Biomedical subjects

J F Gusella

Publications and source records attributed to J F Gusella.

At least 19 recordsLinked to original sources

PubMed1995

Neurofibromatosis 2 gene in human colorectal cancer.

Colon cancers commonly have allelic losses of chromosome 22q, which suggests the presence of a tumor suppressor gene on 22q. The candidate tumor suppressor gene on 22q is the neurofibromatosis 2 (NF2) gene. Using single strand conformation polymorphism (SSCP) analysis, we screened 24 pairs of colorectal cancer and adjacent normal mucosa, as well as 10 colon cancer cell lines from non-NF2 patients, for mutations in the coding sequence of the NF2 gene. Two SSCP variants, one in exon 14 and another one in exon 16, were detected in two of the sporadic colorectal cancers, but not in adjacent normal mucosa samples. Sequencing of these variants in one tumor detected an A-to-G transition in bp 1459 of the NF2 cDNA, resulting in the change of Ile to Val at codon 487 of merlin, the NF2 protein product. The other tumor showed a 2-bp (CT) deletion in the intronic sequence of the alternatively spliced exon 16. These results suggest that the NF2 gene is probably involved in some colorectal tumors, but is not the critical chromosome 22q tumor suppressor gene involved in colon tumorigenesis.

Base Sequence↗

PubMed1995

Molecular characterization of a second melatonin receptor expressed in human retina and brain: the Mel1b melatonin receptor.

A G protein-coupled receptor for the pineal hormone melatonin was recently cloned from mammals and designated the Mel1a melatonin receptor. We now report the cloning of a second G protein-coupled melatonin receptor from humans and designate it the Mel1b melatonin receptor. The Mel1b receptor cDNA encodes a protein of 362 amino acids that is 60% identical at the amino acid level to the human Mel1a receptor. Transient expression of the Mel1b receptor in COS-1 cells results in high-affinity 2-[125I]iodomelatonin binding (Kd = 160 +/- 30 pM). In addition, the rank order of inhibition of specific 2-[125I]iodomelatonin binding by eight ligands is similar to that exhibited by the Mel1a melatonin receptor. Functional studies of NIH 3T3 cells stably expressing the Mel1b melatonin receptor indicate that it is coupled to inhibition of adenylyl cyclase. Comparative reverse transcription PCR shows that the Mel1b melatonin receptor is expressed in retina and, to a lesser extent, brain. PCR analysis of human-rodent somatic cell hybrids maps the Mel1b receptor gene (MTNR1B) to human chromosome 11q21-22. The Mel1b melatonin receptor may mediate the reported actions of melatonin in retina and participate in some of the neurobiological effects of melatonin in mammals.

Amino Acid Sequence↗

PubMed1995

Exon scanning for mutations of the NF2 gene in pediatric ependymomas, rhabdoid tumors and meningiomas.

Deletions of chromosome 22 have been identified in 3 types of childhood primary brain tumor: meningiomas, rhabdoid or atypical teratoid tumors (ATT) and ependymomas. This implicates the involvement of tumor suppressor genes on chromosome 22 in the genesis of these rare tumors. One such candidate tumor suppressor gene is the recently cloned neurofibromatosis 2 (NF2) locus. The purpose of our study was to determine the frequency of germ-line and somatic NF2 mutations in a selected group of brain tumors in children. Using single-strand conformation polymorphism (SSCP) assays we screened 17 exons of the NF2 gene in 13 pediatric brain tumors and 9 matched normal blood DNA samples. Tumors included 3 meningiomas, 2 rhabdoid or ATTs, 7 ependymomas and 1 malignant tumor of glial lineage. In addition, lymphoblastoid cell lines from 3 patients with rhabdoid/ATT in whom no tumor tissue was available were analyzed for germ-line mutations. Migration shifts were not detected in any of the normal DNA samples analyzed. Of the 13 tumors screened by SSCP, 1 meningioma with monosomy 22 produced a migration shift in exon 13. DNA sequencing of exon 13 revealed a deletion of a single guanine nucleotide (base 1397) in codon 466, causing a frame shift. While not all mutations might have been picked up by this technique, the data suggest that, similar to adult sporadic meningiomas, some pediatric meningiomas may result from somatic mutations in the NF2 gene. For rhabdoid tumors and ependymomas it appears that a locus distinct from NF2 might be responsible for tumorigenesis.

