Characterization of the exon structure of the polycystic kidney disease 2 gene (PKD2)

By use of differential display, we have isolated a new early auxin-responsive cDNA in Nicotiana tabacum. Nt-gh3 had 70% identity with the unique GH3 sequence isolated in soybean by Hagen et al. [Planta 162 (1984) 147-153] and is thus the first reported cDNA related to this gene until now. Nt-gh3 mRNA accumulates within a short time after auxin treatment, responds to very low concentrations of NAA (as little as 10[-9] M) and specifically to active auxins. Nt-gh3 mRNA is demonstrated to be one of the most relevant early molecular markers of primary auxin response.     

Potassium citrate/citric acid intake improves renal function in rats with polycystic kidney disease

Polycystic kidney disease (PKD) has been shown to be exacerbated by acidosis or a low potassium intake, and there is evidence that administration of alkali might have a beneficial effect. This study determined whether ingestion of potassium citrate and citric acid would ameliorate PKD. Healthy normal and heterozygous littermate Han:SPRD rats with autosomal dominant PKD were provided with either tap water or 55 mM K3citrate/67 mM citric acid solution (KCitr) to drink starting at the age of 1 mo. Renal clearance measurements and histologic assessments were performed when the rats were 3 mo old. KCitr intake did not affect body weight or urine flow, but completely prevented the decline in GFR found in untreated rats with PKD. In rats that drank tap water, left kidney GFR averaged (in microliter/min per 100 g body wt) 503 +/- 78 (n = 9) in normal animals and 242 +/- 56 (n = 6) in rats with PKD. In rats that drank KCitr, GFR averaged 562 +/- 123 (n = 7) in normal animals and 534 +/- 103 (n = 7) in rats with PKD. Kidneys of rats with PKD were approximately double normal size. KCitr treatment did not affect kidney size, but led to fewer interstitial abnormalities and smaller cysts in cystic kidneys. KCitr ingestion led to a significantly lower (P < 0.001) plasma [K+] in rats with PKD (3.3 +/- 0.2 versus 4.1 +/- 0.2 mEq/L in rats on tap water). Chronic KCitr intake in the young heterozygous Han:SPRD rat with PKD yields a modest improvement of kidney histology and a dramatic improvement in GFR. The mechanism of action of KCitr and the long-term effects of this treatment on renal structure and function in PKD deserve further study.     

Long RT-PCR Amplification of the entire coding sequence of the polycystic kidney disease 1 (PKD1) gene

The peptidoglycan cortex of endospores of Bacillus species is required for maintenance of spore dehydration and dormancy, and the structure of the cortex may also allow it to function in attainment of spore core dehydration. A significant difference between spore and growing cell peptidoglycan structure is the low degree of peptide cross-linking in cortical peptidoglycan; regulation of the degree of this cross-linking is exerted by D,D-carboxypeptidases. We report here the construction of mutant B. subtilis strains lacking all combinations of two and three of the four apparent D, D-carboxypeptidases encoded within the genome and the analysis of spore phenotypic properties and peptidoglycan structure for these strains. The data indicate that while the dacA and dacC products have no significant role in spore peptidoglycan formation, the dacB and dacF products both function in regulating the degree of cross-linking of spore peptidoglycan. The spore peptidoglycan of a dacB dacF double mutant was very highly cross-linked, and this structural modification resulted in a failure to achieve normal spore core dehydration and a decrease in spore heat resistance. A model for the specific roles of DacB and DacF in spore peptidoglycan synthesis is proposed.     

A missense mutation, Val62Ala, in the glucokinase gene in a Norwegian family with maturity-onset diabetes of the young

Hodgkin's disease primarily originating from the chest wall is very rare. A 48-year-old man was admitted to our hospital because of an abnormal shadow on a chest X-ray. Radiographic examinations suggested a neurogenic tumor located in the right second-intercostal space, and it was thus extirpated thoracoscopically. The tumor was thought to have arisen from the subpleural space, probably from a lymph node of the chest wall. The resected specimen measured 5.5 x 2.0 cm in size, and the pathological diagnosis was Hodgkin's disease of the diffuse lymphocyte predominant type. A clinical examination showed no other lesions in any other part of the body, including the bone marrow. Following surgery, adjuvant chemotherapy (COPP-ABVD) was given because of the possible scattering of malignant cells during surgery. To the best of our knowledge, this is the first report of Hodgkin's disease originating in the chest wall.     

