Search PubMed⌕ Search

Biomedical subjects

R R Frants

Publications and source records attributed to R R Frants.

At least 199 records · Page 11Linked to original sources
PubMed1990

Characterisation of the LDL receptor in Epstein-Barr virus transformed lymphocytes.

Non-dividing human lymphocytes were transformed upon infection with the Epstein-Barr virus (EBV) into lymphoblasts which are capable of continuous growth in culture. We studied the properties of the LDL receptor in EBV-transformed human lymphocytes (EBV-L) by binding experiments and by ligand blotting. EBV-L show a high affinity binding of LDL in the same order of magnitude as found with fibroblasts; EBV-L obtained from a homozygous familial hypercholesterolemic (FH) patient fail to express LDL receptor activity. Similar to that of fibroblasts, the LDL receptor activity in EBV-L is Ca2(+)-dependent and is down-regulated by the presence of an exogenous source of cholesterol in the medium. The LDL receptor protein of EBV-L has an apparent molecular weight of 130,000. Since our results show that EBV-L display a LDL receptor protein similar to the LDL receptor present in fibroblasts, we conclude that in comparison with other cell types the EBV-L offer a suitable model system to investigate LDL receptor protein abnormalities in FH patients.

Cell Transformation, Viral↗
PubMed1990

Influence of apo E polymorphism on the response to simvastatin treatment in patients with heterozygous familial hypercholesterolemia.

In a group of 120 patients with heterozygous familial hypercholesterolemia (FH) the influence of the apolipoprotein E (apoE) polymorphism on pre-treatment plasma lipid levels and on the response to treatment with simvastatin was studied. The apoE phenotype distribution did not differ significantly between the FH group and a sample group of the Dutch population. Differences in pre-treatment lipid levels were not related to the apoE polymorphism in this FH population. After 12 weeks use of a daily dose of 40 mg simvastatin, the plasma total cholesterol, low density lipoprotein (LDL)-cholesterol and plasma triglyceride levels were reduced on average by 33%, 38% and 19%, respectively. At the same time high density lipoprotein (HDL)-cholesterol concentration increased on average by 7%. In the combined FH patient group (males and females) a considerable interindividual variation in response to simvastatin was observed, but was not related to the apoE polymorphism. However, considering males and females separately, we found that female FH patients with the apoE3E3 phenotype responded better on simvastatin treatment with respect to LDL-cholesterol than male FH patients with the apoE3E3 phenotype.

Adult↗
PubMed1990

Rearrangements in the LDL receptor gene in Dutch familial hypercholesterolemic patients and the presence of a common 4 kb deletion.

DNA samples from 53 unrelated Dutch patients with familial hypercholesterolemia (FH) were screened for rearrangements in the gene for the LDL receptor (LDLR) by Southern analysis. Four different mutations have been detected by hybridisation of BglII digested genomic DNA with an exon 10-14 containing cDNA probe. The mutations are defined by a 7 kb insertion near exon 11, a partial gene duplication encompassing exons 9-12, a 4 kb deletion of exons 7 and 8 and an 0.4 kb deletion comprising the 5'-part of exon 16. These four different rearrangements in the LDLR gene account for 17% of the mutations in the Dutch FH population sample. Interestingly, the 4 kb deletion was detected in 5 unrelated FH patients (9.5%) and appeared to be identical to the deletion previously described (Russell, D.W. et al., Arteriosclerosis, 9 (Suppl. I) (1989) I-8; Russell, D.W. et al., Cold Spring Harbor Symp. Quant. Biol., 51 (1987) 401). in an FH patient of Dutch origin. This suggests that the 4 kb deletion is a common mutation in the Dutch FH population.

Chromosome Deletion↗
PubMed1990

Facioscapulohumeral muscular dystrophy gene in Dutch families is not linked to markers for familial adenomatous polyposis on the long arm of chromosome 5.

Cosegregation of facioscapulohumeral muscular dystrophy (FSHD) and familial adenomatous polyposis (FAP) has been described in two small families. The gene for FAP is located on the long arm of chromosome 5. We studied two large Dutch families with FSHD and found no evidence for linkage with gene markers closely linked to FAP. These results strongly suggest that the FSHD gene segregating in the Dutch families is not localized close to the FAP locus on chromosome 5.

