The neurodevelopmental disorders Prader-Willi syndrome (PWS) and Schaaf-Yang syndrome (SYS) both arise from genomic alterations within human chromosome 15q11–q13. A deletion of the SNORD116 cluster, ...encoding small nucleolar RNAs, or frameshift mutations within MAGEL2 result in closely related phenotypes in individuals with PWS or SYS, respectively. By investigation of their subcellular localization, we observed that in contrast to a predominant cytoplasmic localization of wild-type (WT) MAGEL2, a truncated MAGEL2 mutant was evenly distributed between the cytoplasm and the nucleus. To elucidate regulatory pathways that may underlie both diseases, we identified protein interaction partners for WT or mutant MAGEL2, in particular the survival motor neuron protein (SMN), involved in spinal muscular atrophy, and the fragile-X-messenger ribonucleoprotein (FMRP), involved in autism spectrum disorders. The interactome of the non-coding RNA SNORD116 was also investigated by RNA-CoIP. We show that WT and truncated MAGEL2 were both involved in RNA metabolism, while regulation of transcription was mainly observed for WT MAGEL2. Hence, we investigated the influence of MAGEL2 mutations on the expression of genes from the PWS locus, including the SNORD116 cluster. Thereby, we provide evidence for MAGEL2 mutants decreasing the expression of SNORD116, SNORD115, and SNORD109A, as well as protein-coding genes MKRN3 and SNRPN, thus bridging the gap between PWS and SYS.
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Mutations within MAGEL2 from chromosomal region 15q11–q13 cause Schaaf-Yang syndrome, which is phenotypically related to Prader-Willi syndrome, caused by deletion of the SNORD116 cluster within the same locus. We correlate mutations within MAGEL2 to spinal muscular atrophy and autism and also demonstrate its influence on the abundance of SNORD116.
Prader-Willi syndrome (PWS) is the prototypic genomic disorder resulting from deficiency of paternally expressed genes in the human chromosome 15q11-q13 region. The unique molecular mechanism ...involving epigenetic modifications renders PWS as the most attractive candidate to explore a proof-of-concept of epigenetic therapy in humans. The premise is that epigenetic modulations could reactivate the repressed PWS candidate genes from the maternal chromosome and offer therapeutic benefit. Our prior study identifies an EHMT2/G9a inhibitor, UNC0642, that reactivates the expression of PWS genes via reduction of H3K9me2. However, low brain permeability and poor oral bioavailability of UNC0642 preclude its advancement into translational studies in humans. In this study, a newly developed inhibitor, MS152, modified from the structure of UNC0642, has better brain penetration and greater potency and selectivity against EHMT2/G9a. MS152 reactivated maternally silenced PWS genes in PWS patient fibroblasts and in brain and liver tissues of PWS mouse models. Importantly, the molecular efficacy of oral administration is comparable with the intraperitoneal route. MS152 treatment in newborns ameliorates the perinatal lethality and poor growth, maintaining reactivation in a PWS mouse model at postnatal 90 days. Our findings provide strong support for MS152 as a first-in-class inhibitor to advance the epigenetic therapy of PWS in humans.
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Jiang and colleagues report the findings that new EHMT2 inhibitors, MS152 and MS1262, are more potent and specific. The efficacy was demonstrated in preclinical studies of Prader-Willi Syndrome (PWS) mouse and cell models. Our findings support MS152 and MS1262 as promising candidates to advance the epigenetic therapy of PWS.
Prader-Willi syndrome (PWS) is a rare genetic imprinting disorder resulting from the expression loss of genes on the paternally inherited chromosome 15q11–13. Early-onset life-thriving obesity and ...hyperphagia represent the clinical hallmarks of PWS. The noncoding RNA gene SNORD116 within the minimal PWS genetic lesion plays a critical role in the pathogenesis of the syndrome. Despite advancements in understanding the genetic basis for PWS, the pathophysiology of obesity development in PWS remains largely uncharacterized. Here, we aimed to investigate the signatures of adipose tissue development and expansion pathways and associated adipose biology in PWS children without obesity-onset at an early stage, mainly from the perspective of the adipogenesis process, and further elucidate the underlying molecular mechanisms.
