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M E Fortini

Publications and source records attributed to M E Fortini.

30 records · Page 2Linked to original sources
PubMed1994

The suppressor of hairless protein participates in notch receptor signaling.

In a genetic screen for mutations that attenuate Notch signaling in the developing Drosophila eye, we isolated rare, gain-of-function alleles of Suppressor of Hairless (Su(H)), the fly homolog of the mammalian C promoter-binding factor 1 (CBF1) gene. Su(H) exhibits numerous allele-specific genetic interactions with Notch as well as with Delta, deltex, and mastermind. In cultured Drosophila cells, the Su(H) protein is sequestered in the cytoplasm when coexpressed with Notch protein and is translocated to the nucleus when Notch binds to its ligand Delta. Cytoplasmic retention of Su(H) requires the intracellular cdc10/ankyrin repeats of Notch, which associate with Su(H) protein in the yeast interaction trap assay. These results indicate that Notch activity may regulate nuclear events by controlling the activity of a DNA-binding protein.

Amino Acid Sequence↗
PubMed1993

An activated Notch receptor blocks cell-fate commitment in the developing Drosophila eye.

The Notch locus of Drosophila melanogaster encodes a 2,703-amino-acid transmembrane protein required for a variety of developmental processes, including neurogenesis, oogenesis and ommatidial assembly. The Notch protein contains a large extracellular domain of 36 epidermal growth factor-like repeats as well as three Notch/Lin-12 repeats and an intracellular domain with 6 Cdc10/ankyrin repeats, motifs that are highly conserved in several vertebrate Notch homologues. Truncation of the extracellular domain of the Drosophila Notch protein produces an activated receptor, as judged by its ability to cause phenotypes similar to gain-of-function alleles of duplications of the Notch locus. Equivalent truncations of vertebrate Notch-related proteins have been associated with malignant neoplasma and other developmental abnormalities. We present here an analysis of activated Notch function at single-cell resolution in the Drosophila compound eye. We find that overexpression of full-length Notch in defined cell types has no apparent effects but that overexpression of activated Notch in the same cells transiently blocks their proper cell-fate commitment, causing them either to adopt incorrect cell fates or to differentiate incompletely. Moreover, an activated Notch protein lacking the transmembrane domain is translocated to the nucleus, raising the possibility that Notch may participate directly in nuclear events.

Animals↗
PubMed1993

Analysis of phenotypic abnormalities and cell fate changes caused by dominant activated and dominant negative forms of the Notch receptor in Drosophila development.

The Notch gene of Drosophila plays an important role in cell fate specification throughout development. The Notch protein contains a large extracellular domain of 36 EGF-like repeats as well as 3 Notch/lin-12 repeats and an intracellular domain with 6 cdc10/ankyrin repeats, motifs which are highly conserved in several vertebrate Notch homologues [1-7]. In this review we summarize the results of two recent studies which attempt to establish structure-function relationships of the various domains of the Notch gene product [8, 9]. The functions of various structural domains of the Notch protein in vivo were investigated using a series of deletion mutants which have been ectopically expressed either under the hsp70 heat-shock promoter or under the sevenless eye-specific promoter. Truncation of the extracellular domain of Drosophila Notch produces an activated receptor as judged by its ability to cause phenotypes matching those of gain-of-function alleles or duplications of the Notch locus [8]. Equivalent truncations of vertebrate Notch-related proteins have been associated with malignant neoplasms and other developmental abnormalities [3, 6, 10, 11]. In contrast, dominant negative phenotypes result from overexpression of a protein lacking most intracellular sequences. These results were extended by an analysis of activated Notch function at single-cell resolution in the Drosophila compound eye [9]. It was shown that while overexpression of full-length Notch in defined cell types has no apparent effects, overexpression of activated Notch in the same cells transiently blocks their proper cell-fate commitment, causing them to either adopt incorrect cell fates or to differentiate incompletely. Moreover, an activated Notch protein lacking the transmembrane domain is translocated to the nucleus, raising the possibility that Notch may participate directly in nuclear events.

Animals↗
PubMed1992

Signalling by the sevenless protein tyrosine kinase is mimicked by Ras1 activation.

Cell-fate specification of R7 photoreceptors in the developing Drosophila eye depends on an inductive signal from neighbouring R8 cells. Mutations in three genes, sevenless (sev), bride-of-sevenless (boss) and seven-in-absentia (sina) cause the R7 precursor to become a non-neural cone cell. The sev gene encodes a receptor protein tyrosine kinase (Sev) localized on the R7 surface, activated by a boss-encoded ligand presented by R8. The sina gene encodes a nuclear factor required in R7. Reduction in the dosage of the Ras1 gene impairs Sev-mediated signalling, suggesting that activation of Ras1 may be an important consequence of Sev activation. We report here that Ras1 activation may account for all of the signalling action of Sev; an activated Ras1Va112 protein rescues the normal R7 precursor from transformation into a cone cell in sev and boss null mutants and induces the formation of supernumerary R7 cells. Similar activation of the Drosophila Ras2 protein does not produce these effects, demonstrating Ras protein specificity.

Animals↗
PubMed1991

The optic lobe projection pattern of polarization-sensitive photoreceptor cells in Drosophila melanogaster.

