Abstract
Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am−/p+ were reduced in the maternal inherited deletion group with no observable change in the Ube3am+/p− paternal transmission cohort. We also discovered Ube3am−/p+ exhibited delayed reflex development, motor deficits in rearing and fine motor skills, aberrant social communication, and impaired touchscreen learning and memory in young adults. These behavioral deficits were large in effect size and easily apparent in the larger rodent species. Low social communication was detected using a playback task that is unique to rats. Structural imaging illustrated decreased brain volume in Ube3am−/p+ and a variety of intriguing neuroanatomical phenotypes while Ube3am+/p− did not exhibit altered neuroanatomy. Our report identifies, for the first time, unique AS relevant functional phenotypes and anatomical markers as preclinical outcomes to test various strategies for gene and molecular therapies in AS.
Highlights
Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication skills, ataxia, motor and balance deficits, poor attention, intellectual disabilities, microcephaly, and seizures[1,2,3]
Two genomic RNAs were designed to target the 5ʹ-end of the Ube3a gene and two gRNAs target sequences downstream of Ube3a. gRNA pairs were used on each end of the deletion to maximize the probability of a complete deletion of the 90-kb region encompassing the Ube3a gene. 5′ CRISPR-1 Target site GGCCCTGCAGAGATGC AATC, 5′CRISPR-2 Target site GGAGCCCTCCGC CGGCA, 3′CRISPR-1 Target site TACCCTTCCCA GGCCCC, and 3′CRISPR-2 Target site GCATTTCT AGTACATCATCC
Genetically engineered rat models are becoming a widely feasible investigative approach for preclinical research that retains a high degree of genetic conservation relative to humans for targeted therapeutic development while providing enhanced behavioral capabilities relative to mice
Summary
Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication skills, ataxia, motor and balance deficits, poor attention, intellectual disabilities, microcephaly, and seizures[1,2,3]. The Foundation for Angelman Syndrome Therapeutics (FAST) funded the generation of a genetic rat model of AS via a 90-kb deletion on chromosome 1, which includes the entire Ube3a gene This has opened new possible avenues of research into the neurobiological and behavioral effects of loss of all isoforms of UBE3A and, crucially, the development of novel therapeutics in the near future, including gene replacement therapies. This unique rat model of AS provides opportunities to investigate complex AS relevant behaviors that have been difficult to capture with highsignal sensitivity, rigor, and reproducibility in mice, such as behaviors across developmental time points, juvenile acoustic social communication, and cognitive dysfunction
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