The Heritability of Kidney Function Using an Older Australian Twin Population

Figures

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  Figure 1. Scatterplot of eGFR as an estimate of kidney function between twin pairs. The correlation in MZ twins (0.51 [95% CI 0.41–0.65]) was slightly less than twice that of DZ twins (0.35 [95% CI 0.22–0.56]). DZ, dizygotic; eGFR, estimated glomerular filtration rate; MZ, monozygotic.

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  Figure 2. ACE model. A refers to additive genetic effects, which are considered 100% in monozygotic twins and 50% in dizygotic twins. C refers to common environment effects, presumed shared environment until age 18 years. E refers to unshared environmental effects, such as difference in smoking status.

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  Figure 3. Difference between narrow and broad sense heritability. Heritability is a measure of much of a characteristic that is determined by underlying genetics. Narrow sense heritability (panel 1) estimates heritability only using additive genetic effects. Va is where if allele A contributes 2 ml/min of eGFR and allele a contributes 1 ml/min of eGFR, then AA will contribute 4 ml/min, Aa 3 ml/min, and aa 2 ml/min. Broad sense heritability takes into consideration Vd, Va, and Ve. Vd found in panel 2, where the dominant allele is the genetic determinant, an example of which is ADPKD—either you have cystic kidneys or not. Ve is the environmental modulator on genes, such as histone modifications, as found in panel 3. Phenotypic variance reflects the population level of a trait, such as measured eGFR. ADPKD, autosomal dominant polycystic kidney disease; eGFR, estimated glomerular filtration rate; Va, variance additive; Vd, variance dominant; Ve, variance environmental. Created with BioRender.com.