Linda L Restifo
- Professor, Neurology
- Professor, Neuroscience
- Professor, BIO5 Institute
- Professor, Cellular and Molecular Medicine
- Professor, Entomology / Insect Science - GIDP
- Professor, Genetics - GIDP
- Professor, Neuroscience - GIDP
- Ph.D. Genetics
- University of Pennsylvania, Philadelphia, Pennsylvania, United States
- “Organization and transcriptional analysis of a developmentally regulated gene cluster in an ecdysterone-responsive puff site of Drosophila melanogaster”
- M.D. Medicine
- University of Pennsylvania, Philadelphia, Pennsylvania, United States
- B.A. Biology
- University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Search Committee for founding Director of Pharmacogenomics Center (UA) (2015 - 2016)
- Genomic Medical Review Board (UA) (2013 - 2015)
- Neuroscience Advisory Council, University of Arizona Health Sciences (UA) (2013 - 2014)
- College of Science Promotion & Tenure Committee (UA) (2011 - 2013)
Licensure & Certification
- Licensed Phyisican, Arizona Medical Board (1993)
Developmental neurogenetics;Developmental brain disorders;Neurotoxicity;Human genetic disease;Technology development in cellular neuroscience;Drug discovery
Human genetic disease;History of genetic technology;Translational medical research;Cultural divide between science and medicine
Human Genetic DiseasesCMM 695D (Spring 2021)
ThesisCMM 910 (Spring 2021)
Intro Gen Counseling ResearchCMM 600 (Fall 2020)
ThesisCMM 910 (Fall 2020)
Independent StudyMCB 599 (Spring 2020)
ThesisCMM 910 (Spring 2020)
Fundamental Genetic MechanismsCMM 518 (Fall 2019)
Independent StudyMCB 399 (Fall 2019)
Intro Gen Counseling ResearchCMM 600 (Fall 2019)
Independent StudyNRSC 599 (Spring 2019)
Modern GeneticsCMM 518 (Fall 2018)
DissertationNRSC 920 (Spring 2018)
Human Genetic DiseasesCMM 695D (Spring 2018)
DissertationNRSC 920 (Fall 2017)
Honors Independent StudyNSCS 299H (Fall 2017)
Honors ThesisNSCS 498H (Fall 2017)
ThesisNRSC 910 (Summer I 2017)
DissertationNRSC 920 (Spring 2017)
Independent StudyCMM 599 (Spring 2017)
Independent StudyNSCS 299 (Spring 2017)
Independent StudyNSCS 399 (Spring 2017)
Systems NeuroscienceNRSC 560 (Spring 2017)
ThesisNRSC 910 (Spring 2017)
DissertationNRSC 920 (Fall 2016)
Human Genetic DiseasesCMM 695D (Fall 2016)
Human Genetic DiseasesGENE 695D (Fall 2016)
Human Genetic DiseasesMCB 695D (Fall 2016)
ResearchNRSC 900 (Fall 2016)
Directed RsrchMCB 392 (Spring 2016)
DissertationNRSC 920 (Spring 2016)
Honors Independent StudyNSCS 299H (Spring 2016)
Honors Independent StudyNSCS 399H (Spring 2016)
Systems NeuroscienceNRSC 560 (Spring 2016)
- Jiang, L., Restifo, L. L., & Zohar, Y. (2015). Dissociation of brain tissue into viable single neurons in a microfluidic device.. IEEE Nano/Molecular Medicine and Engineering, 9, 29-32.
- Smrt, R. D., Lewis, S. A., Kraft, R., & Restifo, L. L. (2015). Primary neuronal culture of Drosophila larval neurons, with morphological analysis using NeuronMetrics. Drosophila Information Service, 98, 125-140.
