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Biomedical subjects

R L Nussbaum

Publications and source records attributed to R L Nussbaum.

8 recordsLinked to original sources
PubMed1992

Cloning of human and bovine homologs of SNF2/SWI2: a global activator of transcription in yeast S. cerevisiae.

We performed positional cloning of genes carried on yeast artificial chromosomes that span a human translocation breakpoint associated with a human disease and isolated by chance human and bovine genes with strong homology to the S. cerevisiae genes, SNF2/SWI2 and STH1, and the D. melanogaster gene brahma. We report here sequence analysis, expression data, and functional studies for this human SNF2-like gene (hSNF2L) and its bovine homolog (bovSNF2L). Despite strong homology at the amino acid level, hSNF2L is not capable of complementing the yeast mutations snf2 or sth1 in S. cerevisiae. Furthermore, in contrast to SNF2 itself, a fusion protein consisting of the DNA binding domain of LexA and hSNF2L did not transactivate a reporter gene downstream of LexA binding sites in a yeast expression system. The strong similarity between hSNF2L and these yeast and drosophila genes suggest that the mammalian genes are part of an evolutionarily conserved family that has been implicated as global activators of transcription in yeast and fruitflies but whose function in mammals remains unknown.

Adenosine Triphosphatases↗
PubMed1992

The Lowe's oculocerebrorenal syndrome gene encodes a protein highly homologous to inositol polyphosphate-5-phosphatase.

Lowe's oculocerebrorenal syndrome (OCRL) is a human X-linked developmental disorder of unknown pathogenesis and has a pleiotropic phenotype affecting the lens, brain and kidneys. The OCRL locus has been mapped to Xq25-q26 by linkage and by finding de novo X; autosome translocations at Xq25-q26 in two unrelated females with OCRL. Here we use yeast artificial chromosomes with inserts that span the X chromosomal breakpoint from a female OCRL patient in order to isolate complementary DNAs for a gene that is interrupted by the translocation. We show that the transcript is absent in both female OCRL patients with X; autosome translocations and that it is absent or abnormally sized in 9 of 13 unrelated male OCRL patients with no detectable genomic rearrangement. The open reading frame encodes a new protein with 71% similarity to human inositol polyphosphate-5-phosphatase. Our results suggest that OCRL may be an inborn error of inositol phosphate metabolism.

Amino Acid Sequence↗
PubMed1992

Isolation of a candidate gene for choroideremia.

Choroideremia is an X chromosome-linked retinal dystrophy of unknown pathogenesis. We have isolated cDNAs from a human retinal library with a genomic probe located at the X chromosomal breakpoint in a female with choroideremia and an X;13 translocation. This cDNA spans the breakpoint in the X;13 translocation female and is deleted in males who have choroideremia as part of a complex phenotype including mental retardation and deafness. However, this cDNA detects no alterations in the DNA of 34 males with isolated choroideremia. Nonetheless, the cDNA does detect reduced or absent levels of mRNA in three-quarters of male patients with an apparently intact gene. These data support the hypothesis that this cDNA represents the gene in which mutations cause choroideremia.

Amino Acid Sequence↗
PubMed1992

Isolation of cDNA sequences around the chromosomal breakpoint in a female with Lowe syndrome by direct screening of cDNA libraries with yeast artificial chromosomes.

The Lowe oculocerebrorenal syndrome (OCRL; McKusick 309000) is an X-linked disorder characterized by congenital cataracts, muscular hypotonia, mental retardation, and Fanconi syndrome of the renal tubules. A pair of yeast artificial chromosomes (YACs) that span the Xq25-q26 translocation breakpoint in a female with OCRL were used as probes to screen cDNA libraries made from bovine lens and human kidney. The methods used to prepare the YACs as probes and to screen the libraries are presented in detail. Two different transcripts were found that map to the region around the Xq25-q26 breakpoint. These transcripts are now being studied to determine whether one or the other is a candidate gene for OCRL.

Blotting, Southern↗
PubMed1992

Construction and characterization of a yeast artificial chromosome library for Xpter-Xq27.3: a systematic determination of cocloning rate and X-chromosome representation.

We describe the construction and characterization of a human X-chromosome-specific yeast artificial chromosome (YAC) library. Starting with 60 micrograms of hybrid cell line genomic DNA, we generated over 150,000 recombinants, over 90% of which range from 150 to 500 kb. From these recombinants, 3300 human-positive YACs (representing coverage of 4.5 X chromosomes) were identified by genomic human DNA hybridization. Mapping of random clones revealed that they are derived from the X chromosome in a regionally unbiased fashion, and screening with single-copy X-chromosome probes has repeatedly produced YACs from the library. By determining the frequency of YAC clones containing both hamster and human repetitive sequences, we estimated that approximately 11% of clones contain discontiguous sequences. Taken together, the low cocloning rate, the unbiased coverage, and a consistent recovery of YACs using specific X-chromosome markers indicate that YAC technology can be used for extensive cloning and mapping purposes. Because a certain amount of genomic rearrangement is present in YAC libraries, chromosome walking must be undertaken with a degree of caution.

Animals↗
PubMed1992

Maximum-likelihood analysis of human T-cell X chromosome inactivation patterns: normal women versus carriers of X-linked severe combined immunodeficiency.

Lymphocytes of female carriers of X-linked severe combined immunodeficiency (XSCID; McKusick 300400; HGM genetic locus designation SCIDX1) exhibit nonrandom X chromosome inactivation. This phenomenon reflects a tissue-specific selective disadvantage for lymphocyte progenitors with an XSCID mutation on the active X chromosome and presumably is analogous to the process that inhibits T-cell development in affected boys with a single XSCID-bearing X chromosome. We investigated the specificity of T-cell X chromosome inactivation pattern as an indicator of immunodeficiency carrier status, as follows: X-inactivation ratios determined in a control group of noncarrier women exhibited a wide range, 20%-86% of T-cells with the paternal X active. Maximum-likelihood analysis of these data suggested that, in humans, mature T-cells are derived from a small pool of only about 10 randomly inactivated stem cells. Despite the wide variability in normal X-inactivation ratios, X inactivation in XSCID carriers appeared far more markedly skewed. Therefore a maximum-likelihood odds-ratio test was developed and proved to be successful in predicting the carrier status of women in XSCID pedigrees. This test has made it possible to identify XSCID carriers among mothers of boys with the heterogeneous syndrome of sporadic severe combined immunodeficiency.

Adolescent↗
PubMed1991

Linkage analysis in X-linked ocular albinism.

We studied the linkage of X-linked Nettleship-Falls ocular albinism (OA1) to Xp22.1-Xp22.3 RFLPs at 12 loci in five families, including one in which OA1 cosegregates with a deletion of steroid sulfatase (STS). We found evidence for tight linkage of OA1 to the Xp22.3 loci DXS143, STS, and DXS452. DXS452, a newly described polymorphism detected by the probe E25B1.8, is part of the sequence family "DXS278" (pCRI-S232), but represents a single genetic locus. Every female in this study was heterozygous for the DXS452 RFLP. Thus, this marker will be extremely useful for family studies and genetic counseling. Analysis of individual recombinations suggests that OA1 maps between DXS143 and DXS85. Multipoint linkage analysis was consistent with this localization but was not statistically significant. These data suggest that OA1 lies proximal to the deletion in a previously described family with OA1 and STS deletion, but maps within the Xp22.3-Xp22.2 region.

Albinism, Ocular↗