Adenomatous Polyposis Coli↗
PubMed1990

Evolution of the human alpha-amylase multigene family through unequal, homologous, and inter- and intrachromosomal crossovers.

Human amylase haplotypes differ from each other by different numbers of a long direct repeat unit of approximately 100 kb, encompassing two complete salivary amylase genes and one amylase pseudogene lacking the first three exons. The two salivary genes are part of a 75-kb-long inverted repeat. Two short sequences, hybridizing with a probe containing exons 1-3, were found in the central part of the inverted repeat. Sequencing showed that these fragments, designated r, contain exon 3 sequences. We present evidence that these r-fragments and the pseudogene most likely are remnants of the same ancestral pancreatic gene. We determined the orientation of the exon 3 sequences present in the r-fragment and show that an inversion can explain their origination. Hybridization studies, using random fragments from the intergenic region of the AMY gene cluster as probes, enabled us to detect more extended homologous regions in this cluster than were found previously on the basis of restriction maps only. Together, these results allow us to present a model for the evolution of the human amylase multigene family by a number of consecutive events involving inter- and intrachromosomal crossovers.

Base Sequence↗
PubMed1990

Pseudoinflammatory fundus dystrophy: a follow-up study.

We have performed a reinvestigation of a family with a presumably autosomal recessive form of pseudoinflammatory dystrophy, which we have followed for 25 years. The symptoms in this family are subretinal haemorrhages appearing at age 13-40 years in the central fundus, resulting in glial cicatrication in the outer retinal layers, progressive myopia and profound choroidal atrophy in the advanced stages of the disease. During the follow-up study, a new affected subject was found in the younger generation, and two collateral cases, who had earlier been considered as probably affected subjects, were now considered to have other fundus affections. The new case is the daughter of an affected female. The possibilities of an autosomal dominant mode of inheritance or pseudodominance are discussed. Extended genealogical studies showed that the parents of all the affected subjects, with the exception of the new case, have their origin in an area which was isolated until recently and have several common ancestors within the last 8-10 generations. Recessive inheritance also logically explains the appearance of the disease in so few other members in the vertical line of the family. To this fundus dystrophy, the rule of Lenz seems to apply: If more or less the same phenotype can be caused by both a recessive and a dominant gene, the phenotype caused by the recessive gene is generally manifested earlier and by more severe symptoms.

Adolescent↗
PubMed1990

Genetic heterogeneity in familial dysbetalipoproteinemia. The E2(lys146----gln) variant results in a dominant mode of inheritance.

As determined by isoelectric focusing, most patients with familial dysbetalipoproteinemia (FD) exhibit the homozygous apolipoprotein (apo) E2E2 phenotype. Only rarely does FD develop in the more common heterozygous phenotypes E3E2 or E4E2. In fact, only 1 to 4% of the E2E2 homozygotes will develop FD. We wondered whether this reduced penetrance of FD in E2E2 homozygotes could be due to additional heterogeneity in the APOE*2 allele. In the literature a number of different mutations causing an E2 isoelectric focusing variant have been described. To study the genetic heterogeneity of the APOE gene, hybridization of enzymatically amplified genomic DNA with mutation-specific oligonucleotide probes was applied. All FD patients (n = 40) with the E2E2 phenotype appeared to be homozygous for the common E2(arg158----cys) mutation. However, all three unrelated patients with the E3E2 phenotype exhibited the rare E2(lys146----gln) mutation due to an A----C substitution at nucleotide position 3,847 of the APOE gene. This mutation was not found among normolipidemic individuals with the E2E2 (n = 13) or E3E2 phenotype (n = 120) selected from a random population sample. Family studies of the three probands heterozygous for the E*2(lys146----gln) allele showed that this rare allele predisposes to FD with high penetrance. We conclude that FD is a genetically heterogeneous disease entity, displaying a recessive mode of inheritance with strongly reduced penetrance in case of the common E2(arg158----cys) variant and with a dominant mode of inheritance with high penetrance in case of the rare E2(lys146----gln) mutant. It should be noted that in this dominant form presymptomatic diagnosis is possible.

