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Biomedical subjects

R L Nussbaum

Publications and source records attributed to R L Nussbaum.

At least 37 records · Page 2Linked to original sources
PubMed1998

Genomic organization and expression of the human beta-synuclein gene (SNCB).

The beta-synuclein protein is highly homologous to the alpha-synuclein protein for which two mutations were reported in some familial cases of Parkinson disease. It has been shown that both alpha- and beta-synucleins may be able to inhibit phospholipase D2 selectively. We have observed that the beta-synuclein gene (HGMW-approved symbol, SNCB) is highly expressed in brain including the substantia nigra, the main region of neuronal degeneration in patients with Parkinson disease. We have determined the intron-exon structure of the beta-synuclein gene and established sequencing assays that will facilitate the search for mutations in the beta-synuclein gene in patients with Parkinson disease or other neurodegenerative disorders.

Amino Acid Sequence↗
PubMed1998

Long uninterrupted CGG repeats within the first exon of the human FMR1 gene are not intrinsically unstable in transgenic mice.

Despite the increasing number of disorders known to result from trinucleotide repeat amplification, the molecular mechanism underlying these dynamic mutations is still unknown. In an attempt to create a mouse model for the CGG repeat instability seen in Fragile X syndrome, we constructed transgenes corresponding to FMR1 premutation alleles. While in humans these alleles would expand to full mutation with almost 100% certainty upon maternal transmission, they remain stable in our transgenic mice. Therefore, the presence of a large number of uninterrupted CGGs is not sufficient to cause instability in mice, even in the context of flanking human FMR1 sequences.

Alleles↗
PubMed1998

Functional overlap between murine Inpp5b and Ocrl1 may explain why deficiency of the murine ortholog for OCRL1 does not cause Lowe syndrome in mice.

The oculocerebrorenal syndrome of Lowe (OCRL) is an X-linked human genetic disorder characterized by mental retardation, congenital cataracts, and renal tubular dysfunction. The Lowe syndrome gene, OCRL1, encodes a phosphatidylinositol 4,5-bisphosphate 5-phosphatase in the Golgi complex. The pathogenesis of Lowe syndrome due to deficiency of a phosphatidylinositol 4,5-bisphosphate 5-phosphatase in the Golgi complex is unknown. We have used targeted disruption in embryonic stem cells to make mice deficient in Ocrl1, the mouse homologue for OCRL1, as an animal model for the disease. Surprisingly, mice deficient in Ocrl1 do not develop the congenital cataracts, renal Fanconi syndrome, or neurological abnormalities seen in the human disorder. We hypothesized that Ocrl1 deficiency is complemented in mice by inositol polyphosphate 5-phosphatase (Inpp5b), an autosomal gene that encodes a phosphatidylinositol bisphosphate 5-phosphatase highly homologous to Ocrl1. We created mice deficient in Inpp5b; the mice were viable and fertile without phenotype except for testicular degeneration in males beginning after sexual maturation. We crossed mice deficient in Ocrl1 to mice deficient in Inpp5b. No liveborn mice or embryos lacking both enzymes were found, demonstrating that Ocrl1 and Inpp5b have overlapping functions in mice and suggesting that the lack of phenotype in Ocrl1-deficient mice may be due to compensating Inpp5b function.

Amino Acid Sequence↗
PubMed1998

Contig map of the Parkinson's disease region on 4q21-q23.

We have constructed a yeast artificial chromosome contig (YAC) map of human chromosome 4q21-q23 across the Parkinson's disease region by combining molecular and fluorescence in situ hybridization techniques. This map contains 55 YACs and 51 molecular markers, including 23 polymorphic markers. We have also isolated one P1 and 33 bacterial artificial chromosomes located within this contig. Plasmid libraries were generated from 11 of these BAC and P1 clones, and 614 random plasmid clones were sequenced for a total of about 200 kb. This contig allowed us to precisely determine the location of 18 transcripts within the D4S2460-D4S2986 interval, including the alpha-synuclein gene found to be mutated in some families with Parkinson's disease.

Chromosome Mapping↗
PubMed1998

First report of prenatal biochemical diagnosis of Lowe syndrome.

