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Familial forms of focal segmental glomerulosclerosis (FSGS) have been linked to gain-of-function mutations in the gene encoding the transient receptor potential channel C6 (TRPC6). GPCRs coupled to Gq signaling activate TRPC6, suggesting that Gq-dependent TRPC6 activation underlies glomerular diseases. Here, we developed a murine model in which a constitutively active Gq a subunit ([Gq.sup.Q209L] referred to herein as GqQ>L) is specifically expressed in podocytes and examined the effects of this mutation in response to puromycin aminonucleoside (PAN) nephrosis. We found that compared with control animals, animals expressing GqQ>L exhibited robust albuminuria, structural features of FSGS, and reduced numbers of glomerular podocytes. Gq activation stimulated calcineurin (CN) activity, resulting in CN-dependent upregulation of TRPC6 in murine kidneys. Deletion of TRPC6 in GqQ>L-expressing mice prevented FSGS development and inhibited both tubular damage and podocyte loss induced by PAN nephrosis. Similarly, administration of the CN inhibitor FK506 reduced proteinuria and tubular injury but had more modest effects on glomerular pathology and podocyte numbers in animals with constitutive Gq activation. Moreover, these Gq-dependent effects on podocyte injury were generalizable to diabetic kidney disease, as expression of GqQ>L promoted albuminuria, mesangial expansion, and increased glomerular basement membrane width in diabetic mice. Together, these results suggest that targeting Gq/TRPC6 signaling may have therapeutic benefits for the treatment of glomerular diseases., Introduction GPCRs linked to Gq activation play a key role in glomerular diseases including receptors for angiotensin II (AT1), endothelins (ETA), thromboxanes (TP), cysteinyl-leukotrienes, and E-series prostaglandins (EP1) (1, 2). [...]

The specialized epithelial cell of the kidney, the podocyte, has a complex actinbased cytoskeleton. Dynamic regulation of this cytoskeleton is required for efficient barrier function of the kidney. Podocytes are a useful cell type to study the control of the actin cytoskeleton in vivo, because disruption of components of the cytoskeleton results in podocyte damage, cell loss, and a prototypic injury response called focal segmental glomerulosclerosis (FSGS). Searching for actin regulatory proteins that are expressed in podocytes, we identified a RhoA-activated Rac1 GTPase-activating protein (Rac1-GAP), Arhgap24, that was upregulated in podocytes as they differentiated, both in vitro and in vivo. Increased levels of active Rac1 and Cdc42 were measured in Arhgap24 knockdown experiments, which influenced podocyte cell shape and membrane dynamics. Consistent with a role for Arhgap24 in normal podocyte functioning in vivo, sequencing of the ARHGAP24 gene in patients with FSGS identified a mutation that impaired its Rac1-GAP activity and was associated with disease in a family with FSGS. Thus, Arhgap24 contributes to the careful balancing of RhoA and Rac1 signaling in podocytes, the disruption of which may lead to kidney disease., Introduction The kidneys filter plasma and reabsorb solutes and nutrients to maintain the appropriate extracellular environment. The proximal component of the nephron, the glomerulus, is the primary filtration barrier that [...]

Background: Mutations in podocin (NPHS2) are the most common cause of childhood onset autosomal recessive steroid-resistant nephrotic syndrome (SRNS). The disease is characterized by early-onset proteinuria, resistance to immunosuppressive therapy and rapid progression to end-stage renal disease. Compound heterozygous changes involving the podocin variant R229Q combined with another pathogenic mutation have been associated with a mild phenotype with disease onset often in adulthood. Methods: We screened 19 families with early-onset SRNS for mutations in NPHS2 and WT1 and identified four disease-causing mutations (three in NPHS2 and one in WT1) prior to planned whole-exome sequencing. Results: We describe two families with three individuals presenting in childhood who are compound heterozygous for R229Q and one other pathogenic NPHS2 mutation, either L327F or A297V. One child presented at age 4 years (A297V plus R229Q) and the other two at age 13 (L327F plus R229Q), one with steadily deteriorating renal function. Conclusions: These cases highlight the phenotypic variability associated with the NPHS2 R229Q variant plus pathogenic mutation. Individuals may present with early aggressive disease. [ABSTRACT FROM AUTHOR]