- Ito, K., Shinomiya, K., Ito, M., Armstrong, J. D., Boyan, G., Hartenstein, V., Harzsch, S., Heisenberg, M., Homberg, U., Jenett, A., Keshishian, H., Restifo, L. L., Rössler, W., Simpson, J. H., Strausfeld, N. J., Strauss, R., Vosshall, L. B., & , I. B. (2014). A systematic nomenclature for the insect brain. Neuron, 81(4), 755-65.More infoDespite the importance of the insect nervous system for functional and developmental neuroscience, descriptions of insect brains have suffered from a lack of uniform nomenclature. Ambiguous definitions of brain regions and fiber bundles have contributed to the variation of names used to describe the same structure. The lack of clearly determined neuropil boundaries has made it difficult to document precise locations of neuronal projections for connectomics study. To address such issues, a consortium of neurobiologists studying arthropod brains, the Insect Brain Name Working Group, has established the present hierarchical nomenclature system, using the brain of Drosophila melanogaster as the reference framework, while taking the brains of other taxa into careful consideration for maximum consistency and expandability. The following summarizes the consortium's nomenclature system and highlights examples of existing ambiguities and remedies for them. This nomenclature is intended to serve as a standard of reference for the study of the brain of Drosophila and other insects.
- Kraft, R., Kahn, A., Medina-Franco, J. L., Orlowski, M. L., Baynes, C., Loṕez-Vallejo, F., Barnard, K., Maggiora, G. M., & Restifo, L. L. (2013). A cell-based fascin bioassay identifies compounds with potential anti-metastasis or cognition-enhancing functions. DMM Disease Models and Mechanisms, 6(1), 217-235.More infoPMID: 22917928;PMCID: PMC3529353;Abstract: The actin-bundling protein fascin is a key mediator of tumor invasion and metastasis and its activity drives filopodia formation, cell-shape changes and cell migration. Small-molecule inhibitors of fascin block tumor metastasis in animal models. Conversely, fascin deficiency might underlie the pathogenesis of some developmental brain disorders. To identify fascin-pathway modulators we devised a cell-based assay for fascin function and used it in a bidirectional drug screen. The screen utilized cultured fascin-deficient mutant Drosophila neurons, whose neurite arbors manifest the 'filagree' phenotype. Taking a repurposing approach, we screened a library of 1040 known compounds, many of them FDA-approved drugs, for filagree modifiers. Based on scaffold distribution, molecular-fingerprint similarities, and chemical-space distribution, this library has high structural diversity, supporting its utility as a screening tool. We identified 34 fascin-pathway blockers (with potential anti-metastasis activity) and 48 fascin-pathway enhancers (with potential cognitive-enhancer activity). The structural diversity of the active compounds suggests multiple molecular targets. Comparisons of active and inactive compounds provided preliminary structure-activity relationship information. The screen also revealed diverse neurotoxic effects of other drugs, notably the 'beads-on-a-string' defect, which is induced solely by statins. Statin-induced neurotoxicity is enhanced by fascin deficiency. In summary, we provide evidence that primary neuron culture using a genetic model organism can be valuable for early-stage drug discovery and developmental neurotoxicity testing. Furthermore, we propose that, given an appropriate assay for target-pathway function, bidirectional screening for brain-development disorders and invasive cancers represents an efficient, multipurpose strategy for drug discovery. © 2012. Published by The Company of Biologists Ltd.