Base Sequence↗

PubMed1995

Expression of PTPH1, a rat protein tyrosine phosphatase, is restricted to the derivatives of a specific diencephalic segment.

Studies to date have identified only a few proteins that are expressed in a segment-specific manner within the mammalian brain. Here we report that a nonreceptor protein tyrosine phosphatase, PTPH1, is selectively expressed in the adult thalamus. Expression of PTPH1 mRNA is detected in most, but not all, thalamic nuclei. Nuclei that are derived embryonically from the dorsal thalamus and project to the neocortex express this gene, whereas those derived from the ventral thalamus do not. PTPH1 mRNA expression is also restricted to the dorsal thalamus during development and, thus, can serve as a specific marker for the dorsal thalamic nuclei. Since the subcellular localization of PTPH1 protein is not known, its functional role is not clear. However, the restriction of its expression to the thalamic nuclei that have thalamocortical connections suggests that PTPH1 may play a role in the maintenance of these connections or in determining the physiological properties of thalamic relay nuclei.

Aging↗

PubMed1995

Inactivation of the mouse Huntington's disease gene homolog Hdh.

Huntington's disease (HD) is a dominant neurodegenerative disorder caused by expansion of a CAG repeat in the gene encoding huntingtin, a protein of unknown function. To distinguish between "loss of function" and "gain of function" models of HD, the murine HD homolog Hdh was inactivated by gene targeting. Mice heterozygous for Hdh inactivation were phenotypically normal, whereas homozygosity resulted in embryonic death. Homozygotes displayed abnormal gastrulation at embryonic day 7.5 and were resorbing by day 8.5. Thus, huntingtin is critical early in embryonic development, before the emergence of the nervous system. That Hdh inactivation does not mimic adult HD neuropathology suggests that the human disease involves a gain of function.

Animals↗

PubMed1995

Mapping of the gene for the Mel1a-melatonin receptor to human chromosome 4 (MTNR1A) and mouse chromosome 8 (Mtnr1a).

The pineal hormone melatonin elicits potent circadian and reproductive effects in mammals. We report the chromosomal location of the gene for the Mel1a-melatonin receptor that likely mediates these circadian and reproductive actions. PCR analysis of human-rodent somatic cell hybrids showed that the receptor gene (MTNR1A) maps to human chromosome 4q35.1. An interspecific backcross analysis revealed that the mouse gene (Mtnr1a) maps to the proximal portion of chromosome 8. These loci may be involved in genetically based circadian and neuroendocrine disorders.

Animals↗

PubMed1995

Apolipoprotein E4 allele and Alzheimer disease: examination of allelic association and effect on age at onset in both early- and late-onset cases.

An increased frequency of the apolipoprotein E type 4 allele (APOE-4) has previously been associated with both late-onset sporadic and late-onset familial Alzheimer disease (AD) [Strittmatter et al. (1993) Proc Natl Acad Sci USA 90:1977-1981; Saunders et al. (1993a) Neurology 43:1467-1472]. To further investigate this association we genotyped affected individuals from 92 separate AD pedigrees including both early- and late-onset cases. An increased frequency of the APOE-4 allele was found only among the late-onset cases, both familial and sporadic, confirming the earlier reports. In addition, age at onset was significantly decreased in the APOE-4 homozygotes (in late onset families) compared to either APOE-4 heterozygotes or individuals not carrying an APOE-4 allele. We also observed a significantly decreased frequency of the APOE-2 allele in both the early- and late-onset familial cases. These results strengthen the argument for a direct role of APOE in susceptibility to AD.

