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Deshpande G, Ng C, Jourjine N, Chiew JW, Dasilva J, Schedl P. Hedgehog signaling guides migration of primordial germ cells to the Drosophila somatic gonad. Genetics 2023; 225:iyad165. [PMID: 37708366 PMCID: PMC10627259 DOI: 10.1093/genetics/iyad165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/18/2023] [Accepted: 08/21/2023] [Indexed: 09/16/2023] Open
Abstract
In addition to inducing nonautonomous specification of cell fate in both Drosophila and vertebrates, the Hedgehog pathway guides cell migration in a variety of different tissues. Although its role in axon guidance in the vertebrate nervous system is widely recognized, its role in guiding the migratory path of primordial germ cells (PGCs) from the outside surface of the Drosophila embryo through the midgut and mesoderm to the SGPs (somatic gonadal precursors) has been controversial. Here we present new experiments demonstrating (1) that Hh produced by mesodermal cells guides PGC migration, (2) that HMG CoenzymeA reductase (Hmgcr) potentiates guidance signals emanating from the SGPs, functioning upstream of hh and of 2 Hh pathway genes important for Hh-containing cytonemes, and (3) that factors required in Hh receiving cells in other contexts function in PGCs to help direct migration toward the SGPs. We also compare the data reported by 4 different laboratories that have studied the role of the Hh pathway in guiding PGC migration.
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Affiliation(s)
- Girish Deshpande
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Chris Ng
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Nicholas Jourjine
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Joy Wan Chiew
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Juliana Dasilva
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Paul Schedl
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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Eberwein AE, Kulkarni SS, Rushton E, Broadie K. Glycosphingolipids are linked to elevated neurotransmission and neurodegeneration in a Drosophila model of Niemann Pick type C. Dis Model Mech 2023; 16:dmm050206. [PMID: 37815467 PMCID: PMC10581387 DOI: 10.1242/dmm.050206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 09/27/2023] [Indexed: 10/11/2023] Open
Abstract
The lipid storage disease Niemann Pick type C (NPC) causes neurodegeneration owing primarily to loss of NPC1. Here, we employed a Drosophila model to test links between glycosphingolipids, neurotransmission and neurodegeneration. We found that Npc1a nulls had elevated neurotransmission at the glutamatergic neuromuscular junction (NMJ), which was phenocopied in brainiac (brn) mutants, impairing mannosyl glucosylceramide (MacCer) glycosylation. Npc1a; brn double mutants had the same elevated synaptic transmission, suggesting that Npc1a and brn function within the same pathway. Glucosylceramide (GlcCer) synthase inhibition with miglustat prevented elevated neurotransmission in Npc1a and brn mutants, further suggesting epistasis. Synaptic MacCer did not accumulate in the NPC model, but GlcCer levels were increased, suggesting that GlcCer is responsible for the elevated synaptic transmission. Null Npc1a mutants had heightened neurodegeneration, but no significant motor neuron or glial cell death, indicating that dying cells are interneurons and that elevated neurotransmission precedes neurodegeneration. Glycosphingolipid synthesis mutants also had greatly heightened neurodegeneration, with similar neurodegeneration in Npc1a; brn double mutants, again suggesting that Npc1a and brn function in the same pathway. These findings indicate causal links between glycosphingolipid-dependent neurotransmission and neurodegeneration in this NPC disease model.
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Affiliation(s)
- Anna E. Eberwein
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
| | - Swarat S. Kulkarni
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
| | - Emma Rushton
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
- Department of Cell and Developmental Biology, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
- Vanderbilt Brain Institute, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
- Kennedy Center for Research on Human Development, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
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Daggubati V, Hochstelter J, Bommireddy A, Choudhury A, Krup AL, Kaur P, Tong P, Li A, Xu L, Reiter JF, Raleigh DR. Smoothened-activating lipids drive resistance to CDK4/6 inhibition in Hedgehog-associated medulloblastoma cells and preclinical models. J Clin Invest 2021; 131:141171. [PMID: 33476305 DOI: 10.1172/jci141171] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 01/14/2021] [Indexed: 12/14/2022] Open
Abstract
Medulloblastoma is an aggressive pediatric brain tumor that can be driven by misactivation of the Hedgehog (HH) pathway. CDK6 is a critical effector of oncogenic HH signaling, but attempts to target the HH pathway in medulloblastoma have been encumbered by resistance to single-agent molecular therapy. We identified mechanisms of resistance to CDK6 inhibition in HH-associated medulloblastoma by performing orthogonal CRISPR and CRISPR interference screens in medulloblastoma cells treated with a CDK4/6 inhibitor and RNA-Seq of a mouse model of HH-associated medulloblastoma with genetic deletion of Cdk6. Our concordant in vitro and in vivo data revealed that decreased ribosomal protein expression underlies resistance to CDK6 inhibition in HH-associated medulloblastoma, leading to ER stress and activation of the unfolded protein response (UPR). These pathways increased the activity of enzymes producing Smoothened-activating (SMO-activating) sterol lipids that sustained oncogenic HH signaling in medulloblastoma despite cell-cycle attenuation. We consistently demonstrated that concurrent genetic deletion or pharmacological inhibition of CDK6 and HSD11ß2, an enzyme producing SMO-activating lipids, additively blocked cancer growth in multiple mouse genetic models of HH-associated medulloblastoma. Our data reveal what we believe to be a novel pathway of resistance to CDK4/6 inhibition as well as a novel combination therapy to treat the most common malignant brain tumor in children.
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Affiliation(s)
- Vikas Daggubati
- Department of Radiation Oncology.,Department of Neurological Surgery.,Biomedical Sciences Graduate Program, and.,Medical Scientist Training Program, UCSF, San Francisco, California, USA
| | | | | | - Abrar Choudhury
- Department of Radiation Oncology.,Department of Neurological Surgery.,Biomedical Sciences Graduate Program, and.,Medical Scientist Training Program, UCSF, San Francisco, California, USA
| | | | | | - Pakteema Tong
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington, USA
| | - Amy Li
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington, USA
| | - Libin Xu
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington, USA
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, Chan Zuckerberg Biohub, UCSF, San Francisco, California, USA
| | - David R Raleigh
- Department of Radiation Oncology.,Department of Neurological Surgery.,Biomedical Sciences Graduate Program, and
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