P4‐091: the Trem2*r47h Variant Alters Expression and Function in Mouse Models of Alzheimer's Disease
Year: 2019
Type: article
Abstract: Alzheimer's disease (AD) is a debilitating neurodegenerative disorder with no effective treatment available. Research into understanding AD has been fueled by animal models with familial mutations. While these models have proved fruitful to understanding some baseline phenotypes, they have not been adequate to develop therapeutics to understand processes leading to AD. The brain's immune system has long been implicated as a key factor in the development of Alzheimer's disease, particularly microglia. Variants in the gene encoding TREM2 have been found to increase the risk for developing AD and TREM2 is predominately expressed on microglia. We have created a mouse model carrying the Trem2*R47H KI allele using CRISP/Cas9 containing a nucleotide G>A point mutation for amino acid sequence change at R47H into the gene. Mice were aged to 2, 8 and 12 months. In addition, the 5xFAD model was crossed with mice carrying the Trem2*R47H variant. Tissue was analyzed using RNA-sequencing, IP Western Blotting and immunohistochemistry. In mice carrying the R47H variant, there is an alternate splicing event, resulting in a 119bp deletion inside exon 2 and decreased mRNA levels. This segment includes the R47H mutation. We have observed a similar alternate splicing event in some of non-mutant mice as well, but it is more prominent in Trem2*R47H sample as we have identified this alternate splice junction in 30 out of 34 Trem2*R47H mice. This finding suggested an alternate splicing effect on Trem2 due to R47H mutation. Using IP Western Blots, we found the protein level of Trem2 to be reduced by approximately 60% in brain homogenates. This correlates with RNA-sequencing results. Despite the reduction in messenger RNA, there is significant full-length expression of mutant Trem2 mRNA in mice carrying the Trem2*R47H variant. This is consistent with the reduction in Trem2 protein is observed from brains. Furthermore, this model does not phenocopy a Trem2KO since significant expression of Trem2 protein in brain tissue is observed and transcriptome alterations are different and less pronounced. Further studies with this model will enable us to gain a deeper understanding of how Trem2 plays a role in the progression of AD.
Source: Alzheimer s & Dementia
Language: English
Subfield: Neurology
Field: Neuroscience
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2981016631