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Richard E Person

Publications and source records attributed to Richard E Person.

10 recordsLinked to original sources
PubMed2004

Paradoxical homozygous expression from heterozygotes and heterozygous expression from homozygotes as a consequence of transcriptional infidelity through a polyadenine tract in the AP3B1 gene responsible for canine cyclic neutropenia.

Canine cyclic neutropenia is an autosomal recessive disease in which the number of neutrophils, the primary blood phagocyte, oscillates between almost zero and normal values with two week frequency. We previously found that the causative mutation is an insertion of an extra adenine residue within a tract of nine A's in exon 21 of the 27 exon canine AP3B1 gene. In the course of identifying the mutation, however, we observed an unusual phenomenon: heterozygous carrier dogs, who have one normal allele and one mutant allele, produce a homogeneous population of normal AP3B1 transcripts (containing nine A's), but homozygous affected dogs, who have two mutant alleles, produce a heterogeneous population of AP3B1 mRNA containing mutant transcripts with ten A's and, unexpectedly, wild-type transcripts with nine A's. By RT-PCR subclone analysis and use of an in vitro reporter assay, we show that there is a high frequency of errors made during the transcription of homopolymeric adenine sequences, such that the A tract in the mRNA is frequently shortened or lengthened by an extra residue. Out of frame transcripts are degraded, accounting for this paradox through the preferential accumulation of normal message from mutant alleles.

Adaptor Protein Complex 3↗
PubMed2004

Hereditary neutropenia: dogs explain human neutrophil elastase mutations.

Mutations in ELA2, the gene encoding neutrophil elastase (NE), cause the human diseases cyclic neutropenia (CN) and severe congenital neutropenia (SCN). Numerous mutations are known, but their lack of consistent biochemical effect has proven puzzling. The recent finding that mutation of AP3B1, which encodes the beta subunit of adaptor protein complex 3 (AP3), is the cause of canine CN suggests a model for the molecular basis of hereditary neutropenias, involving the mistrafficking of NE: AP3 recognizes NE as a cargo protein, and their interaction implies that NE is a transmembrane protein. Computerized algorithms predict two NE transmembrane domains. Most CN mutations fall within predicted transmembrane domains and lead to excessive deposition of NE in granules, whereas SCN mutations usually disrupt the AP3 recognition sequence, resulting in excessive transport to the plasma membrane.

Adaptor Protein Complex 3↗
PubMed2003

Lymphoid enhancer factor-1 links two hereditary leukemia syndromes through core-binding factor alpha regulation of ELA2.

Two hereditary human leukemia syndromes are severe congenital neutropenia (SCN), caused by mutations in the gene ELA2, encoding the protease neutrophil elastase, and familial platelet disorder with acute myelogenous leukemia (AML), caused by mutations in the gene AML1, encoding the transcription factor core-binding factor alpha (CBFalpha). In mice, CBFalpha regulates the expression of ELA2, suggesting a common link for both diseases. However, gene-targeted mouse models have failed to reproduce either human disease, thus prohibiting further in vivo studies in mice. Here we investigate CBFalpha regulation of the human ELA2 promoter, taking advantage of bone marrow obtained from patients with either illness. In particular, we have identified novel ELA2 promoter substitutions (-199 C to A) within a potential motif for lymphoid enhancer factor-1 (LEF-1), a transcriptional mediator of Wnt/beta-catenin signaling, in SCN patients. The LEF-1 motif lies adjacent to a potential CBFalpha binding site that is in a different position in human compared with mouse ELA2. We find that LEF-1 and CBFalpha co-activate ELA2 expression. In vitro, the high mobility group domain of LEF-1 interacts with the runt DNA binding and proline-, serine-, threonine-rich activation domains of CBFalpha. ELA2 transcript levels are up-regulated in bone marrow of an SCN patient with the -199 C to A substitution. Conversely, a mutation of the CBFalpha activation domain, found in a patient with familial platelet disorder with AML, fails to stimulate the ELA2 promoter in vitro, and bone marrow correspondingly demonstrates reduced ELA2 transcript. Observations in these complementary patients indicate that LEF-1 cooperates with CBFalpha to activate ELA2 in vivo and also suggest the possibility that up-regulating promoter mutations can contribute to SCN. Two hereditary AML predisposition syndromes may therefore intersect via LEF-1, potentially linking them to more generalized cancer mechanisms.

