aPKCzeta cortical loading is associated with Lgl cytoplasmic release and tumor growth in Drosophila and human epithelia.

Atypical protein kinase C (aPKC) and Lethal giant larvae (Lgl) regulate apical-basal polarity in Drosophila and mammalian epithelia. At the apical domain, aPKC phosphorylates and displaces Lgl that, in turn, maintains aPKC inactive at the basolateral region. The mutual exclusion of these two proteins seems to be crucial for the correct epithelial structure and function. Here we show that a cortical aPKC loading induces Lgl cytoplasmic release and massive overgrowth in Drosophila imaginal epithelia, whereas a cytoplasmic expression does not alter proliferation and epithelial overall structure. As two aPKC isoforms (iota and zeta) exist in humans and we previously showed that Drosophila Lgl is the functional homologue of the Human giant larvae-1 (Hugl-1) protein, we argued if the same mechanism of mutual exclusion could be impaired in human epithelial disorders and investigated aPKCiota, aPKCzeta and Hugl-1 localization in cancers deriving from ovarian surface epithelium. Both in mucinous and serous histotypes, aPKCzeta showed an apical-to-cortical redistribution and Hugl-1 showed a membrane-to-cytoplasm release, perfectly recapitulating the Drosophila model. Although several recent works support a causative role for aPKCiota overexpression in human carcinomas, our results suggest a key role for aPKCzeta in apical-basal polarity loosening, a mechanism that seems to be driven by changes in protein localization rather than in protein abundance.

Cell behaviour of Drosophila fat cadherin mutations in wing development.

We have studied several cell behaviour parameters of mutant alleles of fat (ft) in Drosophila imaginal wing disc development. Mutant imaginal discs continue growing in larvae delayed in pupariation and can reach sizes of several times those of wild-type. Their growth is, however, basically allometric. Homozygous ft cells grow faster than their twin cells in clones and generate larger territories, albeit delimited by normal clonal restrictions. Moreover, ft cells in clones tend to grow towards wing proximal regions. These behaviours can be related with failures in cell adhesiveness and cell recognition. Double mutant combinations with alleles of other genes, e.g. of the Epidermal growth factor receptor (DER) pathway, modify ft clonal phenotypes, indicating that adhesiveness is modulated by intercellular signalling. Mutant ft cells show, in addition, smaller cell sizes during proliferation and abnormal cuticular differentiation, which reflect cell membrane and cytoskeleton anomalies, which are not modulated by the DER pathway.

Screening of larval/pupal P-element induced lethals on the second chromosome in Drosophila melanogaster: clonal analysis and morphology of imaginal discs.

We have carried out screens for lethal mutations on the second chromosome of Drosophila melanogaster that are associated with abnormal imaginal disc morphologies, particularly in the wing disc. From a collection of 164 P element-induced mutations with a late larva/pupa lethal phase we have identified 56 new loci whose gene products are required for normal wing disc development and for normal morphology of other larval organs. Genetic mosaics of these 56 mutant lines show clonal mutant phenotypes for 23 cell-viable mutations. These phenotypes result from altered cell parameters. Causal relationships between disc and clonal phenotypes are discussed.

Developmental constraints in the Drosophila wing.

Selection experiments for shortening the four longitudinal veins in a wild population of Drosophila melanogaster have been performed to evaluate how a local change is integrated in the wing development. Our results show that, though many units of selection seem to exist within a given organ, these are strongly constrained within the developmental programme, in such a way that only some predictable forms are expected. The results are discussed in terms of the 'Entelechia' model proposed by Garcia-Bellido in which the intercalarity of positional values promoted by 'martial' genes in a given organ is the driving force for controlled cell proliferation.

Developmental constraints and wing shape variation in natural populations of Drosophila melanogaster.

The body sizes and shapes of poikilothermic animals generally show clinal variation with latitude. Among the environmental factors responsible for the cline, temperature seems to be the most probable candidate. In the present work we analysed natural populations of Drosophila melanogaster collected at different geographical localities to determine whether the same selective forces acting on wing development in the laboratory are also at work in the wild. We show that the temperature selection acting on wing development in the laboratory is only one of the selective forces operating in the wild. The size differences between natural populations seem to depend exclusively on cell number whereas they depend on cell area in the laboratory. The two wing compartments behave as distinct units of selection subjected to different genetic control, confirming our previous observations on laboratory populations. In addition, subunits of development defined as regions of cell proliferation centres restricted within longitudinal veins can, in turn, be considered as subunits of selection. Their interaction during development and continuous natural selection around an optimum could explain the high wing shape stability generally found in natural populations.

Genetic interactions among vestigial, hairy, and Notch suggest a role of vestigial in the differentiation of epidermal and neural cells of the wing and halter of Drosophila melanogaster.

In this paper we describe the results of genetic analysis of the vestigial locus by studying its interactions with hairy and Notch loci in Drosophila melanogaster. Different vestigial alleles in homo- and heterozygous combination with different hairy alleles show synergism in increasing both cell death and formation of ectopic bristles and produce ectopic veins. Interactions between N and vg also show synergism in increasing cell death and formation of ectopic bristles. Only synergism in cell death is seen between h and N. The interactions indicate that vg product plays a role in the differentiation of epidermal and neural cells of the wing disc by interacting with N and h products either directly or indirectly. Mechanisms of molecular interactions among the three loci are discussed.

