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H T Orr

Publications and source records attributed to H T Orr.

At least 55 records · Page 3Linked to original sources
PubMed1996

Familial cerebral cavernous angioma: a gene localized to a 15-cM interval on chromosome 7q.

Cerebral cavernous angiomas are collections of closely clustered vessels without intervening normal brain parenchyma, with microscopic evidence of hemorrhage, frequently multiple; they are best visualized with magnetic resonance imaging. Familial cerebral cavernous angioma occurs as an autosomal dominant disorder, although carriers of the gene are often asymptomatic. Recently, a gene responsible for familial cerebral cavernous angioma in a large Hispanic kindred was mapped to human chromosome 7q11-22, representing a large segment of DNA containing approximately 33 cM (about 33 million base pairs). This distance did not allow more restricted isolation of the region containing the familial cerebral cavernous angioma gene. In this report, we present a large white kindred with familial cerebral cavernous angioma and confirm the mapping to 7q11-22, including the genetic markers D7S558/D7S1789 and D7S804. Recombination between several markers in the region suggests that the candidate region is distal to D7S804. Combining our results with those previously published, we suggest that the gene is likely to reside within a 15-cM region bounded by markers D7S660 and D7S558/D7S1789. These results should assist the further refinement of the candidate region for familial cerebral cavernous angioma and facilitate the search for the gene.

Brain↗
PubMed1996

Isolation, characterization and in vivo analysis of the murine calbindin-D28K upstream regulatory region.

The genomic locus containing the murine calbindin-D28K gene has been isolated and partially characterized. Genomic cloning revealed an exon/intron chromosomal structure very similar to the avian gene previously described. The ability of the calbindin-D28K upstream region to direct cell-specific expression was tested in vivo. Varying lengths of upstream sequence were used to drive expression of lacZ in transgenic mice. Characterization of 23 transgenic mouse lines revealed that even as much as 3.0 kb of upstream sequence was unable to direct expression independently of integration site effects, suggesting the absence of important elements. Despite the small number of expressing transgenic lines and the great variability, there was a tendency of cell specificity of transgene expression exhibited in distinct brain regions. In the cerebellum, Purkinje cell-specific expression was observed with the shortest (1.0 kb) upstream sequence tested. Specificity of transgene expression in Purkinje cells was abolished with longer portions of upstream sequence. The same observation was made for transgene expression in granule cells of the dentate gyrus, while the opposite effect was observed for expression in CA1 hippocampal cells. The absence of any transgenic lines exhibiting appropriate transgene expression in the kidney suggested that the VDREs described previously for the murine calbindin gene are not sufficient to direct kidney expression in vivo. It is concluded that 3.0 kb of calbindin upstream sequence includes the regulatory elements dictating a portion of cell-specificity in the CNS of transgenic mice, albeit lacking regions that allow expression independently of chromosomal effects.

Animals↗
PubMed1996

Cloning and developmental expression analysis of the murine homolog of the spinocerebellar ataxia type 1 gene (Sca1).

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG trinucleotide repeat which encodes glutamine in the novel protein ataxin-1. In order to characterize the developmental expression pattern of SCA1 and to identify putative functional domains in ataxin-1, the murine homolog (Sca1) was isolated. Cloning and characterization of the murine Sca1 gene revealed that the gene organization is similar to that of the human gene. The murine and human ataxin-1 are highly homologous but the CAG repeat is virtually absent in the mouse sequence suggesting that the polyglutamine stretch is not essential for the normal function of ataxin-1 in mice. Cellular and developmental expression of the murine homolog was examined using RNA in situ hybridization. During cerebellar development, there is a transient burst of Sca1 expression at postnatal day 14 when the murine cerebellar cortex becomes physiologically functional. There is also marked expression of Sca1 in mesenchymal cells of the intervertebral discs during development of the spinal column. These results suggest that the normal Sca1 gene, has a role at specific stages of both cerebellar and vertebral column development.

Amino Acid Sequence↗
PubMed1996

Spinocerebellar ataxia type-1 and spinobulbar muscular atrophy gene products interact with glyceraldehyde-3-phosphate dehydrogenase.

