Quantile-Dependent Expressivity of Serum Uric Acid Concentrations

Area of Science:

• Genetics
• Human Physiology
• Biostatistics

Background:

• Quantile-dependent expressivity describes how a genetic variant's effect size differs based on phenotype distribution (e.g., serum uric acid levels).
• Understanding this phenomenon is crucial for accurate genetic association studies and identifying gene-environment interactions.

Purpose of the Study:

• To investigate whether serum uric acid heritability is specific to different quantiles of its distribution.
• To determine if quantile-specific heritability can explain previously observed gene-environment interactions.

Main Methods:

• Utilized data from 2151 sibships and 12,068 offspring-parent pairs from the Framingham Heart Study.
• Employed quantile regression to robustly estimate quantile-specific heritability (h²) from offspring-parent and full-sib regression slopes.
• Assigned nonparametric significance using 1000 bootstrap samples.

Main Results:

• Serum uric acid heritability (h²) significantly increased with higher percentiles of the sex- and age-adjusted distribution, both from offspring-parent (Ptrend = 0.001) and full-sib estimates (Ptrend = 0.006).
• Observed increases in h² ranged from 0.34 ± 0.03 at the 10th percentile to 0.49 ± 0.05 at the 90th percentile.
• Findings align with larger genetic effect sizes observed for specific polymorphisms (e.g., SLC2A9, ABCG2) in various clinical and lifestyle subgroups, suggesting quantile-dependent expressivity plays a role.

Conclusions:

• The heritability of serum uric acid concentrations is demonstrably quantile-specific.
• This quantile-specificity offers a potential explanation for gene-environment interactions previously reported in the literature.