BACH1 Binding Links the Genetic Risk for Severe Periodontitis with ST8SIA1

Area of Science:

• Genetics
• Molecular Biology
• Periodontology

Background:

• Genome-wide association studies (GWAS) link genetic loci to periodontal diseases, but identifying causal variants and biological mechanisms is challenging.
• The gene ST8SIA1 has been associated with increased risk for severe periodontitis, particularly in smokers.

Purpose of the Study:

• To characterize the genetic association at ST8SIA1, identify its interaction partners, and elucidate its function in periodontitis pathogenesis.
• To determine the regulatory mechanisms and functional impact of single-nucleotide polymorphisms (SNPs) associated with ST8SIA1 and periodontitis risk.

Main Methods:

• CRISPR/dCas9 activation and RNA-sequencing to identify ST8SIA1 interaction partners and cellular functions.
• Reporter gene assays to map regulatory elements and assess allele-specific enhancer activity.
• Antibody electrophoretic mobility shift assays (EMSAs) to confirm allele-specific transcription factor binding.

Main Results:

• ST8SIA1 activation upregulated the periodontitis risk gene ABCA1 and significantly impacted integrin cell surface interactions and cell cycle regulation.
• Two intronic repressor elements in ST8SIA1 were identified, binding the transcriptional repressor BACH1. The risk variant rs2012722 reduced BACH1 binding by 40%.
• ST8SIA1 was confirmed as the target gene, inhibiting cell adhesion, integrin interactions, cell cycle, and promoting apoptosis, mirroring effects of tobacco smoke.

Conclusions:

• Impaired ST8SIA1 repression, caused by reduced BACH1 binding at the T allele and/or tobacco smoke exposure, increases ST8SIA1 levels.
• In smokers with the risk T allele, these additive factors likely compromise gingival barrier integrity, increasing periodontitis severity.
• ST8SIA1 activity is functionally linked to the periodontitis risk gene ABCA1.