Age of Onset↗

PubMed1995

Peripherin gene is linked to keratin 18 gene on human chromosome 12.

Peripherin is a neuron-specific intermediate filament (IF) protein, found primarily in phylogenetically old regions of the nervous system. Whereas other neuronal IF genes have only two to three introns and are scattered in the genome, the peripherin gene (PRPH) has a complex intron-exon structure like nonneuronal IF genes that are clustered in tandem arrays, e.g., those encoding the keratins. We used a cosmid containing the human peripherin gene (PRPH) to determine its chromosomal location in relationship to nonneuronal IF genes. Using a rodent-human mapping panel, we localized the PRPH gene to human chromosome 12. Since a cluster of keratin genes maps to 12q12-13, polymorphic markers were developed for PRPH and for one of the keratin genes presumed to be in the cluster, keratin 18 (KRT18). Both markers were typed in CEPH reference families. Pairwise and multipoint analyses of the CEPH data revealed that KRT18 is tightly linked to DNA markers D12S4, D12S22, D12S90, D12S96 and D12S103, which lie between D12S18 and D12S8, with odds greater than 1000:1. These markers are physically located at 12q11-13, thus supporting the fine localization of KRT18 in or near the group of type II keratins in this region. Furthermore, linkage analysis showed that the peripherin gene (PRPH) is tightly linked to KRT18 (Z = 15.73, theta = 0.013), and therefore appears to be in close proximity to the cluster.

Base Sequence↗

PubMed1995

Huntington's disease.

Early in 1993, an unstable, expanded trinucleotide repeat in a novel gene of unknown function was identified on HD chromosomes. This discovery unleased a flurry of experimentation that has established the expanded CAG repeat the almost universal cause of the characteristic neurologic symptoms and pathology of this neurodegenerative disorder of midlife onset. The biochemical basis for the specific neuronal loss of HD remains uncertain, but the genetic lesion probably acts via its consequent polyglutamine segment in the protein product, huntingtin. This review will describe the basic parameters of the HD repeat's behavior and the knowledge that has accumulated concerning its potential mechanisms of action.

Age of Onset↗

PubMed1995

A tiger behind many doors: multiple genetic pathways to malignant glioma.

Malignant gliomas are the most common primary human brain tumours, but their classification remains controversial and effective therapies remain elusive. As a result, malignant gliomas have come under intense scientific scrutiny, in the hope of elucidating the molecular basis of glial tumourigenesis. These studies have yielded insights into the genetic events that underlie glioma formation and progression, and have shown multiple distinct genetic pathways that lead to the common malignant endpoint of glioblastoma multiforme. Such genetic pathways mirror clinicopathological avenues of glioma progression and suggest that molecular genetic approaches might have clinical utility in the coming years.

Astrocytoma↗

PubMed1995

Chromosome 19q deletions in human gliomas overlap telomeric to D19S219 and may target a 425 kb region centromeric to D19S112.

Chromosome 19q harbors a tumor suppressor gene that is involved in astrocytoma, oligodendroglioma and mixed glioma tumorigenesis. We had previously mapped this gene to an approximately 5 megabase region of chromosome 19q13.2-13.3 between APOC2 and HRC. To narrow the location of this tumor suppressor further, we studied 138 gliomas for loss of allelic heterozygosity at six microsatellite polymorphisms between APOC2 and HRC, including a newly described polymorphism in the ERCC2 gene. Allelic loss occurred in 48 gliomas (35%), including 25 of 41 oligodendroglial tumors (61%). Four cases had proximal breakpoints within the APOC2-HRC region, two telomeric to ERCC2 and two telomeric to D19S219. In addition, one of the latter tumors had an interstitial deletion between D19S219 and D19S112, a distance of only 425 kilobases surrounding the DM (myotonic dystrophy) gene. These findings suggest that the glioma tumor suppressor on chromosome 19q maps to 19q13.3, telomeric to D19S219 and perhaps centromeric to D19S112. The data exclude a number of candidate genes from 19q13.2-13.3, including a putative phosphatase gene and the DNA repair/metabolism genes ERCC1, ERCC2 and probably LIG1.