The emerging role of the transient receptor potential cation channel isotype 6 (TRPC6) as a central contributor to various pathological processes affecting podocytes has generated interest in the development of therapeutics to modulate its function. Recent insights into the regulation of TRPC6 have revealed PKG as a potent negative modulator of TRPC6 conductance and associated signaling via its phosphorylation at two highly conserved amino acid residues: Thr69/Thr70 (Thr69 in mice and Thr70 in humans) and Ser321/Ser322 (Ser321 in mice and Ser322 in humans). Here, we tested the role of PKG in modulating TRPC6-dependent responses in primary and conditionally immortalized mouse podocytes. TRPC6 was phosphorylated at Thr69 in nonstimulated podocytes, but this declined upon ANG II stimulation or overexpression of constitutively active calcineurin phosphatase. ANG II induced podocyte motility in an in vitro wound assay, and this was reduced 30-60% in cells overexpressing a phosphomimetic mutant TRPC6 (TRPC6T70E/S322E) or activated PKG (P < 0.05). Pretreatment of podocytes with the PKG agonists S-nitroso-N-acetyl-DL-penicillamine (nitric oxide donor), 8-bromo-cGMP, Bay 41-2772 (soluble guanylate cyclase activator), or phosphodiesterase 5 (PDE5) inhibitor 4-{[3=,4=-(methylenedioxy) benzyl]amino}[7]-6-methoxyquinazoline attenuated ANG II-induced Thr69 dephosphorylation and also inhibited TRPC6-dependent podocyte motility by 30-60%. These data reveal that PKG activation strategies, including PDE5 inhibition, ameliorate ANG II-induced podocyte dysmotility by targeting TRPC6 in podocytes, highlighting the potential therapeutic utility of these approaches to treat hyperactive TRPC6-dependent glomerular disease. [ABSTRACT FROM AUTHOR]

BackgroundEssential hypertension results from the interaction of several genetic and environmental factors. Identification of genetic factors that modulate blood pressure (BP) response to interventions can lead to improved strategies for prevention and control. The purpose of this study was to identify genes that modulate BP response to dietary interventions.MethodsWe used data and samples collected in two randomized feeding studies to determine the extent to which genetic architecture is associated with the effect on BP of sodium intake and the Dietary Approaches to Stop Hypertension (DASH) dietary pattern. Participants in both trials were adults with above-optimal BP or unmedicated stage 1 hypertension. Genomic DNA was typed for several candidate genes.ResultsThe effect of sodium intake on BP differed by genotype at the angiotensinogen, β2-adrenergic receptor, and kallikrein loci. The effect of DASH dietary pattern on BP differed by genotype at the β2-adrenergic receptor locus.ConclusionsThese findings have implications for understanding the mechanism(s) through which diet affects BP, the heterogeneity of these effects, and the extent to which dietary interventions can modulate genetic predisposition.American Journal of Hypertension (2011). doi:10.1038/ajh.2010.223 [ABSTRACT FROM AUTHOR]

The article discusses the study which explores how transient receptor potential canonical (TRPC) channels influence cardiomyocyte calcium signaling. In the study, researchers used whole cell patch clamp of adult cardiomyocytes to upregulate the cation reminiscent to pressure maladaptive cardiac hypertrophy and cardiac function. The study found that TRPC1 channels contribute to biomechanical stress and failure to maladaptive hypertrophy.

Abstract: Focal and segmental glomerulosclerosis (FSGS) is a common cause of nephrotic syndrome in children and adults throughout the world. In the past 50 years, significant advances have been made in the identification and characterization of familial forms of nephrotic syndrome and FSGS. Resultant to these pursuits, several podocyte structural proteins such as nephrin, podocin, alpha-actinin 4 (ACTN4), and CD2-associated protein (CD2AP) have emerged to provide critical insight into the pathogenesis of hereditary nephrotic syndromes. The latest advance in familial FSGS has been the discovery of a mutant form of canonical transient receptor potential cation channel 6 (TRPC6), which causes an increase in calcium transients and essentially a gain of function in this cation channel located on the podocyte cell membrane. The TRP ion channel family is a diverse group of cation channels united by a common primary structure which contains six membrane-spanning domains, with both carboxy and amino termini located intracellularly. TRP channels are unique in their ability to activate independently of membrane depolarization. TRPC6 channels have been shown to be activated via phospholipase C stimulation. The mechanisms by which mutant TRPC6 causes an increase in intracellular calcium and leads to glomerulosclerosis are unknown. Mutant TRPC6 may affect critical interactions with the aforementioned podocyte structural proteins, leading to abnormalities in the slit diaphragm or podocyte foot processes. Mutant TRPC6 may also amplify injurious signals mediated by Ang II, a common final pathway of podocyte apoptosis in various mammalian species. Current evidence also suggests that blocking TRPC6 channels may be of therapeutic benefit in idiopathic FSGS, a disease with a generally poor prognosis. Preliminary experiments reveal the commonly used immunosuppressive agent FK-506 can inhibit TRPC6 activity in vivo. This creates the exciting possibility that blocking TRPC6 channels within the podocyte may translate into long-lasting clinical benefits in patients with FSGS. [Copyright &y& Elsevier]

