Expression of L-APP mRNA in brain cells

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Alternative splicing of amyloid precursor protein (APP) pre-mRNA is tissue-specific.
• Exon 7 inclusion in APP isoforms is relevant due to its serine protease inhibitor domain and potential role in amyloidogenic catabolism.
• A novel alternative splice site near the beta A4-amyloid region may increase APP amyloidogenicity.

Purpose of the Study:

• To investigate the regulation of alternative splicing at a novel 3' splice site in the APP gene within central nervous system cells.
• To determine the usage of different APP splice isoforms in various neural cell types.

Main Methods:

• Development of an assay to resolve different APP splice isoforms.
• Analysis of APP splicing patterns in rat brain microglia, astrocyte-enriched cultures, and neurons.

Main Results:

• Six out of eight potential APP isoforms generated from alternatively spliced exons 7, 8, and 15 were resolved.
• Microglia and astrocytes skip the alternative 3' splice site before exon 15, producing L-APP mRNA.
• Neurons predominantly use the 3' splice site of intron 14 (~100%), which perfectly matches the consensus branchpoint sequence.

Conclusions:

• Neuronal splicing of APP pre-mRNA differs significantly from other CNS cells, with near-exclusive use of the intron 14 3' splice site.
• This neuronal preference suggests a potential lack of a specific splicing factor that would inhibit the use of the alternative 3' splice site before exon 15.
• Further research is needed to determine if this splicing pattern is altered in neurons affected by Alzheimer's disease.