PubMed Health⌕ Search

Biomedical subjects

J R Lupski

Publications and source records attributed to J R Lupski.

At least 55 records · Page 3Linked to original sources
PubMed2001

Null missense ABCR (ABCA4) mutations in a family with stargardt disease and retinitis pigmentosa.

PURPOSE: To determine the type of ABCR mutations that segregate in a family that manifests both Stargardt disease (STGD) and retinitis pigmentosa (RP), and the functional consequences of the underlying mutations. METHODS: Direct sequencing of all 50 exons and flanking intronic regions of ABCR was performed for the STGD- and RP-affected relatives. RNA hybridization, Western blot analysis, and azido-adenosine triphosphate (ATP) labeling was used to determine the effect of disease-associated ABCR mutations in an in vitro assay system. RESULTS: Compound heterozygous missense mutations were identified in patients with STGD and RP. STGD-affected individual AR682-03 was compound heterozygous for the mutation 2588G-->C and a complex allele, [W1408R; R1640W]. RP-affected individuals AR682-04 and-05 were compound heterozygous for the complex allele [W1408R; R1640W] and the missense mutation V767D. Functional analysis of the mutation V767D by Western blot and ATP binding revealed a severe reduction in protein expression. In vitro analysis of ABCR protein with the mutations W1408R and R1640W showed a moderate effect of these individual mutations on expression and ATP-binding; the complex allele [W1408R; R1640W] caused a severe reduction in protein expression. CONCLUSIONS: These data reveal that missense ABCR mutations may be associated with RP. Functional analysis reveals that the RP-associated missense ABCR mutations are likely to be functionally null. These studies of the complex allele W1408R; R1640W suggest a synergistic effect of the individual mutations. These data are congruent with a model in which RP is associated with homozygous null mutations and with the notion that severity of retinal disease is inversely related to residual ABCR activity.

ATP-Binding Cassette Transporters↗
PubMed2000

Periaxin mutations cause recessive Dejerine-Sottas neuropathy.

The periaxin gene (PRX) encodes two PDZ-domain proteins, L- and S-periaxin, that are required for maintenance of peripheral nerve myelin. Prx(-/-) mice develop a severe demyelinating peripheral neuropathy, despite apparently normal initial formation of myelin sheaths. We hypothesized that mutations in PRX could cause human peripheral myelinopathies. In accordance with this, we identified three unrelated Dejerine-Sottas neuropathy patients with recessive PRX mutations-two with compound heterozygous nonsense and frameshift mutations, and one with a homozygous frameshift mutation. We mapped PRX to 19q13.13-13.2, a region recently associated with a severe autosomal recessive demyelinating neuropathy in a Lebanese family (Delague et al. 2000) and syntenic to the location of Prx on murine chromosome 7 (Gillespie et al. 1997).

Adult↗
PubMed2000

Isolation and preliminary characterization of the human and mouse homologues of the bacterial cell cycle gene era.

Era is an essential GTPase that is required for proper cell cycle progression and cell division in Escherichia coli and is found in nearly all bacteria sequenced to date. To determine whether Era is also present in eukaryotic organisms, we searched the dbEST database and found EST clones coding for proteins that were similar to Era. Full sequencing of these ESTs from human and mouse identified a conserved homologue, ERAL1 (Era-like 1). ERAL1 maps to 17q11.2 in human and is located in the syntenic region of mouse chromosome 11. ERAL1 may be an attractive candidate for a tumor suppressor gene since ERAL1 is located in a chromosomal region where loss of heterozygosity is often associated with various types of cancer.

Amino Acid Sequence↗
PubMed2000

Macular degeneration: the emerging genetics.

Discovery of the gene responsible for a recessive, early-onset maculopathy has focused attention on a biomolecular pathway in which subtle metabolic flaws become toxic to irreplaceable retinal cells. The pathway's identification points toward specific ways of intervening. Among patients with age-related macular degeneration, carriers of single mutations in the same gene are proving to be remarkably common.

ATP-Binding Cassette Transporters↗
PubMed2000

Multiple CYP1B1 mutations and incomplete penetrance in an inbred population segregating primary congenital glaucoma suggest frequent de novo events and a dominant modifier locus.

