Distinct p53 phosphorylation patterns in chronic lymphocytic leukemia patients are reflected in the activation of circumjacent pathways upon DNA damage.

TP53 gene abnormalities represent the most important biomarker in chronic lymphocytic leukemia (CLL). Altered protein modifications could also influence p53 function, even in the wild-type protein. We assessed the impact of p53 protein phosphorylations on p53 functions as an alternative inactivation mechanism. We studied p53 phospho-profiles induced by DNA-damaging agents (fludarabine, doxorubicin) in 71 TP53-intact primary CLL samples. Doxorubicin induced two distinct phospho-profiles: profile I (heavily phosphorylated) and profile II (hypophosphorylated). Profile II samples were less capable of activating p53 target genes upon doxorubicin exposure, resembling TP53-mutant samples at the transcriptomic level, whereas standard p53 signaling was triggered in profile I. ATM locus defects were more common in profile II. The samples also differed in the basal activity of the hypoxia pathway: the highest level was detected in TP53-mutant samples, followed by profile II and profile I. Our study suggests that wild-type TP53 CLL cells with less phosphorylated p53 show TP53-mutant-like behavior after DNA damage. p53 hypophosphorylation and the related lower ability to respond to DNA damage are linked to ATM locus defects and the higher basal activity of the hypoxia pathway.

Functional analysis of germline ETV6 W380R mutation causing inherited thrombocytopenia and secondary acute lymphoblastic leukemia or essential thrombocythemia.

Germline mutations in ETV6 gene cause inherited thrombocytopenia with leukemia predisposition. Here, we report on functional validation of ETV6 W380R mutation segregating with thrombocytopenia in a family where two family members also suffered from acute lymphoblastic leukemia (ALL) or essential thrombocythemia (ET). In-silico analysis predicted impaired DNA binding due to W380R mutation. Functional analysis showed that this mutation prevents the ETV6 protein from localizing into the cell nucleus and impairs the transcriptional repression activity of ETV6. Based on the germline ETV6 mutation, ET probably started with somatic JAK2 V617F mutation, whereas ALL could be caused by diverse mechanisms: high-hyperdiploidity; somatic deletion of exon 1 IKZF1 gene; or somatic mutations of other genes found by exome sequencing of the ALL sample taken at the diagnosis.

A novel germline mutation of the SFTPA1 gene in familial interstitial pneumonia.

Different genes related to alveolar stability have been associated with familial interstitial pneumonia (FIP). Here, we report a novel, rare SFTPA1 variant in a family with idiopathic interstitial pneumonia (IIP). We performed whole-exome sequencing on germline DNA samples from four members of one family; three of them showed signs of pulmonary fibrosis (idiopathic interstitial pneumonia) with autosomal-dominant inheritance. A heterozygous single nucleotide variant c.532 G > A in the SFTPA1 gene has been identified. This variant encodes the substitution p.(Val178Met), localized within the carbohydrate recognition domain of surfactant protein A and segregates with the genes causing idiopathic interstitial pneumonia. This rare variant has not been previously reported. We also analyzed the detected sequence variant in the protein structure in silico. The replacement of valine by the larger methionine inside the protein may cause a disruption in the protein structure. The c.532 G > A variant was further validated using Sanger sequencing of the amplicons, confirming the diagnosis in all symptomatic family members. Moreover, this variant was also found by Sanger sequencing in one other symptomatic family member and one young asymptomatic family member. The autosomal-dominant inheritance, the family history of IIP, and the evidence of a mutation occurring in part of the SFTPA1 gene all suggest a novel variant that causes FIP.

A novel germline mutation in GP1BA gene N-terminal domain in monoallelic Bernard-Soulier syndrome.

Mutations in the GP1BA gene have been associated with platelet-type von Willebrand disease and Bernard-Soulier syndrome. Here, we report a novel GP1BA mutation in a family with autosomal dominant macrothrombocytopenia and mild bleeding. We performed analyses of seven family members. Using whole-exome sequencing of germline DNA samples, we identified a heterozygous single-nucleotide change in GP1BA (exone2:c.176T>G), encoding a p.Leu59Arg substitution in the N-terminal domain, segregating with macrothrombocytopenia. This variant has not been previously reported. We also analysed the structure of the detected sequence variant in silico. In particular, we used the crystal structure of the human platelet receptor GP Ibα N-terminal domain. Replacement of aliphatic amino-acid Leu 59 with charged, polar and larger arginine probably disrupts the protein structure. An autosomal dominant mode of inheritance, a family history of mild bleeding episodes, aggregation pattern in affected individuals together with evidence of mutation occurring in part of the GP1BA gene encoding the leucine-rich repeat region suggest a novel variant causing monoallelic Bernard-Soulier syndrome.

C-terminal RUNX1 mutation in familial platelet disorder with predisposition to myeloid malignancies.

Here we report a C-terminal RUNX1 mutation in a family with platelet disorder and predisposition to myeloid malignancies. We identified the mutation c.866delG:p.Gly289Aspfs*22 (NM_001754) (RUNX1 b-isoform NM_001001890; c.785delG:p.Gly262Aspfs*22) using exome sequencing of samples obtained from eight members of a single family. The mutation found in our pedigree is within exon eight and the transactivation domain of RUNX1. One of the affected individuals developed myelodysplastic syndrome (MDS), which progressed to acute myelogenous leukemia (AML). A search for the second hit which led to the development of MDS and later AML in this individual revealed the PHF6 gene variant (exon9:c.872G > A:p.G291E; NM_001015877), BCORL1 (exon3:c.1111A > C:p.T371P; NM_001184772) and BCOR gene variant (exon4:c.2076dupT:p.P693fs; NM_001123383), which appear to be very likely second hits participating in the progression to myeloid malignancy.