We collected inguinal (subcutaneous) white adipose tissues (ingWATs) from phase 1 PWS and healthy children with normal weight aged from 6 M to 2 Y. Adipose morphology and histological characteristics were assessed. Primary adipose stromal vascular fractions (SVFs) were isolated, cultured in vitro, and used to determine the capacity and function of white and beige adipogenic differentiation. High-throughput RNA-sequencing (RNA-seq) was performed in adipose-derived mesenchymal stem cells (AdMSCs) to analyze transcriptome signatures in PWS subjects. Transient repression of SNORD116 was conducted to evaluate its functional relevance in adipogenesis. The changes in alternative pre-mRNA splicing were investigated in PWS and SNORD116 deficient cells.
In phase 1 PWS children, impaired white adipose tissue (WAT) development and unusual fat expansion occurred long before obesity onset, which was characterized by the massive enlargement of adipocytes accompanied by increased apoptosis. White and beige adipogenesis programs were impaired and differentiated adipocyte functions were disturbed in PWS-derived SVFs, despite increased proliferation capacity, which were consistent with the results of RNA-seq analysis of PWS AdMSCs. We also experimentally validated disrupted beige adipogenesis in adipocytes with transient SNORD116 downregulation. The transcript and protein levels of PPARγ, the adipogenesis master regulator, were significantly lower in PWS than in control AdMSCs as well as in SNORD116 deficient AdMSCs/adipocytes than in scramble (Scr) cells, resulting in the inhibited adipogenic program. Additionally, through RNA-seq, we observed aberrant transcriptome-wide alterations in alternative RNA splicing patterns in PWS cells mediated by SNORD116 loss and specifically identified a changed PRDM16 gene splicing profile in vitro.
Imbalance in the WAT expansion pathway and developmental disruption are primary defects in PWS displaying aberrant adipocyte hypertrophy and impaired adipogenesis process, in which SNORD116 deficiency plays a part. Our findings suggest that dysregulated adiposity specificity existing at an early phase is a potential pathological mechanism exacerbating hyperphagic obesity onset in PWS. This mechanistic evidence on adipose biology in young PWS patients expands knowledge regarding the pathogenesis of PWS obesity and may aid in developing a new therapeutic strategy targeting disturbed adipogenesis and driving AT plasticity to combat abnormal adiposity and associated metabolic disorders for PWS patients.
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•Dysregulated adipose tissue expansion is a primary defect in Prader-Willi syndrome (PWS) children before obesity-onset.•White and beige adipogenesis programs are impaired which might result from PPARγ downregulation in PWS adipose-derived SVFs.•SNORD116 deficiency is associated with blunted beige adipogenesis process in adipocyte.•SNORD116 loss mediates aberrant transcriptional signatures and alterations in alternative pre-mRNA splicing in PWS AdMSCs.
•A lack of the gene cluster SNORD116 may be responsible for some aspects of PWS.•Heterozygous Snord116 mutation mice had learning and memory deficits in three assays.•Heterozygous deletions in ...Snord116 did not impair exploratory or motor abilities.•Snord116+/− model is a valuable preclinical tool for investigating PWS.
Prader-Willi syndrome (PWS) is an imprinted neurodevelopmental disease caused by a loss of paternal genes on chromosome 15q11-q13. It is characterized by cognitive impairments, developmental delay, sleep abnormalities, and hyperphagia often leading to obesity. Clinical research has shown that a lack of expression of SNORD116, a paternally expressed imprinted gene cluster that encodes multiple copies of a small nucleolar RNA (snoRNA) in both humans and mice, is most likely responsible for many PWS symptoms seen in humans. The majority of previous research using PWS preclinical models focused on characterization of the hyperphagic and metabolic phenotypes. However, a crucial understudied clinical phenotype is cognitive impairments and thus we investigated the learning and memory abilities using a model of PWS, with a heterozygous deletion in Snord116. We utilized the novel object recognition task, which doesn’t require external motivation, or exhaustive swim training. Automated findings were further confirmed with manual scoring by a highly trained blinded investigator. We discovered deficits in Snord116+/− mutant mice in the novel object recognition, location memory and tone cue fear conditioning assays when compared to age-, sex- matched, littermate control Snord116+/+ mice. Further, we confirmed that despite physical neo-natal developmental delays, Snord116+/− mice had normal exploratory and motor abilities. These results show that the Snord116+/− deletion murine model is a valuable preclinical model for investigating learning and memory impairments in individuals with PWS without common confounding phenotypes.
