Exploring the genetic architecture of circulating 25-hydroxyvitamin D

Area of Science:

• Human Genetics
• Nutritional Biochemistry
• Complex Trait Analysis

Background:

• Circulating 25-hydroxy vitamin D (25(OH)D) levels are influenced by environmental factors and genetics.
• Heritability estimates for 25(OH)D range from 43% to 80%, indicating a substantial genetic component.
• Genome-wide association studies (GWAS) have identified specific single nucleotide polymorphisms (SNPs) associated with 25(OH)D, but these explain only a small fraction of the heritability.

Purpose of the Study:

• To investigate whether genome-wide data, including polygenic scores and linear mixed models, could explain additional variance in 25(OH)D levels beyond known significant SNPs.
• To assess the genetic architecture of 25(OH)D variability.

Main Methods:

• Analysis of 25(OH)D concentrations and GWAS data from 5,575 individuals across five cohorts.
• Construction of polygenic scores using SNPs, including those not reaching genome-wide significance.
• Application of linear mixed models for genome-wide complex trait analysis (GCTA).

Main Results:

• SNPs identified through GWAS explained 5.2% of the variation in circulating 25(OH)D.
• Polygenic scores composed of GWAS-identified SNPs explained more variation than scores using thousands of non-significant SNPs.
• Linear mixed models explained minimal additional variability (0-22%), suggesting limited polygenic effects.

Conclusions:

• The identified GWAS SNPs and genome-wide approaches did not substantially improve the prediction of 25(OH)D levels beyond established markers.
• The findings suggest an oligogenetic architecture for 25(OH)D, where a few genes have a larger effect, rather than a highly polygenic one.