Primary congenital glaucoma (PCG) is an autosomal recessive disorder associated with unknown developmental defect(s) in the anterior chamber. Recently, we reported three distinct mutations in CYP1B1, the gene for cytochrome P4501B1, in 25 Saudi families segregating PCG. For this report, we analyzed 37 additional families and confirmed the initial finding of decreased penetrance. Mutations and intragenic single-nucleotide polymorphisms (SNPs) were also analyzed from direct sequencing of all CYP1B1 coding exons. Eight distinct mutations were identified: G61E, R469W and D374N, the most common Saudi mutations, account for 72, 12 and 7%, respectively, of all the PCG chromosomes. Five additional homozygous mutations (two deletions and three missense mutations) were detected, each in a single family. Affected individuals from five families had no CYP1B1 coding mutations, and each family had a unique SNP profile. The identification of eight distinct mutations in a single gene, on four distinct haplotypes, suggests a relatively recent occurrence of multiple mutations in CYP1B1 in Saudi Arabia. These data demonstrate decreased penetrance of the PCG phenotype in the Saudi population, because 40 apparently unaffected individuals in 22 families have mutations and haplotypes identical to their affected siblings. Two individuals were subsequently diagnosed with glaucoma and two others had abnormal ocular findings that are consistent with milder forms of glaucoma. Analysis of these 22 kindreds suggests the presence of a dominant modifier locus that is not linked genetically to CYP1B1. Linkage and Southern analyses excluded three candidate modifier loci.

Amino Acid Sequence↗
PubMed2000

Unusual electrophysiological findings in X-linked dominant Charcot-Marie-Tooth disease.

X-linked Charcot-Marie-Tooth disease (CMTX) is the second most common form of Charcot-Marie-Tooth disease. Variable histopathological and nerve conduction velocity (NCV) results have suggested either a primary demyelinating or axonal polyneuropathy. We identified five individuals across three generations in a family with CMTX associated with a mutation in the gene coding for connexin 32. All individuals were studied by clinical neurological examination, DNA analysis, and nerve conduction studies. The proband (1174/KD) also underwent a sural nerve biopsy. As expected, all the affected males were more clinically affected than the females. All affected males and obligate female carriers exhibited some electrophysiological characteristics of demyelination. However, striking heterogeneity of nerve conduction velocities was seen. This family shows that CMTX is a heterogeneous and distinctly nonuniform demyelinating polyneuropathy, the severity of which varies with sex and age. Such electrophysiological variability is unique among hereditary neuropathies.

Charcot-Marie-Tooth Disease↗
PubMed2000

Isolation of a paralog of the Doyne honeycomb retinal dystrophy gene from the multiple retinopathy critical region on 11q13.

A large number of extracellular matrix proteins have been found to contain variations of the epidermal growth factor (EGF) domain and have been implicated in functions as diverse as blood coagulation, activation of complement, and determination of cell fate during development. The gene for one such protein, S1-5, was identified from a subtractively enriched cDNA library from a patient with Werner syndrome and was shown to be preferentially expressed in senescent and quiescent fibroblasts. We have cloned and characterized, in human and mouse, a novel gene that shows significant homology to the gene for S1-5. We have determined that the encoded protein contains four EGF domains and six calcium-binding EGF domains. On the basis of its homology to known proteins, we have designated this gene EFEMP2 (Egf-containing fibulin-like extracellular matrix protein 2) and the gene for the S1-5 protein EFEMP1. Like EFEMP1, this novel gene is expressed in a wide range of adult and fetal tissues. In contrast to EFEMP1, however, EFEMP2 is not significantly overexpressed in senescent or quiescent fibroblasts, suggesting a diversity of function within this new EGF-like domain subfamily. We have mapped EFEMP2 to 11q13, in an area where several retinopathies have been genetically linked. Given that mutations in EFEMP1 have been recently described in patients with Doyne honeycomb retinal dystrophy, EFEMP2 becomes a good candidate for such disorders.

Amino Acid Sequence↗
PubMed2000

Complex inheritance of ABCR mutations in Stargardt disease: linkage disequilibrium, complex alleles, and pseudodominance.

Stargardt disease is a recessively transmitted disease caused by mutations in the ABCR gene. Linkage disequilibrium has recently been reported between a polymorphism, 2828 A, and a common Western European founder mutation, 2588 C. Here, we confirm this linkage disequilibrium in a North American population. We also describe two complex alleles involving the 2828 A and 2588 C alterations and suggest a possible order of clinical severity of mutations identified in trans to the complex alleles. Finally, we report pseudodominance of Stargardt disease in a family with the 2588 C mutation, further supporting a high frequency of carriers for ABCR mutations in our population.

ATP-Binding Cassette Transporters↗
PubMed2000

Molecular mechanism for duplication 17p11.2- the homologous recombination reciprocal of the Smith-Magenis microdeletion.