- Restifo, L. L., Kraft, R., Kahn, A., Medina-Franco, J. L., Orlowski, M. L., Baynes, C., López-Vallejo, F., Barnard, K., & Maggiora, G. M. (2013). A cell-based fascin bioassay identifies compounds with potential anti-metastasis or cognition-enhancing functions. Disease Models & Mechanisms, 6(1), 217-235.More infoThe actin-bundling protein fascin is a key mediator of tumor invasion and metastasis and its activity drives filopodia formation, cell-shape changes and cell migration. Small-molecule inhibitors of fascin block tumor metastasis in animal models. Conversely, fascin deficiency might underlie the pathogenesis of some developmental brain disorders. To identify fascin-pathway modulators we devised a cell-based assay for fascin function and used it in a bidirectional drug screen. The screen utilized cultured fascin-deficient mutant Drosophila neurons, whose neurite arbors manifest the 'filagree' phenotype. Taking a repurposing approach, we screened a library of 1040 known compounds, many of them FDA-approved drugs, for filagree modifiers. Based on scaffold distribution, molecular-fingerprint similarities, and chemical-space distribution, this library has high structural diversity, supporting its utility as a screening tool. We identified 34 fascin-pathway blockers (with potential anti-metastasis activity) and 48 fascin-pathway enhancers (with potential cognitive-enhancer activity). The structural diversity of the active compounds suggests multiple molecular targets. Comparisons of active and inactive compounds provided preliminary structure-activity relationship information. The screen also revealed diverse neurotoxic effects of other drugs, notably the 'beads-on-a-string' defect, which is induced solely by statins. Statin-induced neurotoxicity is enhanced by fascin deficiency. In summary, we provide evidence that primary neuron culture using a genetic model organism can be valuable for early-stage drug discovery and developmental neurotoxicity testing. Furthermore, we propose that, given an appropriate assay for target-pathway function, bidirectional screening for brain-development disorders and invasive cancers represents an efficient, multipurpose strategy for drug discovery.
- Veeramah, K. R., Johnstone, L., Karafet, T. M., Wolf, D., Sprissler, R., Salogiannis, J., Barth-Maron, A., Greenberg, M. E., Stuhlmann, T., Weinert, S., Jentsch, T. J., Pazzi, M., Restifo, L. L., Talwar, D., Erickson, R. P., & Hammer, M. F. (2013). Exome sequencing reveals new causal mutations in children with epileptic encephalopathies. Epilepsia, 54(7), 1270-81.More infoThe management of epilepsy in children is particularly challenging when seizures are resistant to antiepileptic medications, or undergo many changes in seizure type over time, or have comorbid cognitive, behavioral, or motor deficits. Despite efforts to classify such epilepsies based on clinical and electroencephalographic criteria, many children never receive a definitive etiologic diagnosis. Whole exome sequencing (WES) is proving to be a highly effective method for identifying de novo variants that cause neurologic disorders, especially those associated with abnormal brain development. Herein we explore the utility of WES for identifying candidate causal de novo variants in a cohort of children with heterogeneous sporadic epilepsies without etiologic diagnoses.
- Veeramah, K. R., O'Brien, J. E., Meisler, M. H., Cheng, X., Dib-Hajj, S. D., Waxman, S. G., Talwar, D., Girirajan, S., Eichler, E. E., Restifo, L. L., Erickson, R. P., & Hammer, M. F. (2012). De novo pathogenic SCN8A mutation identified by whole-genome sequencing of a family quartet affected by infantile epileptic encephalopathy and SUDEP. American Journal of Human Genetics, 90(3), 502-10.More infoIndividuals with severe, sporadic disorders of infantile onset represent an important class of disease for which discovery of the underlying genetic architecture is not amenable to traditional genetic analysis. Full-genome sequencing of affected individuals and their parents provides a powerful alternative strategy for gene discovery. We performed whole-genome sequencing (WGS) on a family quartet containing an affected proband and her unaffected parents and sibling. The 15-year-old female proband had a severe epileptic encephalopathy consisting of early-onset seizures, features of autism, intellectual disability, ataxia, and sudden unexplained death in epilepsy. We discovered a de novo heterozygous missense mutation (c.5302A>G [p.Asn1768Asp]) in the voltage-gated sodium-channel gene SCN8A in the proband. This mutation alters an evolutionarily conserved residue in Nav1.6, one of the most abundant sodium channels in the brain. Analysis of the biophysical properties of the mutant channel demonstrated a dramatic increase in persistent sodium current, incomplete channel inactivation, and a depolarizing shift in the voltage dependence of steady-state fast inactivation. Current-clamp analysis in hippocampal neurons transfected with p.Asn1768Asp channels revealed increased spontaneous firing, paroxysmal-depolarizing-shift-like complexes, and an increased firing frequency, consistent with a dominant gain-of-function phenotype in the heterozygous proband. This work identifies SCN8A as the fifth sodium-channel gene to be mutated in epilepsy and demonstrates the value of WGS for the identification of pathogenic mutations causing severe, sporadic neurological disorders.