The oculocerebrorenal syndrome of Lowe (OCRL) is a rare X-linked disorder with a severe phenotype characterized by congenital cataracts, renal tubular dysfunction and neurological deficits. The gene has been characterized and mutations have been identified in patients. Owing to the allelic heterogeneity exhibited by this gene, prenatal diagnosis by molecular analysis is limited to families in which the mutation is already known or in which linkage is informative. A more generally applicable diagnostic test would be valuable for families at risk for Lowe syndrome. Since ocrl1 is now known to encode a phosphatidylinositol 4,5-bisphosphate 5-phosphatase (Ptdlns(4,5)P2 phosphatase), we assessed whether biochemical testing could be used for prenatal diagnosis. We report here the first case of prenatal diagnosis for Lowe syndrome by measuring phosphatidylinositol 4,5-bisphosphate 5-phosphatase activity in cultured amniocytes.

Amniocentesis↗
PubMed1998

Mutations are not uniformly distributed throughout the OCRL1 gene in Lowe syndrome patients.

Lowe syndrome (OCRL) is an X-linked disorder involving the eyes, kidney, and nervous system that is caused by loss of function in the OCRL1 gene. OCRL1 contains 24 exons (23 of which are coding) and encodes a 105-kDa enzyme with phosphatidylinositol 4,5 bisphosphate (PtdIns[4,5]P2) 5-phosphatase activity. We published previously (1,2) 13 different mutations in 10 families. Four are missense other 8 mutations in 10 families. Four are missense mutations in highly conserved PtdIns (4,5)P2 5-phosphatase caused by nonsense mutations, and three others are premature terminations caused by frameshift mutations. One frameshift, a GT deletion in exon 21, has been observed previously in two unrelated Lowe syndrome patients, suggesting that it may be a relative "hotspot" for mutation in a disorder marked otherwise by allelic heterogeneity. We have also seen two other recurrent mutations. One is a nonsense mutation CGA > TGA in exon 2 observed in two patients and the second is a missense mutation CGA > CAA in exon 15 present in two unrelated patients. These 21 distinct mutations we have found in 25 Lowe syndrome patients occur in only 9 of the 24 exons: 10, 12, 13, 14, 15, 18, 19, 21, and 22. Interestingly, missense mutations have occurred only in exons 12 through 15 in highly conserved residues among the phosphatidylinositol 5-phosphatases. These observations suggest useful strategies for mutation screening in OCRL.

Alleles↗
PubMed1998

Identification, localization and characterization of the human gamma-synuclein gene.

We have identified and characterized a new member of the human synuclein gene family, gamma-synuclein (SNCG). This gene is composed of five exons, which encode a 127 amino acid protein that is highly homologous to alpha-synuclein, which is mutated in some Parkinson's disease families, and to beta-synuclein. The gamma-synuclein gene is localized to chromosome 10q23 and is principally expressed in the brain, particularly in the substantia nigra. We have determined its genomic sequence, and established conditions for sequence analysis of each of the exons. The gamma-synuclein gene, also known as BCSG1, was recently found to be overexpressed in advanced infiltrating carcinoma of the breast. Our survey of the EST database indicated that it might also be overexpressed in an ovarian tumor.

Adult↗
PubMed1998

Alpha synuclein is present in Lewy bodies in sporadic Parkinson's disease.

A missense mutation in the human alpha synuclein gene was recently identified in some cases of familial Parkinson's disease (FPD). We have developed an antibody that recognizes the C-terminal 12 amino acids of the human alpha synuclein protein and have demonstrated that alpha synuclein is an abundant component of the Lewy bodies found within the degenerating neurons of patients with Parkinson's disease (PD). The presence of alpha synuclein in Lewy bodies of sporadic PD patients suggests a central role for alpha synuclein in the pathogenesis of PD.

Aged↗
PubMed1997

Mutation in the alpha-synuclein gene identified in families with Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disorder with a lifetime incidence of approximately 2 percent. A pattern of familial aggregation has been documented for the disorder, and it was recently reported that a PD susceptibility gene in a large Italian kindred is located on the long arm of human chromosome 4. A mutation was identified in the alpha-synuclein gene, which codes for a presynaptic protein thought to be involved in neuronal plasticity, in the Italian kindred and in three unrelated families of Greek origin with autosomal dominant inheritance for the PD phenotype. This finding of a specific molecular alteration associated with PD will facilitate the detailed understanding of the pathophysiology of the disorder.