Alleles↗
PubMed1989

Apolipoprotein E*3-Leiden allele results from a partial gene duplication in exon 4.

The apolipoprotein E3-Leiden variant has been shown to be associated with familial dysbetalipoproteinemia (FD) in a dominant manner (Havekes et al., Hum Genet 1986;73:157-163). Applying the polymerase chain reaction technique, we have cloned and sequenced relevant parts of both APOE alleles of the original proband. In exon 4 of the E*3-Leiden allele a partial gene duplication encompassing 21 nucleotides was found, leading to a tandem repeat of the codons 120-126 or 121-127. Using an E3-Leiden mutation specific oligonucleotide probe, the same mutation was found in two additional independently ascertained FD patients with an E3E3 phenotype based on isoelectric focusing. The E*3-Leiden mutation will be useful in the elucidation of the etiology of dominantly inherited forms of FD.

Amino Acid Sequence↗
PubMed1989

A Pro----Leu substitution in codon 369 of the alpha-1-antitrypsin deficiency variant PI MHeerlen.

The molecular defect has been elucidated in the alpha-1-antitrypsin (PI) gene of a patient with a serum level of only 5 mg/100 ml and a PI M-like phenotype, designated PI MHeerlen. The restriction fragment patterns obtained by probes covering the whole gene and flanking sequences were normal, suggesting no major rearrangements. The nucleotide sequence of the exons, intron/exon junctions, and a part of the promoter region is similar to that of a PI M1(Ala213) gene except for an C----T mutation in codon 369, causing a Pro----Leu substitution. Haplotype analysis and oligonucleotide hybridization studies demonstrated the homozygous state of the mutation in the index case. It is most likely that the Pro369----Leu substitution is responsible for the low serum alpha-1-antitrypsin concentration of the patient because this mutation is solely confined to the PI MHeerlen allele and no other relevant mutations could be revealed. As proline is important for the secondary and tertiary structure of proteins, the mutation may cause an abnormal processing of the nascent polypeptide. The same mutation was observed in two unrelated subjects known to carry a PI allele giving a low serum alpha-1-antitrypsin level.

Blotting, Southern↗
PubMed1989

Family and population studies on the human pepsinogen A multigene family.

Human pepsinogen A (PGA) displays highly polymorphic isozymogen patterns after polyacrylamide gel electrophoresis and activity staining. The patterns differ with respect to the presence and the relative intensity of the individual fractions. Family studies strongly suggest that these isozymogen patterns are encoded by allelic haplotypes, encompassing different numbers and types of PGA genes. In this paper, we confirm the essential features of this multigene model. We establish the relationship between the haplotypes and the corresponding isozymogen patterns by determination of the PGA polymorphism at both the DNA and the protein level in 117 Dutch individuals, 60 of whom were unrelated. The combination of HindIII and EcoRI restriction fragment length polymorphisms (RFLPs) has enabled us to define different haplotypes, which are shown to segregate within families. Most genes are characterized by their specific EcoRI fragments. The HindIII RFLP is in strong linkage disequilibrium with PGA genes showing strong expression of the relevant isozymogen. Although a general picture of the relationship between genotypes and phenotypes is emerging, there are exceptions, suggesting that rare haplotypes evolve by unique crossover events.

DNA↗
PubMed1989

The human alpha-amylase multigene family consists of haplotypes with variable numbers of genes.

Polymorphic amylase protein patterns have suggested the presence in the human genome of various haplotypes encoding these allozymes. To investigate the genomic organization of the human alpha-amylase genes, we isolated the pertinent genes from a cosmid library constructed of DNA from an individual expressing three different salivary amylase allozymes. From the restriction maps of the overlapping cosmids and a comparison of these maps with the restriction enzyme patterns of DNA from the donor and family members, we were able to identify two haplotypes consisting of very different numbers of salivary amylase genes. The short haplotype contains two pancreatic genes (AMY2A and AMY2B) and one salivary amylase gene (AMY1C), arranged in the order 2B-2A-1C, encompassing a total length of approximately 100 kb. The long haplotype spans about 300 kb and contains six additional genes arranged in two repeats, each one consisting of two salivary amylase genes (AMY1A and AMY1B) and a pseudogene lacking the first three exons (AMYP1). The order of the amylase genes within the repeat is 1A-1B-P1. All genes are in a head-to-tail orientation except AMY1B, which has the reverse orientation with respect to the other genes. Analysis of somatic cell hybrids confirmed the presence of these short and long haplotypes. Furthermore, we present evidence for the existence of additional haplotypes in the human population and propose a general model for the evolution of the human alpha-amylase multigene family. A general designation 2B-2A-(1A-1B-P)n-1C can describe these haplotypes, n being 0 and 2 for the short and the long haplotypes presented in this paper, respectively.