- Kim, S., Jeong, J., Restifo, L. L., & Kwon, H. (2011). Drosophila as a model system for studying lifespan and neuroprotective activities of plant-derived compounds. Journal of Asia-Pacific Entomology, 14(4), 509-517.More infoThe fruit fly, Drosophila melanogaster, has been intensively used as a genetic model system for basic and applied research on human neurological diseases because of advantages over mammalian model systems such as ease of laboratory maintenance and genetic manipulations. Disease-associated gene mutations, whether endogenous or transgenically-inserted, often cause phenotypes in vivo that are similar to the clinical features of the human disorder. The Drosophila genome is simpler than that of mammals, in terms of gene and chromosome number, but nonetheless demonstrates extraordinary phylogenetic conservation of gene structure and function, especially notable among the genes whose mutations cause neurodevelopmental, neuropsychiatric, or neurodegenerative disorders. In addition, its well-established neuroanatomical, developmental, and molecular genetic research techniques allow many laboratories worldwide to study complex biological and genetic processes. Based on these merits of the Drosophila model system, it has been used for screening lifespan expansion and neuroprotective activities of plant extracts or their secondary metabolites to counteract pathological events such as mitochondrial damage by oxidative stress, which may cause sporadic neurodegenerative diseases. In this review, we have summarized that the fruit fly can be used for early-stage drug discovery and development to identify novel plant-derived compounds to protect against neurodegeneration in Alzheimer's disease and Parkinson's disease, and other neurological disorders caused by oxidative stress. Thus, the Drosophila system can directly or indirectly contribute to translational research for new therapeutic strategies to prevent or ameliorate neurodegenerative diseases.
- Restifo, L. L., & Phelan, G. R. (2011). The cultural divide: exploring communication barriers between scientists and clinicians. Disease Models & Mechanisms, 4(4), 423-6.More infoDespite remarkable advances in basic biomedical science that have led to improved patient care, there is a wide and persistent gap in the abilities of researchers and clinicians to understand and appreciate each other. In this Editorial, the authors, a scientist and a clinician, discuss the rift between practitioners of laboratory research and clinical medicine. Using their first-hand experience and numerous interviews throughout the United States, they explore the causes of this 'cultural divide'. Members of both professions use advanced problem-solving skills and typically embark on their career paths with a deeply felt sense of purpose. Nonetheless, differences in classroom education, professional training environments, reward mechanisms and sources of drive contribute to obstacles that inhibit communication, mutual respect and productive collaboration. More than a sociological curiosity, the cultural divide is a significant barrier to the bench-to-bedside goals of translational medicine. Understanding its roots is the first step towards bridging the gap.
- Halladay, A. K., Amaral, D., Aschner, M., Bolivar, V. J., Bowman, A., DiCicco-Bloom, E., Hyman, S. L., Keller, F., Lein, P., Pessah, I., Restifo, L., & Threadgill, D. W. (2009). Animal models of autism spectrum disorders: information for neurotoxicologists. Neurotoxicology, 30(5), 811-21.More infoRecent findings derived from large-scale datasets and biobanks link multiple genes to autism spectrum disorders. Consequently, novel rodent mutants with deletions, truncations and in some cases, overexpression of these candidate genes have been developed and studied both behaviorally and biologically. At the Annual Neurotoxicology Meeting in Rochester, NY in October of 2008, a symposium of clinicians and basic scientists gathered to present the behavioral features of autism, as well as strategies to model those behavioral features in mice and primates. The aim of the symposium was to provide researchers with up-to-date information on both the genetics of autism and how they are used in differing in vivo and in vitro animal models as well as to provide a background on the environmental exposures being tested on several animal models. In addition, researchers utilizing complementary approaches, presented on cell culture, in vitro or more basic models, which target neurobiological mechanisms, including Drosophila. Following the presentation, a panel convened to explore the opportunities and challenges of using model systems to investigate genetic and environment interactions in autism spectrum disorders. The following paper represents a summary of each presentation, as well as the discussion that followed at the end of the symposium.
