Cloning of macaque monkeys by somatic cell nucleus transfer (SCNT) allows the generation of monkeys with uniform genetic backgrounds that are useful for the development of non-human primate models of human diseases. Here, we report the feasibility of this approach by SCNT of fibroblasts from a macaque monkey (Macaca fascicularis), in which a core circadian transcription factor BMAL1 was knocked out by clustered regularly interspaced short palindromic repeat/Cas9 gene editing (see accompanying paper). Out of 325 SCNT embryos transferred into 65 surrogate monkeys, we cloned five macaque monkeys with BMAL1 mutations in both alleles without mosaicism, with nuclear genes identical to that of the fibroblast donor monkey. Further peripheral blood mRNA analysis confirmed the complete absence of the wild-type BMAL1 transcript. This study demonstrates that the SCNT approach could be used to generate cloned monkeys from fibroblasts of a young adult monkeys and paves the way for the development of macaque monkey disease models with uniform genetic backgrounds.
Summary
RNA splicing is related to many human diseases; however, lack of efficient genetic approaches to modulate splicing has prevented us from dissecting their functions in human diseases. Recently developed base editors (BEs) offer a new strategy to modulate RNA splicing by converting conservative splice sites, but it is limited by the editing precision and scope. To overcome the limitations of currently available BE-based tools, we combined SpCas9-NG with ABEmax to generate a new BE, ABEmax-NG. We demonstrated that ABEmax-NG performed precise A⋅T to G⋅C conversion with an expanded scope, thus covering many more splicing sites. Taking advantage of this tool, we precisely achieved A⋅T to G⋅C conversion exactly at the splice sites. We further modeled pathogenic RNA splicing
in vitro
and
in vivo
. Taken together, we successfully generated a versatile tool suitable for precise and broad editing at the splice sites.
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