Transcriptional analysis of brain tissue from people with molecularly defined causes of obesity may highlight disease mechanisms and therapeutic targets. We performed RNA sequencing of hypothalamus ...from individuals with Prader-Willi syndrome (PWS), a genetic obesity syndrome characterized by severe hyperphagia. We found that upregulated genes overlap with the transcriptome of mouse Agrp neurons that signal hunger, while downregulated genes overlap with the expression profile of Pomc neurons activated by feeding. Downregulated genes are expressed mainly in neuronal cells and contribute to neurogenesis, neurotransmitter release, and synaptic plasticity, while upregulated, predominantly microglial genes are involved in inflammatory responses. This transcriptional signature may be mediated by reduced brain-derived neurotrophic factor expression. Additionally, we implicate disruption of alternative splicing as a potential molecular mechanism underlying neuronal dysfunction in PWS. Transcriptomic analysis of the human hypothalamus may identify neural mechanisms involved in energy homeostasis and potential therapeutic targets for weight loss.
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•Overlap between genes expressed in human PWS hypothalamus and mouse Agrp neurons•Downregulated genes are involved in neuronal development•SNORD116 deletion reduces neural development and survival in cells•Alternative splicing is disturbed in PWS
Prader-Willi syndrome (PWS) is a genetic obesity syndrome. Bochukova et al. report gene expression changes in the hypothalamus of people with PWS that support neurodegeneration and neuroinflammation as key processes involved in this condition.
Prader-Willi syndrome (PWS) is a genetic neurodevelopmental disorder. Global hypothalamic dysfunction is a core feature of PWS and has been implicated as a driver of many of PWS’s phenotypic ...characteristics (e.g., hyperphagia-induced obesity, hypogonadism, short stature). Although the two neuropeptides (i.e., oxytocin OXT and arginine vasopressin AVP) most implicated in mammalian prosocial functioning are of hypothalamic origin, and social functioning is markedly impaired in PWS, there has been little consideration of how dysregulation of these neuropeptide signaling pathways may contribute to PWS’s social behavior impairments. The present article addresses this gap in knowledge by providing a comprehensive review of the preclinical and clinical PWS literature–spanning endogenous neuropeptide measurement to exogenous neuropeptide administration studies–to better understand the roles of OXT and AVP signaling in this population. The preponderance of evidence indicates that OXT and AVP signaling are indeed dysregulated in PWS, and that these neuropeptide pathways may provide promising targets for therapeutic intervention in a patient population that currently lacks a pharmacological strategy for its debilitating social behavior symptoms.
•Prader-Willi syndrome has global hypothalamic dysfunction and social deficits.•Hypothalamic oxytocin and vasopressin signaling are critical for social function.•Oxytocin and vasopressin signaling are abnormal in Prader-Willi syndrome.•Oxytocin or vasopressin administration improves social function in animal models.•These pathways may be therapeutic targets for Prader-Willi syndrome social deficits.
