Generation of isogenic models of Angelman syndrome and Prader-Willi syndrome in CRISPR/Cas9-engineered human embryonic stem cells.

Angelman Syndrome (AS) and Prader-Willi Syndrome (PWS), two distinct neurodevelopmental disorders, result from loss of expression from imprinted genes in the chromosome 15q11-13 locus most commonly caused by a megabase-scale deletion on either the maternal or paternal allele, respectively. Each occurs at an approximate incidence of 1/15,000 to 1/30,000 live births and has a range of debilitating phenotypes. Patient-derived induced pluripotent stem cells (iPSCs) have been valuable tools to understand human-relevant gene regulation at this locus and have contributed to the development of therapeutic approaches for AS. Nonetheless, gaps remain in our understanding of how these deletions contribute to dysregulation and phenotypes of AS and PWS. Variability across cell lines due to donor differences, reprogramming methods, and genetic background make it challenging to fill these gaps in knowledge without substantially increasing the number of cell lines used in the analyses. Isogenic cell lines that differ only by the genetic mutation causing the disease can ease this burden without requiring such a large number of cell lines. Here, we describe the development of isogenic human embryonic stem cell (hESC) lines modeling the most common genetic subtypes of AS and PWS. These lines allow for a facile interrogation of allele-specific gene regulation at the chromosome 15q11-q13 locus. Additionally, these lines are an important resource to identify and test targeted therapeutic approaches for patients with AS and PWS.

The role of UBE3A in the autism and epilepsy-related Dup15q syndrome using patient-derived, CRISPR-corrected neurons.

Chromosome 15q11-q13 duplication syndrome (Dup15q) is a neurodevelopmental disorder caused by maternal duplications of this region. Autism and epilepsy are key features of Dup15q. UBE3A, which encodes an E3 ubiquitin ligase, is likely a major driver of Dup15q because UBE3A is the only imprinted gene expressed solely from the maternal allele. Nevertheless, the exact role of UBE3A has not been determined. To establish whether UBE3A overexpression is required for Dup15q neuronal deficits, we generated an isogenic control line for a Dup15q patient-derived induced pluripotent stem cell line. Dup15q neurons exhibited hyperexcitability compared with control neurons, and this phenotype was generally prevented by normalizing UBE3A levels using antisense oligonucleotides. Overexpression of UBE3A resulted in a profile similar to that of Dup15q neurons except for synaptic phenotypes. These results indicate that UBE3A overexpression is necessary for most Dup15q cellular phenotypes but also suggest a role for other genes in the duplicated region.

Specific ZNF274 binding interference at SNORD116 activates the maternal transcripts in Prader-Willi syndrome neurons.

Prader-Willi syndrome (PWS) is characterized by neonatal hypotonia, developmental delay and hyperphagia/obesity. This disorder is caused by the absence of paternally expressed gene products from chromosome 15q11-q13. We previously demonstrated that knocking out ZNF274, a Kruppel-associated box-A-domain zinc finger protein capable of recruiting epigenetic machinery to deposit the H3K9me3 repressive histone modification, can activate expression from the normally silent maternal allele of SNORD116 in neurons derived from PWS induced pluripotent stem cells (iPSCs). However, ZNF274 has many other targets in the genome in addition to SNORD116. Depleting ZNF274 will surely affect the expression of other important genes and disrupt other pathways. Here, we used CRISPR/Cas9 to delete ZNF274 binding sites at the SNORD116 locus to determine whether activation of the maternal copy of SNORD116 could be achieved without altering ZNF274 protein levels. We obtained similar activation of gene expression from the normally silenced maternal allele in neurons derived from PWS iPSCs, compared with ZNF274 knockout, demonstrating that ZNF274 is directly involved in the repression of SNORD116. These results suggest that interfering with ZNF274 binding at the maternal SNORD116 locus is a potential therapeutic strategy for PWS.

Abundance and localization of human UBE3A protein isoforms.

Loss of UBE3A expression, a gene regulated by genomic imprinting, causes Angelman syndrome (AS), a rare neurodevelopmental disorder. The UBE3A gene encodes an E3 ubiquitin ligase with three known protein isoforms in humans. Studies in mouse suggest that the human isoforms may have differences in localization and neuronal function. A recent case study reported mild AS phenotypes in individuals lacking one specific isoform. Here we have used CRISPR/Cas9 to generate isogenic human embryonic stem cells (hESCs) that lack the individual protein isoforms. We demonstrate that isoform 1 accounts for the majority of UBE3A protein in hESCs and neurons. We also show that UBE3A predominantly localizes to the cytoplasm in both wild type and isoform-null cells. Finally, we show that neurons lacking isoform 1 display a less severe electrophysiological AS phenotype.

Oral Ingestion and Intraventricular Injection of Curcumin Attenuates the Effort-Related Effects of the VMAT-2 Inhibitor Tetrabenazine: Implications for Motivational Symptoms of Depression.

Effort-related choice tasks are used for studying depressive motivational symptoms such as anergia/fatigue. These studies investigated the ability of the dietary supplement curcumin to reverse the low-effort bias induced by the monoamine storage blocker tetrabenazine. Tetrabenazine shifted effort-related choice in rats, decreasing high-effort lever pressing but increasing chow intake. The effects of tetrabenazine were reversed by oral ingestion of curcumin (80.0-160.0 mg/kg) and infusions of curcumin into the cerebral ventricles (2.0-8.0 µg). Curcumin attenuates the effort-related effects of tetrabenazine in this model via actions on the brain, suggesting that curcumin may be useful for treating human motivational symptoms.