Recombination between repeated sequences at various loci of the human genome are known to give rise to DNA rearrangements associated with many genetic disorders. Perhaps the most extensively characterized genomic region prone to rearrangement is 17p12, which is associated with the peripheral neuropathies, hereditary neuropathy with liability to pressure palsies (HNPP) and Charcot-Marie-Tooth disease type 1A (CMT1A;ref. 2). Homologous recombination between 24-kb flanking repeats, termed CMT1A-REPs, results in a 1.5-Mb deletion that is associated with HNPP, and the reciprocal duplication product is associated with CMT1A (ref. 2). Smith-Magenis syndrome (SMS) is a multiple congenital anomalies, mental retardation syndrome associated with a chromosome 17 microdeletion, del(17)(p11.2p11.2) (ref. 3,4). Most patients (>90%) carry deletions of the same genetic markers and define a common deletion. We report seven unrelated patients with de novo duplications of the same region deleted in SMS. A unique junction fragment, of the same apparent size, was identified in each patient by pulsed field gel electrophoresis (PFGE). Further molecular analyses suggest that the de novo17p11.2 duplication is preferentially paternal in origin, arises from unequal crossing over due to homologous recombination between flanking repeat gene clusters and probably represents the reciprocal recombination product of the SMS deletion. The clinical phenotype resulting from duplication [dup(17)(p11.2p11.2)] is milder than that associated with deficiency of this genomic region. This mechanism of reciprocal deletion and duplication via homologous recombination may not only pertain to the 17p11.2 region, but may also be common to other regions of the genome where interstitial microdeletion syndromes have been defined.

Abnormalities, Multiple↗
PubMed2000

Mutations in MKKS cause obesity, retinal dystrophy and renal malformations associated with Bardet-Biedl syndrome.

Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder predominantly characterized by obesity, retinal dystrophy, polydactyly, learning difficulties, hypogenitalism and renal malformations, with secondary features that include diabetes mellitus, endocrinological dysfunction and behavioural abnormalities. Despite an initial expectation of genetic homogeneity due to relative clinical uniformity, five BBS loci have been reported, with evidence for additional loci in the human genome; however, no genes for BBS have yet been identified. We performed a genome screen with BBS families from Newfoundland that were excluded from BBS1-5 and identified linkage with D20S189. Fine-mapping reduced the critical interval to 1.9 cM between D20S851 and D20S189, encompassing a chaperonin-like gene. Mutations in this gene were recently reported to be associated with McKusick-Kaufman syndrome (MKKS; ref. 8). Given both the mapping position and clinical similarities of these two syndromes, we screened MKKS and identified mutations in five Newfoundland and two European-American BBS pedigrees. Most are frameshift alleles that are likely to result in a non-functional protein. Our data suggest that a complete loss of function of the MKKS product, and thus an inability to fold a range of target proteins, is responsible for the clinical manifestations of BBS.

Alleles↗
PubMed2000

Identification of novel genes expressed during metanephric induction through single-cell library screening.

BACKGROUND: Development of the mature kidney is dependent on a series of inductive events between a portion of the epithelial bud at the distal end of the nephric duct and a neighboring domain of committed metanephric mesenchyme. Several genes have been identified to date that are critical in the inductive process. For example, the deletion of Bmp7 from the mouse genome results in dysgenesis or agenesis of the kidney. These findings suggest that Bmp7 controls the expression of genes important for nephrogenesis, but the identity of these genes has remained largely undetermined. METHODS: Single cells were isolated from mouse metanephric mesenchyme during the time of induction (between E11.0 and E11.5) and cDNA libraries constructed from induced and uninduced tissue. Subtractive hybridization was performed to isolate genes that were expressed during E11.5 but not E11.0. RESULTS: Using this approach, we identified eight previously known genes, three of which were known to be involved in metanephric induction, thus validating our approach, and nine novel genes. Eight of these genes were completely novel, whereas one was similar to a member of the yeast Anaphase Promoting Complex. CONCLUSIONS: Through subtractive hybridization of mouse E11.0 and E11.5 metanephric mesenchyme single-cell cDNA libraries, we have identified novel genes that are candidates for involvement in nephrogenesis through their up-regulation during the inductive process.

Amino Acid Sequence↗
PubMed2000

Circadian rhythm abnormalities of melatonin in Smith-Magenis syndrome.

