Transgenic Monkey Model of the Polyglutamine Diseases Recapitulating Progressive Neurological Symptoms

Abstract

Age-associated neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and the polyglutamine (polyQ) diseases, are becoming prevalent as a consequence of elongation of the human lifespan. Although various rodent models have been developed to study and overcome these diseases, they have limitations in their translational research utility owing to differences from humans in brain structure and function and in drug metabolism. Here, we generated a transgenic marmoset model of the polyQ diseases, showing progressive neurological symptoms including motor impairment. Seven transgenic marmosets were produced by lentiviral introduction of the human ataxin 3 gene with 120 CAG repeats encoding an expanded polyQ stretch. Although all offspring showed no neurological symptoms at birth, three marmosets with higher transgene expression developed neurological symptoms of varying degrees at 3–4 months after birth, followed by gradual decreases in body weight gain, spontaneous activity, and grip strength, indicating time-dependent disease progression. Pathological examinations revealed neurodegeneration and intranuclear polyQ protein inclusions accompanied by gliosis, which recapitulate the neuropathological features of polyQ disease patients. Consistent with neuronal loss in the cerebellum, brain MRI analyses in one living symptomatic marmoset detected enlargement of the fourth ventricle, which suggests cerebellar atrophy. Notably, successful germline transgene transmission was confirmed in the second-generation offspring derived from the symptomatic transgenic marmoset gamete. Because the accumulation of abnormal proteins is a shared pathomechanism among various neurodegenerative diseases, we suggest that this new marmoset model will contribute toward elucidating the pathomechanisms of and developing clinically applicable therapies for neurodegenerative diseases.

Oocyte‐activating capacity of fresh and frozen–thawed spermatids in the common marmoset (Callithrix jacchus)

“…This was the first report on the establishment of gene‐modified lines of primates. More recently, the use of transgenic technology in marmosets enabled the generation of a monkey model for human polyglutamine disease, which recapitulated progressive neurological symptoms as found in human patients (Tomioka et al, ). Genetic deletions mediated by genome editing have also become possible in marmosets, and knockout marmoset strains deficient for the interleukin‐2 receptor subunit gamma were generated (Sato et al, ).…”

Generation of genetically engineered non‐human primate models of brain function and neurological disorders

“…After the initial technical breakthrough in making GFP-expressing transgenic marmosets (Sasaki et al, 2009), we reported marmosets expressing functional reporter genes (Park et al, 2016), while another group reported a marmoset model of polyglutamine (polyQ) disease (Tomioka, Ishibashi, et al, 2017; Tomioka, Nogami, et al, 2017). The transgenic marmosets expressing functional reporter genes were generated by our own efforts and the summary of our work and ongoing progress will be discussed later in this review.…”

“…The transgenic marmosets expressing functional reporter genes were generated by our own efforts and the summary of our work and ongoing progress will be discussed later in this review. In an attempt to mimic inherited human neurodegenerative diseases, transgenic marmosets expressing the human ataxin 3 gene with expanded polyQ stretch were developed as a model of polyQ diseases (Tomioka, Ishibashi, et al, 2017). These transgenic marmosets demonstrated no neurological symptoms at birth, but showed slower growth curves, and gradual decreases in spontaneous activity and grip strength.…”

“…However, one caveat when trying to establish transgenic NHP models of disease is that transgenic monkeys may carry a high rate of infant mortality, and even juveniles or young adults may acquire early symptoms with rapid disease progression, making it difficult to use these animals to expand the colony. To circumvent this problem, the same group pursued a parallel effort to develop transgenic marmosets expressing the mutant human ataxin 3 gene under control of a tetracyclin-inducible transgene expression (tet-on) system (Tomioka, Nogami, et al, 2017). The offspring harboring the transgene under the control of tet-on system showed increased transgene expression with doxycycline administered in the drinking water and live F1 transgenic marmosets were easily produced from a founder marmoset before the disease onset.…”

Haplotype-phased common marmoset embryonic stem cells for genome editing using CRISPR/Cas9

“…The first transgenic primate showing successful germline transmission of transgenes was accomplished using the marmoset in which lentiviruses expressing enhanced green fluorescent protein (EGFP) were injected into preimplantation embryos (Sasaki et al 2009). A similar technology was also used to generate transgenic marmosets expressing genetically encoded calcium indicators ((Sasaki et al 2009; Park et al 2016; Tomioka et al 2017). Shortly after the reporting of the first genetically modified marmosets, the marmoset genome was sequenced and assembled using various strategies including Sanger sequencing at 6× coverage (Marmoset Genome Sequencing and Analysis Consortium 2014; Sato et al 2015).…”