Biological Evolution↗
PubMed1989

Exclusion of the dysplastic nevus syndrome (DNS) locus from the short arm of chromosome 1 by linkage studies in Dutch families.

Familial dysplastic nevus syndrome (DNS) is an autosomal dominant premalignant condition characterized by multiple large moles of variable size and color and a strongly increased risk for cutaneous malignant melanoma. In order to determine the chromosomal localization of the DNS gene, linkage studies were initiated in six large Dutch families. No support was obtained for linkage between the loci for DNS and the rhesus blood group on chromosome 1. Data from additional markers (DNF15S1, D1Z2, FUCA1, D1S17, D1S57, and PGM1) make it possible to exclude the DNS gene from the short arm of chromosome 1 in these Dutch families.

Chromosomes, Human, Pair 1↗
PubMed1989

Autosomal dominant aniridia linked to the chromosome 11p13 markers catalase and D11S151 in a large Dutch family.

In a large pedigree with autosomal dominant aniridia, we found close linkage between the aniridia locus AN2 and the markers catalase (CAT) (zeta = 7.27 at theta = 0.00) and D11S151 (zeta = 3.86 at theta = 0.10) flanking the AN2 locus on 11p13. Positive lod scores were also obtained for the 11p13----11p14 markers D11S16 and FSHB with the linkage group CAT/AN2/D11S151. We conclude that the autosomal dominant aniridia in this family is due to a mutation at the AN2 locus on 11p13. We have excluded linkage (zeta less than -2 at theta less than 0.18) between the aniridia and the chromosome 2p25 marker D2S1 (linked to ACP1).

Aniridia↗
PubMed1988

Cloning and characterization of an alpha 1-antitrypsin like gene 12 KB downstream of the genuine alpha 1-antitrypsin gene.

Cosmid clones containing alpha 1-antitrypsin (alpha 1AT) gene sequences were observed to contain alpha 1AT-like sequences approximately 12 kb downstream of the authentic alpha 1AT gene. Restriction mapping suggested the alpha 1AT-like gene lacks promoter sequences. Cosmid clones from one library contained a truncated alpha 1AT-like gene with a deletion encompassing 1745 bp, including the whole exon IV and part of exon V. Sequencing of exon II of this truncated gene revealed a nucleotide homology of 76% but included critical mutations in the start codon (ATG - greater than ATA) and the 3' exon-intron junction. These results strongly suggest that the truncated alpha 1AT-like gene is a pseudogene, which is present at a frequency of 0.30 in the Dutch population.

Animals↗
PubMed1988

Cloning and sequencing of rhesus monkey pepsinogen A cDNA.

The complete nucleotide sequence of Rhesus monkey (Macaca mulatta) pepsinogen A (PGA) cDNA was determined from two partially overlapping cDNA clones, covering the whole coding sequence and part of the flanking sequences. The nucleotide and deduced amino acid sequences were compared to known PGA sequences from other species. The degree of similarity with human PGA appeared to be 96% at the nucleotide sequence level and 94% at the amino acid sequence level. In the coding region the divergence was highest in the activation peptide. The amino acid sequence similarity between Japanese monkey (Macaca fuscata) PGA and Rhesus monkey PGA was shown to be 99%. Using the cDNA as probe in Southern hybridization of EcoRI-digested human and Rhesus monkey genomic DNAs, PGA patterns with inter-individual differences were observed. The hybridization patterns are compatible with the existence of a PGA multigene family in both species.

Amino Acid Sequence↗