Animals↗
PubMed2003

Mutations associated with neutropenia in dogs and humans disrupt intracellular transport of neutrophil elastase.

Cyclic hematopoiesis is a stem cell disease in which the number of neutrophils and other blood cells oscillates in weekly phases. Autosomal dominant mutations of ELA2, encoding the protease neutrophil elastase, found in lysosome-like granules, cause cyclic hematopoiesis and most cases of the pre-leukemic disorder severe congenital neutropenia (SCN; ref. 3) in humans. Over 20 different mutations of neutrophil elastase have been identified, but their consequences are elusive, because they confer no consistent effects on enzymatic activity. The similar autosomal recessive disease of dogs, canine cyclic hematopoiesis, is not caused by mutations in ELA2 (data not shown). Here we show that homozygous mutation of the gene encoding the dog adaptor protein complex 3 (AP3) beta-subunit, directing trans-Golgi export of transmembrane cargo proteins to lysosomes, causes canine cyclic hematopoiesis. C-terminal processing of neutrophil elastase exposes an AP3 interaction signal responsible for redirecting neutrophil elastase trafficking from membranes to granules. Disruption of either neutrophil elastase or AP3 perturbs the intracellular trafficking of neutrophil elastase. Most mutations in ELA2 that cause human cyclic hematopoiesis prevent membrane localization of neutrophil elastase, whereas most mutations in ELA2 that cause SCN lead to exclusive membrane localization.

Adaptor Protein Complex 3↗
PubMed2003

Mutations in proto-oncogene GFI1 cause human neutropenia and target ELA2.

Mice lacking the transcriptional repressor oncoprotein Gfi1 are unexpectedly neutropenic. We therefore screened GFI1 as a candidate for association with neutropenia in affected individuals without mutations in ELA2 (encoding neutrophil elastase), the most common cause of severe congenital neutropenia (SCN; ref. 3). We found dominant negative zinc finger mutations that disable transcriptional repressor activity. The phenotype also includes immunodeficient lymphocytes and production of a circulating population of myeloid cells that appear immature. We show by chromatin immunoprecipitation, gel shift, reporter assays and elevated expression of ELA2 in vivo in neutropenic individuals that GFI1 represses ELA2, linking these two genes in a common pathway involved in myeloid differentiation.

Adult↗
PubMed2003

Leukemia in severe congenital neutropenia: defective proteolysis suggests new pathways to malignancy and opportunities for therapy.

Severe congenital neutropenia (SCN), a heterogeneous disorder that includes Kostmann syndrome, predisposes to myelodysplasia and acute myelogenous leukemia. Recently identified heterozygous mutations in the gene ELA2, encoding neutrophil elastase on human chromosome 19pter, account for the majority of autosomal dominant cases of SCN, including those demonstrating neoplastic progression. The involvement of the serine protease neutrophil elastase, localized to the granules of neutrophils and monocytes, implies an unexpected role for proteolytic regulation of hematopoiesis. Continued elucidation of the clinical features, molecular genetics, and biochemistry is likely to provide insight into novel pathways of leukemia induction with attendant prospects for new avenues of therapy.

Diagnosis, Differential↗
PubMed2003

Role of neutrophil elastase in bone marrow failure syndromes: molecular genetic revival of the chalone hypothesis.

