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Biomedical subjects

R R Frants

Publications and source records attributed to R R Frants.

At least 37 records · Page 2Linked to original sources
PubMed2003

Gene expression profiling identifies tumour markers potentially playing a role in uveal melanoma development.

Microarray is a powerful tool to compare the gene expression of different tumour specimens and cell lines simultaneously and quantitatively. To get a better insight into genes that are involved in uveal melanoma tumorigenesis, we compared the gene expression profiles of 12 different uveal melanoma cell lines with three melanocyte cell cultures obtained from healthy donor eyes. Gene expression profiles were obtained by nylon filter arrays, containing 1176 gene spots related to cancer development. The expression levels of selected genes were validated on cell lines and primary uveal melanomas by real time RT-PCR, and were subsequently included in cluster analysis. Four candidate tumour markers, Laminin Receptor 1, Endothelin 2, Von Hippel Lindau Binding protein 1 and Cullin 2, have been selected from genes that were differentially expressed in the uveal melanoma cell lines compared to the normal uveal melanocytes. In primary uveal melanomas, these four markers could discriminate between two classes of uveal melanoma, which may be indicative of a differential disease process.

Biomarkers, Tumor↗
PubMed2003

Possible phenotypic dosage effect in patients compound heterozygous for FSHD-sized 4q35 alleles.

OBJECTIVE: Autosomal dominant facioscapulohumeral muscular dystrophy (FSHD) is associated with a contraction of the D4Z4 repeat array on chromosome 4. So far, homozygosity or compound heterozygosity for FSHD alleles has not been described, and it has been debated whether the absence of such subjects is because of the rarity or the lethality of the disorder. METHODS: Two unrelated families in which the probands are compound heterozygous for two FSHD-sized alleles were studied. Clinical examination, pulsed-field gel electrophoresis (PFGE) studies of DNA with probes proximal and distal to D4Z4, and cytogenetic analysis of metaphase chromosomes by FISH were performed. RESULTS: Complementary molecular and cytogenetic approaches confirmed the chromosome 4qA origin of all FSHD-sized repeat arrays that segregate in the families. CONCLUSIONS: Heterozygosity for FSHD-sized alleles is compatible with life in men and women. A possible dosage effect was observed in both probands in whom each 4qA allele contributed to the FSHD phenotype. Because at least one of the FSHD alleles in both families showed an unusual low penetrance, the authors propose that susceptibility for FSHD is partly determined by intrinsic properties of the disease allele other than the residual D4Z4 repeat size alone.

Aged↗
PubMed2003

D4F104S1 deletion in facioscapulohumeral muscular dystrophy: phenotype, size, and detection.

BACKGROUND: The facioscapulohumeral muscular dystrophy (FSHD) locus maps to 4q35 where it is closely linked to D4F104S1 (p13E-11), a probe that recognizes the pathognomonic FSHD deletion involving the subtelomeric D4Z4 tandem repeat array. Extended deletions that include both the more proximal D4F104S1 region and the D4Z4 repeat array proper do, however, occur, albeit rarely, and such deletions can lead to difficulties of interpretation in the diagnostic setting. OBJECTIVE: To devise a means to determine the true frequency of proximally extended deletions in individuals with FSHD. METHODS: Three families selected for this study were originally identified during routine FSHD analysis on the basis that the affected individuals in each family had failed to exhibit a small (<38-kb) EcoRI fragment. High molecular weight DNA from these families was analyzed with both conventional and pulsed-field gel electrophoresis using DNA markers p13E-11, 9B6A, B31, 4qA, and 4qB. RESULTS: Large genomic deletions were identified involving both D4Z4 and D4F104S1. The precise number of D4Z4 repeat units borne by the p13E11 deletion allele was established by the use of an additional restriction enzyme (MseI) digest. All three cases carry different sizes of deletion proximal to the D4Z4 repeat units. With use of a recently described telomeric probe, 4qA, a method was developed that identifies large genomic deletions involving both D4Z4 and D4F104S1 using conventional gel electrophoresis. CONCLUSION: Proximally extended deletions can be found in patients with a normal spectrum of the disease. This assay promises to allow estimation of the true frequency of proximally extended deletions and should improve the accuracy and reliability of molecular diagnostic testing for FSHD.