- Spokony, R. F., & Restifo, L. L. (2009). Broad Complex isoforms have unique distributions during central nervous system metamorphosis in Drosophila melanogaster. Journal of Comparative Neurology, 517(1), 15-36.More infoBroad Complex (BRC) is a highly conserved, ecdysone-pathway gene essential for metamorphosis in Drosophila melanogaster, and possibly all holometabolous insects. Alternative splicing among duplicated exons produces several BRC isoforms, each with one zinc-finger DNA-binding domain (Z1, Z2, Z3, or Z4), highly expressed at the onset of metamorphosis. BRC-Z1, BRC-Z2, and BRC-Z3 represent distinct genetic functions (BRC complementation groups rbp, br, and 2Bc, respectively) and are required at discrete stages spanning final-instar larva through very young pupa. We showed previously that morphogenetic movements necessary for adult CNS maturation require BRC-Z1, -Z2, and -Z3, but not at the same time: BRC-Z1 is required in the mid-prepupa, BRC-Z2 and -Z3 are required earlier, at the larval-prepupal transition. To explore how BRC isoforms controlling the same morphogenesis events do so at different times, we examined their central nervous system (CNS) expression patterns during the approximately 16 hours bracketing the hormone-regulated start of metamorphosis. Each isoform had a unique pattern, with BRC-Z3 being the most distinctive. There was some colocalization of isoform pairs, but no three-way overlap of BRC-Z1, -Z2, and -Z3. Instead, their most prominent expression was in glia (BRC-Z1), neuroblasts (BRC-Z2), or neurons (BRC-Z3). Despite sequence similarity to BRC-Z1, BRC-Z4 was expressed in a unique subset of neurons. These data suggest a switch in BRC isoform choice, from BRC-Z2 in proliferating cells to BRC-Z1, BRC-Z3, or BRC-Z4 in differentiating cells. Together with isoform-selective temporal requirements and phenotype considerations, this cell-type-selective expression suggests a model of BRC-dependent CNS morphogenesis resulting from intercellular interactions, culminating in BRC-Z1-controlled, glia-mediated CNS movements in late prepupa.
- Restifo, L., Narro, M. L., Yang, F., Kraft, R., Wenk, C., Efrat, A., & Restifo, L. L. (2007). NeuronMetrics: software for semi-automated processing of cultured neuron images. Brain research, 1138.More infoUsing primary cell culture to screen for changes in neuronal morphology requires specialized analysis software. We developed NeuronMetrics for semi-automated, quantitative analysis of two-dimensional (2D) images of fluorescently labeled cultured neurons. It skeletonizes the neuron image using two complementary image-processing techniques, capturing fine terminal neurites with high fidelity. An algorithm was devised to span wide gaps in the skeleton. NeuronMetrics uses a novel strategy based on geometric features called faces to extract a branch number estimate from complex arbors with numerous neurite-to-neurite contacts, without creating a precise, contact-free representation of the neurite arbor. It estimates total neurite length, branch number, primary neurite number, territory (the area of the convex polygon bounding the skeleton and cell body), and Polarity Index (a measure of neuronal polarity). These parameters provide fundamental information about the size and shape of neurite arbors, which are critical factors for neuronal function. NeuronMetrics streamlines optional manual tasks such as removing noise, isolating the largest primary neurite, and correcting length for self-fasciculating neurites. Numeric data are output in a single text file, readily imported into other applications for further analysis. Written as modules for ImageJ, NeuronMetrics provides practical analysis tools that are easy to use and support batch processing. Depending on the need for manual intervention, processing time for a batch of approximately 60 2D images is 1.0-2.5 h, from a folder of images to a table of numeric data. NeuronMetrics' output accelerates the quantitative detection of mutations and chemical compounds that alter neurite morphology in vitro, and will contribute to the use of cultured neurons for drug discovery.
