Heparan sulfate gene polymorphism in calcium oxalate nephrolithiasis

Whole exome sequencing reveals heparan sulfate proteoglycan 2 (HSPG2) as a potential causative gene for kidney stone disease in a Thai family

Kidney stone disease (KSD) is a prevalent and complex condition, with an incidence of 85 cases per 100,000 individuals in Thailand. Notably, over 40% of cases are concentrated in the northeastern region, indicating a potential genetic influence, which is supported by genetic mutations reported in several families by our research group. Despite this, the genetic basis of KSD remains largely unknown for many Thai families. This study aimed to identify the genetic mutation responsible for KSD in a specific Thai family, the UBRS131 family, which includes four affected individuals. Whole exome sequencing was performed, and variant filtering using the VarCards2 program identified 10 potentially causative mutations across 9 genes. These mutations were subjected to segregation analysis among family members and screened in 180 control and 179 case samples using real-time PCR-HRM or PCR-RFLP techniques. Prioritization of these variants using GeneDistiller identified the p.Asp775Glu mutation in the heparan sulfate proteoglycan 2 (HSPG2) gene as the likely causative mutation for KSD in this family. The Asp775 residue is highly conserved across vertebrates, and structural analysis suggests that the Glu775 substitution may disrupt the formation of two crucial hydrogen bonds, potentially altering the mutant protein's configuration. Immunohistochemistry confirmed the presence of perlecan (HSPG2 protein) in the proximal tubules in nephrons. These findings highlight the significant role of the HSPG2 gene in familial KSD within this study family.

Epidemiology of stone disease across the world

Nephrolithiasis is a highly prevalent disease worldwide with rates ranging from 7 to 13% in North America, 5-9% in Europe, and 1-5% in Asia. Due to high rates of new and recurrent stones, management of stones is expensive and the disease has a high level of acute and chronic morbidity. The goal of this study is to review the epidemiology of stone disease in order to improve patient care. A review of the literature was conducted through a search on Pubmed^®, Medline^®, and Google Scholar^®. This review was presented and peer-reviewed at the 3rd International Consultation on Stone Disease during the 2014 Société Internationale d'Urologie Congress in Glasgow. It represents an update of the 2008 consensus document based on expert opinion of the most relevant studies. There has been a rising incidence in stone disease throughout the world with a narrowing of the gender gap. Increased stone prevalence has been attributed to population growth and increases in obesity and diabetes. General dietary recommendations of increased fluid, decreased salt, and moderate intake of protein have not changed. However, specific recommended values have either changed or are more frequently reported. Geography and environment influenced the likelihood of stone disease and more information is needed regarding stone disease in a large portion of the world including Asia and Africa. Randomized controlled studies are lacking but are necessary to improve recommendations regarding diet and fluid intake. Understanding the impact of associated conditions that are rapidly increasing will improve the prevention of stone disease.

Human SLC26A1 gene variants: a pilot study

Kidney stones are a global health problem, incurring massive health costs annually. Why stones recur in many patients remains unknown but likely involves environmental, physiological, and genetic factors. The solute linked carrier (SLC) 26A1 gene has previously been linked to kidney stones in mice. SLC26A1 encodes the sulfate anion transporter 1 (SAT1) protein, and its loss in mice leads to hyperoxaluria and calcium oxalate renal stones. To investigate the possible involvement of SAT1 in human urolithiasis, we screened the SLC26A1 gene in a cohort of 13 individuals with recurrent calcium oxalate urolithiasis, which is the commonest type. DNA sequence analyses showed missense mutations in seven patients: one individual was heterozygous R372H; 4 individuals were heterozygous Q556R; one patient was homozygous Q556R; and one patient with severe nephrocalcinosis (requiring nephrectomy) was homozygous Q556R and heterozygous M132T. The M132 amino acid in human SAT1 is conserved with 15 other species and is located within the third transmembrane domain of the predicted SAT1 protein structure, suggesting that this amino acid may be important for SAT1 function. These initial findings demonstrate genetic variants in SLC26A1 of recurrent stone formers and warrant wider independent studies of SLC26A1 in humans with recurrent calcium oxalate stones.