Age of Onset↗
PubMed1997

Physical mapping and genomic structure of the Lowe syndrome gene OCRL1.

The oculocerebrorenal syndrome of Lowe (OCRL; McKusick 309,000) is a rare X-linked disorder characterized by mental retardation, congenital cataracts, and Fanconi syndrome of the proximal renal tubules. We have carried out physical mapping of the OCRL1 gene and determined that it contains 24 exons occupying 58 kb. The gene, located in Xq25-26, is transcribed in a centromeric to telomeric direction. Primers have been developed that allow all coding exons and their intron/exon boundaries to be amplified from genomic DNA for mutation detection. Two tetranucleotide tandem repeat polymorphisms were characterized that immediately flank the OCRL1 gene and, together, are informative in over 90% of females. Variable splicing was seen in the OCRL1 transcript, involving a small 24-bp exon. These results should prove useful to medical and molecular geneticists studying mutations and providing DNA diagnostic services to families dealing with Lowe syndrome as well as to cell biologists interested in structure-function relationships for the OCRL1 protein.

Animals↗
PubMed1997

Trinucleotide repeats (CGG)22TGG(CGG)43TGG(CGG)21 from the fragile X gene remain stable in transgenic mice.

Unstable premutation alleles in fragile X contain CGG repeats ranging from 34 to about 200. To study the mechanism of formation and the behavior of dynamic mutations, we constructed and cloned 88 trinucleotide repeats including 43 uninterrupted CGGs and injected them into mouse fertilized oocytes. We analyzed 342 transgenic animals obtained from 6 different founders after one to four generations, and found that the repeats remained stable regardless of the sex of the transmitting mouse. Therefore, we may need to consider factors other than trinucleotide repeat length alone to explain CGG instability and create an animal model.

Animals↗
PubMed1997

Spectrum of mutations in the OCRL1 gene in the Lowe oculocerebrorenal syndrome.

The oculocerebrorenal syndrome of Lowe (OCRL) is a multisystem disorder characterized by congenital cataracts, mental retardation, and renal Fanconi syndrome. The OCRL1 gene, which, when mutated, is responsible for OCRL, encodes a 105-kD Golgi protein with phosphatidylinositol (4,5)bisphosphate (PtdIn[4,5]P2) 5-phosphatase activity. We have examined the OCRL1 gene in 12 independent patients with OCRL and have found 11 different mutations. Six were nonsense mutations, and one a deletion of one or two nucleotides that leads to frameshift and premature termination. In one, a 1.2-kb genomic deletion of exon 14 was identified. In four others, missense mutations or the deletion of a single codon were found to involve amino acid residues known to be highly conserved among proteins with PtdIns(4,5)P2 5-phosphatase activity. All patients had markedly reduced PtdIns(4,5)P2 5-phosphatase activity in their fibroblasts, whereas the ocrl1 protein was detectable by immunoblotting in some patients with either missense mutations or a codon deletion but was not detectable in those with premature termination mutations. These results confirm and extend our previous observation that the OCRL phenotype results from loss of function of the ocrl1 protein and that mutations are generally heterogeneous. Missense mutations that abolish enzyme activity but not expression of the protein will be useful for studying structure-function relationships in PtdIns(4,5)P2 5-phosphatases.

Amino Acid Sequence↗
PubMed1997

Genetics of Parkinson's disease.

For the past 40 years, research into Parkinson's disease (PD) has been predominantly the province of epidemiologists interested in pursuing the connection between the disease and environmental factors such as viral infection or neurotoxins. Hereditary influences were actually discounted because of a high monozygotic twin discordance rate found in studies that were later shown to be inadequate and inconclusive. There has recently been a resurgence of interest in investigating hereditary factors in PD when it became more and more apparent that a positive family history was a major risk factor for the disease. Meanwhile, it also became increasingly apparent from neuropathological studies that the common, idiopathic form of Parkinson's disease had, in fact, a pathological correlate, i.e., the existence of Lewy bodies, an eosinophilic cytoplasmic inclusion body, distributed diffusely throughout the substantia nigra, hypothalamus, hippocampus, autonomic ganglia and olfactory tracts. Although candidate gene approaches to linkage in PD families have not been rewarding, a genome wide scan mapped PD to 4q21-23 in one large family with PD with diffuse Lewy bodies, where a candidate gene, alpha-synuclein, resides. This gene encodes a presynaptic protein of which a peptide fragment is known to be a constituent of Alzheimer's disease plaques. The identification of a missense mutation in the alpha-synuclein gene in four independent PD families suggests that at least some fraction of familial PD with diffuse Lewy bodies is the result of an abnormal protein that interferes with normal protein degradation leading to the development of inclusions and ultimately neuronal cell death. There may be common pathogenetic mechanisms involved in alpha-synuclein mutations in PD and beta-amyloid and presenilin gene mutations in Alzheimer's disease.