Spinocerebellar ataxia type1 (SCA1) is one of several neurodegenerative disorders caused by expansions of translated CAG trinucleotide repeats which code for polyglutamine in the respective proteins. Most hypotheses about the molecular defect in these disorders suggest a gain of function, which may involve interactions with other proteins via the expanded polyglutamine tract. In this study we used ataxin-1, the SCA1 gene product, as a bait in the yeast two-hybrid system and identified the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase as an ataxin-1 interacting protein. In addition, the yeast two hybrid data demonstrate that wild type and mutant ataxin-1 form homo and heterodimers. Physical interaction between GAPDH and ataxin-1 was also demonstrated in vitro. To investigate if GAPDH might interact with other glutamine repeat-containing proteins involved in neurodegenerative disorders, we tested its binding to the androgen receptor which is mutated in spinobulbar muscular atrophy. The androgen receptor interacts with GAPDH both in the yeast two-hybrid system and in vitro. The binding of both ataxin-1 and the androgen receptor to GAPDH does not vary with the length of the polyglutamine tract. While provocative, these findings do not address the selective neuronal loss in each of these disorders in light of the wide expression patterns of GAPDH and the respective polyglutamine containing proteins. Nonetheless, such interactions may increase the susceptibility of specific neurons to a variety of insults and initiate degeneration.

Animals↗
PubMed1995

SCA1 transgenic mice: a model for neurodegeneration caused by an expanded CAG trinucleotide repeat.

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant inherited disorder characterized by degeneration of cerebellar Purkinje cells, spinocerebellar tracts, and selective brainstem neurons owing to the expansion of an unstable CAG trinucleotide repeat. To gain insight into the pathogenesis of the SCA1 mutation and the intergenerational stability of trinucleotide repeats in mice, we have generated transgenic mice expressing the human SCA1 gene with either a normal or an expanded CAG tract. Both transgenes were stable in parent to offspring transmissions. While all six transgenic lines expressing the unexpanded human SCA1 allele had normal Purkinje cells, transgenic animals from five of six lines with the expanded SCA1 allele developed ataxia and Purkinje cell degeneration. These data indicate that expanded CAG repeats expressed in Purkinje cells are sufficient to produce degeneration and ataxia and demonstrate that a mouse model can be established for neurodegeneration caused by CAG repeat expansions.

Animals↗
PubMed1995

Temporal and spatial expression of HLA-G messenger RNA in extraembryonic tissues of transgenic mice.

HLA-G, a nonclassical class I molecule, is expressed by trophoblasts, the only fetal cells in direct contact with maternal tissue. Results of previous experiments suggested that a 244-bp region located over 1 kb 5' from exon 1 is critical for extraembryonic expression of HLA-G in transgenic mice. We report here the production of HLA-G transgenic lines with a 6.0-kb HLA-G transgene that includes the 244-bp region. These lines exhibit copy number-dependent and developmentally appropriate transgene expression. One HLA-G transgenic line, G.3.2, exhibits extraembryonic HLA-G mRNA expression levels similar to those seen in human extraembryonic tissues. Studies of the cell-type-specific localization of HLA-G mRNA in placentas from the G.3.2 HLA-G transgenic mouse line show predominant localization of the HLA-G message in the spongiotrophoblast layer. This layer is in a similar anatomic location to the HLA-G-expressing human cytotrophoblast shell. The G.3.2 HLA-G transgenic mouse line should serve as an appropriate model for the study of HLA-G function at the maternal-fetal interface.

Animals↗
PubMed1995

In vivo viability of postmitotic Purkinje neurons requires pRb family member function.

The product of the retinoblastoma susceptibility gene, pRb, is known to be an important regulator of cell division. Disrupted central nervous system development in RB null mice suggests a critical function for pRb in the proliferative arrest and initiation of terminal differentiation of certain neurons. Previously, we have shown that SV40 T-ag expression targeted to Purkinje neurons in transgenic mice causes cell-specific death. Here we describe that T-ag expression induces DNA synthesis and results in DNA fragmentation in Purkinje neurons. Characterization of transgenic mouse lines expressing mutant T-ags demonstrate that the pRb binding domain of T-ag is required for induction of Purkinje cell loss. These findings indicate that a pRb function is required well beyond the completion of Purkinje neuron differentiation and provide a link between cell cycle regulation and neurodegeneration in vivo.

Animals↗
PubMed1995

Spinocerebellar ataxia type 1.

Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disorder characterized by ataxia, dysarthria and progressive bulbar dysfunction. The SCA 1 gene which maps to the short arm of chromosome 6 has been isolated using a positional cloning approach. The SCA1 transcript is 10660 bases and encodes a novel protein, ataxin-1, with a predicted molecular weight of 87 kDa. Expansion of a CAG repeat localized near the amino terminus of ataxin-1 has been found to be the mutational mechanism in SCA1. This CAG repeat is highly polymorphic with normal alleles containing 6-39 repeats. Individuals affected with SCA1 have one normal allele and one expanded allele containing 40-81 repeats. The size of the repeat correlates inversely with the age of onset of symptoms and the severity of disease. The repeat is a continuous CAG repeat tract on SCA1 chromosomes whereas in > or = 98% of normal alleles one or more CAT interruptions break the CAG repeat tracts into two tracts containing less than 18 repeats each. This suggests that loss of CAT interruptions within the SCA1 CAG repeat on normal chromosomes leads to triplet instability.

Base Sequence↗
PubMed1995

Expression analysis of the ataxin-1 protein in tissues from normal and spinocerebellar ataxia type 1 individuals.

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by expansion of a CAG trinucleotide repeat which codes for glutamine in the protein ataxin-1. We have investigated the effect of this expansion on ataxin-1 by immunoblot analysis. The wild-type protein is detected in both normal and affected individuals; however, a mutant protein which varies in its migration properties according to the size of the CAG repeat is detected in cultured cells and tissues from SCA1 individuals. The protein has a nuclear localization in all normal and SCA1 brain regions examined but a cytoplasmic localization of ataxin-1 was also observed in cerebellar Purkinje cells. Our data show that in SCA1, the expanded alleles are faithfully translated into proteins of apparently normal stability and distribution.

Animals↗
PubMed1995

Gametic and somatic tissue-specific heterogeneity of the expanded SCA1 CAG repeat in spinocerebellar ataxia type 1.

Spinocerebellar ataxia type 1 is associated with expansion of an unstable CAG repeat within the SCA1 gene. Male gametic heterogeneity of the expanded repeat is demonstrated using single sperm and low-copy genome analysis. Low-copy genome analysis of peripheral blood also reveals somatic heterogeneity of the expanded SCA1 allele, thus establishing mitotic instability at this locus. Comparative analysis of a large normal allele and a small affected allele suggests a role of midstream CAT interspersions in stabilizing long (CAG)n stretches. Within the brain, tissue-specific mosaicism of the expanded allele is also observed. The differences in SCA1 allele heterogeneity between sperm and blood and within the brain parallels the findings in Huntington disease, suggesting that both disorders share a common mechanism for tissue-specific instability.

Alleles↗
PubMed1995

A gene responsible for cavernous malformations of the brain maps to chromosome 7q.

Cavernous malformations of the brain are vascular lesions which are present in up to 0.4% of all individuals and which are often accompanied by seizures, migraine, hemorrhage and other neurologic problems. Using linkage analysis and a set of short tandem repeat polymorphisms, a gene responsible for cavernous malformations in a large Hispanic kindred was mapped to the q11-q22 region of chromosome 7. A maximum pairwise lod score of 4.2 was obtained at zero recombination with marker PY5-18 at locus D7S804. Lod scores in excess of 3.0 were obtained with four additional markers closely linked to PY5-18. A broad chromosome 7q haplotype of 33 cM length on the sex average map was shared by all affected individuals indicating that the gene lies between loci D7S502 and D7S479.

Brain Neoplasms↗
PubMed1995

Refined localization of the cerebral cavernous malformation gene (CCM1) to a 4-cM interval of chromosome 7q contained in a well-defined YAC contig.

Cerebral cavernous malformations (CCM) are vascular lesions present in some 20 million people worldwide that are responsible for seizures, migraine, hemorrhage, and other neurologic problems. Familial cases ofCCM can be inherited as an autosomal dominant disorder with variable expression. A gene for CCM (CCM/)was recently mapped to a 33-cM segment of chromosome 7q in a large Hispanic family (Dubovsky et al.1995). Here, the collection of several new short tandem repeat polymorphisms (STRPs) within the region of interest on 7q and the refinement of the marker order in this region using both linkage analysis in CEPH families and especially YAC-based STS content mapping are described. Affected members of three Hispanic families share allele haplotypes indicating a common ancestral mutation within these families. Using the shared haplotype information along with analysis of crossovers in affected individuals from both the Hispanic and Caucasian families, the region likely to contain the CCMI gene has been reduced to a 4-cM segment of 7q between D7S2410 and D7S689. All markers within the refined chromosomal segment were located on a single YAC contig estimated to be approximately 2 Mb in size. Four potential candidate genes have been mapped to this region.