Abstract
The eutherian-specific SNORD116 family of repeated box C/D snoRNA genes is suspected to play a major role in the Prader–Willi syndrome (PWS), yet its molecular function remains poorly ...understood. Here, we combined phylogenetic and molecular analyses to identify candidate RNA targets. Based on the analysis of several eutherian orthologs, we found evidence of extensive birth-and-death and conversion events during SNORD116 gene history. However, the consequences for phylogenetic conservation were heterogeneous along the gene sequence. The standard snoRNA elements necessary for RNA stability and association with dedicated core proteins were the most conserved, in agreement with the hypothesis that SNORD116 generate genuine snoRNAs. In addition, one of the two antisense elements typically involved in RNA target recognition was largely dominated by a unique sequence present in at least one subset of gene paralogs in most species, likely the result of a selective effect. In agreement with a functional role, this ASE exhibited a hybridization capacity with putative mRNA targets that was strongly conserved in eutherians. Moreover, transient downregulation experiments in human cells showed that Snord116 controls the expression and splicing levels of these mRNAs. The functions of two of them, diacylglycerol kinase kappa and Neuroligin 3, extend the description of the molecular bases of PWS and reveal unexpected molecular links with the Fragile X syndrome and autism spectrum disorders.
The hypothalamus regulates fundamental aspects of physiological homeostasis and behavior, including stress response, reproduction, growth, sleep, and feeding, several of which are affected in ...patients with Prader–Willi (PWS) and Schaaf–Yang syndrome (SYS). PWS is caused by paternal deletion, maternal uniparental disomy, or imprinting defects that lead to loss of expression of a maternally imprinted region of chromosome 15 encompassing non-coding RNAs and five protein-coding genes; SYS patients have a mutation in one of them, MAGEL2. Throughout life, PWS and SYS patients suffer from musculoskeletal deficiencies, intellectual disabilities, and hormonal abnormalities, which lead to compulsive behaviors like hyperphagia and temper outbursts. Management of PWS and SYS is mostly symptomatic and cures for these debilitating disorders do not exist, highlighting a clear, unmet medical need. Research over several decades into the molecular and cellular roles of PWS genes has uncovered that several impinge on the neuroendocrine system. In this review, we will discuss the expression and molecular functions of PWS genes, connecting them with hormonal imbalances in patients and animal models. Besides the observed hormonal imbalances, we will describe the recent findings about how the loss of individual genes, particularly MAGEL2, affects the molecular mechanisms of hormone secretion. These results suggest that MAGEL2 evolved as a mammalian-specific regulator of hypothalamic neuroendocrine function.
Prader‐Willi syndrome is a complex condition caused by lack of expression of imprinted genes in the paternally derived region of chromosome 15 (15q11q13). A small number of patients with Prader‐Willi ...phenotype have been discovered to have narrow deletions, not encompassing the whole critical region, but only the SNORD116 cluster, which includes genes codifying for small nucleolar RNAs. This kind of deletion usually is not detected by the classic DNA methylation analysis test. We present the case of a male patient with a mild Prader‐Willi phenotype and a small deletion including SNORD116, diagnosed by methylation‐sensitive multiplex ligation‐dependent probe amplification (MLPA. The patient showed neonatal hypotonia, hyperphagia, obesity, central hypogonadism, hypothyroidism, strabismus. Stature and intellectual development are within the normal range. The presence of macrocephaly, observed in other cases of SNORD116 deletions as well, is uncommon for the classic phenotype of the syndrome.
We report a 17-year-old boy who met most of the major Prader-Willi syndrome (PWS) diagnostic criteria, including infantile hypotonia and poor feeding followed by hyperphagia, early-onset morbid ...obesity, delayed development, and characteristic facial features. However, unlike many children with PWS, he had spontaneous onset of puberty and reached a tall adult stature without growth hormone replacement therapy. A phenotype-driven genetic analysis using exome sequencing identified a heterozygous microdeletion of 71 kb in size at chr15:25,296,613-25,367,633, genome build hg 19. This deletion does not affect the
locus, but results in the loss of several of the PWS-associated non-coding RNA species, including the
cluster. We compared with six previous reports of patients with PWS who carried small atypical deletions encompassing the snoRNA
cluster. These patients share similar core symptoms of PWS while displaying some atypical features, suggesting that other genes in the region may make lesser phenotypic contributions. Altogether, these rare cases provide convincing evidence that loss of the paternal copy of the
snoRNA is sufficient to cause most of the major clinical features of PWS.
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