Peri-implantation lethality in mice carrying megabase-scale deletion on 5qc3.3 is caused by Exoc1 null mutation

Abstract

We found a novel spontaneous mouse mutant with depigmentation in the ventral body, which we called White Spotting (WS) mouse. Genetic investigation revealed deletion of aa >1.2-Mb genomic region containing nine genes (Kit, Kdr, Srd5a3, Tmeme165, Clock, Pdcl2, Nmu, Exoc1, and Cep135). We designated this mutant allele Kit WS. Interestingly, homozygous mutants (Kit WS/WS) showed a peri-implantation lethal phenotype. Expression analyses of these nine genes in blastocysts suggested that Exoc1 was a prime candidate for this phenotype. We produced Exoc1 knockout mice, and the same peri-implantation lethal phenotype was seen in Exoc1 ' embryos. In addition, the polygenic effect without Exoc1 was investigated in genome-edited Kit WE mice carrying the Mb-scale deletion induced by the CRISPR/Cas9 system. As Kit WE/WE embryos did not exhibit the abnormal phenotype, which was seen in Kit WS/WS. We concluded that peri-implantation lethality in Kit WS/WS was caused by a monogenic defect of Exoc1.