Adult↗
PubMed2003

Expanding the phenotypic spectrum of the CACNA1A gene T666M mutation: a description of 5 families with familial hemiplegic migraine.

BACKGROUND: Familial hemiplegic migraine (FHM) is a rare autosomal dominant subtype of migraine with aura. Missense mutations in the chromosome 19 CACNA1A calcium channel gene have been found in approximately half of the families. The T666M mutation, replacing a threonine by a methionine at residue number 666, is the most frequent mutation, reported in 14 independent FHM families; other mutations have so far been described in only 1 or 2 families each. The clinical features of T666M families have been reported, but the course is unknown. OBJECTIVE: To present a detailed description of the clinical features of new FHM families in which we identified the T666M mutation in our CACNA1A screening program. METHODS: As part of our ongoing genetic screening, mutation analysis of the CACNA1A gene was performed by single-strand conformational polymorphism analysis in 33 probands of families with FHM. RESULTS: We identified the T666M mutation in 5 unrelated FHM families. In 3 of the families, patients displayed cerebellar ataxia. In 1 family, some affected members with the mutation had attacks with confusion but without hemiparesis. In 1 family, patients had progressive cognitive dysfunction. CONCLUSIONS: The T666M mutation is the most frequent CACNA1A mutation in FHM; it was found in 5 of 33 FHM families at our laboratory, and in 19 of 39 families with a known mutation reported in the literature (including the present study). Screening for the T666M mutation should therefore be the first step when screening families with FHM. There is a remarkable clinical heterogeneity among families with the T666M mutation.

Adult↗
PubMed2003

Llama-derived phage display antibodies in the dissection of the human disease oculopharyngeal muscular dystrophy.

Functional analysis of the estimated 30,000 genes of the human genome requires fast and reliable high-throughput methods to study spatio-temporal protein dynamics. To explore the suitability of heavy-chain antibodies (HCAbs) for studying mechanisms underlying human disease, we used oculopharyngeal muscular dystrophy (OPMD) as a paradigm for the expanding group of protein aggregation disorders that is characterized by subcellular dislocalization and aggregation of mutant protein. OPMD is caused by a moderate alanine expansion in the poly-A binding protein nuclear 1 (PABPN1) and is associated with intranuclear PABPN1 deposition exclusively in muscle. An experimental approach was designed in which the primary sequence of the PABPN1 gene was employed for generating a prokaryotic expression construct that permitted its expression in the host Escherichia coli. The purified product was used for immunization of a llama as well as for the selection of an antigen-specific antibody fragment from the derived phage display library. This single-domain antibody was able to recognize the native gene product in mammalian cell lines and in human muscle tissue by immunocytochemical, immunohistochemical and immunoblot analysis. Our results suggest that phage display derived heavy-chain antibodies can be used in proteomics to study the localization and function of hypothetical gene products, relevant to human disease.

Amino Acid Sequence↗
PubMed2002

Episodic ataxia type 2. Three novel truncating mutations and one novel missense mutation in the CACNA1A gene.

We analysed the CACNA1A gene, located on chromosome 19p13, in three unrelated families and one sporadic case with episodic ataxia type 2 (EA-2). In two of the families and the sporadic patient, novel truncating mutations, which disrupt the reading frame and result in a premature stop of the CACNA1A protein, were identified in exons 14, 16 and 26. In the remaining family, a novel missense mutation (H253Y) was found. Of the twenty two EA-2 mutations identified thus far, including those of the present study, seventeen are truncating mutations and five are missense mutations, all resulting in an EA-2 clinical phenotype.

Adult↗
PubMed2001

Melanocortin-1 receptor variant R151C modifies melanoma risk in Dutch families with melanoma.