- Spokony, R. F., & Restifo, L. L. (2007). Anciently duplicated Broad Complex exons have distinct temporal functions during tissue morphogenesis. Development Genes and Evolution, 217(7).More infoBroad Complex (BRC) is an essential ecdysone-pathway gene required for entry into and progression through metamorphosis in Drosophila melanogaster. Mutations of three BRC complementation groups cause numerous phenotypes, including a common suite of morphogenesis defects involving central nervous system (CNS), adult salivary glands (aSG), and male genitalia. These defects are phenocopied by the juvenile hormone mimic methoprene. Four BRC isoforms are produced by alternative splicing of a protein-binding BTB/POZ-encoding exon (BTBBRC) to one of four tandemly duplicated, DNA-binding zinc-finger-encoding exons (Z1BRC, Z2BRC, Z3BRC, Z4BRC). Highly conserved orthologs of BTBBRC and all four ZBRC were found among published cDNA sequences or genome databases from Diptera, Lepidoptera, Hymenoptera, and Coleoptera, indicating that BRC arose and underwent internal exon duplication before the split of holometabolous orders. Tramtrack subfamily members, abrupt, tramtrack, fruitless, longitudinals lacking (lola), and CG31666 were characterized throughout Holometabola and used to root phylogenetic analyses of ZBRC exons, which revealed that the ZBRC clade includes Zabrupt. All four ZBRC domains, including Z4BRC, which has no known essential function, are evolving in a manner consistent with selective constraint. We used transgenic rescue to explore how different BRC isoforms contribute to shared tissue-morphogenesis functions. As predicted from earlier studies, the common CNS and aSG phenotypes were rescued by BRC-Z1 in rbp mutants, BRC-Z2 in br mutants, and BRC-Z3 in 2Bc mutants. However, the isoforms are required at two different developmental stages, with BRC-Z2 and -Z3 required earlier than BRC-Z1. The sequential action of BRC isoforms indicates subfunctionalization of duplicated ZBRC exons even when they contribute to common developmental processes.
- Kraft, R., Escobar, M. M., Narro, M. L., Kurtis, J. L., Efrat, A., Barnard, K., & Restifo, L. L. (2006). Phenotypes of Drosophila brain neurons in primary culture reveal a role for fascin in neurite shape and trajectory. Journal of Neuroscience, 26(34), 8734-8747.More infoSubtle cellular phenotypes in the CNS may evade detection by routine histopathology. Here, we demonstrate the value of primary culture for revealing genetically determined neuronal phenotypes at high resolution. Gamma neurons of Drosophila melanogaster mushroom bodies (MBs) are remodeled during metamorphosis under the control of the steroid hormone 20-hydroxyecdysone (20E). In vitro, wild-type gamma neurons retain characteristic morphogenetic features, notably a single axon-like dominant primary process and an arbor of short dendrite-like processes, as determined with microtubule-polarity markers. We found three distinct genetically determined phenotypes of cultured neurons from grossly normal brains, suggesting that subtle in vivo attributes are unmasked and amplified in vitro. First, the neurite outgrowth response to 20E is sexually dimorphic, being much greater in female than in male gamma neurons. Second, the gamma neuron-specific "naked runt" phenotype results from transgenic insertion of an MB-specific promoter. Third, the recessive, pan-neuronal "filagree" phenotype maps to singed, which encodes the actin-bundling protein fascin. Fascin deficiency does not impair the 20E response, but neurites fail to maintain their normal, nearly straight trajectory, instead forming curls and hooks. This is accompanied by abnormally distributed filamentous actin. This is the first demonstration of fascin function in neuronal morphogenesis. Our findings, along with the regulation of human Fascin1 (OMIM 602689) by CREB (cAMP response element-binding protein) binding protein, suggest FSCN1 as a candidate gene for developmental brain disorders. We developed an automated method of computing neurite curvature and classifying neurons based on curvature phenotype. This will facilitate detection of genetic and pharmacological modifiers of neuronal defects resulting from fascin deficiency.
