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The article discusses research which investigated the heritability estimates of gout, including its subtypes, in Japanese populations via genome-wide association study (GWS) meta-analyses. Cited are the findings of the investigation on single nucleotidepolymorphism (SNP)-based heritability of three major subtypes of gout, the estimated polygenetic contributions to the heritability of gout, and results indicating that genetic factors are contributors to individual variability in gout.

Objectives Up to 0.3% of Japanese have hypouricaemia. Most cases appear to result from a hereditary disease, renal hypouricaemia (RHUC), which causes exercise-induced acute kidney injury and urolithiasis. However, to what extent RHUC accounts for hypouricaemia is not known. We therefore investigated its frequency and evaluated its risks by genotyping a general Japanese population. Methods A cohort of 4993 Japanese was examined by genotyping the non-functional variants R90H (rs121907896) and W258X (rs121907892) of URAT1/SLC22A12 , the two most common causative variants of RHUC in Japanese. Results Participants' fractional excretion of uric acid and risk allele frequencies markedly increased at lower serum uric acid (SUA) levels. Ten participants (0.200%) had an SUA level ≤2.0 mg/dl and nine had R90H or W258X and were likely to have RHUC. Logistic regression analysis revealed these URAT1 variants to be significantly and independently associated with the risk of hypouricaemia and mild hypouricaemia (SUA ≤3.0 mg/dl) as well as sex, age and BMI, but these URAT1 variants were the only risks in the hypouricaemia population (SUA ≤2.0 mg/dl). W258X was only a risk in males with SUA ≤3.0 mg/dl. Conclusion Our study accurately reveals the prevalence of RHUC and provides genetic evidence for its definition (SUA ≤2.0 mg/dl). We also show that individuals with SUA ≤3.0 mg/dl, especially males, are prone to RHUC. Our findings will help to promote a better epidemiological understanding of RHUC as well as more accurate diagnosis, especially in males with mild hypouricaemia. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the contribution of genetic variations in the X chromosome to serum urate (SU) levels. Topics covered include the gender differences in the homeostasis of urate, the circulating form of uric acid, 12 single nucleotide polymorphisms (SNP) at the Xq28 locus that influence SU identified by the study, and the functional annotation of the newly identified locus in the context of SU.