Germline mutations of the cell-cycle regulator p16 (also called "CDKN2A") in kindreds with melanoma implicate this gene in susceptibility to malignant melanoma. Most families with familial atypical multiple-mole melanoma (FAMMM) who are registered at the Leiden dermatology clinic share the same p16-inactivating deletion (p16-Leiden). Incomplete penetrance and variable clinical expression suggest risk modification by other genetic and/or environmental factors. Variants of the melanocortin-1 receptor (MC1R) gene have been shown to be associated with red hair, fair skin, and melanoma in humans. Carriers of the p16-Leiden deletion in Dutch families with FAMMM show an increased risk of melanoma when they also carry MC1R variant alleles. The R151C variant is overrepresented in patients with melanoma who are from families with the p16-Leiden mutation. Although some of the effect of the R151C variant on melanoma risk may be attributable to its effect on skin type, our analyses indicate that the R151C variant contributes an increased melanoma risk even after statistical correction for its effect on skin type. These findings suggest that the R151C variant may be involved in melanoma tumorigenesis in a dual manner, both as a determinant of fair skin and as a component in an independent additional pathway.

Adult↗
PubMed2001

Promoter hypermethylation: a common cause of reduced p16(INK4a) expression in uveal melanoma.

Tumors often display unrestricted cell cycling attributable to a dysfunctional G(1)-S checkpoint. One of the mechanisms leading to such a defect is the inactivation of the cyclin-dependent kinase inhibitor p16(INK4a). Although inactivation of p16(INK4a) is observed in a wide range of tumors, including cutaneous melanoma, genetic alteration of p16(INK4a) is reportedly uncommon in uveal melanoma. Here we show that the p16(INK4a) promoter is hypermethylated in 6 of 12 uveal melanoma cell lines and in 7 of 22 primary uveal melanomas analyzed. Five of seven patients with a methylated primary tumor died of metastatic disease compared with 2 of 15 patients with a nonmethylated primary tumor. We also show that all uveal melanoma cell lines with a hypermethylated p16(INK4a) promoter have lost p16(INK4a) expression but have maintained the expression of p14(ARF). Treatment of uveal melanoma cell lines with 5-aza-2'-deoxycytidine results in demethylation of p16(INK4a) and in reexpression of p16(INK4a) mRNA, which is maintained upon withdrawal of the 5-aza-2'-deoxycytidine. In conclusion, p16(INK4a) promoter methylation appears to be a common event in uveal melanoma and is accompanied by the loss of p16(INK4a) expression.

Adult↗
PubMed2001

Hereditary vascular retinopathy, cerebroretinal vasculopathy, and hereditary endotheliopathy with retinopathy, nephropathy, and stroke map to a single locus on chromosome 3p21.1-p21.3.

We performed a genomewide search for linkage in an extended Dutch family with hereditary vascular retinopathy associated with migraine and Raynaud phenomenon. Patients with vascular retinopathy are characterized by microangiopathy of the retina, accompanied by microaneurysms and telangiectatic capillaries. The genome search, using a high throughput capillary sequencer, revealed significant evidence of linkage to chromosome 3p21.1-p21.3 (maximum pairwise LOD score 5.25, with D3S1578). Testing of two additional families that had a similar phenotype, cerebroretinal vasculopathy, and hereditary endotheliopathy with retinopathy, nephropathy, and stroke, revealed linkage to the same chromosomal region (combined maximum LOD score 6.30, with D3S1588). Haplotype analysis of all three families defined a 3-cM candidate region between D3S1578 and D3S3564. Our study shows that three autosomal dominant vasculopathy syndromes with prominent cerebroretinal manifestations map to the same 3-cM interval on 3p21, suggesting a common locus.

Chromosome Mapping↗
PubMed2001

Involvement of the CACNA1A gene containing region on 19p13 in migraine with and without aura.

OBJECTIVE: To assess the involvement of the 19p13 familial hemiplegic migraine (FHM) locus in migraine with and without aura. BACKGROUND: Migraine with and without aura are likely to be polygenetic multifactorial disorders. FHM is a rare dominantly inherited type of migraine with aura. In about 50% of families, FHM is caused by mutations in the P/Q-type calcium channel alpha(1A)-subunit (CACNA1A) gene on chromosome 19p13. The CACNA1A gene is thus a good candidate gene for "nonhemiplegic" migraine with or without aura. METHODS: The authors performed an affected sibpair analysis using flanking and CACNA1A intragenic markers. The authors assessed the occurrence of shared parental marker alleles among 189 affected siblings from 36 extended families with typical migraine with or without aura. RESULTS: Sibling pairs with any form of migraine had inherited the same 19p13 CACNA1A-containing region significantly more frequently than expected by chance (maximum multipoint lod score = 1.22). This result was almost exclusively dependent on the increased sharing found in sibling pairs with migraine with aura (maximum multipoint lod score = 1.41). The locus-specific relative risk for a sibling (lambda(s)) to suffer from migraine with aura, defined as the increase in risk of the trait attributable to the 19p13 locus, was lambda(s) = 1.56. When combining migraine with and without aura, lambda(s) was 1.22. CONCLUSIONS: The increased allele sharing in the CACNA1A gene region on 19p13 is consistent with an important involvement of this region in migraine, especially migraine with aura.