Two forms of inherited deficiency of neutrophil numbers are cyclic hematopoiesis and severe congenital neutropenia. In cyclic hematopoiesis, neutrophil counts oscillate opposite monocytes in a 3-week cycle. Severe congenital neutropenia consists of static neutropenia and a predisposition to myelodysplasia and acute myelogenous leukemia. All cases of cyclic neutropenia and most cases of severe congenital neutropenia result from heterozygous germline mutations in the gene encoding neutrophil elastase, ela2. Recent work extends the list of neutropenia genes to include WASp, Gfi-1, adaptin, and tafazzin. Studies of mosaic patients suggest that ela2 mutations act in a cell-autonomous fashion. A hypothetical feedback circuit potentially interconnects these genes. Genetic dissection of signaling in model organisms along with experimental hematology implicate C/EPBepsilon, RUNX1/AML1, Notch family members, LEF1, and Cdc42 as additional nodes in this pathway. The authors propose that neutrophil elastase acts as an inhibitor of myelopoiesis, substantiating a chalone hypothesis proposed many years ago.

Bone Marrow Diseases↗
PubMed2002

Further evidence for the role of free radicals in the limb teratogenicity of L-NAME.

BACKGROUND: L-NAME (N(G)-nitro-(L)-arginine methyl ester), a nitric oxide synthase inhibitor, causes severe limb reduction malformations when gravid rats are treated intraperitoneally on gd-17. Hemorrhages, appearing within hours of L-NAME administration, and defects at term can be significantly reduced by co-treatment with PBN (alpha-phenyl-N-t-butylnitrone), a spin trap antioxidant. We have proposed that limb defects result from ischemia-reperfusion injury. We examine the role of xanthine oxidase and ROS formation in the limb effects of L-NAME. METHODS: Gravidas were treated with L-NAME (50 mg/kg) in the presence or absence of allopurinol, a xanthine oxidase inhibitor. Spatial patterns of limb hemorrhage were determined promptly and at term as was digit length at the latter interval. Xanthine oxidase activities were assayed in control and treated limbs with and without allopurinol co-treatment. RESULTS: Allopurinol significantly reduced hemorrhage severity in a dose-responsive fashion when fetuses were examined at term. Higher doses of allopurinol significantly preserved digit length. Xanthine oxidase activities in fetal limb were significantly increased by L-NAME treatment whereas co-treatment with allopurinol restored activities to near-control levels. CONCLUSIONS: These findings support the role of excess reactive oxygen species (ROS) formation in L-NAME-induced limb reduction. We propose that nitric oxide (NO) depletion by L-NAME interferes with vascular integrity, and causes vasoconstriction. Resultant hypoxia stimulates superoxide formation and nitric oxide formation catalyzed by the inducible isoform of nitric oxide synthase. The reduction products of superoxide or the products of its reaction with nitric oxide oxidize or nitrate endothelial components resulting in limb reduction defects.

Allopurinol↗
PubMed2002

Involvement of mitochondria and other free radical sources in normal and abnormal fetal development.

Shepard and Mackler have documented quantitative increases in mitochondrial cristae between gestational days 10 and 14 in rats accompanied by decreased glucose utilization and increased NADH oxidase activity. Findings show a shift from glycolytic to oxidative metabolism starting at around the time of implantation. Exposure to many substances that cause transient uteroplacental hypoperfusion, including cocaine, phenytoin, calcium channel blockers, and nitric oxide synthase (NOS) inhibitors, induce limb and central nervous system (CNS) malformations while sparing the heart. We have reported that isolated electron transport particles prepared from sensitive tissues show reduced NADH oxidase activities compared with insensitive heart. They also have significantly greater superoxide formation in association with significantly reduced superoxide dismutase activities. NOS inhibitors induce severe limb reductions in late gestation. Exposure is associated with hemorrhage and nitrotyrosine (NT) formation shortly after treatment. Hemorrhage, malformations, and NT formation can be significantly reduced by coadministration of PBN, allopurinol, or aminoguanidine. On the basis of these findings, we have proposed a role for the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the genesis of limb reduction defects. It is important to note that limb reduction defects occur in humans ( approximately 0.22/1000) and have been associated with the agents listed above.

Animals↗