Induced pluripotent stem cell models of the genomic imprinting disorders Angelman and Prader–Willi syndromes

Abstract

Angelman syndrome (AS) and Prader-Willi syndrome (PWS) are neurodevelopmental disorders of genomic imprinting. AS results from loss of function of the ubiquitin protein ligase E3A (UBE3A) gene, whereas the genetic defect in PWS is unknown. Although induced pluripotent stem cells (iPSCs) provide invaluable models of human disease, nuclear reprogramming could limit the usefulness of iPSCs from patients who have AS and PWS should the genomic imprint marks be disturbed by the epigenetic reprogramming process. Our iPSCs derived from patients with AS and PWS show no evidence of DNA methylation imprint erasure at the cis-acting PSW imprinting center. Importantly, we find that, as in normal brain, imprinting of UBE3A is established during neuronal differentiation of AS iPSCs, with the paternal UBE3A allele repressed concomitant with up-regulation of the UBE3A antisense transcript. These iPSC models of genomic imprinting disorders will facilitate investigation of the AS and PWS disease processes and allow study of the developmental timing and mechanism of UBE3A repression in human neurons.antisense transcript | epigenetic | neuronal differentiation A ngelman syndrome (AS) is a neurogenetic disorder characterized by profound intellectual disability, absent speech, frequent seizures, motor dysfunction, and a characteristic happy demeanor (1, 2). Prader-Willi syndrome (PWS) is characterized hyperphagia/obesity; small stature, hands, and feet; and behavioral problems that are likened to obsessive compulsive disorder (3). AS is caused by loss of function of the maternally inherited allele of the E3 ubiquitin ligase UBE3A. UBE3A is subject to tissuespecific genomic imprinting; although both alleles are expressed in most tissues, the paternally inherited allele is repressed in the brain (4-6). Imprinted expression of UBE3A is thought to occur as a result of reciprocal expression of a long noncoding antisense transcript, UBE3A-ATS, which is part of a >600-kb transcript initiating at the differentially methylated PWS imprinting center (IC) located in exon 1 of the SNURF-SNRPN gene (7-9). PWS is associated with the loss of several species of small nucleolar RNAs (snoRNAs) (10); however, its genetic basis is currently unknown, and there is no mouse model that recapitulates all features of PWS.Mouse models of AS have proved significant in studying important aspects of the AS disease mechanism. There are, however, differences in the tissue specificity of the transcript that harbors UBE3A-ATS between humans and mice (11), indicating that the timing and mechanism of UBE3A repression may diverge between these species. The ability to study the developmental timing and mechanism of brain-specific repression of the paternal UBE3A allele in a model of human development is critical for better understanding the AS disease process and for using live neurons from patients with AS to discover previously undescribed therapeutic interventions. Here, we have developed such a model via human induced pluripotent stem cell (iPSC)-technology. ResultsHu...

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“…With the development of culture systems to efficiently generate neural lineage and functional neurons from human pluripotent stem cells, these systems have been used to model neurogenetic disorders through the manipulation of disease-determining genes in hESCs or the generation of patient-specific iPSCs [26,[40][41][42][43][44]. To be an ideal disease model, the culture system should be able to generate the target neurons efficiently and to recapitulate the in vivo pathological process in these target neurons.…”

Induced Pluripotent Stem Cell Models to Enable In Vitro Models for Screening in the Central Nervous System

“…However, there are reports illustrating that imprinting is maintained following iPSC reprogramming in diseases such as in Prader-Willi and Angelman syndrome [38]. Finally, modeling diseases, in which the mitochondria are affected, particularly those resulting from mutations in the mitochondrial genome, could be challenging as this genome is much more susceptible to mutation and may be more likely to succumb to mutational events during the process of iPSC reprogramming [39][40][41][42][43].…”

“…For instance, panels for Parkinson's disease and Huntington's disease are already being developed and are available through the National Institute of Neurological Disorders and Stroke (NINDS) repository. These patient diversity panels along with others in development will prove instrumental in lowering the attrition rates for phase II and III clinical trials [38] by providing a layer of sophistication to cell-based assays for drug safety and efficacy that reflects patient diversity and can identify subgroups (eg, responders vs. nonresponders) critical for success in the clinic. The ability to use genomic engineering technologies to further modify these iPSC lines offers another method to better understand diseases through modeling.…”

iPSCs and small molecules: a reciprocal effort towards better approaches for drug discovery

“…Disease modeling based on iPSC technology has also been applied to many other neurological or psychiatry disorders, including Alzheimer's disease [32] , Huntington's disease [33,34] , Angelman and Prader-Willi syndromes [35,36] , schizophrenia [37] , and others (Table 1).…”