority of MPN patients are pre‐disposed to acquiring multiple CALR mutations, a phenomenon that has been identified for the JAK2 mutations (Olcaydu et al , ; Scott & Rebel, ). Recently, CALR mutations were found to occur more frequently on the T allele of individuals heterozygous for the rs1049481 (G/T) SNP, with an allelic bias of 1·7 in those with a type‐1 mutation, and 2·1 in those with a type‐2 mutation (Harutyunyan et al , ). Patient C was informative at this locus; however, BFU‐e positive for a type‐2 mutation had the T allele mutated, and the minority with a type‐1 mutation had the G allele mutated (data not shown).…”

Section: Discussionmentioning

confidence: 99%

Progenitor genotyping reveals a complex clonal architecture in a subset of CALR‐mutated myeloproliferative neoplasms

2017

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The identification of acquired CALR mutations in patients with essential thrombocythaemia (ET) or myelofibrosis (MF) has meant that disease-initiating mutations can now be detected in about 90% of all patients with a myeloproliferative neoplasm (MPN). Here, we show that only those CALR mutations that cause a +1 frameshift, thereby altering the carboxy-terminus of calreticulin, promote cytokine independence in vitro; in-frame deletions were not functional, and are unlikely to be the pathogenetic mutation underlying some MPN cases. Expression of the thrombopoietin receptor, MPL, was also necessary for factor-independence. Although the CALR mutations are considered to occur only in JAK2 V617F-negative cases and in a heterozygous state, progenitor genotyping revealed that this is not always true. Notably, CALR mutation-positive MPNs can be polyclonal: in one case, two distinct CALR mutation-positive subpopulations could be identified; in another, separate populations of JAK2 V617F-positive and CALR-mutated cells were present. Mitotic recombination involving chromosome 19 in a third instance resulted in the emergence of a CALR mutation-homozygous subclone. Collectively, our studies demonstrate that occasional patients with CALR mutation-positive ET or MF carry other MPN-initiating genetic mutations (including JAK2 V617F), acquire "secondary mutations" before or after the CALR mutation, or evolve over time to being CALR mutation-homozygous.

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Section: Discussionmentioning

confidence: 99%

Progenitor genotyping reveals a complex clonal architecture in a subset of CALR‐mutated myeloproliferative neoplasms

2017

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“…No false-negative samples were found using Sanger analysis and the comparison of CALR -mutant burden obtained with the two methods showed a very high Pearson's correlation (ρ 0.94, P < 0.001). Sanger sequencing allowed also the genotyping of the rs1049481 [ 13 ].…”

Section: Methodsmentioning

confidence: 99%

Sequential evaluation of CALR mutant burden in patients with myeloproliferative neoplasms

et al. 2017

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We investigated the variation of CALR-mutant burden during follow-up in 105 CALR-mutant MPN and compared it to the variation of JAK2-mutant burden in 226 JAK2-mutant MPN.The median allele burden at last evaluation was significantly higher than at first evaluation in essential thrombocythemia (ET) (49.5% vs 45%, P < .001) but not in primary myelofibrosis (PMF) (52% vs 51%, P 0.398). Median values of slope were positive both in ET (0.071) and in PMF (0.032). In CALR-mutant ET there was a difference between natural and therapy-related slope (P 0.006).In the JAK2-mutated cohort, the median allele burden at last evaluation was not different respect to that at first evaluation, neither in ET (22.9% vs 23.2%, P = 0.216) nor in PMF (50.5% vs 45.0%, P = 0.809), despite a positive slope. Multivariate analysis to evaluate the effect of mutation (CALR vs JAK2) on the slope of mutant burden in not treated pts with a positive slope adjusting for diagnosis (ET vs PMF) showed a trend toward a higher increase of mutant burden in CALR vs JAK2 (β = 0.19, P = 0.061) with no difference between diagnosis (P = 0.419). The findings of this study suggest that clonal expansion in CALR-mutant MPN is faster than that observed in JAK2-mutant MPN.

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“…10,11 Recently it has been suggested there is a constitutional allelic imbalance at the CALR locus associated with somatic CALR mutations which may indicate a genetic influence on the probability of acquiring a CALR mutation and/or the probability of such a mutation leading to the development of an MPN. 12 Harutyunyan and colleagues analyzed 162 CALR-mutated cases that were heterozygous (T/G) for rs1049481, a common SNP located 54 bp downstream of the CALR stop codon. If there was no allelic imbalance, CALR mutations would be expected to be distributed 50:50 between the G and T alleles but Harutyunyan et al observed that CALR mutations occurred more frequently on the T allele (100 on the T-allele versus 62 on the Gallele; P=0.0028).…”

Section: Constitutional Genetic Association With Calr Mutations?mentioning

confidence: 99%

“…12 An unlabeled forward primer (5'-GGCAAGGCCCTGAGGTGT-3') that binds to the intron upstream of the CALR mutation cluster was used in combination with specific labeled reverse primers that bind either to the G or T allelic variants of rs1049481. We used a T reverse primer that was six nucleotides longer than the G allele primer (5'-TTTTTTAGACATTATTTGGCGCGGCA-3' and 5'-AGACATTATTTGGCGCGGCC-3' respectively) to facilitate the analysis.…”

Section: Constitutional Genetic Association With Calr Mutations?mentioning

confidence: 99%