Base Sequence↗
PubMed1995

HLA-G transgenic mice: a model for studying expression and function at the maternal/fetal interface.

Experiments designed to identify all HLA class I genes led to the cloning of the HLA-G gene (Geraghty et al. 1987). Very low levels of HLA-G mRNA expression have been demonstrated in the eye, thymus, peripheral blood lymphocytes and in keratinocytes (Shukla et al. 1990, Ishitani & Geraghty 1992, Kirszenbaum et al. 1994, Ulbrecht et al. 1994). Higher levels of HLA-G expression were demonstrated in certain subpopulations of trophoblasts (Ellis et al. 1990, Kovats et al. 1990). Specifically, those subpopulations of trophoblasts in direct contact with decidua, i.e. the cytotrophoblasts of the cytotrophoblast shell and columns, invasive cytotrophoblasts, and cytotrophoblasts of the chorionic membrane, express HLA-G (Yelavarthi et al. 1991, Chumbley et al. 1993). HLA-G molecules on these cells are in a position to interact directly with the maternal immune system. HLA-G transgenic mice have been produced in an effort to produce a model in which antigen presentation by HLA-G can be studied. Studies utilizing these transgenic mice have led to the definition of a previously unknown regulatory region and have yielded some basic information about HLA-G's ability to function as a class I molecule (Schmidt et al., in press; manuscript in preparation). One of the HLA-G transgenic mouse lines produced, G.3.2, has been shown to have a cell-type specific extraembryonic HLA-G expression pattern paralleling that seen in human extraembryonic tissues (Schmidt et al, in press). In addition, the levels of HLA-G mRNA expression seen in the extraembryonic tissues from this transgenic mouse line are similar to the levels of HLA-G mRNA expression detectable in human extraembryonic tissues. As cells expressing HLA-G come in direct contact with decidual cells, these mice will serve as a model in which HLA-G's ability to present foreign antigens to the maternal immune system can be studied. The G.3.2 HLA-G transgenic mouse line also exhibits thymic HLA-G expression levels similar to those seen in human thymus (Schmidt et al., manuscript in preparation). HLA-G expression in the transgenic murine thymus is largely restricted to dendritic cells. It is possible that this thymic HLA-G mRNA expression is responsible for the tolerance to HLA-G which is seen in the HLA-G transgenic mice. Further studies will be necessary to determine whether the lymphocytic repertoire of the HLA-G transgenic mouse can recognize HLA-G molecules presenting foreign peptides.

Animals↗
PubMed1995

Spinocerebellar ataxia type 1 and Machado-Joseph disease: incidence of CAG expansions among adult-onset ataxia patients from 311 families with dominant, recessive, or sporadic ataxia.

The ataxias are a complex group of diseases with both environmental and genetic causes. Among the autosomal dominant forms of ataxia the genes for two, spinocerebellar ataxia type 1 (SCA1) and Machado-Joseph disease (MJD), have been isolated. In both of these disorders the molecular basis of disease is the expansion of an unstable CAG trinucleotide repeat. To assess the frequency of the SCA1 and MJD trinucleotide repeat expansions among individuals diagnosed with ataxia we have collected DNA from individuals representing 311 families with adult-onset ataxia of unknown etiology and screened these samples for trinucleotide repeat expansions within the SCA1 and MJD genes. Within this group there are 149 families with dominantly inherited ataxia. Of these, 3% had SCA1 trinucleotide repeat expansions, whereas 21% were positive for the MJD trinucleotide expansion. Thus, together SCA1 and MJD represent 24% of the autosomal dominant ataxias in our group, and the frequency of MJD is substantially greater than that of SCA1. For the 57 patients with MJD trinucleotide repeat expansions, a strong inverse correlation between CAG repeat size and age at onset was observed (r = -.838). Among the MJD patients, the normal and affected ranges of CAG repeat size are 14-40 and 68-82 repeats, respectively. For SCA1 the normal and affected ranges are much closer, containing 19-38 and 40-81 CAG repeats, respectively.

Adult↗
PubMed1994

Unstable trinucleotide repeats and the diagnosis of neurodegenerative disease.

Human genes containing unstable triplet repeats are associated with several neuropsychiatric diseases. These diseases all show a marked variation in clinical symptoms and genetic anticipation. The molecular understanding of these diseases provides the diagnostic laboratory with the capability to test directly whether an individual's DNA contains the disease-causing mutation, either as a confirmation of a clinical diagnosis or presymptomatically.

Bulbar Palsy, Progressive↗