Familial forms of focal segmental glomerulosclerosis (FSGS) have been linked to gain-of-function mutations in the gene encoding the transient receptor potential channel C6 (TRPC6). GPCRs coupled to Gq signaling activate TRPC6, suggesting that Gq-dependent TRPC6 activation underlies glomerular diseases. Here, we developed a murine model in which a constitutively active Gq α subunit (GqQ209L, referred to herein as GqQ>L) is specifically expressed in podocytes and examined the effects of this mutation in response to puromycin aminonucleoside (PAN) nephrosis. We found that compared with control animals, animals expressing GqQ>L exhibited robust albuminuria, structural features of FSGS, and reduced numbers of glomerular podocytes. Gq activation stimulated calcineurin (CN) activity, resulting in CN-dependent upregulation of TRPC6 in murine kidneys. Deletion of TRPC6 in GqQ>L-expressing mice prevented FSGS development and inhibited both tubular damage and podocyte loss induced by PAN nephrosis. Similarly, administration of the CN inhibitor FK506 reduced proteinuria and tubular injury but had more modest effects on glomerular pathology and podocyte numbers in animals with constitutive Gq activation. Moreover, these Gq-dependent effects on podocyte injury were generalizable to diabetic kidney disease, as expression of GqQ>L promoted albuminuria, mesangial expansion, and increased glomerular basement membrane width in diabetic mice. Together, these results suggest that targeting Gq/TRPC6 signaling may have therapeutic benefits forthe treatment of glomerular diseases. [ABSTRACT FROM AUTHOR]

Focal segmental glomerulosclerosis (FSGS) is a histological lesion with many causes, including inherited genetic defects, with significant proteinuria being the predominant clinical finding at presentation. Mutations in COL4A3 and COL4A4 are known to cause Alport syndrome (AS), thin basement membrane nephropathy, and to result in pathognomonic glomerular basement membrane (GBM) findings. Secondary FSGS is known to develop in classic AS at later stages of the disease. Here, we present seven families with rare or novel variants in COL4A3 or COL4A4 (six with single and one with two heterozygous variants) from a cohort of 70 families with a diagnosis of hereditary FSGS. The predominant clinical finding at diagnosis was proteinuria associated with hematuria. In all seven families, there were individuals with nephrotic-range proteinuria with histologic features of FSGS by light microscopy. In one family, electron microscopy showed thin GBM, but four other families had variable findings inconsistent with classical Alport nephritis. There was no recurrence of disease after kidney transplantation. Families with COL4A3 and COL4A4 variants that segregated with disease represent 10% of our cohort. Thus, COL4A3 and COL4A4 variants should be considered in the interpretation of next-generation sequencing data from such patients. Furthermore, this study illustrates the power of molecular genetic diagnostics in the clarification of renal phenotypes. [ABSTRACT FROM AUTHOR]

Focal and segmental glomerulosclerosis (FSGS) is a major cause of end-stage kidney disease. Recent advances in molecular genetics show that defects in the podocyte play a major role in its pathogenesis and mutations in inverted formin 2 (INF2) cause autosomal dominant FSGS. In order to delineate the role of INF2 mutations in familial and sporadic FSGS, we sought to identify variants in a large cohort of patients with FSGS. A secondary objective was to define an approach for genetic screening in families with autosomal dominant disease. A total of 248 individuals were identified with FSGS, of whom 31 had idiopathic disease. The remaining patients clustered into 64 families encompassing 15 from autosomal recessive and 49 from autosomal dominant kindreds. There were missense mutations in 8 of the 49 families with autosomal dominant disease. Three of the detected variants were novel and all mutations were confined to exon 4 of INF2, a regulatory region responsible for 90% of all changes reported in FSGS due to INF2 mutations. Thus, in our series, INF2 mutations were responsible for 16% of all cases of autosomal dominant FSGS, with these mutations clustered in exon 4. Hence, screening for these mutations may represent a rapid, non-invasive and cost-effective method for the diagnosis of autosomal dominant FSGS. [ABSTRACT FROM AUTHOR]

