Genetic variation of DKK3 may modify renal disease severity in ADPKD.

Significant variation in the course of autosomal dominant polycystic kidney disease ( ADPKD) within families suggests the presence of effect modifiers. Recent studies of the variation within families harboring PKD1 mutations indicate that genetic background may account for 32 to 42% of the variance in estimated GFR (eGFR) before ESRD and 43 to 78% of the variance in age at ESRD onset, but the genetic modifiers are unknown. Here, we conducted a high-throughput single-nucleotide polymorphism (SNP) genotyping association study of 173 biological candidate genes in 794 white patients from 227 families with PKD1. We analyzed two primary outcomes: (1) eGFR and (2) time to ESRD (renal survival). For both outcomes, we used multidimensional scaling to correct for population structure and generalized estimating equations to account for the relatedness among individuals within the same family. We found suggestive associations between each of 12 SNPs and at least one of the renal outcomes. We genotyped these SNPs in a second set of 472 white patients from 229 families with PKD1 and performed a joint analysis on both cohorts. Three SNPs continued to show suggestive/significant association with eGFR at the Dickkopf 3 (DKK3) gene locus; no SNPs significantly associated with renal survival. DKK3 antagonizes Wnt/beta-catenin signaling, which may modulate renal cyst growth. Pending replication, our study suggests that genetic variation of DKK3 may modify severity of ADPKD resulting from PKD1 mutations.

Epigenetic chromatin modifiers in barley: I. Cloning, mapping and expression analysis of the plant specific HD2 family of histone deacetylases from barley, during seed development and after hormonal treatment.

Epigenetic phenomena have been associated with modifications of chromatin structure. These are achieved, in part, by histone post-translational modifications including acetylations and deacetylations, the later being catalyzed by histone deacetylaces (HDACs). Eukaryotic HDACs are grouped into three major families, RPD3/HDA1, SIR2 and the plant-specific HD2. HDAC genes have been analyzed from model plants such as Arabidopsis, rice and maize and have been shown to be involved in various cellular processes including seed development, vegetative and reproductive growth and responses to abiotic and biotic stress, but reports on HDACs from other crops are limited. In this work two full-length cDNAs (HvHDAC2-1 and HvHDAC2-2) encoding two members of the plant-specific HD2 family, respectively, were isolated and characterized from barley (Hordeum vulgare), an agronomically important cereal crop. HvHDAC2-1 and HvHDAC2-2 were mapped on barley chromosomes 1H and 3H, respectively, which could prove useful in developing markers for marker-assisted selection in breeding programs. Expression analysis of the barley HD2 genes demonstrated that they are expressed in all tissues and seed developmental stages examined. Significant differences were observed among tissues and seed stages, and between cultivars with varying seed size, suggesting an association of these genes with seed development. Furthermore, the HD2 genes from barley were found to respond to treatments with plant stress-related hormones such as jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA) implying an association of these genes with plant resistance to biotic and abiotic stress. The expression pattern of HD2 genes suggests a possible role for these genes in the epigenetic regulation of seed development and stress response.

Evidence for association of endothelial cell nitric oxide synthase gene polymorphism with earlier progression to end-stage renal disease in a cohort of Hellens from Greece and Cyprus.

