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Kos P, Baumann O. Spatial arrangement, polarity, and posttranslational modifications of the microtubule system in the Drosophila eye. Cell Tissue Res 2024:10.1007/s00441-024-03914-6. [PMID: 39152365 DOI: 10.1007/s00441-024-03914-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 08/02/2024] [Indexed: 08/19/2024]
Abstract
We have analyzed the organization of the microtubule system in photoreceptor cells and pigment cells within the adult Drosophila compound eye. Immunofluorescence localization of tubulin and of Short stop, a spectraplakin that has been reported to be involved in the anchorage of microtubule minus ends at the membrane, suggests the presence of non-centrosomal microtubule-organizing centers at the distal tip of the visual cells. Ultrastructural analyses confirm that microtubules emanate from membrane-associated plaques at the site of contact with cone cells and that all microtubules are aligned in distal-proximal direction within the photoreceptor cells. Determination of microtubule polarities demonstrated that about 95% of the microtubules in photoreceptor cells are oriented with their plus end in the direction of the synapse. Pigment cells in the eye contain only microtubules aligned in distal-proximal direction, with their plus end pointing towards the retinal floor. There, two populations of microtubules can be distinguished, single microtubules and bundled microtubules, the latter associated with actin filaments. Whereas microtubules in both photoreceptor cells and pigment cells are acetylated and mono/bi-glutamylated on α-tubulin, bundled microtubules in pigment cells are apparently also mono/bi-glutamylated on β-tubulin, providing the possibility of binding different microtubule-associated proteins.
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Affiliation(s)
- Piotr Kos
- Unit of Animal Physiology, Institute of Biochemistry and Biology, University of Potsdam, 14476, Potsdam, Germany
| | - Otto Baumann
- Unit of Animal Physiology, Institute of Biochemistry and Biology, University of Potsdam, 14476, Potsdam, Germany.
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2
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Candia N, Ibacache A, Medina-Yáñez I, Olivares GH, Ramírez M, Vega-Macaya F, Couve A, Sierralta J, Olguín P. Identification of atlastin genetic modifiers in a model of hereditary spastic paraplegia in Drosophila. Hum Genet 2023; 142:1303-1315. [PMID: 37368047 DOI: 10.1007/s00439-023-02577-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 05/30/2023] [Indexed: 06/28/2023]
Abstract
Hereditary spastic paraplegias (HSPs) are a group of neurodegenerative disorders characterized by progressive dysfunction of corticospinal motor neurons. Mutations in Atlastin1/Spg3, a small GTPase required for membrane fusion in the endoplasmic reticulum, are responsible for 10% of HSPs. Patients with the same Atlastin1/Spg3 mutation present high variability in age at onset and severity, suggesting a fundamental role of the environment and genetic background. Here, we used a Drosophila model of HSPs to identify genetic modifiers of decreased locomotion associated with atlastin knockdown in motor neurons. First, we screened for genomic regions that modify the climbing performance or viability of flies expressing atl RNAi in motor neurons. We tested 364 deficiencies spanning chromosomes two and three and found 35 enhancer and four suppressor regions of the climbing phenotype. We found that candidate genomic regions can also rescue atlastin effects at synapse morphology, suggesting a role in developing or maintaining the neuromuscular junction. Motor neuron-specific knockdown of 84 genes spanning candidate regions of the second chromosome identified 48 genes required for climbing behavior in motor neurons and 7 for viability, mapping to 11 modifier regions. We found that atl interacts genetically with Su(z)2, a component of the Polycomb repressive complex 1, suggesting that epigenetic regulation plays a role in the variability of HSP-like phenotypes caused by atl alleles. Our results identify new candidate genes and epigenetic regulation as a mechanism modifying neuronal atl pathogenic phenotypes, providing new targets for clinical studies.
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Affiliation(s)
- Noemi Candia
- Programa de Genética Humana, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Andrés Ibacache
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Ignacio Medina-Yáñez
- Programa de Genética Humana, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Gonzalo H Olivares
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
- Escuela de Kinesiología, Facultad de Medicina y Ciencias de la Salud, Center for Integrative Biology (CIB), Universidad Mayor, Santiago, Chile
| | - Mauricio Ramírez
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Franco Vega-Macaya
- Programa de Genética Humana, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Andrés Couve
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Jimena Sierralta
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile
| | - Patricio Olguín
- Programa de Genética Humana, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile.
