Identification of functional single nucleotide polymorphisms in the branchpoint site

Area of Science:

• Genomics
• Molecular Biology
• Bioinformatics

Background:

• Millions of human single nucleotide polymorphisms (SNPs) exist, many intronic with unknown functions.
• Intronic SNPs at branchpoint sites, especially adenine (A), are hypothesized to impact RNA splicing but lack systematic study.

Purpose of the Study:

• To identify human intron branchpoint sites using a splicing prediction tool.
• To screen dbSNP for SNPs within these predicted sites, creating a genome-wide branchpoint site SNP database.

Main Methods:

• Utilized a splicing prediction tool to identify branchpoint sites.
• Screened the dbSNP database for SNPs within identified branchpoint sites.
• Generated minigene constructs to experimentally test the splicing effects of selected SNPs.

Main Results:

• Identified 600 SNPs in branchpoint sites, with 216 involving an adenine (A) change.
• Four SNPs lacked additional As in the surrounding region; three caused abnormal splicing (exon skipping/intron inclusion).
• One SNP deletion at the branchpoint A showed normal splicing, suggesting alternative downstream As were used.

Conclusions:

• Generated a high-confidence genome-wide branchpoint site SNP database.
• Experimentally confirmed the critical role of adenine (A) in branchpoint function.
• Demonstrated that adjacent adenine residues can mitigate the impact of branchpoint A substitutions on splicing.