Deletion in chromosome 6 spanning alpha-synuclein and multimerin1 loci in the Rab27a/b double knockout mouse

Abstract

We report an incidental 358.5 kb deletion spanning the region encoding for alpha-synuclein (αsyn) and multimerin1 (Mmrn1) in the Rab27a/Rab27b double knockout (DKO) mouse line previously developed by Tolmachova and colleagues in 2007. Western blot and RT-PCR studies revealed lack of αsyn expression at either the mRNA or protein level in Rab27a/b DKO mice. PCR of genomic DNA from Rab27a/b DKO mice demonstrated at least partial deletion of the Snca locus using primers targeted to exon 4 and exon 6. Most genes located in proximity to the Snca locus, including Atoh1, Atoh2, Gm5570, Gm4410, Gm43894, and Grid2, were shown not to be deleted by PCR except for Mmrn1. Using whole genomic sequencing, the complete deletion was mapped to chromosome 6 (60,678,870–61,037,354), a slightly smaller deletion region than that previously reported in the C57BL/6J substrain maintained by Envigo. Electron microscopy of cortex from these mice demonstrates abnormally enlarged synaptic terminals with reduced synaptic vesicle density, suggesting potential interplay between Rab27 isoforms and αsyn, which are all highly expressed at the synaptic terminal. Given this deletion involving several genes, the Rab27a/b DKO mouse line should be used with caution or with appropriate back-crossing to other C57BL/6J mouse substrain lines without this deletion.

Rab27b promotes lysosomal function and alpha-synuclein clearance in neurons

“…We generated Rab27b single KO mice after crossing Rab27a/Rab27b double KO (DKO) mice obtained from Dr. Seabra [34] with wildtype (WT) C57BL/6J mice. Of note, we previously found that the Rab27a/b DKO mouse carries a spontaneous deletion that includes Snca , the gene that encodes αsyn, and Mmrn1 , the gene that encodes multimerin 1 [35]. This deleted region on chromosome 6 was restored in a subset of progeny after crossing the DKO mice with C57BL/6J mice.…”

“…For maintenance breeding, Rab27b +/- heterozygous mice were bred together to generate litters with both WT control (Rab27b +/+ ) and Rab27b-KO (Rab27b -/- ) pups for experimental use. Mice were genotyped for Rab27b and αsyn Exon 4 as previously described [35].…”

“…The copyright holder for this preprint this version posted June 24, 2024. ; https://doi.org/10.1101/2024.06.20.599785 doi: bioRxiv preprint experimental use. Mice were genotyped for Rab27b and αsyn Exon 4 as previously described [35].…”