- Departamento de Neurociencia, Biomedical Neuroscience Institute (BNI), Facultad de Medicina, Universidad de Chile, Independencia 1027, 8380453, Santiago, Chile.
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3
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Rylee J, Mahato S, Aldrich J, Bergh E, Sizemore B, Feder LE, Grega S, Helms K, Maar M, Britt SG, Zelhof AC. A TRiP RNAi screen to identify molecules necessary for Drosophila photoreceptor differentiation. G3 GENES|GENOMES|GENETICS 2022; 12:6758253. [DOI: 10.1093/g3journal/jkac257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/15/2022] [Indexed: 11/06/2022]
Abstract
Abstract
Drosophila rhabdomeric terminal photoreceptor differentiation is an extended process taking several days to complete. Following ommatidial patterning by the morphogenetic furrow, photoreceptors are sequentially recruited and specified, and terminal differentiation begins. Key events of terminal differentiation include the establishment of apical and basolateral domains, rhabdomere and stalk formation, inter-rhabdomeral space formation, and expression of phototransduction machinery. While many key regulators of these processes have been identified, the complete network of transcription factors to downstream effector molecules necessary for regulating each of these major events remains incomplete. Here, we report an RNAi screen to identify additional molecules and cellular pathways required for photoreceptor terminal differentiation. First, we tested several eye-specific GAL4 drivers for correct spatial and temporal specificity and identified Pph13-GAL4 as the most appropriate GAL4 line for our screen. We screened lines available through the Transgenic RNAi Project and isolated lines that when combined with Pph13-GAL4 resulted in the loss of the deep pseudopupil, as a readout for abnormal differentiation. In the end, we screened 6,189 lines, representing 3,971 genes, and have identified 64 genes, illuminating potential new regulatory molecules and cellular pathways for the differentiation and organization of Drosophila rhabdomeric photoreceptors.
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Affiliation(s)
- Johnathan Rylee
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Simpla Mahato
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - John Aldrich
- Department of Neurology and Ophthalmology, Dell Medical School, University of Texas , Austin, TX 78712, USA
| | - Emma Bergh
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Brandon Sizemore
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Lauren E Feder
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Shaun Grega
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Kennedy Helms
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Megan Maar
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Steven G Britt
- Department of Neurology and Ophthalmology, Dell Medical School, University of Texas , Austin, TX 78712, USA
| | - Andrew C Zelhof
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
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Ochi Y, Yamashita H, Yamada Y, Satoh T, Satoh AK. Stratum is required for both apical and basolateral transport through stable expression of Rab10 and Rab35 in Drosophila photoreceptors. Mol Biol Cell 2022; 33:br17. [PMID: 35767331 DOI: 10.1091/mbc.e21-12-0596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Post-Golgi transport for specific membrane domains, also termed polarized transport, is essential for the construction and maintenance of polarized cells. Highly polarized Drosophila photoreceptors serve as a good model system for studying the mechanisms underlying polarized transport. The Mss4 Drosophila ortholog, Stratum (Strat), controls basal restriction of basement membrane proteins in follicle cells, and Rab8 acts downstream of Strat. We investigated the function of Strat in fly photoreceptors and found that polarized transport in both the basolateral and the rhabdomere membrane domains was inhibited in Strat-deficient photoreceptors. We also observed 79 and 55% reductions in Rab10 and Rab35 levels, respectively, but no reduction in Rab11 levels in whole-eye homozygous clones of Stratnull. Moreover, Rab35 was localized in the rhabdomere, and loss of Rab35 resulted in impaired Rh1 transport to the rhabdomere. These results indicate that Strat is essential for the stable expression of Rab10 and Rab35, which regulate basolateral and rhabdomere transport, respectively, in fly photoreceptors.
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Affiliation(s)
- Yuka Ochi
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Hitomi Yamashita
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Yumi Yamada
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Takunori Satoh
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Akiko K Satoh
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
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Smylla TK, Wagner K, Huber A. Application of Fluorescent Proteins for Functional Dissection of the Drosophila Visual System. Int J Mol Sci 2021; 22:8930. [PMID: 34445636 PMCID: PMC8396179 DOI: 10.3390/ijms22168930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/13/2021] [Accepted: 08/14/2021] [Indexed: 11/22/2022] Open
Abstract
The Drosophila eye has been used extensively to study numerous aspects of biological systems, for example, spatio-temporal regulation of differentiation, visual signal transduction, protein trafficking and neurodegeneration. Right from the advent of fluorescent proteins (FPs) near the end of the millennium, heterologously expressed fusion proteins comprising FPs have been applied in Drosophila vision research not only for subcellular localization of proteins but also for genetic screens and analysis of photoreceptor function. Here, we summarize applications for FPs used in the Drosophila eye as part of genetic screens, to study rhodopsin expression patterns, subcellular protein localization, membrane protein transport or as genetically encoded biosensors for Ca2+ and phospholipids in vivo. We also discuss recently developed FPs that are suitable for super-resolution or correlative light and electron microscopy (CLEM) approaches. Illustrating the possibilities provided by using FPs in Drosophila photoreceptors may aid research in other sensory or neuronal systems that have not yet been studied as well as the Drosophila eye.
