Loss of the imprinted, non-coding Snord116 gene cluster in the interval deleted in the Prader Willi syndrome results in murine neuronal and endocrine pancreatic developmental phenotypes

Abstract

Global neurodevelopmental delay is a prominent characteristic of individuals with Prader-Willi syndrome (PWS). The neuromolecular bases for these delays are unknown. We identified neuroanatomical changes in the brains of mice deficient for a gene in the minimal critical deletion region for PWS (Snord116p-/m+). In Snord116p-/m+ mice, reduced primary forebrain neuron cell body size is apparent in embryonic day 15.5 fetuses, and persists until postnatal day 30 in cerebellar Purkinje neurons. Snord116 is a snoRNA gene cluster of unknown function that can localize to the nucleolus. In cerebellar Purkinje neurons from postnatal day 30 Snord116p-/m+ mice the reduction in neuronal cell body size was associated with decreased neuronal nucleolar size. We also identified developmental changes in the endocrine pancreas of Snord116p-/m+ animals that persist into adulthood. Mice lacking Snord116 have smaller pancreatic islets; within the islet the percentage of δ-cells is increased, while the percentage of α-cells is reduced. The α-cell markers, Sst and Hhex, are upregulated in Snord116p-/m+ isolated islets while Ins1, Ins2, Pdx1, Nkx6-1, and Pax6 are downregulated. There is a 3-fold increase in the percentage of polyhormonal cells in the neonatal pancreata of Snord116p-/m+ mice, due primarily to an increase in cells co-positive with somatostatin. Snord116 may play a role in islet cell lineage specification. The Snord116 gene cluster is important for developmental processes in the brain as well as the endocrine pancreas.

A Transcriptomic Signature of the Hypothalamic Response to Fasting and BDNF Deficiency in Prader-Willi Syndrome

“…Postnatal deletion of SNORD116 in the mediobasal hypothalamus has recently been shown to lead to increased food intake in mice ( Polex-Wolf et al., 2018 ). To test whether loss of SNORD116 affects neuronal development and maintenance, as suggested by our transcriptomics analysis and in line with a rodent model ( Burnett et al., 2017a ), we deleted a 57.4 kb genomic segment encompassing the SNORD116 cluster using CRISPR-Cas9 in a SH-SY5Y neuroblastoma human cell line ( Figure S4 A). We found that SNORD116-deficient cells exhibited reduced neuronal differentiation, cell proliferation, and survival compared with wild-type cells ( Figures 4 A–4C).…”

Small molecule inhibitors of G9a reactivate the maternal PWS genes in Prader-Willi-Syndrome patient derived neural stem cells and differentiated neurons

“…This result was further supported by the transcriptional profiling of hypothalami from the Snord116 p-/m+ mouse model (Bochukova et al, 2018; Burnett et al, 2017b; Wang et al, 2015; Zhang et al, 2012). In addition, SNORD116 has been indicated to play the most critical role in PWS etiology, which is corroborated with various genetic ablation studies using murine models (Bortolin-Cavaille and Cavaille, 2012; Burnett et al, 2017a; Ding et al, 2008; Gallagher et al, 2002; Polex-Wolf et al, 2018; Qi et al, 2016; Zhang et al, 2012). In this study, we derived neural progenitor cells and NGN2-induced glutamatergic neurons with high purity from PWS patient iPSCs with a ∼ 5 Mb deletion on the paternal PWS locus (PWS1-7) (Figure 1A&B).…”

“…Modeling imprinting disorders such as PWS using animal models remains challenging. For example, murine models usually do not recapitulate the diverse segmental deletion haplotypes on the 15q11-q13 in PWS patients, and do not recapitulate the whole array of PWS patient phenotypes, including obesity, a phenotype central to the disorder (Burnett et al, 2017a; Ding et al, 2008; Garfield et al, 2016; Matarazzo et al, 2017; Qi et al, 2016). In addition, lengthy transgenerational mouse crossing is required to precisely capture the parent-of-origin imprinting genetics of PWS.…”

“…These genes are present on the maternal copy of chromosome 15 but silenced by hypermethylation and repressive histone modulation of the PWS imprinting center (PWS-IC) (Cassidy et al, 2000; Fulmer-Smentek and Francke, 2001; Henckel et al, 2009). Genetic ablation studies in murine models attempting to dissect the genetic underpinnings of PWS have converged on the SNORD116 snoRNA cluster as the major contributor to PWS etiology (Bortolin-Cavaille and Cavaille, 2012; Burnett et al, 2017a; Ding et al, 2008; Gallagher et al, 2002; Polex-Wolf et al, 2018; Qi et al, 2016; Zhang et al, 2012). However, human genetic and clinical data suggested that other PWS genes, such as NDN, MAGEL2 and SNRPN also contribute to PWS etiology by regulation of hypothalamic neural function (Kuslich et al, 1999; Matarazzo et al, 2017; Miller et al, 2009; Wijesuriya et al, 2017).…”

The paternally imprinted geneSnord116regulates cortical neuronal activity

“…This data suggests that TRN/thalamus circuits or in corticothalamic afferents to these intra-thalamic circuits may probably not affected in the mutant mice, while, an impairment of cortical amplification may explain the alterations of sleep spindles properties. Since it has been shown that sleep spindles facilitate neuroplasticity and support learning, memory consolidation, and intellectual performance (Gruber & Wise, 2016), and since sleep spindle alterations have been documented in children with neurodevelopmental disorders (Burnett et al, 2017; Gruber & Wise, 2016), we speculate that the neurodevelopmental and cognitive alterations observed in these mice (Adhikari et al, 2018) may also arise from altered thalamocortical input. Thus, we believe that sleep spindle alterations may either reflect the severity of the underlying disorder or directly exacerbate the severity of impairments.…”