Growth and differentiation signals regulated by the M-CSF receptor

The normal proto-oncogene c-fms encodes the macrophage growth factor (M-CSF) receptor involved in growth, survival, and differentiation along the monocyte-macrophage lineage of hematopoietic cell development. A major portion of our research concerns unraveling the temporal, molecular, and structural features that determine and regulate these events. Previous results indicated that c-fms can transmit a growth signal as well as a signal for differentiation in the appropriate cells. To investigate the role of the Fms tyrosine autophosphorylation sites in proliferation vs. differentiation signaling, four of these sites were disrupted and the mutant receptors expressed in a clone derived from the myeloid FDC-P1 cell line. These analyses revealed that: (1) none of the four autophosphorylation sites studied (Y697, Y706, Y721, and Y807) are essential for M-CSF-dependent proliferation of the FDC-P1 clone; (2) Y697, Y706, and Y721 sites, located in the kinase insert region of Fms, are not necessary for differentiation but their presence augments this process; and (3) the Y807 site is essential for the Fms differentiation signal: its mutation totally abrogates the differentiation of the FDC-P1 clone and conversely increases the rate of M-CSF-dependent proliferation. This suggests that the Y807 site may control a switch between growth and differentiation. The assignment of Y807 as a critical site for the reciprocal regulation of growth and differentiation may provide a paradigm for Fms involvement in leukemogenesis, and we are currently investigating the downstream signals transmitted by the tyrosine-phosphorylated 807 site. In Fms-expressing FDC-P1 cells, M-CSF stimulation results in the rapid (30 sec) tyrosine phosphorylation of Fms on the five cytoplasmic tyrosine autophosphorylation sites, and subsequent tyrosine phosphorylation of several host cell proteins occurs within 1–2 min. Complexes are formed between Fms and other signal transduction proteins such as Grb2, Shc, Sos1, and p85. In addition, a new signal transduction protein of 150 kDa is detectable in the FDC-P1 cells. The p150 is phosphorylated on tyrosine, and forms a complex with Shc and Grb2. The interaction with Shc occurs via a protein tyrosine binding (PTB) domain at the N-terminus of Shc. The p150 is not detectable in Fms signaling within fibroblasts, yet the PDGF receptor induces the tyrosine phosphorylation of a similarly sized protein. In hematopoietic cells, this protein is involved in signaling by receptors for GM-CSF, IL-3, KL, MPO, and EPO. We have now cloned a cDNA for this protein and found at least one related family member. The related family member is a Fanconia Anemia gene product, and this suggests potential ways the p150 protein may function in Fms signaling. Mol Reprod Dev 46:96–103, 1997. © 1997 Wiley-Liss, Inc.     

A model of visual perception

In this paper we propose a model of visual perception in which a positive feedback mechanism can reproduce the pattern stimulus on a neurons screen. The pattern stimulus reproduction is based on informations coming from the spatial derivatives of visual pattern. This information together with the response of the feature extractors provides to the reproduction of the visual pattern as neuron screen electric activity. We simulate several input patterns and prove that the model reproduces the percept.     

Nuclear metabolism. II. Further studies on epoxide hydrolase activity

Apparent K_m- and V_max-values of nuclear styrene 7,8-oxide hydrolase were determined at different protein concentrations. In the protein concentrations range used no significant differences in the apparent K_m-values were observed. The influence of the incubation with different modifiers (i.e. SKF-525A, metyrapone, 1,2-epoxy-3,3,3 trichloropropane, cyclohexene oxide) at two different concentrations on this enzyme activity was also determined. Cyclohexene oxide and 1,2-epoxy-3,3,3-trichloropropane, two well known inhibitors of the microsomal epoxide hydrolase(s) caused a marked inhibition, metyrapone had a strong activating effect whereas SKF-525A had no effect. In vivo pretreatment with phenobarbital significantly induced the nuclear epoxide hydrolase whereas β-naphthoflavone caused a lower degree of induction. This pattern is quantitatively different but qualitatively very similar to the microsomal one. Moreover a toxifying to detoxifying enzymatic activity balance is attempted for the metabolization of the alkenic double bond of styrene, taking into account the ratio between the styrene monooxygenase (toxifying enzyme) and the styrene 7,8-oxide hydrolase (detoxifying enzyme) after the above mentioned pretreatments, both in the microsomal and nuclear fractions.     

Gram-positive merA gene in gram-negative oral and urine bacteria

Clinical mercury resistant (Hg(r)) Gram-negative bacteria carrying Gram-positive mercury reductase (merA)-like genes were characterized using DNA-DNA hybridization, PCR and sequencing. A PCR assay was developed which discriminated between the merA genes related to Staphylococcus and those related to the Bacillus/Streptococcus merA genes by the difference in size of the PCR product. DNA sequence analysis correlated with the PCR assay. The merA genes from Acinetobacter junii, Enterobacter cloacae and Escherichia coli were sequenced and shared 98-99% identical nucleotide (nt) and 99.6-100% amino acid identity with the Staphylococcus aureus MerA protein. A fourth merA gene, from Pantoeae agglomerans, was partially sequenced (60%) and had 99% identical nt and 100% amino acid identity with the Streptococcus oralis MerA protein. All the Hg(r) Gram-negative bacteria transferred their Gram-positive merA genes to a Gram-positive Enterococcus faecalis recipient with the resulting transconjugants expressing mercury resistance. These Gram-positive merA genes join Gram-positive tetracycline resistance and Gram-positive macrolide resistance genes in their association with mobile elements which are able to transfer and express in Gram-negative bacteria.     

