Functional analysis of Niemann-Pick disease type C family protein, NPC1a, in Drosophila melanogaster

Abstract

During embryonic gonad coalescence, primordial germ cells (PGCs) follow a carefully choreographed migratory route circumscribed by guidance signals towards somatic gonadal precursor cells (SGPs). In Drosophila melanogaster, SGP-derived Hedgehog (Hh), which serves as a guidance cue for the PGCs, is potentiated by mesodermally restricted HMGCoA-reductase (Hmgcr) and the ABC transporter Multi-drug-resistant-49 (Mdr49). Given the importance of cholesterol modification in the processing and long-distance transmission of the Hh ligand, we have analyzed the involvement of the Niemann-Pick disease type C-1a (NPC1a) protein, a cholesterol transporter, in germ cell migration and Hedgehog signaling. We show that mesoderm-specific inactivation of Npc1a results in germ cell migration defects. Similar to Mdr49, PGC migration defects in the Npc1a embryos are ameliorated by a cholesterol-rich diet. Consistently, reduction in Npc1a weakens the ability of ectopic HMG Coenzyme A reductase (Hmgcr) to induce germ cell migration defects. Moreover, compromising Npc1a levels influences Hh signaling adversely during wing development, a process that relies upon long-range Hh signaling. Last, doubly heterozygous embryos (Mdr49/Npc1a) display enhanced germ cell migration defects when compared with single mutants (Npc1a/+ or Mdr49/+), supporting cooperative interaction between the two.

Smoothened-activating lipids drive resistance to CDK4/6 inhibition in Hedgehog-associated medulloblastoma cells and preclinical models

“…To identify mechanisms underlying resistance to CDK4/6 inhibitors in HH-associated medulloblastoma, cellular and biochemical mechanisms of HH signal transduction were studied in DAOY, UW228, and ONS76 human medulloblastoma cells (12). Compared to DAOY cells, the majority of UW228 cells lacked primary cilia (Supplemental Figure 1A), and ONS76 cells expressed shortened cilia (Supplemental Figure 1B), a marker of reduced HH signal transduction (13)(14)(15). When stimulated with recombinant Sonic Hedgehog (SHH), neither UW228 nor ONS76 cells accumulated SMO in cilia (Supplemental Figure 1C, D) or activated the HH transcriptional program (Supplemental Figure 1E, F) to the same extent as DAOY cells.…”

Glycosphingolipids are linked to elevated neurotransmission and neurodegeneration in a Drosophila model of Niemann Pick type C

“…Our previous work in this model demonstrated age-dependent cholesterol accumulation and neurodegeneration in the adult brain, and shortened adult lifespan ( Phillips et al, 2008 ). Others have reported cholesterol accumulation in Npc1a null first instars ( Huang et al, 2005 ) and even earlier defects in Hedgehog signaling in mutant embryos ( Bialistoky et al, 2019 ). The current study fills an important gap in third instars, demonstrating elevated neurotransmission and neurodegeneration in Npc1a nulls.…”