Alleles↗
PubMed2001

Mutations of MLC1 (KIAA0027), encoding a putative membrane protein, cause megalencephalic leukoencephalopathy with subcortical cysts.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive disorder characterized by macrocephaly, deterioration of motor functions with ataxia, and spasticity, eventuating in mental decline. The brain appears swollen on magnetic resonance imaging, with diffuse white-matter abnormalities and the invariable presence of subcortical cysts. MLC was recently localized on chromosome 22q(tel). We have narrowed down the critical region by linkage analysis of 11 informative families with MLC to a region of approximately 250 kb, containing four known genes. One family with two patients who were siblings did not display linkage between the MLC phenotype and any of the analyzed microsatellite markers on chromosome 22q(tel), suggesting genetic heterogeneity and the existence of at least a second MLC locus. The maximum two-point LOD score for the 11 families was 6.6 at recombination fraction .02. Twelve different mutations in seven informative and six uninformative families were found in one of the candidate genes, KIAA0027, which we renamed "MLC1." The gene encodes a putative membrane protein with eight predicted transmembrane domains. The patients of one family were compound heterozygotes for mutations that both introduced stop codons. The mutations further included frameshifts, splice-acceptor mutations, a putative splice-donor mutation, and amino acid substitutions of residues in predicted transmembrane domains. These data provide strong evidence that mutations of MLC1 cause the disease.

Alleles↗
PubMed2001

[From gene to disease; from CACNA1A to migraine].

Familial hemiplegic migraine (FHM) is a rare autosomal dominant subtype of migraine with aura. FHM is associated in half the families with mutations in the CACNA1A gene on chromosome 19P13, encoding the alpha-1A subunit of brain-specific P/Q-type calcium channels. P/Q-type calcium channels are important in neurotransmitter release. The first functional studies indicate that mutations causing FHM result in a gain or loss of function of P/Q-type calcium channels. Affected sib-pair analysis in families with migraine with and without aura indicates involvement of the CACNA1A gene in these more frequent types of migraine.

Calcium Channels↗
PubMed2001

The impact of pharmacogenetics for migraine.

Migraine is a paroxysmal neurological disorder affecting up to 12% of males and 24% of females in the general population. As migraine has been demonstrated to have a strong, but complex, genetic component, pharmacogenetics bears great promise in providing new targets for drug development and optimization of individual specific therapy. Better, preferably prophylactic, treatment of migraine patients is desired because the drugs now used are not effective in all patients, allow recurrence of the headache in a high percentage of patients and sometimes have severe adverse side-effects. With the recent identification of the brain-specific P/Q-type Ca(2+)channel gene CACNA1A as a pivotal player in the pathogenesis of migraine, the first step has been taken to identify primary biochemical pathways leading to migraine. The work on migraine can also have implications for the increasing number of additional neurological episodic disorders having the common denominator of channelopathy.

Animals↗
PubMed2001

Active genes in junk DNA? Characterization of DUX genes embedded within 3.3 kb repeated elements.