Heat-shock resistance in Drosophila populations: analysis of variation in reciprocal cross progeny.

Genetic variation for resistance to high temperature stress was studied in populations of D. melanogaster and D. buzzatii from different geographic regions. Drosophila melanogaster individuals were presented with either a direct short exposure to a high temperature or exposure to high temperature after receiving a pretreatment, which increased resistance. Heat-stress resistance varied among populations, with one much more resistant than all others under both treatments. Another possessed low stress resistance when exposed without the heat pretreatment; but with pretreatment, resistance increased relative to the other populations. Evidence from reciprocal crosses suggests that the X chromosome of the more resistant population carries alleles that greatly increase resistance, and that one or more factors on the autosomes also affect resistance. Non-additive interaction effects among the three less resistant population, were suggestive that all differ for various elements that contribute to stress resistance, and that some clearly change inducible resistance more than basal levels. In D. buzzatii, the two least resistant populations were genetically very similar. Crosses to the more resistant population gave results suggesting that the low resistance to heat is dominant. A small X-chromosome effect that increased resistance, and a dominant enhancer of male resistance also may have contributed to variation in resistance.

Quality of clinical information: a new approach of EQA in Emilia-Romagna, Italy.

For correct enforcement of an external quality assessment (EQA) scheme, suitable parameters are required for the assessment of analytical performance. Traditional EQA schemes have always been chiefly concerned with the agreement of analytical results between laboratories. Although we consider this concept to be important, we also believe that particular attention must be paid to the quality of the clinical information, in relation to correct use of the results. On the basis of this principle, we have developed an EQA model which, besides considering the absolute value, also take the reference limits (RLs) into consideration by means of the normalization procedure. The evaluation of clinical information is of vital importance, especially in relation to immunoassays, since the low degree of standardization between methods, and the ensuing phenomenon of relative inaccuracy, make the use of suitable RLs essential. Actually, analysis of the results reveals a high degree of heterogeneity in the RLs used by the laboratories, even within the same method-groups.

Developmental effects of modifiers of the vg mutant in Drosophila melanogaster.

An analysis of the modifiers affecting the expression of the vg gene was performed. We selected for weak and strong expression of the vg mutant in F2 segregating populations obtained by crossing a vestigial stock with an Oregon laboratory stock (O) and with a wild strain (B) captured near Bologna, Italy. The selection for enlarged wings was more effective in the vg B population where wild wings appeared from the 10th generation. The assay of the three major chromosomes showed that the modifiers are located on chromosomes 2 and 3. The mutant imaginal disc cell death phenotype is evident in vg/vg strains that have a wild-type wing phenotype. It is suggested that the selected modifiers do not prevent cell death but induce regenerative growth.

Temperature-Related Divergence in Experimental Populations of DROSOPHILA MELANOGASTER. I. Genetic and Developmental Basis of Wing Size and Shape Variation.

The effects of environmental temperature on wing size and shape of Drosophila melanogaster were analyzed in populations derived from an Oregon laboratory strain kept at three temperatures (18 degrees , 25 degrees , 28 degrees ) for 4 yr. Temperature-directed selection was identified for both wing size and shape. The length of the four longitudinal veins, used as a test for wing size variations in the different populations, appears to be affected by both genetic and maternal influences. Vein expression appears to be dependent upon developmental pattern of the wing: veins belonging to the same compartment are coordinated in their expression and relative position, whereas veins belonging to different compartments are not. Both wing and cell areas show genetic divergence, particularly in the posterior compartment. Cell number seems to compensate for cell size variations. Such compensation is carried out both at the level of single organisms and at the level of population as a whole. The two compartments behave as individual units of selection.

Univariate and multivariate analysis on phenotypic divergence in Phleum.

An analysis of phenotypic and genetic variability was performed on Phleum ambiguum populations obtained by vegetative propagation and grown in different environments. The investigation on a single character and the canonical analysis on several plant traits indicate that, while genetic variability (h(2)) is essentially constant, phenotypic variance and covariance are affected by different environments and successive clonations. The observed changes seem not to be reversible when plants, transferred to a different environment, are returned to the original one. Within-clones variability seems to be affected by environmental conditions without being directly related to them. The results reported seem to be in good agreement with the phenotypic divergence hypothesis.

Multivariate analysis of visual evoked response.

The visual potentials evoked by flash are analyzed in healthy subjects in cases of retinal detachment, of optic nerve lesions, and of amblyopia by means of different statistical methods: 1. Analysis of the various features of the response, evaluated separately 2. Analysis of the interdependence between the measures of the various features The first method supplies information on the differences in 'size' of the curves in the various samples, the second method reveals differences of 'shape'. The second method has proved to be able to distinguish both normal conditions from pathologic impairment of optic structures and the different sites of the lesions.