Nitric oxide (NO) is thought to be an important factor in the deterioration of renal function. A variable-number tandem 27-bp repeat in intron 4 of the endothelial cell nitric oxide synthase (NOS3) gene has been found to be associated with the plasma levels of NO metabolites. Two alleles are of varied frequencies in different populations (a and b). The shorter allele a has been associated in Japanese populations with the progression of renal disease. Here we investigated this hypothesis by studying the putative role of this polymorphism in a Hellenic population of patients with end-stage renal disease (ESRD). We analyzed the genotypes of 361 ESRD patients and 295 healthy Hellens from Greece and Cyprus. The frequencies of NOS3-4bb, NOS3-4ab, and NOS3-4aa were 0.69, 0.27, and 0.03, respectively, in the control group and 0.71, 0.24, and 0.04 in the group of patients. The data in the two populations were analyzed by the chi-square and Fisher's exact tests. The frequencies of these three genotypes of NOS3-4 polymorphism in the Hellenic population of Greece and Cyprus are similar to those observed in other Caucasian populations. Moreover, our results from three patient groups, autosomal dominant polycystic kidney disease (ADPKD), diabetes mellitus (DM), and non-DM, showed that the frequencies of aa and ab genotypes in the patient populations were not significantly different from those observed in the control group. This work indicates that NOS3-4 polymorphism does not show any association with the development of ESRD in this studied European population. However, examination of the data regarding progression to ESRD within 5 years or after more than 5 years following clinical diagnosis of ADPKD provided evidence of statistical difference (p = 0.048, before Bonferroni correction), with faster progression in the group of ADPKD patients who carried allele a.

Frequency of COL4A3/COL4A4 mutations amongst families segregating glomerular microscopic hematuria and evidence for activation of the unfolded protein response. Focal and segmental glomerulosclerosis is a frequent development during ageing.

Familial glomerular hematuria(s) comprise a genetically heterogeneous group of conditions which include Alport Syndrome (AS) and thin basement membrane nephropathy (TBMN). Here we investigated 57 Greek-Cypriot families presenting glomerular microscopic hematuria (GMH), with or without proteinuria or chronic kidney function decline, but excluded classical AS. We specifically searched the COL4A3/A4 genes and identified 8 heterozygous mutations in 16 families (28,1%). Eight non-related families featured the founder mutation COL4A3-p.(G1334E). Renal biopsies from 8 patients showed TBMN and focal segmental glomerulosclerosis (FSGS). Ten patients (11.5%) reached end-stage kidney disease (ESKD) at ages ranging from 37-69-yo (mean 50,1-yo). Next generation sequencing of the patients who progressed to ESKD failed to reveal a second mutation in any of the COL4A3/A4/A5 genes, supporting that true heterozygosity for COL4A3/A4 mutations predisposes to CRF/ESKD. Although this could be viewed as a milder and late-onset form of autosomal dominant AS, we had no evidence of ultrastructural features or extrarenal manifestations that would justify this diagnosis. Functional studies in cultured podocytes transfected with wild type or mutant COL4A3 chains showed retention of mutant collagens and differential activation of the unfolded protein response (UPR) cascade. This signifies the potential role of the UPR cascade in modulating the final phenotype in patients with collagen IV nephropathies.

Characterization and expression analysis of AGAMOUS-like, SEEDSTICK-like, and SEPALLATA-like MADS-box genes in peach (Prunus persica) fruit.

MADS-box genes encode transcriptional regulators that are critical for flowering, flower organogenesis and plant development. Although there are extensive reports on genes involved in flower organogenesis in model and economically important plant species, there are few reports on MADS-box genes in woody plants. In this study, we have cloned and characterized AGAMOUS (AG), SEEDSTICK (STK) and SEPALLATA (SEP) homologs from peach tree (Prunus persica L. Batsch) and studied their expression patterns in different tissues as well as in fruit pericarp during pit hardening. AG- STK- and SEP-like homologs, representative of the C-, D-, E-like MADS-box gene lineages, respectively, play key roles in stamen, carpel, ovule and fruit development in Arabidopsis thaliana. Sequence similarities, phylogenetic analysis and structural characteristics were used to provide classification of the isolated genes in type C (PPERAG), type D (PPERSTK) and type E (PPERSEP1, PPERSEP3, PPERFB9) organ identity genes. Expression patterns were determined and in combination with phylogenetic data provided useful indications on the function of these genes. These data suggest the involvement of MADS-box genes in peach flower and fruit development and provide further evidence for the role of these genes in woody perennial trees that is compatible with their function in model plant species.

A family with the branchio-oto-renal syndrome: clinical and genetic correlations.