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Affiliation(s)
- Thomas K. Smylla
- Department of Biochemistry, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany; (K.W.); (A.H.)
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Garcia-Delgado AB, Valdes-Sanchez L, Morillo-Sanchez MJ, Ponte-Zuñiga B, Diaz-Corrales FJ, de la Cerda B. Dissecting the role of EYS in retinal degeneration: clinical and molecular aspects and its implications for future therapy. Orphanet J Rare Dis 2021; 16:222. [PMID: 34001227 PMCID: PMC8127272 DOI: 10.1186/s13023-021-01843-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 04/23/2021] [Indexed: 01/22/2023] Open
Abstract
Mutations in the EYS gene are one of the major causes of autosomal recessive retinitis pigmentosa. EYS-retinopathy presents a severe clinical phenotype, and patients currently have no therapeutic options. The progress in personalised medicine and gene and cell therapies hold promise for treating this degenerative disease. However, lack of understanding and incomplete comprehension of disease's mechanism and the role of EYS in the healthy retina are critical limitations for the translation of current technical advances into real therapeutic possibilities. This review recapitulates the present knowledge about EYS-retinopathies, their clinical presentations and proposed genotype–phenotype correlations. Molecular details of the gene and the protein, mainly based on animal model data, are analysed. The proposed cellular localisation and roles of this large multi-domain protein are detailed. Future therapeutic approaches for EYS-retinopathies are discussed.
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Affiliation(s)
- Ana B Garcia-Delgado
- Andalusian Center for Molecular Biology and Regenerative Medicine (CABIMER), Avda. Americo Vespucio 24, 41092, Seville, Spain
| | - Lourdes Valdes-Sanchez
- Andalusian Center for Molecular Biology and Regenerative Medicine (CABIMER), Avda. Americo Vespucio 24, 41092, Seville, Spain
| | | | - Beatriz Ponte-Zuñiga
- Department of Ophthalmology, University Hospital Virgen Macarena, Seville, Spain.,Retics Oftared, Institute of Health Carlos III, Madrid, Spain
| | - Francisco J Diaz-Corrales
- Andalusian Center for Molecular Biology and Regenerative Medicine (CABIMER), Avda. Americo Vespucio 24, 41092, Seville, Spain.
| | - Berta de la Cerda
- Andalusian Center for Molecular Biology and Regenerative Medicine (CABIMER), Avda. Americo Vespucio 24, 41092, Seville, Spain
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Hebbar S, Lehmann M, Behrens S, Hälsig C, Leng W, Yuan M, Winkler S, Knust E. Mutations in the splicing regulator Prp31 lead to retinal degeneration in Drosophila. Biol Open 2021; 10:10/1/bio052332. [PMID: 33495354 PMCID: PMC7860132 DOI: 10.1242/bio.052332] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Retinitis pigmentosa (RP) is a clinically heterogeneous disease affecting 1.6 million people worldwide. The second-largest group of genes causing autosomal dominant RP in human encodes regulators of the splicing machinery. Yet, how defects in splicing factor genes are linked to the aetiology of the disease remains largely elusive. To explore possible mechanisms underlying retinal degeneration caused by mutations in regulators of the splicing machinery, we induced mutations in Drosophila Prp31, the orthologue of human PRPF31, mutations in which are associated with RP11. Flies heterozygous mutant for Prp31 are viable and develop normal eyes and retina. However, photoreceptors degenerate under light stress, thus resembling the human disease phenotype. Degeneration is associated with increased accumulation of the visual pigment rhodopsin 1 and increased mRNA levels of twinfilin, a gene associated with rhodopsin trafficking. Reducing rhodopsin levels by raising animals in a carotenoid-free medium not only attenuates rhodopsin accumulation, but also retinal degeneration. Given a similar importance of proper rhodopsin trafficking for photoreceptor homeostasis in human, results obtained in flies presented here will also contribute to further unravel molecular mechanisms underlying the human disease. This paper has an associated First Person interview with the co-first authors of the article. Summary: Retinitis pigmentosa (RP) is a human disease resulting in blindness, which affects 1 in 4.000 people worldwide. So far >90 genes have been identified that are causally related to RP. Mutations in the splicing factor PRPF31 are linked to RP11. We induced mutations in the Drosophila orthologue Prp31 and show that flies heterozygous for Prp31 undergo light-dependent retinal degeneration. Degeneration is associated with increased accumulation of the light-sensitive molecule, rhodopsin 1. In fact, reducing rhodopsin levels by dietary intervention modifies the extent of retinal degeneration. This model will further contribute to better understand the aetiology of the human disease.