Base Sequence↗

PubMed1995

Evidence for subarachnoid spread in the development of multiple meningiomas.

Meningiomas are among the most common human brain tumors. Occasionally patients develop multiple meningiomas. While it has been surmised that these are multiple primary meningiomas, it is possible that they represent spread of a single primary tumor. Recently, the neurofibromatosis type 2 (NF2) tumor suppressor gene has been shown to carry mutations in meningiomas. In the present study we have analyzed multiple meningiomas from two patients for point mutations in the NF2 gene by SSCP analysis and direct sequencing. We detected point mutations in the meningiomas from both patients. The first patient from which six tumors were available had a three base pair deletion in the splice donor region of exon 7. All tumors showed the identical mutation. The second patient with two independent meningiomas had a nonsense mutation in exon 8 which was the same in both tumors. Analysis of constitutional DNA revealed a wildtype DNA sequence in both cases. There was no family history of neurofibromatosis type 2 in either patient. These data provide strong evidence for a monoclonal origin of multiple meningiomas. Early subarachnoid spread is the most likely mechanism for the formation of these tumors.

Aged↗

PubMed1995

Neuropathology and molecular genetics of neurofibromatosis 2 and related tumors.

Neurofibromatosis 2 (NF2) is an uncommon, autosomal dominant disorder in which patients are predisposed to neoplastic and dysplastic lesions of Schwann cells (schwannomas and schwannosis), meningeal cells (meningiomas and meningioangiomatosis) and glial cells (gliomas and glial hamartomas). Clinical and genetic criteria that distinguish NF2 from neurofibromatosis 1 have allowed more accurate assignment of specific pathological features to NF2. The NF2 tumor suppressor gene on chromosome 22q12 encodes a widely expressed protein, named merlin, which may link the cytoskeleton and cell membrane. Germline NF2 mutations in NF2 patients and somatic NF2 mutations in sporadic schwannomas and meningiomas have different mutational spectra, but most NF2 alterations result in a truncated, inactivated merlin protein. In NF2 patients, specific mutations do not necessarily correlate with phenotypic severity, although grossly truncating alterations may result in a more severe phenotype. In schwannomas, NF2 mutations are common and may be necessary for tumorigenesis. In meningiomas, NF2 mutations occur more commonly in fibroblastic than meningothelial subtypes, and may cluster in the first half of the gene. In addition, in meningiomas, a second, non-NF2 meningioma locus is probably also involved. Future efforts in NF2 research will be directed toward elucidating the role of merlin in the normal cell and the sequelae of its inactivation in human tumors.

Humans↗

PubMed1995

NF2 gene analysis distinguishes hemangiopericytoma from meningioma.

The histogenesis of dural-based or "central" hemangiopericytomas (cHPCs) remains controversial. Some authors consider these tumors variants of meningiomas while others consider them akin to peripheral hemangiopericytomas (pHPCs). Meningiomas frequently have mutations in the neurofibromatosis 2 (NF2) gene, providing a molecular marker for meningiomas and other NF2-related tumors. We therefore analyzed the NF2 gene in cHPCs, pHPCs, and meningiomas to determine whether cHPCs are more similar at the molecular genetic level to meningiomas or pHPCs. Using paraffin-embedded archival material from 28 cHPCs (including three primary and recurrent tumors), 10 pHPCs, and 26 meningiomas, we scanned all 17 exons of the NF2 gene and flanking intronic sequences for mutations with single strand conformation polymorphism analysis and DNA sequencing. No NF2 mutations were found in either cHPCs or pHPCs, whereas 35% of meningiomas had NF2 gene alterations (P < 0.001). The NF2 gene mutations in meningiomas were all truncating mutations, consistent with previous studies. Our findings suggest that cHPCs are distinct from meningiomas at the molecular genetic level and support prior clinico-pathological data that distinguish these tumor-entities.