- Restifo, L. L. (2005). Mental retardation genes in Drosophila: New approaches to understanding and treating developmental brain disorders. Mental Retardation and Developmental Disabilities Research Reviews, 11(4), 286-294.More infoDrosophila melanogaster is emerging as a valuable genetic model system for the study of mental retardation (MR). MR genes are remarkably similar between humans and fruit flies. Cognitive behavioral assays can detect reductions in learning and memory in flies with mutations in MR genes. Neuroanatomical methods, including some at single-neuron resolution, are helping to reveal the cellular bases of faulty brain development caused by MR gene mutations. Drosophila fragile X mental retardation 1 (dfmr1) is the fly counterpart of the human gene whose malfunction causes fragile X syndrome. Research on the fly gene is leading the field in molecular mechanisms of the gene product's biological function and in pharmacological rescue of brain and behavioral phenotypes. Future work holds the promise of using genetic pathway analysis and primary neuronal culture methods in Drosophila as tools for drug discovery for a wide range of MR and related disorders.
- Restifo, L., Consoulas, C., Levine, R. B., & Restifo, L. L. (2005). The steroid hormone-regulated gene Broad Complex is required for dendritic growth of motoneurons during metamorphosis of Drosophila. The Journal of comparative neurology, 485(4).More infoDendrites are subject to subtle modifications as well as extensive remodeling during the assembly and maturation of neural circuits in a wide variety of organisms. During metamorphosis, Drosophila flight motoneurons MN1-MN4 undergo dendritic regression, followed by regrowth, whereas MN5 differentiates de novo (Consoulas et al.  J. Neurosci. 22:4906-4917). Many cellular changes during metamorphosis are triggered and orchestrated by the steroid hormone 20-hydroxyecdysone, which initiates a cascade of coordinated gene expression. Broad Complex (BRC), a primary response gene in the ecdysone cascade, encodes a family of transcription factors (BRC-Z1-Z4) that are essential for metamorphic reorganization of the central nervous system (CNS). Using neuron-filling techniques that reveal cellular morphology with very high resolution, we tested the hypothesis that BRC is required for metamorphic development of MN1-MN5. Through a combination of loss-of-function mutant analyses, genetic mapping, and transgenic rescue experiments, we found that 2Bc function, mediated by BRC-Z3, is required selectively for motoneuron dendritic regrowth (MN1-MN4) and de novo outgrowth (MN5), as well as for soma expansion of MN5. In contrast, larval development and dendritic regression of MN1-MN4 are BRC-independent. Surprisingly, BRC proteins are not expressed in the motoneurons, suggesting that BRC-Z3 exerts its effect in a non-cell-autonomous manner. The 2Bc mutants display no gross defects in overall thoracic CNS structure, or in peripheral structures such as target muscles or sensory neurons. Candidates for mediating the effect of BRC-Z3 on dendritic growth of MN1-MN5 include their synaptic inputs and non-neuronal CNS cells that interact with them through direct contact or diffusible factors.
