Mitochondrial complex I deficiency leads to the retardation of early embryonic development in knockout mice.

Background: The gene encodes an 18-kD subunit of mitochondria complex I, and mutations in this gene lead to the development of a severe neurodegenerative disease called Leigh syndrome (LS) in humans. To investigate the disease phenotypes and molecular mechanisms of Leigh syndrome, the knockout (KO) mouse has been widely used as a novel animal model. Because the homozygotes cannot survive beyond child-bearing age, whether and mitochondrial complex I influence early embryonic development remains unknown. In our study, we attempted to investigate embryonic development in KO mice, which can be regarded as a Leigh disease model and were created through the CRISPR (clustered regularly interspaced short palindromic repeat) and Cas9 (CRISPR associated)-mediated genome editing system.

Methods: We first designed a single guide RNA (sgRNA) targeting exon 2 of to delete the NDUFS4 protein in mouse embryos to mimic Leigh syndrome. Then, we described the phenotypes of our mouse model by forced swimming and the open-field test as well as by assessing other behavioral characteristics. Intracytoplasmic sperm injection (ICSI) was performed to obtain KO embryos to test the influence of NDUFS4 deletion on early embryonic development.

Results: In this study, we first generated KO mice with physical and behavioral phenotypes similar to Leigh syndrome using the CRISPR/Cas9 system. The low developmental rate of KO embryos that were derived from knockout gametes indicated that the absence of NDUFS4 impaired the development of preimplantation embryos.

Discussion: In this paper, we first obtained KO mice that could mimic Leigh syndrome using the CRISPR/Cas9 system. Then, we identified the role of NDUFS4 in early embryonic development, shedding light on its roles in the respiratory chain and fertility. Our model provides a useful tool with which to investigate the function of . Although the pathological mechanisms of the disease need to be discovered, it helps to understand the pathogenesis of NDUFS4 deficiency in mice and its effects on human diseases.