Targeted Depletion of Primary Cilia in Dopaminoceptive Neurons in a Preclinical Mouse Model of Huntington’s Disease

BRIEF RESEARCH REPORT published: 20 December 2019 doi: 10.3389/fncel.2019.00565 Targeted Depletion of Primary Cilia in Dopaminoceptive Neurons in a Preclinical Mouse Model of Huntington’s Disease Rasem Mustafa 1,2 , Grzegorz Kreiner 3 , Katarzyna Kamińska 4,5 , Amelia-Elise J. Wood 6 , Joachim Kirsch 2 , Kerry L. Tucker 6 and Rosanna Parlato 1,2 * 1 Institute of Applied Physiology, University of Ulm, Ulm, Germany, 2 Institute of Anatomy and Cell Biology, Medical Cell Biology, University of Heidelberg, Heidelberg, Germany, 3 Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland, 4 Department of Pharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland, 5 Jagiellonian Center for Experimental Therapeutics, Jagiellonian University, Kraków, Poland, 6 Department of Biomedical Sciences, Center for Excellence in the Neurosciences, College of Osteopathic Medicine, University of New England, Biddeford, ME, United States Edited by: Thomas Fath, Macquarie University, Australia Reviewed by: Jiro Kasahara, Tokushima University, Japan Erik B. Malarkey, Vertex Pharmaceuticals, United States *Correspondence: Rosanna Parlato Received: 10 July 2019 Accepted: 05 December 2019 Published: 20 December 2019 Citation: Mustafa R, Kreiner G, Kamińska K, Wood A-EJ, Kirsch J, Tucker KL and Parlato R (2019) Targeted Depletion of Primary Cilia in Dopaminoceptive Neurons in a Preclinical Mouse Model of Huntington’s Disease. Front. Cell. Neurosci. 13:565. doi: 10.3389/fncel.2019.00565 Multiple pathomechanisms triggered by mutant Huntingtin (mHTT) underlie progressive degeneration of dopaminoceptive striatal neurons in Huntington’s disease (HD). The primary cilium is a membrane compartment that functions as a hub for various pathways that are dysregulated in HD, for example, dopamine (DA) receptor transmission and the mechanistic target of rapamycin (mTOR) pathway. The roles of primary cilia (PC) for the maintenance of striatal neurons and in HD progression remain unknown. Here, we investigated PC defects in vulnerable striatal neurons in a progressive model of HD, the mHTT-expressing knock-in zQ175 mice. We found that PC length is affected in striatal but not in cortical neurons, in association with the accumulation of mHTT. To explore the role of PC, we generated conditional mutant mice lacking IFT88, a component of the anterograde intraflagellar transport-B complex lacking PC in dopaminoceptive neurons. This mutation preserved the expression of the dopamine 1 receptor (D1R), and the survival of striatal neurons, but resulted in a mild increase of DA metabolites in the striatum, suggesting an imbalance of ciliary DA receptor transmission. Conditional loss of PC in zQ175 mice did not trigger astrogliosis, however, mTOR signaling was more active and resulted in a more pronounced accumulation of nuclear inclusions containing mHTT. Further studies will be required of aged mice to determine the role of aberrant ciliary function in more advanced stages of HD. Keywords: primary cilium, dopamine system, Huntington’s disease, mTOR, p62 Abbreviations: ACIII, adenylate cyclase III; AD, Alzheimer’s disease; DA, dopamine; DAPI, 40 ,60 -diamidino-2pheylindol; DOPAC, 3,4-dihydroxyphenylacetic acid; D1R, dopaminoceptive D1-receptor; GFAP, glial fibrillary acidic protein; HD, Huntington’s disease; HPLC-EC, High-performance liquid chromatography-electrochemical detection; 5-HT, 5-hydroxytryptamine; HVA, homovanillic acid; IF, immunofluorescence; IFT-B, intraflagellar transport B; IHC, immunohistochemistry; mHTT, mutant Huntingtin; MSNs, medium spiny neurons; mTOR, mechanistic target of rapamycin; NeuN, neuronal nuclei; NPC1, Niemann-Pick type C1; PC, primary cilia; PD, Parkinson’s disease; PFA, paraformaldehyde; phospho-S6, phosphorylated ribosomal protein S6; p62/SQSTM1, p62/sequestosome 1; TH, tyrosine-hydroxylase. Frontiers in Cellular Neuroscience | www.frontiersin.org 1 December 2019 | Volume 13 | Article 565 Mustafa et al. Primary Cilia in Dopaminoceptive Neurons INTRODUCTION MATERIALS AND METHODS Huntington’s disease (HD) is an autosomal dominant progressive neurodegenerative disorder caused by the toxic expansion of CAG trinucleotide repeats at the N-terminus of the Huntingtin gene. The mechanisms underlying selective vulnerability of dopaminoceptive medium spiny neurons (MSNs), resulting in impaired control of voluntary movement in HD, remain elusive (Ghosh and Tabrizi, 2018). The variability of disease onset and progression depends on the CAG number, and on genetic modifiers interacting with the Huntingtin mutation [Genetic Modifiers of Huntington’s Disease (GeMHD) Consortium (2015)]. Multiple signaling pathways and cellular functions are affected by mutant Huntingtin (mHTT), including protein aggregate degradation, which results in the accumulation of toxic proteins (Saudou and Humbert, 2016). Primary cilia (PC) are single, non-motile microtubule-based organelles resembling a cellular antenna that represents a hub for receptors and components of numerous signaling pathways (Malicki and Johnson, 2017). Lack of HTT results in reduced and aberrant PC growth, and increased mHTT results in increased ciliogenesis (Keryer et al., 2011). Notably, longer PC have been observed in immortalized cellular models of HD in culture, and ependymal cilia in the lateral ventricles are disorganized in a mouse model of HD and in HD human post-mortem brains (Keryer et al., 2011). Another study showed that photoreceptor cilia pathology accounts for their degeneration in the retina of R6/2 transgenic mice overexpressing exon 1 of the human mHTT (Karam et al., 2015). It has been previously proposed that PC altered structure might affect the function of signaling pathways whose components are localized in the PC (Maiuri et al., 2013; Kaliszewski et al., 2015). Interestingly, increased PC length results in the induction of autophagy by inhibition of the mechanistic target of rapamycin (mTOR) kinase activity (Kaliszewski et al., 2015), and components essential for ciliogenesis are degraded by autophagy (Pampliega et al., 2013; Tang et al., 2013). Because autophagy is altered in HD (Ravikumar et al., 2004), as well as dopamine (DA)-mediated signaling (Chen et al., 2013), it is possible that HD pathophysiology depends, at least in part, on defective cilia. These previous studies investigated neither PC dysfunction in the most vulnerable striatal neurons, nor the impact of defective PC on HD pathogenesis in the striatum. A deeper understanding of the role of PC in mHTT-dependent neurotoxicity might help to identify new determinants modifying HD progression. To this end, we monitored neuron- and stage-specific changes of PC structure in a full-length progressive mouse model of HD, called zQ175 (Menalled et al., 2012; Carty et al., 2015). This knock-in model carries a chimeric human/mouse HTT exon 1 containing expanded CAG repeats within th (...truncated)