- Restifo, L. L., Michel, C. I., & Kraft, R. (2004). Defective neuronal development in the mushroom bodies of Drosophila fragile X mental retardation 1 mutants. Journal of Neuroscience, 24(25), 5798-5809.More infoFragile X mental retardation 1 (Fmr1) is a highly conserved gene with major roles in CNS structure and function. Its product, the RNA-binding protein FMRP, is believed to regulate translation of specific transcripts at postsynaptic sites in an activity-dependent manner. Hence, Fmr1 is central to the molecular mechanisms of synaptic plasticity required for normal neuronal maturation and cognitive ability. Mutations in its Drosophila ortholog, dfmr1, produce phenotypes of brain interneurons and axon terminals at the neuromuscular junction, as well as behavioral defects of circadian rhythms and courtship. We hypothesized that dfmr1 mutations would disrupt morphology of the mushroom bodies (MBs), highly plastic brain regions essential for many forms of learning and memory. We found developmental defects of MB lobe morphogenesis, of which the most common is a failure of beta lobes to stop at the brain midline. A similar recessive beta-lobe midline-crossing phenotype has been previously reported in the memory mutant linotte. The dfmr1 MB defects are highly sensitive to genetic background, which is reminiscent of mammalian fragile-X phenotypes. Mutations of dfmr1 also interact with one or more third-chromosome loci to promote alpha/beta-lobe maturation. These data further support the use of the Drosophila model system for study of hereditary cognitive disorders of humans.
- Restifo, L., Helvig, C., Tijet, N., Feyereisen, R., Walker, F. A., & Restifo, L. L. (2004). Drosophila melanogaster CYP6A8, an insect P450 that catalyzes lauric acid (omega-1)-hydroxylation. Biochemical and biophysical research communications, 325(4).More infoOnly a handful of P450 genes have been functionally characterized from the approximately 90 recently identified in the genome of Drosophila melanogaster. Cyp6a8 encodes a 506-amino acid protein with 53.6% amino acid identity with CYP6A2. CYP6A2 has been shown to catalyze the metabolism of several insecticides including aldrin and heptachlor. CYP6A8 is expressed at many developmental stages as well as in adult life. CYP6A8 was produced in Saccharomyces cerevisiae and enzymatically characterized after catalytic activity was reconstituted with D. melanogaster P450 reductase and NADPH. Although several saturated or non-saturated fatty acids were not metabolized by CYP6A8, lauric acid (C12:0), a short-chain unsaturated fatty acid, was oxidized by CYP6A8 to produce 11-hydroxylauric acid with an apparent V(max) of 25 nmol/min/nmol P450. This is the first report showing that a member of the CYP6 family catalyzes the hydroxylation of lauric acid. Our data open new prospects for the CYP6 P450 enzymes, which could be involved in important physiological functions through fatty acid metabolism.
- Restifo, L., Inlow, J. K., & Restifo, L. L. (2004). Molecular and comparative genetics of mental retardation. Genetics, 166(2).More infoAffecting 1-3% of the population, mental retardation (MR) poses significant challenges for clinicians and scientists. Understanding the biology of MR is complicated by the extraordinary heterogeneity of genetic MR disorders. Detailed analyses of >1000 Online Mendelian Inheritance in Man (OMIM) database entries and literature searches through September 2003 revealed 282 molecularly identified MR genes. We estimate that hundreds more MR genes remain to be identified. A novel test, in which we distributed unmapped MR disorders proportionately across the autosomes, failed to eliminate the well-known X-chromosome overrepresentation of MR genes and candidate genes. This evidence argues against ascertainment bias as the main cause of the skewed distribution. On the basis of a synthesis of clinical and laboratory data, we developed a biological functions classification scheme for MR genes. Metabolic pathways, signaling pathways, and transcription are the most common functions, but numerous other aspects of neuronal and glial biology are controlled by MR genes as well. Using protein sequence and domain-organization comparisons, we found a striking conservation of MR genes and genetic pathways across the approximately 700 million years that separate Homo sapiens and Drosophila melanogaster. Eighty-seven percent have one or more fruit fly homologs and 76% have at least one candidate functional ortholog. We propose that D. melanogaster can be used in a systematic manner to study MR and possibly to develop bioassays for therapeutic drug discovery. We selected 42 Drosophila orthologs as most likely to reveal molecular and cellular mechanisms of nervous system development or plasticity relevant to MR.
- Lewis, S. A., & Restifo, L. L. (2015, March). Pak (p21-activated kinase) mutations cause defects in brain structure and neurite-arbor morphogenesis through regulation of non-muscle myosin. 56th Annual Drosophila Research Conference. Chicago, IL: Genetics Society of America.