Histological staining of wild-type and sevenless transgenic Drosophila melanogaster bearing Rh3-lacZ fusion genes permits the selective visualization of polarization-sensitive R7 and R8 photoreceptor cells located along the dorsal anterior eye margin. Diffusion of beta-galactosidase throughout these cells reveals that they project long axons to the two most peripheral synaptic target rows of the dorsal posterior medulla, defining a specialized marginal zone of this optic lobe. Comparison of the staining patterns of marginal and nonmarginal Rh3-lacZ-expressing photoreceptor cells in the same histological preparations suggest that the marginal cells possess morphologically specialized axons and synaptic terminals. These findings are discussed with reference to the neuroanatomy of the corresponding dorsal marginal eye and optic lobe regions of the larger dipterans Musca and Calliphora, and in relation to the ability of Drosophila to orient to polarized light.

Animals↗
PubMed1991

The Drosophila zfh-1 and zfh-2 genes encode novel proteins containing both zinc-finger and homeodomain motifs.

Two of the most common DNA-binding motifs found in eukaryotic transcriptional regulatory proteins are the homeodomain and the C2-H2 zinc finger. In Drosophila, homeodomain and zinc-finger proteins have been implicated in a wide variety of developmental processes. Until now, no proteins have been described in which both these DNA-binding motifs are present. We report here the isolation of genes encoding two such Drosophila proteins from a cDNA expression library. The product of the zfh-1 gene (zinc-finger homeodomain protein 1) contains one homeodomain and nine C2-H2 zinc fingers. The product of the zfh-2 gene possesses three homeodomains and sixteen C2-H2 zinc fingers. For zfh-1, antisera raised against nonoverlapping regions of the gene product all recognize a 145 kDa protein on protein immunoblots, suggesting that the different DNA-binding motifs are actually all present in the mature gene product. The novel arrangement of interspersed homeodomain and zinc-finger motifs in the primary sequences of the zfh-1 and zfh-2 gene products may signify an unusual mechanism of transcriptional regulation by these proteins.

Amino Acid Sequence↗
PubMed1991

The embryonic expression patterns of zfh-1 and zfh-2, two Drosophila genes encoding novel zinc-finger homeodomain proteins.

The zfh-1 and zfh-2 genes of D. melanogaster encode novel proteins containing both homeodomain and C2-H2 zinc-finger DNA-binding motifs. Antisera against these proteins were used to investigate their expression patterns during embryonic development. The zfh-1 gene is expressed in the mesoderm of early embryos and in a number of mesodermally-derived structures of late embryos, including the dorsal vessel, support cells of the gonads, and segment-specific arrays of adult muscle precursors. In addition, zfh-1 is expressed in the majority of identified motor neurons of the developing CNS. The mesodermal zfh-1 expression requires the products of the twist and snail genes. The zfh-2 gene displays a more limited expression pattern, largely restricted to the CNS of late embryos. Ubiquitous zfh-1 expression in transgenic flies bearing an hsp70-zfh-1 construct has specific developmental consequences, including embryonic CNS defects as well as adult eye and bristle abnormalities. The expression patterns of zfh-1 and zfh-2 suggest that both genes may be involved in Drosophila neurogenesis and that zfh-1 may have additional functions in mesoderm development.

Animals↗
PubMed1990

Analysis of cis-acting requirements of the Rh3 and Rh4 genes reveals a bipartite organization to rhodopsin promoters in Drosophila melanogaster.

The rhodopsin genes of Drosophila melanogaster are expressed in nonoverlapping subsets of photoreceptor cells within the insect visual system. Two of these genes, Rh3 and Rh4, are known to display complementary expression patterns in the UV-sensitive R7 photoreceptor cell population of the compound eye. In addition, we find that Rh3 is expressed in a small group of paired R7 and R8 photoreceptor cells at the dorsal eye margin that are apparently specialized for the detection of polarized light. In this paper we present a detailed characterization of the cis-acting requirements of both Rh3 and Rh4. Promoter deletion series demonstrate that small regulatory regions (less than 300 bp) of both R7 opsin genes contain DNA sequences sufficient to generate their respective expression patterns. Individual cis-acting elements were further identified by oligonucleotide-directed mutagenesis guided by interspecific sequence comparisons. Our results suggest that the Drosophila rhodopsin genes share a simple bipartite promoter structure, whereby the proximal region constitutes a functionally equivalent promoter "core" and the distal region determines cell-type specificity. The expression patterns of several hybrid rhodopsin promoters, in which all or part of the putative core regions have been replaced with the analogous regions of different rhodopsin promoters, provide additional evidence in support of this model.

Animals↗
PubMed1987

Attitudes and behavior toward students with handicaps by their nonhandicapped peers.

The theory of reasoned action (Ajzen & Fishbein, 1973) was used to examine the relationship between attitudes toward becoming a peer tutor for a student with handicaps and actually volunteering to become a peer tutor. This model suggests that intention is the best predictor of behavior and that intention consists of an attitudinal component (attitudes toward the behavior) and a normative component (perceptions of what other people think you should do). Subjects were 125 students in Grades 5 through 7 who were told about peer tutoring and asked to volunteer. Results showed that this model can be used to predict behavior of nonhandicapped students toward their handicapped peers in an educational setting. The importance and implications of these findings were discussed.

Attitude↗
PubMed1983

Prevention of Unwanted Pregnancy.

These two studies explored the cognitive decision-making process which differentiate effective contraceptors form the ineffective contraceptors (Study 1), and applied these findings to the development and testing of educational and cognitive interventions aimed at a group of sexually active young women at risk of becoming pregnant (Study 2). The results identified factors related to unnecessary contraceptive risk-taking. The interventions changed attitudes and knowledge about contraception in the college population in general and increased effective contraception in the at-risk population of women who were initially using either ineffective methods of birth control or no methods at all.

Contraception↗