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Affiliation(s)
- Sarita Hebbar
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Malte Lehmann
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Sarah Behrens
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Catrin Hälsig
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Weihua Leng
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Michaela Yuan
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Sylke Winkler
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Elisabeth Knust
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
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Fujii S, Kurokawa K, Tago T, Inaba R, Takiguchi A, Nakano A, Satoh T, Satoh AK. Sec71 separates Golgi stacks in Drosophila S2 cells. J Cell Sci 2020; 133:jcs245571. [PMID: 33262309 PMCID: PMC10668125 DOI: 10.1242/jcs.245571] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 11/18/2020] [Indexed: 01/19/2023] Open
Abstract
Golgi stacks are the basic structural units of the Golgi. Golgi stacks are separated from each other and scattered in the cytoplasm of Drosophila cells. Here, we report that the ARF-GEF inhibitor Brefeldin A (BFA) induces the formation of BFA bodies, which are aggregates of Golgi stacks, trans-Golgi networks and recycling endosomes. Recycling endosomes are located in the centers of BFA bodies, while Golgi stacks surround them on their trans sides. Live imaging of S2 cells revealed that Golgi stacks repeatedly merged and separated on their trans sides, and BFA caused successive merger by inhibiting separation, forming BFA bodies. S2 cells carrying genome-edited BFA-resistant mutant Sec71M717L did not form BFA bodies at high concentrations of BFA; S2 cells carrying genome-edited BFA-hypersensitive mutant Sec71F713Y produced BFA bodies at low concentrations of BFA. These results indicate that Sec71 is the sole BFA target for BFA body formation and controls Golgi stack separation. Finally, we showed that impairment of Sec71 in fly photoreceptors induces BFA body formation, with accumulation of both apical and basolateral cargoes, resulting in inhibition of polarized transport.
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Affiliation(s)
- Syara Fujii
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Kazuo Kurokawa
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Tatsuya Tago
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Ryota Inaba
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Arata Takiguchi
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Akihiko Nakano
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Takunori Satoh
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Akiko K Satoh
- Program of Life and Environmental Science, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
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Hebbar S, Schuhmann K, Shevchenko A, Knust E. Hydroxylated sphingolipid biosynthesis regulates photoreceptor apical domain morphogenesis. J Cell Biol 2020; 219:211460. [PMID: 33048164 PMCID: PMC7557679 DOI: 10.1083/jcb.201911100] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 08/07/2020] [Accepted: 09/08/2020] [Indexed: 01/04/2023] Open
Abstract
Apical domains of epithelial cells often undergo dramatic changes during morphogenesis to form specialized structures, such as microvilli. Here, we addressed the role of lipids during morphogenesis of the rhabdomere, the microvilli-based photosensitive organelle of Drosophila photoreceptor cells. Shotgun lipidomics analysis performed on mutant alleles of the polarity regulator crumbs, exhibiting varying rhabdomeric growth defects, revealed a correlation between increased abundance of hydroxylated sphingolipids and abnormal rhabdomeric growth. This could be attributed to an up-regulation of fatty acid hydroxylase transcription. Indeed, direct genetic perturbation of the hydroxylated sphingolipid metabolism modulated rhabdomere growth in a crumbs mutant background. One of the pathways targeted by sphingolipid metabolism turned out to be the secretory route of newly synthesized Rhodopsin, a major rhabdomeric protein. In particular, altered biosynthesis of hydroxylated sphingolipids impaired apical trafficking via Rab11, and thus apical membrane growth. The intersection of lipid metabolic pathways with apical domain growth provides a new facet to our understanding of apical growth during morphogenesis.
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