Sodium pump distribution is not reversed in the DBA/2FG-pcy, polycystic kidney disease model mouse

Recently, it has been reported that Na,K-ATPase in the renal epithelia of human autosomal dominant polycystic kidney disease and cpk mouse, a murine model of autosomal recessive polycystic kidney disease, mislocates to apical plasma membrane and that mislocated Na,K-ATPase causes the cyst formation. Whether the DBA/2FG-pcy mice, which are presumably a suitable model for autosomal dominant polycystic kidney disease, also exhibit the reversal polarity of Na,K-ATPase localization was examined. Kidneys of newborn DBA/2FG-pcy mice, and those at early and late stages of cyst development were examined by immunohistochemical techniques. At any stage, abnormal distribution of Na,K-ATPase on the apical membranes of tubular epithelial cells could not be detected. It is suggested that cysts can be formed without reversed polarity of Na,K-ATPase distribution in pcy mice.     

Germinal and somatic mutations in the PKD2 gene of renal cysts in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in one of three genes: PKD1 on chromosome 16 accounts for approximately 85% of cases whereas PKD2 on chromosome 4 accounts for approximately 15%. Mutations in the PKD3 gene are rare. All patients present with similar clinical phenotypes, and the cardinal symptom is the formation of fluid-filled cysts in the kidneys. Previous work has provided data supporting the notion that cysts in ADPKD1 are focal in nature and form after loss of function of polycystin 1. This became evident by demonstrating that the normal PKD1 allele was inactivated somatically by loss of heterozygosity or by mutagenesis in a subset of renal or liver cysts examined. We show in this report, for the first time, multiple novel somatic mutations within the PKD2 gene of epithelial cells, in both kidneys of an ADPKD2 patient. From a total of 21 cysts examined, seven (33%) had the same C insertion within the inherited wild-type allele. In two other cysts, a nonsense mutation and a splice site AG deletion had occurred in a PKD2 allele that could not be identified as the inherited wild-type or mutant. We suggest that the autosomal dominant form of ADPKD2 occurs by a cellular recessive mechanism, supporting a two-hit model for cyst formation.     

Confirmation of an association between a polymorphism in exon 3 of the low-density lipoprotein receptor-related protein gene and Alzheimer's disease

C766T, a polymorphism in exon 3 of the gene for the low-density lipoprotein receptor-related protein (LRP), was found to be associated with late-onset Alzheimer's disease (AD). We developed a PCR-restriction enzyme-based assay to analyze this allele in 234 AD patients and 103 controls. We confirmed that the LRP C766T polymorphism was in disequilibrium with AD--the C/C genotype was present in 76% of AD patients and 60% of controls (p < 0.01); however, the LRP polymorphism did not influence age at onset of AD.     

Association between pancreatic cystadenocarcinoma, malignant liver cysts, and polycystic disease of the kidney

Polycystic kidney disease is an autosomal dominant disease that may be associated with cystic disease of the liver. In women, the cysts may develop early and be more troublesome than in men. Cystadenocarcinoma of the pancreas is uncommon, comprising 1% of primary pancreatic malignancies. This case report is the first to describe a familial association between polycystic kidney disease and cystadenocarcinoma of the pancreas and liver in the English medical literature. A patient with autosomal dominant polycystic kidney disease (ADPKD) and multiple hepatic cysts developed cystadenocarcinoma of the pancreas with multiple malignant liver cysts. The patient's mother, sister, and niece had ADPKD, and the patient's sister also died of pancreatic cystadenocarcinoma. We believe that the development of these two disease entities in which the primary pathology is cyst formation has a genetic association.     

Efficacy of taxol in the orpk mouse model of polycystic kidney disease

Studies on conscious Sprague-Dawley rats using intracerebral dialysis in live animals combined with high-performance liquid chromatography with electrochemical detection showed that administration of apomorphine into the nucleus accumbens decreased the levels of dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid in the extracellular space of the dorsal striatum throughout the observation period and produced a transient reduction in the level of homovanillic acid in the dialysate from this structure. The studies demonstrated that reversible exclusion of the nucleus accumbens with procaine produced a transient increase in the levels of dopamine metabolites, without an increase in serotonin metabolites, in the extracellular space of the dorsal striatum. These results demonstrate that the nucleus accumbens affects dopamine metabolism in the striatum, this being mediated by the dopamine-reactive system in the nucleus accumbens.     

The Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene contributes to the interindividual variation in serum C-peptide response during an oral glucose tolerance test: evidence from studies of 231 glucose-tolerant first degree relatives of type 2 diabetic probands

The third form of maturity-onset diabetes of the young is caused by mutations in the hepatocyte nuclear factor-1alpha gene. Recently, we demonstrated an association between a prevalent polymorphism at codon 98, Ala/Val98, of this gene and a 20% decreased insulin release during an oral glucose tolerance test (OGTT) in middle-aged glucose-tolerant Danish Caucasian subjects. The major objective of the present study was to replicate this finding among glucose-tolerant first degree relatives of type 2 diabetic patients of the same ethnic origin. All participants, 231 glucose-tolerant offspring of 62 type 2 diabetic probands, underwent an OGTT with measurements of plasma glucose, serum insulin, and serum C peptide during the test. Thirty-three heterozygous carriers of the Ala/Val variant were identified, whereas no subjects had the variant in its homozygous form. Ala/Val carriers had a 20% reduction in serum C peptide at 30 min during the OGTT (1225+/-636 vs. 1507+/-624 pmol/L; P=0.02) compared to wild-type carriers. No significant differences in serum insulin levels during the OGTT were observed between carriers of the variant and Ala/Ala homozygotes. In conclusion, among Danish glucose-tolerant first degree relatives of type 2 diabetic patients the Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene is associated with a decreased serum C-peptide secretion during an OGTT. This finding confirms our previously reported observation of the functional importance of the variant to insulin secretion during an OGTT among middle-aged healthy subjects.     

Thermus thermophilus: a link in evolution of the tRNA-dependent amino acid amidation pathways

Thermus thermophilus possesses an aspartyl-tRNA synthetase (AspRS2) able to aspartylate efficiently tRNAAsp and tRNAAsn. Aspartate mischarged on tRNAAsn then is converted into asparagine by an omega amidase that differs structurally from all known asparagine synthetases. However, aspartate is not misincorporated into proteins because the binding capacity of aminoacylated tRNAAsn to elongation factor Tu is only conferred by conversion of aspartate into asparagine. T. thermophilus additionally contains a second aspartyl-tRNA synthetase (AspRS1) able to aspartylate tRNAAsp and an asparaginyl-tRNA synthetase able to charge tRNAAsn with free asparagine, although the organism does not contain a tRNA-independent asparagine synthetase. In contrast to the duplicated pathway of tRNA asparaginylation, tRNA glutaminylation occurs in the thermophile via the usual pathway by using glutaminyl-tRNA synthetase and free glutamine synthesized by glutamine synthetase that is unique. T. thermophilus is able to ensure tRNA aminoacylation by alternative routes involving either the direct pathway or by conversion of amino acid mischarged on tRNA. These findings shed light on the interrelation between the tRNA-dependent and tRNA-independent pathways of amino acid amidation and on the processes involved in fidelity of the aminoacylation systems.     

Somatic mutations of the PTEN/MMAC1 gene in fifteen Japanese endometrial cancers: evidence for inactivation of both alleles

Loss of heterozygosity (LOH) of chromosome 10q is observed in approximately 40% of endometrial cancers. Mutations in PTEN/MMAC1, a gene recently isolated from the 10q23 region, are responsible for two dominantly inherited neoplastic syndromes, Cowden disease and Bannayan-Zonana syndrome. Somatic mutations of this gene have also been detected in sporadic cancers of the brain, prostate and breast. To investigate the potential role of this putative tumor suppressor gene in endometrial carcinogenesis as well, we examined 46 primary endometrial cancers for LOH at the 10q23 region, and for mutations in the entire coding region and exon-intron boundaries of the PTEN/MMAC1 gene. LOH was identified in half of the 38 informative cases, and subtle somatic mutations were detected in 15 tumors (33%). Our results suggest that of the genes studied so far in endometrial carcinomas, PTEN/MMAC1 is the most commonly mutated one, and that inactivation of both copies by allelic loss and/or mutation, a pattern that defines genes as "tumor suppressors," contributes to tumorigenesis in endometrial cancers.