Adult↗

PubMed1995

Analysis of the neurofibromatosis 2 gene reveals molecular variants of meningioma.

There is evidence from cytogenetic and loss of heterozygosity studies for the involvement of a tumor suppressor gene on chromosome 22 in the formation of meningiomas. Recently, the NF2 gene, which causes neurofibromatosis type 2 and which is located in the affected region on chromosome 22, has been identified. A previous study on 8 of the 17 exons of the NF2 gene described mutations in 16% of meningiomas. We have analyzed the entire coding region of the NF2 gene in 70 sporadic meningiomas and identified 43 mutations in 41 patients. These resulted predominantly in immediate truncation, splicing abnormalities, or an altered reading frame of the predicted protein product. Although there was no evidence for distinct hotspots, all mutations occurred in the first 13 exons, the region of homology with the filopodial proteins moesin, ezrin, and radixin. The association of loss of heterozygosity on chromosome 22 with mutations in the NF2 gene was significant. These data suggest that NF2 represents the meningioma locus on chromosome 22. NF2 mutations occurred significantly more frequently in fibroblastic meningioma (70%) and transitional meningioma (83%) than in meningiothelial meningioma (25%), thus indicating a differential molecular pathogenesis of these meningioma variants.

Adult↗

PubMed1994

Sequence analysis and mapping of a novel human mitochondrial ATP synthase subunit 9 cDNA (ATP5G3).

We describe the cloning, sequence analysis, and chromosomal mapping of a novel mitochondrial ATP synthase subunit 9cDNA, P3. Subunit 9 transports protons across the inner mitochondrial membrane to the F1-ATPase protruding on the matrix side, resulting in the generation of ATP. Sequence analysis of the P3 cDNA reveals only 80% identity with the human subunit 9 genes P1 and P2 in the DNA sequence encoding the mature peptide. However, this sequence predicts a mature protein identical to P1 and P2. The predicted sequence of the P3 leader peptide differs from the P1 and P2 leaders, but retains the "RFS" motif critical for mitochondrial import and maturation. The P3 gene (ATP5G3) maps to chromosome 2.

Amino Acid Sequence↗

PubMed1993

Characterization of a duplication in the terminal band of 4p by molecular cytogenetics.

An infant with multiple anomalies including small head, large apparently low-set ears, beaked nose, micrognathia, choanal stenosis, proptosis, atrial-septal defect, and left inguinal hernia was found, on chromosome analysis, to have a longer than normal terminal band 4p16 by G and R-banding. In situ hybridization of biotin-labeled DNA probes C39, BJ14, BJ54, BJ19, BJ7, and BJ11 showed them to be duplicated. Probes I14, A157.1, and the telomeric sequence, (TTAGGG)n, which hybridized to the more distal part of 4p16.3, were not duplicated. These results confirm the impression by G and R-banding of a duplication within band 4p16, a region extending from approximately 2.1 Mb from the telomere, proximally, to the junction of 4p16.1 and 4p15.3. This is the smallest confirmed duplication of distal 4p reported to date, with many of the classical findings of dup(4p) syndrome.

Abnormalities, Multiple↗

PubMed1993

Modification of the Na+ current conducted by the rat skeletal muscle alpha subunit by coexpression with a human brain beta subunit.

Sodium channels are multimeric structures composed of alpha and beta subunits. Oocytes injected with RNA encoding only the alpha subunit express voltage-gated Na+ currents. The kinetics of inactivation, however, are abnormal. Co-injection of rat brain alpha and beta subunits modifies inactivation of INa such that it closely resembles endogenous currents. Here we show that a beta subunit derived from human brain directs the same functional modification of INa expressed by a rat skeletal muscle alpha subunit. This implies that functional domains for the interaction of alpha and beta subunits are highly conserved across both tissues and species.

Animals↗