All about CRISPR/Cas9

Alzheimer’s Disease is a progressive neurodegenerative disorder accounting for two-thirds of the cases of Dementia. The causes are both genetic and environmental. There are two forms of the disease: FAD (familial Alzheimer's disease) and Sporadic Alzheimer's disease. The genes: APP (amyloid precursor protein), PSEN1 (Presenilin 1), and PSEN2 (Presenilin 2) are responsible for the presence of the first-mentioned form, and the APOE gene is responsible for the latter. The deposition of beta-amyloid plaques and hyperphosphorylation of tau protein is responsible for the onset of the disorder.

CRISPR/Cas9 is a biotechnological procedure that can be used to edit genes and therefore can be widely used for scientific research. It is used to target key enzymes of Aβ -protein and various pro-inflammatory molecules like CD33, GMF (Glia Maturation Factor), cysLT1R for the treatment of AD.

This article will focus on the mechanistic detail of the CRISPR/Cas9 technology and its role as a possible treatment of this disorder by targeting key enzymes such as BACE 1, γ Secretase Protease etc. Cas9 is a nuclease guided by small RNAs through Watson-Crick base pairing with target DNA. It represents a system that is markedly easier to design, highly specific, efficient, and well-suited for high-throughput and multiplexed gene editing for a variety of cell types and organisms.

CRISPR/Cas9 is a simple two-component system used for effective targeted gene editing. The first component is the single-effector Cas9 protein, which contains the endonuclease domains RuvC and HNH. RuvC cleaves the DNA strand non-complementary to the spacer sequence and HNH cleaves the complementary strand. Together, these domains generate double-stranded breaks (DSBs) in the target DNA. The second component of effective targeted gene editing is a single guide RNA (sgRNA) carrying a scaffold sequence which enables its anchoring to Cas9 and a 20 base pair spacer sequence complementary to the target gene and adjacent to the PAM (protospacer adjacent motif) sequence. This sgRNA guides the CRISPR/Cas9 complex to its intended genomic location. The editing system then relies on either of two endogenous DNA repair pathways: non-homologous end-joining (NHEJ) or homology-directed repair (HDR).

Targeting Key Enzymes of Aβ Protein

Ø BACE 1 –

Ø γ Secretase Protease

Ø Editing of APOE Genotype

CRISPR/Cas9 technology can also be used to target pro-inflammatory molecules like CD33, GMF (Glia Maturation Factor), cysLT1R for the treatment of AD.

Author: Ambalika Basak

Read the full published paper at iyna_journal_MAY_2022_kMpqhGS.pdf (youthneuro.org) ( page 32 )