Progression of Behavioral and CNS Deficits in a Viable Murine Model of Chronic Neuronopathic Gaucher Disease

RESEARCH ARTICLE Progression of Behavioral and CNS Deficits in a Viable Murine Model of Chronic Neuronopathic Gaucher Disease Mei Dai1, Benjamin Liou2, Brittany Swope1,3, Xiaohong Wang1, Wujuan Zhang4, Venette Inskeep2, Gregory A. Grabowski2, Ying Sun2,3*, Dao Pan1,3* 1 Experimental Hematology and Cancer Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America, 2 Division of Human Genetics, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America, 3 Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, Ohio, United States of America, 4 Division of Pathology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America a11111 * (DP); (YS) Abstract OPEN ACCESS Citation: Dai M, Liou B, Swope B, Wang X, Zhang W, Inskeep V, et al. (2016) Progression of Behavioral and CNS Deficits in a Viable Murine Model of Chronic Neuronopathic Gaucher Disease. PLoS ONE 11(9): e0162367. doi:10.1371/journal.pone.0162367 Editor: Huaibin Cai, National Institutes of Health, UNITED STATES Received: March 5, 2016 Accepted: August 22, 2016 Published: September 6, 2016 Copyright: © 2016 Dai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by NIH grants (R01 NS086134, R01 DK36729, and R01 NS064330) and Cincinnati Children’s Hospital Medical Center RIP awards (to D.P. and to Y.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. To study the neuronal deficits in neuronopathic Gaucher Disease (nGD), the chronological behavioral profiles and the age of onset of brain abnormalities were characterized in a chronic nGD mouse model (9V/null). Progressive accumulation of glucosylceramide (GC) and glucosylsphingosine (GS) in the brain of 9V/null mice were observed at as early as 6 and 3 months of age for GC and GS, respectively. Abnormal accumulation of α-synuclein was present in the 9V/null brain as detected by immunofluorescence and Western blot analysis. In a repeated open-field test, the 9V/null mice (9 months and older) displayed significantly less environmental habituation and spent more time exploring the open-field than age-matched WT group, indicating the onset of short-term spatial memory deficits. In the marble burying test, the 9V/null group had a shorter latency to initiate burying activity at 3 months of age, whereas the latency increased significantly at 12 months of age; 9V/null females buried significantly more marbles to completion than the WT group, suggesting an abnormal response to the instinctive behavior and an abnormal activity in non-associative anxiety-like behavior. In the conditional fear test, only the 9V/null males exhibited a significant decrease in response to contextual fear, but both genders showed less response to auditory-cued fear compared to age- and gender-matched WT at 12 months of age. These results indicate hippocampus-related emotional memory defects. Abnormal gait emerged in 9V/null mice with wider front-paw and hind-paw widths, as well as longer stride in a genderdependent manner with different ages of onset. Significantly higher liver- and spleen-tobody weight ratios were detected in 9V/null mice with different ages of onsets. These data provide temporal evaluation of neurobehavioral dysfunctions and brain pathology in 9V/null mice that can be used for experimental designs to evaluate novel therapies for nGD. Competing Interests: The authors have declared that no competing interests exist. PLOS ONE | DOI:10.1371/journal.pone.0162367 September 6, 2016 1 / 23 Behavioral Profile and CNS Abnormalities in Chronic nGD Mice Introduction Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder with a broad spectrum of severities. In GD, mutations of GBA1 lead to defective function of acid β-glucosidase (GCase) and subsequent accumulation of its substrates, glucosylceramide (GC) and glucosylsphingosine (GS) [1]. Accumulation of these substrates affects normal cell function and promotes disease progression in the viscera and central nervous systems (CNS) [1–4]. Over 350 GBA1 mutations have been identified [5, 6]. Most of the mutations can be found in patients with varying degrees of visceral and/or CNS manifestations that are classified as type 1, type 2 or type 3 variants [1, 7, 8]. Patients with GD type 1 do not exhibit any early-onset progressive CNS abnormalities, but develop hepatomegaly, splenomegaly, bone pain and fractures, growth retardation, anemia and thrombocytopenia with highly variable penetrance and presentation [1]. GD type 2 is an acute neuronopathic disease with onset in the first few months of life and progression to death between 3 and 24 months. In addition to visceral involvement, GD type 2 patients have progressive CNS manifestations that include bulbar signs, ataxia, and seizures [1, 8]. GD type 3 patients present various signs of neuronopathic and visceral involvement with chronic progression, and may survive into the 2nd to the 5th decades of life [1, 4]. Currently, two therapeutic approaches are approved for the visceral manifestations of GD, i.e. enzyme replacement therapy (ERT) and substrate reduction therapy (SRT) [9, 10]. However, there have been no effective treatment options for the neurological sequelae of GD patients and innovative therapies are still needed. Experimental and epidemiological evidence have strongly implicated an excess risk of Parkinson’s disease (PD) and Lewy body disease in GD type 1 patients, as well as heterozygote carriers of GBA1 mutations [11–15]. Indeed, GBA1 GD-causative mutations are broadly recognized as the most common genetic risk factor for the development of Parkinsonism and Lewy Body disease that not only increases susceptibility to PD, but also drives the disease progression with an earlier onset or increased severity [12, 16–21]. The risk of developing PD in otherwise healthy carriers of GBA1 mutations is estimated to be 13.7% at 60 and 29.7% at 80 years of age, significantly higher than in the general population [22]. The mechanism of the connection between GD and PD has not been fully elucidated, although lysosomal and/or mitochondrial dysfunctions with subsequently impaired autophagy have been indicated [21, 23–25]. The clinical and pathogenic heterogeneity of GD is a continuum of disease progression with a difference in the presence or absence of neurologic involvement that may present as an acute or chronic course [26–28]. Identification of the phenotypic expression with diverse manifestations in nGD would be valuable to facilitate th (...truncated)