Insertion mutations at the maizeOpaque2 locus induced by transposable element familiesAc, En/Spm andBg

Eight independently isolated unstable alleles of theOpaque2 (O2) locus were analysed genetically and at the DNA level. The whole series of mutations was isolated from a maize strain carrying a wild-typeO2 allele and the transposable elementActivator (Ac) at thewx-m7 allele. Previous work with another unstable allele of the same series has shown that it was indeed caused by the insertion of anAc element. Unexpectedly, the remaining eight mutations were not caused by the designatedAc element, but by other insertions that are structurally similar or identical to one of two different autonomous transposable elements. Six mutations were caused by the insertion of a transposable element of theEnhancer/Suppressor-Mutator (En/Spm) family. Two mutations were the result of the insertion of a transposable element of theBergamo (Bg) family. Genetic tests carried out with plants carrying the unstable mutations demonstrated that all were caused by the insertion of an autonomous transposable element.     

Surgical treatment of scoliosis in a rare disease: arthrogryposis

Background

The reported incidence of scoliosis in arthrogryposis varies from 30% to 67% and, in most cases, the curves progress rapidly and become stiff from early age. The authors report six cases of scoliosis in arthrogryposis to assess the role of surgical treatment.

Methods

Six cases (3 males, 3 females; mean age at surgery 13.2 years) with arthrogryposis multiplex congenita associated with the characteristic amyoplasia were reviewed: they were operated on for scoliosis at the authors' Spine Surgery Department between 1987 and 2008. Surgery was performed using the Harrington-Luque instrumentation (2 cases), the Luque system (1), a hybrid segmental technique with hooks and screws (1) and spinal anchoring with pedicle screws (2).

Results

The patients were clinically and radiologically reviewed at a mean follow-up of 4.2 years, ± 2.7 (range, 1 to 9 years). Three minor postoperative complications were encountered; a long-term pulmonary complication was seen in one case after reintervention and was successfully resolved after 10 days. Surgery was successful in the other 5 cases, where solid arthrodesis was achieved and no significant curve progression was observed at follow-up.

Conclusions

The experience acquired with the present case series leads the authors to assert that prompt action should be taken when treating such aggressive forms of scoliosis. In case of mild spinal deformities in arthrogryposis, brace treatment should be attempted, the evolution of the curves being unpredictable; however, when the curve exceeds 40° and presents with marked hyperkyphosis, hyperlordosis or pelvic obliquity, surgery should not be delayed.     

Rapid local adaptation in both sexual and asexual invasive populations of monkeyflowers (Mimulus spp.)

Background and AimsTraditionally, local adaptation has been seen as the outcome of a long evolutionary history, particularly with regard to sexual lineages. By contrast, phenotypic plasticity has been thought to be most important during the initial stages of population establishment and in asexual species. We evaluated the roles of adaptive evolution and phenotypic plasticity in the invasive success of two closely related species of invasive monkeyflowers (Mimulus) in the UK that have contrasting reproductive strategies: M. guttatus combines sexual (seeds) and asexual (clonal growth) reproduction while M. × robertsii is entirely asexual.MethodsWe compared the clonality (number of stolons), floral and vegetative phenotype, and phenotypic plasticity of native (M. guttatus) and invasive (M. guttatus and M. × robertsii) populations grown in controlled environment chambers under the environmental conditions at each latitudinal extreme of the UK. The goal was to discern the roles of temperature and photoperiod on the expression of phenotypic traits. Next, we tested the existence of local adaptation in the two species within the invasive range with a reciprocal transplant experiment at two field sites in the latitudinal extremes of the UK, and analysed which phenotypic traits underlie potential local fitness advantages in each species.Key ResultsPopulations of M. guttatus in the UK showed local adaptation through sexual function (fruit production), while M. × robertsii showed local adaptation via asexual function (stolon production). Phenotypic selection analyses revealed that different traits are associated with fitness in each species. Invasive and native populations of M. guttatus had similar phenotypic plasticity and clonality. M. × robertsii presents greater plasticity and clonality than native M. guttatus, but most populations have restricted clonality under the warm conditions of the south of the UK.ConclusionsThis study provides experimental evidence of local adaptation in a strictly asexual invasive species with high clonality and phenotypic plasticity. This indicates that even asexual taxa can rapidly (<200 years) adapt to novel environmental conditions in which alternative strategies may not ensure the persistence of populations.