Spontaneous remission of granulocyte colony-stimulating factor-associated leukemia in a child with severe congenital neutropenia.

Leukemia is observed with increased frequency in patients with severe congenital neutropenia (SCN). In the past decade, recombinant human granulocyte colony-stimulating factor (rh G-CSF) has prolonged the survival of patients with SCN increasingly reported to have leukemias. In this communication acute myelogenous leukemia (AML) associated with a mutation of the G-CSF receptor (G-CSF-R) developed in a patient with SCN maintained on long-term G-CSF therapy. The blast count in the blood and bone marrow fell to undetectable levels twice on withholding G-CSF and without chemotherapy administration, but the mutant G-CSF-R was detectable during this period. The patient subsequently underwent successful allogeneic bone marrow transplantation. After transplantation, the patient's neutrophil elastase (ELA-2) mutation and G-CSF-R mutation became undetectable by polymerase chain reaction. This report provides novel insights on leukemia developing in congenital neutropenia.

Mutations in the gene encoding neutrophil elastase in congenital and cyclic neutropenia.

Congenital neutropenia and cyclic neutropenia are disorders of neutrophil production predisposing patients to recurrent bacterial infections. Recently the locus for autosomal dominant cyclic neutropenia was mapped to chromosome 19p13.3, and this disease is now attributable to mutations of the gene encoding neutrophil elastase (the ELA2 gene). The authors hypothesized that congenital neutropenia is also due to mutations of neutrophil elastase. Patients with congenital neutropenia, cyclic neutropenia, or Shwachman-Diamond syndrome were referred to the Severe Chronic Neutropenia International Registry. Referring physicians provided hematologic and clinical data. Mutational analysis was performed by sequencing polymerase chain reaction (PCR)-amplified genomic DNA for each of the 5 exons of the neutrophil ELA2 gene and 20 bases of the flanking regions. RNA from bone marrow mononuclear cells was used to determine if the affected patients expressed both the normal and the abnormal transcript. Twenty-two of 25 patients with congenital neutropenia had 18 different heterozygous mutations. Four of 4 patients with cyclic neutropenia and 0 of 3 patients with Shwachman-Diamond syndrome had mutations. For 5 patients with congenital neutropenia having mutations predicted to alter RNA splicing or transcript structure, reverse transcriptase-PCR showed expression of both normal and abnormal transcripts. In cyclic neutropenia, the mutations appeared to cluster near the active site of the molecule, whereas the opposite face was predominantly affected by the mutations found in congenital neutropenia. This study indicates that mutations of the gene encoding neutrophil elastase are probably the most common cause for severe congenital neutropenia as well as the cause for sporadic and autosomal dominant cyclic neutropenia.

Mutations in ELA2, encoding neutrophil elastase, define a 21-day biological clock in cyclic haematopoiesis.

Human cyclic haematopoiesis (cyclic neutropenia, MIM 162800) is an autosomal dominant disease in which blood-cell production from the bone marrow oscillates with 21-day periodicity. Circulating neutrophils vary between almost normal numbers and zero. During intervals of neutropenia, affected individuals are at risk for opportunistic infection. Monocytes, platelets, lymphocytes and reticulocytes also cycle with the same frequency. Here we use a genome-wide screen and positional cloning to map the locus to chromosome 19p13.3. We identified 7 different single-base substitutions in the gene (ELA2) encoding neutrophil elastase (EC 3. 4.21.37, also known as leukocyte elastase, elastase 2 and medullasin), a serine protease of neutrophil and monocyte granules, on unique haplotypes in 13 of 13 families as well as a new mutation in a sporadic case. Neutrophil elastase (a 240-aa mature protein predominantly found in neutrophil granules) is the target for protease inhibition by alpha1-antitrypsin, and its unopposed release destroys tissue at sites of inflammation. We hypothesize that a perturbed interaction between neutrophil elastase and serpins or other substrates may regulate mechanisms governing the clock-like timing of haematopoiesis.

Dynamic distribution of the regulatory subunit of cAMP-dependent protein kinase type II in NIH 3T3 cells.

Experiments on the introduction of the regulatory subunit of cAMP-dependent protein kinase type II (RII) into NIH 3T3 cells clearly demonstrated its translocation into the nucleus. The labelled protein was incorporated into erythrocyte ghosts and their fusion with the cells was carried out. The dynamics of distribution of the labelled RII in NIH 3T3 cells was studied by the method of historadiography. It was found that during the next few hours after its penetration into the cytoplasm, the protein translocates into the nucleus and concentrates in the immediate proximity to the nucleoli.