Glycogen storage disease type Ia (GSD-Ia) is caused by the deficiency of glucose-6-phosphatase (G6Pase). Long-term complications of GSD-Ia include life-threatening hypoglycemia and proteinuria progressing to renal failure. A double-stranded (ds) adeno-associated virus serotype 2 (AAV2) vector encoding human G6Pase was pseudotyped with four serotypes, AAV2, AAV7, AAV8, and AAV9, and we evaluated efficacy in 12-day-old G6pase (−/−) mice. Hypoglycemia during fasting (plasma glucose <100 mg/dl) was prevented for >6 months by the dsAAV2/7, dsAAV2/8, and dsAAV2/9 vectors. Prolonged fasting for 8 hours revealed normalization of blood glucose following dsAAV2/9 vector administration at the higher dose. The glycogen content of kidney was reduced by >65% with both the dsAAV2/7 and dsAAV2/9 vectors, and renal glycogen content was stably reduced between 7 and 12 months of age for the dsAAV2/9 vector-treated mice. Every vector-treated group had significantly reduced glycogen content in the liver, in comparison with untreated G6pase (−/−) mice. G6Pase was expressed in many renal epithelial cells of with the dsAAV2/9 vector for up to 12 months. Albuminuria and renal fibrosis were reduced by the dsAAV2/9 vector. Hepatorenal correction in G6pase (−/−) mice demonstrates the potential of AAV vectors for the correction of inherited diseases of metabolism. [ABSTRACT FROM AUTHOR]

Steroid-sensitive nephrotic syndrome (SSNS) accounts for >80% of cases of nephrotic syndrome in childhood. However, the etiology and pathogenesis of SSNS remain obscure. Hypothesizing that coding variation may underlie SSNS risk, we conducted an exome array association study of SSNS. We enrolled a discovery set of 363 persons (214 South Asian children with SSNS and 149 controls) and genotyped them using the Illumina HumanExome Beadchip. Four common single nucleotide polymorphisms (SNPs) in HLA-DQA1 and HLA-DQB1 (rs1129740, rs9273349, rs1071630, and rs1140343) were significantly associated with SSNS at or near the Bonferroni-adjusted P value for the number of single variants that were tested (odds ratio, 2.11; 95% confidence interval, 1.56 to 2.86; P=1.68×10(-6) (Fisher exact test). Two of these SNPs-the missense variants C34Y (rs1129740) and F41S (rs1071630) in HLA-DQA1-were replicated in an independent cohort of children of white European ancestry with SSNS (100 cases and ≤589 controls; P=1.42×10(-17)). In the rare variant gene set-based analysis, the best signal was found in PLCG2 (P=7.825×10(-5)). In conclusion, this exome array study identified HLA-DQA1 and PLCG2 missense coding variants as candidate loci for SSNS. The finding of a MHC class II locus underlying SSNS risk suggests a major role for immune response in the pathogenesis of SSNS., (Copyright © 2015 by the American Society of Nephrology.)

FSGS is a clinical disorder characterized by focal scarring of the glomerular capillary tuft, podocyte injury, and nephrotic syndrome. Although idiopathic forms of FSGS predominate, recent insights into the molecular and genetic causes of FSGS have enhanced our understanding of disease pathogenesis. Here, we report a novel missense mutation of the transcriptional regulator Wilms' Tumor 1 (WT1) as the cause of nonsyndromic, autosomal dominant FSGS in two Northern European kindreds from the United States. We performed sequential genome-wide linkage analysis and whole-exome sequencing to evaluate participants from family DUK6524. Subsequently, whole-exome sequencing and direct sequencing were performed on proband DNA from family DUK6975. We identified multiple suggestive loci on chromosomes 6, 11, and 13 in family DUK6524 and identified a segregating missense mutation (R458Q) in WT1 isoform D as the cause of FSGS in this family. The identical mutation was found in family DUK6975. The R458Q mutation was not found in 1600 control chromosomes and was predicted as damaging by in silico simulation. We depleted wt1a in zebrafish embryos and observed glomerular injury and filtration defects, both of which were rescued with wild-type but not mutant human WT1D mRNA. Finally, we explored the subcellular mechanism of the mutation in vitro. WT1(R458Q) overexpression significantly downregulated nephrin and synaptopodin expression, promoted apoptosis in HEK293 cells and impaired focal contact formation in podocytes. Taken together, these data suggest that the WT1(R458Q) mutation alters the regulation of podocyte homeostasis and causes nonsyndromic FSGS., (Copyright © 2015 by the American Society of Nephrology.)