E-cadherin gene 3'-UTR C/T polymorphism in Turkish patients with nephrolithiasis

Nephrolithiasis is a complex disease and many gene polymorphisms have been associated with stone formation. In this study we aimed to investigate another possible relationship between E-cadherin gene (CHD1) 3'-UTR C/T polymorphism and calcium oxalate nephrolithiasis in the Turkish population. Study population was composed of 143 patients with nephrolithiasis and 158 control subjects. CHD1 3'-UTR C/T polymorphism was analysed using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique. Genotype distribution of the investigated polymorphism was not deviated from Hardy-Weinberg equilibrium (HWE) in patients and control subjects (P > 0.05). C allele frequency was 85.7 and 85.1% in patients and controls, respectively (P = 0.836). Genotype distributions of the CHD1 3'-UTR C/T polymorphism among patients were also not significantly different from those among control subjects (P = 0.636). Our results showed that there is no association between the CHD1 gene 3'-UTR C/T polymorphism and nephrolithiasis in our population.

Increasing incidence of kidney stones in children evaluated in the emergency department

OBJECTIVE

To test the hypothesis that there is an increase in the incidence of childhood nephrolithiasis in the state of South Carolina.

STUDY DESIGN

We analyzed demographic data from a statewide database on incidence of kidney stones from emergency department data and financial charges. Data were compared with population data from the US Census to control for population growth.

RESULTS

There was a significant increase in the incidence of kidney stones in children between 1996 and 2007. The greatest rate of increase was seen in adolescents, pre-adolescents, and Caucasian children. Infants, toddlers, and African-American children did not show significantly increased incidence in the period. Girls show a growing predominance in our population. The amount of money charged for care of children with kidney stones has gone up >4-fold in our state.

CONCLUSION

The incidence of kidney stone disease has risen dramatically in the state of South Carolina since 1996. Further studies investigating potential contributing factors are needed to prevent this costly and painful condition.

Fetuin-A gene polymorphism in patients with calcium oxalate stone disease

OBJECTIVES

To evaluate the association of fetuin-A polymorphisms with calcium oxalate nephrolithiasis. Fetuin-A is a circulating calcium-regulatory glycoprotein that inhibits extraosseous calcification.

METHODS

Fetuin-A c.742C > T and c.766C > G polymorphisms were investigated in 103 patients with calcium oxalate nephrolithiasis and 73 age- and gender-matched healthy volunteers, using polymerase chain reaction-restriction fragment length polymorphism techniques. Additionally, we compared serum fetuin-A levels in the 2 groups.

RESULTS

A statistically significant difference was observed between the control and patient groups (chi(2) test, P = .003) for the genotype of fetuin-A c.766C > G polymorphism. The odds ratio (95% confidence interval) for the CG genotype in those at risk of stone disease was 4.2 (1.73-10.28). The frequency distribution for fetuin-A c.742C > T polymorphism was not statistically different in stone patients and controls (P = .77). Serum mean fetuin-A concentration was significantly lower in the patients (710.38 +/- 156.42 microg/mL) than in the controls (810.89 +/- 173.43 microg/mL, P = .0001). In the patient group (but not in the control group), subjects carrying fetuin-A genotype 1 had significantly higher serum fetuin-A concentrations than the group carrying fetuin-A genotype 2-1 (P = .001).

CONCLUSIONS

These results reveal that the patients with fetuin-A c.766C > G gene polymorphism may be at higher risk for renal calcium oxalate stone formation.

A HindIII polymorphism of fibronectin gene is associated with nephrolithiasis

OBJECTIVES

To evaluate the association between fibronectin gene (FN1) polymorphisms and calcium oxalate nephrolithiasis as a genetic risk factor.

METHODS

Genomic DNA of 143 patients with calcium oxalate nephrolithiasis and 154 healthy controls were screened for polymorphisms (HaeIII b, MspI, and HindIII) of the FN1 gene, using polymerase chain reaction-restriction fragments length polymorphism method. Allele and genotype frequencies were compared between the groups.

RESULTS

Although the observed differences between distribution of genotypes of AA, AB, and BB (for HaeIII b), as well as CC, CD, and DD (MspI) were not significant, FF genotype for HindIII showed significant difference when compared with both EF and EE + EF genotype (P = .00202 and P = .00203, respectively).

CONCLUSIONS

The results of our study revealed that HindIII polymorphism of the FN1 gene is highly associated with calcium oxalate stone disease. This association makes FN a good candidate for further studies about the etiology of stone disease, and in the future it could be a candidate marker for evaluating the genetic risks in patients with nephrolithiasis.