Chromosome Mapping↗
PubMed1996

Mapping of a gene for Parkinson's disease to chromosome 4q21-q23.

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting approximately 1 percent of the population over age 50. Recent studies have confirmed significant familial aggregation of PD and a large number of large multicase families have been documented. Genetic markers on chromosome 4q21-q23 were found to be linked to the PD phenotype in a large kindred with autosomal dominant PD, with a Zmax = 6.00 for marker D4S2380. This finding will facilitate identification of the gene and research on the pathogenesis of PD.

Chromosome Mapping↗
PubMed1995

Identification and chromosomal mapping of the mouse inositol polyphosphate 1-phosphatase gene.

A mouse inositol polyphosphate 1-phosphatase (Inpp1) cDNA fragment (348 bp) was amplified by means of the polymerase chain reaction using a mouse cDNA library as template with primers designed from published human and bovine cDNA sequences. We isolated a 1623-bp full-length Inpp1 cDNA from a mouse brain cDNA library using this amplified cDNA fragment as probe. Amino acid sequences of mouse, human, and bovine inositol polyphosphate 1-phosphatase are highly conserved. Northern blot analysis shows a major transcript of 1.65-kb mRNA and several higher molecular weight mRNAs that are expressed in a variety of mouse tissues. Utilizing the Jackson Lab backcross DNA panel map service, we mapped Inpp1 to chromosome 1, 1.06 cM proximal to Ctla4.

Amino Acid Sequence↗
PubMed1995

The fragile X mental retardation syndrome protein interacts with novel homologs FXR1 and FXR2.

Fragile X Mental Retardation Syndrome is the most common form of hereditary mental retardation, and is caused by defects in the FMR1 gene. FMR1 is an RNA-binding protein and the syndrome results from lack of expression of FMR1 or expression of a mutant protein that is impaired in RNA binding. The specific function of FMR1 is not known. As a step towards understanding the function of FMR1 we searched for proteins that interact with it in vivo. We have cloned and sequenced a protein that interacts tightly with FMR1 in vivo and in vitro. This novel protein, FXR2, is very similar to FMR1 (60% identity). FXR2 encodes a 74 kDa protein which, like FMR1, contains two KH domains, has the capacity to bind RNA and is localized to the cytoplasm. The FXR2 gene is located on human chromosome 17 at 17p13.1. In addition, FMR1 and FXR2 interact tightly with the recently described autosomal homolog FXR1. Each of these three proteins is capable of forming heteromers with the others, and each can also form homomers. FXR1 and FXR2 are thus likely to play important roles in the function of FMR1 and in the pathogenesis of the Fragile X Mental Retardation Syndrome.

Amino Acid Sequence↗
PubMed1995

Mapping of the 75-kDa inositol polyphosphate-5-phosphatase (Inpp5b) to distal mouse chromosome 4 and its exclusion as a candidate gene for dysgenetic lens.

We have determined the chromosomal localization of the murine gene encoding a 75-kDa inositol polyphosphate-5-phosphatase (Inpp5b). Using two independent approaches, fluorescence in situ hybridization and interspecific backcross analysis, we show that Inpp5b maps to distal mouse Chromosome 4. This map position is within the conserved linkage group corresponding to the short arm of human Chromosome 1, where the human homologue, INPP5B, has been shown to map previously. The position of Inpp5b on mouse Chromosome 4 is in the vicinity of the mouse developmental mutation dysgenetic lens (dyl). However, using a genetic approach, we show that Inpp5b maps distal to dyl on mouse Chromosome 4.

Animals↗