FSGS is characterized by segmental scarring of the glomerulus and is a leading cause of kidney failure. Identification of genes causing FSGS has improved our understanding of disease mechanisms and points to defects in the glomerular epithelial cell, the podocyte, as a major factor in disease pathogenesis. Using a combination of genome-wide linkage studies and whole-exome sequencing in a kindred with familial FSGS, we identified a missense mutation R431C in anillin (ANLN), an F-actin binding cell cycle gene, as a cause of FSGS. We screened 250 additional families with FSGS and found another variant, G618C, that segregates with disease in a second family with FSGS. We demonstrate upregulation of anillin in podocytes in kidney biopsy specimens from individuals with FSGS and kidney samples from a murine model of HIV-1-associated nephropathy. Overexpression of R431C mutant ANLN in immortalized human podocytes results in enhanced podocyte motility. The mutant anillin displays reduced binding to the slit diaphragm-associated scaffold protein CD2AP. Knockdown of the ANLN gene in zebrafish morphants caused a loss of glomerular filtration barrier integrity, podocyte foot process effacement, and an edematous phenotype. Collectively, these findings suggest that anillin is important in maintaining the integrity of the podocyte actin cytoskeleton., (Copyright © 2014 by the American Society of Nephrology.)

Primary vesicoureteral reflux (VUR) is the most common congenital anomaly of the kidney and the urinary tract, and it is a major risk factor for pyelonephritic scarring and CKD in children. Although twin studies support the heritability of VUR, specific genetic causes remain elusive. We performed a sequential genome-wide linkage study and whole-exome sequencing in a family with hereditary VUR. We obtained a significant multipoint parametric logarithm of odds score of 3.3 on chromosome 6p, and whole-exome sequencing identified a deleterious heterozygous mutation (T3257I) in the gene encoding tenascin XB (TNXB in 6p21.3). This mutation segregated with disease in the affected family as well as with a pathogenic G1331R change in another family. Fibroblast cell lines carrying the T3257I mutation exhibited a reduction in both cell motility and phosphorylated focal adhesion kinase expression, suggesting a defect in the focal adhesions that link the cell cytoplasm to the extracellular matrix. Immunohistochemical studies revealed that the human uroepithelial lining of the ureterovesical junction expresses TNXB, suggesting that TNXB may be important for generating tensile forces that close the ureterovesical junction during voiding. Taken together, these results suggest that mutations in TNXB can cause hereditary VUR.

Controlled activation of the complement system, a key component of innate immunity, enables destruction of pathogens with minimal damage to host tissue. Complement factor H (CFH), which inhibits complement activation, and five CFH-related proteins (CFHR1-5) compose a family of structurally related molecules. Combined deletion of CFHR3 and CFHR1 is common and confers a protective effect in IgA nephropathy. Here, we report an autosomal dominant complement-mediated GN associated with abnormal increases in copy number across the CFHR3 and CFHR1 loci. In addition to normal copies of these genes, affected individuals carry a unique hybrid CFHR3-1 gene. In addition to identifying an association between these genetic observations and complement-mediated kidney disease, these results provide insight into the protective role of the combined deletion of CFHR3 and CFHR1 in IgA nephropathy.

FSGS is a clinicopathologic entity characterized by nephrotic syndrome and progression to ESRD. Although the pathogenesis is unknown, the podocyte seems to play a central role in this disorder. Here, we present six kindreds with hereditary FSGS that did not associate with mutations in known causal genes, and we report a new locus for the disease on chromosome 2p15 in one kindred. We performed genome-wide linkage analysis and refined the linkage area with microsatellite markers and haplotype analysis to define the minimal candidate region. Genome-wide linkage analysis yielded a maximum two-point logarithm of odds (LOD) score of 3.6 for the six families on chromosome 2p. One family contributed the largest proportion of the additive score (LOD 2.02) at this locus. Multipoint parametric LOD score calculation in this family yielded a significant LOD score of 3.1 at markers D2S393 and D2S337, and fine mapping of this region with microsatellite markers defined a minimal candidate region of 0.9 Mb with observed recombinations at markers D2S2332 and RS1919481. We excluded the remaining five families from linkage to this region by haplotype analysis. These data support a new gene locus for familial FSGS on chromosome 2p15. Identification of the mutated gene at this locus may provide further insight into the disease mechanisms of FSGS.