The human genome contains hundreds of repeats of the 3.3 kb family in regions associated with heterochromatin. We have previously isolated a 3.3 kb-like cDNA encoding a double homeodomain protein (DUX1). Demonstration that the protein was expressed in human rhabdomyosarcoma TE671 cells, and characterization of a homologous promoter suggested that functional DUX genes might be present in 3.3 kb elements. In the present study, we describe two nearly identical 3.3 kb/DUX genes derived from PAC 137F16 (DUX3), and TE671 genomic DNA (DUX5), both mapping to all the acrocentric chromosomes. Their promoters harbor a GC and a TATAA box, and the open reading frame of the intronless structural part encodes two DUX proteins differing by alternative translation initiation. The shorter protein of the DUX5 gene is identical to DUX1. Using a protein truncation test, we could show that these two proteins are encoded by total RNA, but not by poly (A)(+) RNA, from different human tissues and cell lines. Our results indicate that active genes of unusual structure are present in chromosome regions characterized by large amounts of heterochromatic repetitive DNA.

Animals↗
PubMed2001

Complete allele information in the diagnosis of facioscapulohumeral muscular dystrophy by triple DNA analysis.

Facioscapulohumeral muscular dystrophy is caused by partial deletion of the D4Z4 repeat array on chromosome 4q35. Genetic diagnosis is based on sizing of this repeat array, which is complicated by cross-hybridization of a homologous polymorphic repeat array on chromosome 10 and by the frequent exchanges between these chromosomal regions. The restriction enzyme XapI optimizes the diagnosis of facioscapulohumeral muscular dystrophy by uniquely digesting 4-derived repeat units and leaving 10-derived repeat units undigested, thus complementing BlnI, which uniquely digests 10-derived repeat units. A triple analysis with EcoRI, EcoRI/BlnI, and XapI unequivocally allows characterization of each of the four alleles, whether homogeneous or hybrid. This is particularly useful in the case of identical sized 4-derived and 10-derived arrays, in situations of suspected facioscapulohumeral muscular dystrophy with nonstandard allele configurations, and for assignment of hybrid fragments to their original alleles.

Aged↗
PubMed2001

Delayed cerebral edema and fatal coma after minor head trauma: role of the CACNA1A calcium channel subunit gene and relationship with familial hemiplegic migraine.

Trivial head trauma may be complicated by severe, sometimes even fatal, cerebral edema and coma occurring after a lucid interval ("delayed cerebral edema"). Attacks of familial hemiplegic migraine (FHM) can be triggered by minor head trauma and are sometimes accompanied by coma. Mutations in the CACNA1A calcium channel subunit gene on chromosome 19 are associated with a wide spectrum of mutation-specific episodic and chronic neurological disorders, including FHM with or without coma. We investigated the role of the CACNA1A gene in three subjects with delayed cerebral edema. Two subjects originated from a family with extreme FHM, and one subject was the previously asymptomatic daughter of a sporadic patient with hemiplegic migraine attacks. In all three subjects with delayed severe edema, we found a C-to-T substitution resulting in the substitution of serine for lysine at codon 218 (S218L) in the CACNA1A gene. The mutation was absent in nonaffected family members and 152 control individuals. Haplotype analysis excluded a common founder for both families. Neuropathological examination in one subject showed Purkinje cell loss with relative preservation of granule cells and sparing of the dentate and inferior olivary nuclei. We conclude that the novel S218L mutation in the CACNA1A calcium channel subunit gene is involved in FHM and delayed fatal cerebral edema and coma after minor head trauma. This finding may have important implications for the understanding and treatment of this dramatic syndrome.

Adolescent↗
PubMed2001

A powerful and rapid approach to human genome scanning using small quantities of genomic DNA.

Dense maps of short-tandem-repeat polymorphisms (STRPs) have allowed genome-wide searches for genes involved in a great variety of diseases with genetic influences, including common complex diseases. Generally for this purpose, marker sets with a 10 cM spacing are genotyped in hundreds of individuals. We have performed power simulations to estimate the maximum possible intermarker distance that still allows for sufficient power. In this paper we further report on modifications of previously published protocols, resulting in a powerful screening set containing 229 STRPs with an average spacing of 18.3 cM. A complete genome scan using our protocol requires only 80 multiplex PCR reactions which are all carried out using one set of conditions and which do not contain overlapping marker allele sizes. The multiplex PCR reactions are grouped by sets of chromosomes, which enables on-line statistical analysis of a set of chromosomes, as sets of chromosomes are being genotyped. A genome scan following this modified protocol can be performed using a maximum amount of 2.5 micrograms of genomic DNA per individual, isolated from either blood or from mouth swabs.

Alleles↗