Genome-wide association studies (GWAS) have implicated
a number of genes associated with serum urate and
gout. Hereditary renal hypouricaemia type 1 is due to loss
of function mutations in URAT1 (SLC22A12) and is relatively
common in Japan, and can be complicated by nephrolithiasis
or exercise-induced acute renal failure [7].
URAT1 has been genetically associated with urate levels,though no genetic association has been demonstrated for
URAT1 and gout [8,9]. SLC2A9 (GLUT9) is responsible
for approximately 4% of the variance in serum urate levels
and has an association with gout [8,9]. It is a glucose, fructose,
and uric acid transporter, although its greatest affinity
is for uric acid. It reabsorbs urate from the proximal renal
tubule and may also be expressed in the distal nephron
(and the liver and intestine); a homozygous loss-of-function
mutation causes severe hereditary renal hypouricaemia type
2 [10]. ABCG2 is a renal and extra-renal urate exporter responsible
for 140,000 individuals) was published [11]. Of loci
described previously 10 were confirmed and 18 new loci
were identified. However, none of the new loci seemed to
be candidates for urate transport but were instead related
to glycolysis, glucose, insulin and pyruvate, indicating
an importance in de novo purine synthesis and
thereby uric acid production [11].It was also found that
alleles associated with increased serum urate concentrations
were associated with increased risk of gout. Finally,
the rare autosomal dominant diseases collectively
known as uromodulin-associated kidney diseas (UAKD)
should also be mentioned. These are characterized by
hyperuricaemia, gout, and finally end stage renal disease.
They are caused by mutations in the renal specific gene
UMOD [12]. This suggests a coupling between urate
transport and the UMOD gene product uromodulin, also
known as Tamm Horsfall protein, although the details are
still unclear. Uromodulin is produced by the epithelial
cells of the thick ascending limb of the loop of Henle and
is secreted into the urine. It is possible that uromodulin
might regulate sodium transport in the thick ascending limb and that hyperuricaemia in UAKD is secondary to
hypovolaemia and increased reabsorption of urate along
the proximal tubule.