FSGS is a pathologic lesion that frequently causes the nephrotic syndrome and ensuing renal failure. The cause remains unknown in the majority of individuals; however, in the past two decades, rare familial forms have been identified. It has been suggested that known genetic causes of the hereditary form of this disease account for upwards of 18% of cases. Mutations in five genes have been found to cause inherited nephrotic syndromes and FSGS. In this article, I discuss the phenotypic characteristics of hereditary FSGS and the transient receptor potential cation channel 6 (TRPC6) protein, which is the genetic impetus for an autosomal dominant form of FSGS. The TRP channels have been implicated in varied biologic functions such as mechanosensation, ion homeostasis, cell growth, and phospholipase C-dependent calcium entry into cells. The mutated ion channel causes an increase in calcium transients. Current evidence also suggests that blocking TRPC6 channels may be of therapeutic benefit in idiopathic FSGS, a disease with a generally poor prognosis. Preliminary experiments reveal that the commonly used immunosuppressive agent FK-506 can inhibit TRPC6 activity in vivo. This creates the intriguing possibility that blocking TRPC6 channels within the podocyte may translate into long-lasting clinical benefits in patients with FSGS.

Background: Post-cardiac surgery renal dysfunction is a common, serious, multifactorial disorder, with interpatient variability predicted poorly by preoperative clinical, procedural, and biological markers. Therefore, we tested the hypothesis that selected gene variants are associated with acute renal injury, reflected by a serum creatinine level increase after cardiac surgery., Methods: One thousand six hundred seventy-one patients undergoing aortocoronary surgery were studied. Clinical covariates were recorded. DNA was isolated from preoperative blood; mass spectrometry was used for genotype analysis. A model was developed relating clinical and genetic factors to postoperative acute renal injury., Results: A race effect was found; therefore, Caucasians and African Americans were analyzed separately. Overall, clinical factors alone account poorly for postoperative renal injury, although more so in African Americans than Caucasians. When 12 candidate polymorphisms were assessed, 2 alleles (interleukin 6 -572C and angiotensinogen 842C) showed a strong association with renal injury in Caucasians (P < 0.0001; >50% decrease in renal filtration when they present together). Using less stringent criteria for significance (0.01 > P > 0.001), 4 additional polymorphisms are identified (apolipoproteinE 448C [4], angiotensin receptor1 1166C, and endothelial nitric oxide synthase [eNOS] 894T in Caucasians; eNOS 894T and angiotensin-converting enzyme deletion and insertion in African Americans). Adding genetic to clinical factors resulted in the best model, with overall ability to explain renal injury increasing approximately 4-fold in Caucasians and doubling in African Americans (P < 0.0005)., Conclusion: In this study, we identify genetic polymorphisms that collectively provide 2- to 4-fold improvement over preoperative clinical factors alone in explaining post-cardiac surgery renal dysfunction. From a mechanistic perspective, most identified genetic variants are associated with increased renal inflammatory and/or vasoconstrictor responses.

Parkin, an E2-dependent ubiquitin protein ligase, carries pathogenic mutations in patients with autosomal recessive juvenile parkinsonism, but its role in the late-onset form of Parkinson's disease (PD) is not firmly established. Previously, we detected linkage of idiopathic PD to the region on chromosome 6 containing the Parkin gene (D6S305, logarithm of odds score, 5.47) in families with at least one subject with age at onset (AAO) younger than 40 years. Mutation analysis of the Parkin gene in the 174 multiplex families from the genomic screen and 133 additional PD families identified mutations in 18% of early-onset and 2% of late-onset families (5% of total families screened). The AAO of patients with Parkin mutations ranged from 12 to 71 years. Excluding exon 7 mutations, the mean AAO of patients with Parkin mutations was 31.5 years. However, mutations in exon 7, the first RING finger (Cys253Trp, Arg256Cys, Arg275Trp, and Asp280Asn) were observed primarily in heterozygous PD patients with a much later AAO (mean AAO, 49.2 years) but were not found in controls in this study or several previous reports (920 chromosomes). These findings suggest that mutations in Parkin contribute to the common form of PD and that heterozygous mutations, especially those lying in exon 7, act as susceptibility alleles for late-onset form of Parkinson disease.