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Polymorphic expression of CD46 protein isoforms due to tissue-specific RNA splicing
R W Johnstone1, S M Russell, B E Loveland
1Austin Research Institute, Austin Hospital, Heidelberg, Victoria, Australia.
Molecular Immunology
|October 1, 1993
Summary
CD46 (membrane cofactor protein) splicing varies by tissue, with exon 8 inclusion in salivary glands and kidneys, but exclusion in the brain. This demonstrates tissue-specific regulation of CD46 isoforms.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- CD46 (membrane cofactor protein) is a complement regulator protecting cells from lysis.
- CD46 gene splicing generates diverse protein isoforms, influencing cellular function.
- Tissue-specific expression patterns of CD46 isoforms are not fully understood.
Purpose of the Study:
- To investigate tissue-specific regulation of CD46 splicing.
- To identify differential expression of CD46 isoforms in various human tissues.
- To explore the mechanisms controlling CD46 alternative splicing.
Main Methods:
- Analysis of CD46 RNA transcripts in human tissues (salivary gland, kidney, brain, PBL).
- RT-PCR to detect exon inclusion/exclusion patterns.
- Identification of CD46 protein isoforms based on molecular weight.
Main Results:
- Salivary gland and kidney preferentially include exon 8, yielding 66 kDa CD46.
- Brain tissue preferentially excludes exon 8, resulting in 56 kDa CD46.
- Salivary gland, kidney, and brain predominantly produce the CYT 2 cytoplasmic tail isoform, unlike PBLs.
Conclusions:
- CD46 splicing is regulated in a tissue-specific manner, independent of inherited polymorphisms.
- Exon 8 splicing differs significantly between tissues like salivary gland, kidney, and brain.
- Trans-acting splicing factors likely regulate CD46 splicing in specific tissues, suggesting complex gene expression control.