BACKGROUND: Smith-Magenis syndrome (SMS) is a multiple congenital anomalies/mental retardation syndrome associated with a hemizygous deletion of chromosome 17, band p11.2. Characteristic features include neurobehavioural abnormalities such as aggressive and self-injurious behaviour and significant sleep disturbances. The majority of patients have a common deletion characterised at the molecular level. Physical mapping studies indicate that all patients with the common deletion are haploinsufficient for subunit 3 of the COP9 signalosome (COPS3), which is conserved from plants to humans, and in the plant Arabidopis thaliana regulates gene transcription in response to light. Haploinsufficiency of this gene is hypothesised to be potentially involved in the sleep disturbances seen in these patients. Melatonin is a hormone secreted by the pineal gland. SMS patients are reported to have fewer sleep disturbances when given a night time dose of this sleep inducing hormone. METHODS: Urinary excretion of 6-sulphatoxymelatonin (aMT6s), the major hepatic metabolite of melatonin, in 19 SMS patients were measured in conjunction with 24 hour sleep studies in 28 SMS patients. Five of the 28 patients did not have the common SMS deletion. To investigate a potential correlation of COPS3 haploinsufficiency and disturbed melatonin excretion, we performed fluorescence in situ hybridisation (FISH) using two BACs containing coding exons of COPS3. RESULTS: All SMS patients show significant sleep disturbances when assessed by objective criteria. Abnormalities in the circadian rhythm of aMT6s were observed in all but one SMS patient. Interestingly this patient did not have the common deletion. All patients studied, including the one patient with a normal melatonin rhythm, were haploinsufficient for COPS3. CONCLUSIONS: Our data indicate a disturbed circadian rhythm in melatonin and document the disturbed sleep pattern in Smith-Magenis syndrome. Our findings suggest that the abnormalities in the circadian rhythm of melatonin and altered sleep patterns could be secondary to aberrations in the production, secretion, distribution, or metabolism of melatonin; however, a direct role for COPS3 could not be established.

Abnormalities, Multiple↗
PubMed2000

Molecular mechanisms for constitutional chromosomal rearrangements in humans.

Cytogenetic imbalance in the newborn is a frequent cause of mental retardation and birth defects. Although aneuploidy accounts for the majority of imbalance, structural aberrations contribute to a significant fraction of recognized chromosomal anomalies. This review describes the major classes of constitutional, structural cytogenetic abnormalities and recent studies that explore the molecular mechanisms that bring about their de novo occurrence. Genomic features flanking the sites of recombination may result in susceptibility to chromosomal rearrangement. One such substrate for recombination is low-copy region-specific repeats. The identification of genome architectural features conferring susceptibility to rearrangements has been accomplished using methods that enable investigation of regions of the genome that are too small to be visualized by traditional cytogenetics and too large to be resolved by conventional gel electrophoresis. These investigations resulted in the identification of previously unrecognized structural cytogenetic anomalies, which are associated with genetic syndromes and allowed for the molecular basis of some chromosomal rearrangements to be delineated.

Chromosome Aberrations↗
PubMed1999

Molecular mechanisms for CMT1A duplication and HNPP deletion.

As the best characterized human genomic disorders, CMT1A and HNPP illustrate several common mechanistic features of genomic rearrangements. These features include the following: (1) Recombination occurs between homologous sequences flanking the duplicated/deleted genomic segment. (2) The evolution of the mammalian genome may result in an architecture consisting of region-specific low-copy repeats that predispose to rearrangement secondary to providing homologous regions as substrate for recombination. (3) Strand exchange occurs preferentially in a region of perfect sequence identity within the flanking repeat sequences. (4) Double-strand breaks likely initiate recombination between the flanking repeats. (5) The mechanism and rate of homologous recombination resulting in DNA rearrangement may differ for male and female gametogenesis. (6) Homologous recombination resulting in DNA rearrangement occurs with high frequency in the human genome. (7) Genomic disorders result from structural features of the human genome and not population specific alleles or founder effects; therefore, genomic disorders appear to occur with equal frequencies in different world populations.

Charcot-Marie-Tooth Disease↗
PubMed1999

Prenatal diagnosis of Charcot-Marie-Tooth disease type 1A.

Charcot-Marie-Tooth disease (CMT) is the most common cause of peripheral neuropathy, with an incidence of 1: 2500 persons affected. CMT1A is caused by a submicroscopic duplication in 17p12. Several methods exist for determining a diagnosis in an individual. Many of these methods are not suitable for prenatal diagnosis. Previously, we reported the use of fluorescence in situ hybridization (FISH) to detect the common duplication found in more than 98% of individuals with CMT1A. We also have reported the validation of the FISH assay for amniotic fluid specimens and chorionic villus samples. Herein, we report our experience with testing for CMT1A in prenatal specimens.

Amniocentesis↗