BACKGROUND: The branchio-oto-renal (BOR) syndrome is an autosomal dominant disease characterized by hearing loss of early onset, preauricular pits, branchial clefts, and early progressive chronic renal failure in up to 40% of family affected members. So far, it has not received due attention in the adult European nephrology literature and because of the combination of deafness with chronic renal failure it may be confused with the Alport syndrome. The BOR syndrome is caused by mutations in the EYA1 gene that maps on chromosome 8q13.3. METHODS: A three-generation, 20-member large BOR Greek-Cypriot family has been studied and followed up clinically over a 27-year period. The findings in four individuals who developed early onset renal failure are described in detail. Genetic DNA linkage studies have also been carried out. RESULTS: Of the 15 family members at risk, 14 were tested with DNA linkage analysis. Ten members were genetically affected and four were normal. All 10 affected members developed early-onset deafness. Some had different ear lobe abnormalities. Nine affected members had preauricular pits. In some of the patients these pits were deep and prominent while in others they were minor and superficial. Eight affected members had early-onset branchial clefts that needed early corrective surgery without the correct familial diagnosis ever being made. End-stage renal disease (ESRD) developed in four members at ages 36, 14, 17, and 17 with minimal proteinuria, if any. This was due to unilateral renal agenesis with contralateral hypodysplasia or bilateral, severe renal hypodysplasia. CONCLUSION: The BOR syndrome is an infrequent but well-described entity that combines early-onset renal failure and deafness together with branchial clefts and preauricular pits. Renal agenesis and dysplasia are the causes of ESRD in these individuals. Other renal abnormalities include bifid kidneys with double ureters, vesico-ureteric reflux and pelvi-ureteric stenoses. The BOR syndrome should be included in the differential diagnosis of deafness and chronic renal failure in childhood and adolescence.

Genotype-renal function correlation in type 2 autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a common Mendelian disorder that affects approximately 1 in 1000 live births. Mutations of two genes, PKD1 and PKD2, account for the disease in approximately 80 to 85% and 10 to 15% of the cases, respectively. Significant interfamilial and intrafamilial renal disease variability in ADPKD has been well documented. Locus heterogeneity is a major determinant for interfamilial disease variability (i.e., patients from PKD1-linked families have a significantly earlier onset of ESRD compared with patients from PKD2-linked families). More recently, two studies have suggested that allelic heterogeneity might influence renal disease severity. The current study examined the genotype-renal function correlation in 461 affected individuals from 71 ADPKD families with known PKD2 mutations. Fifty different mutations were identified in these families, spanning between exon 1 and 14 of PKD2. Most (94%) of these mutations were predicted to be inactivating. The renal outcomes of these patients, including the age of onset of end-stage renal disease (ESRD) and chronic renal failure (CRF; defined as creatinine clearance < or = 50 ml/min, calculated using the Cockroft and Gault formula), were analyzed. Of all the affected individuals clinically assessed, 117 (25.4%) had ESRD, 47 (10.2%) died without ESRD, 65 (14.0%) had CRF, and 232 (50.3%) had neither CRF nor ESRD at the last follow-up. Female patients, compared with male patients, had a later mean age of onset of ESRD (76.0 [95% CI, 73.8 to 78.1] versus 68.1 [95% CI, 66.0 to 70.2] yr) and CRF (72.5 [95% CI, 70.1 to 74.9] versus 63.7 [95% CI, 61.4 to 66.0] yr). Linear regression and renal survival analyses revealed that the location of PKD2 mutations did not influence the age of onset of ESRD. However, patients with splice site mutations appeared to have milder renal disease compared with patients with other mutation types (P < 0.04 by log rank test; adjusted for the gender effect). Considerable renal disease variability was also found among affected individuals with the same PKD2 mutations. This variability can confound the determination of allelic effects and supports the notion that additional genetic and/or environmental factors may modulate the renal disease severity in ADPKD.