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PubMed1990

Cis-acting sequences from a human surfactant protein gene confer pulmonary-specific gene expression in transgenic mice.

Pulmonary surfactant is produced in late gestation by developing type II epithelial cells lining the alveolar epithelium of the lung. Lack of surfactant at birth is associated with respiratory distress syndrome in premature infants. Surfactant protein C (SP-C) is a highly hydrophobic peptide isolated from pulmonary tissue that enhances the biophysical activity of surfactant phospholipids. Like surfactant phospholipid, SP-C is produced by epithelial cells in the distal respiratory epithelium, and its expression increases during the latter part of gestation. A chimeric gene containing 3.6 kilobases of the promoter and 5'-flanking sequences of the human SP-C gene was used to express diphtheria toxin A. The SP-C-diphtheria toxin A fusion gene was injected into fertilized mouse eggs to produce transgenic mice. Affected mice developed respiratory failure in the immediate postnatal period. Morphologic analysis of lungs from affected pups showed variable but severe cellular injury confined to pulmonary tissues. Ultrastructural changes consistent with cell death and injury were prominent in the distal respiratory epithelium. Proximal components of the tracheobronchial tree were not severely affected. Transgenic animals were of normal size at birth, and structural abnormalities were not detected in nonpulmonary tissues. Lung-specific diphtheria toxin A expression controlled by the human SP-C gene injured type II epithelial cells and caused extensive necrosis of the distal respiratory epithelium. The absence of type I epithelial cells in the most severely affected transgenic animals supports the concept that developing type II cells serve as precursors to type I epithelial cells.

Animals↗

PubMed1990

Major histocompatibility complex haplotype studies in Ashkenazi Jewish patients with pemphigus vulgaris.

Of 26 Ashkenazi Jewish patients with pemphigus vulgaris, 24 (92.3%) carried the major histocompatibility complex (MHC) class II alleles HLA-DR4, DQw3, of which all were of the subtype DR4, DQw8. From studies of the patients and their families, haplotypes were defined. It was found that, of the patients who carried HLA-DR4, DQw8, 75% carried one or the other (and in one case, both) of two haplotypes [HLA-B38, SC21, DR4] or HLA-B35, SC31, DR4. The former is a known extended haplotype among normal Jews, with a frequency of 0.102, and the latter may also be an extended haplotype in this ethnic group, with a frequency of 0.017 among normal haplotypes from Jews. Of the remaining DR4-positive patients, all but one had a presumed D-region segment (defined as SC21, DR4, DQw8 or SC31, DR4, DQw8 with variable HLA-B) of these haplotypes. Only one patient had DR4, DQw8 without any other markers of the extended haplotypes. The number of homozygotes and heterozygotes for DR4, DQw8 was consistent with dominant but not recessive (P less than 0.01) inheritance of a class II or a class II-linked susceptibility gene for the disease. Since the disease is entirely attributable to the presence of an antibody to an intraepidermal intercellular cement substance, it is likely that the class II susceptibility gene (on [HLA-B38, SC21, DR4, DQw8], HLA-B35, SC31, DR4, DQw8, or their segments, in Jewish patients) controls the production of the antibody as a dominantly expressed immune response gene.

Alleles↗

PubMed1990

Possible deletion of a developmentally regulated heavy-chain variable region gene in autoimmune diseases.

Several autoantibody-associated variable region (V) genes are preferentially expressed during early ontogenic development, suggesting strongly that they are of developmental and physiological importance. As such, it is possible that polymorphisms in one or more of these genes may alter susceptibility to autoimmune disease. We have searched extensively for a probe related to a developmentally regulated V gene that has the power to differentiate among highly homologous V genes in human populations. Using such a probe (i.e., Humhv3005/P1) related to both anti-DNA and anti-IgG autoantibodies, we studied restriction fragment length polymorphisms in patients with rheumatoid arthritis and systemic lupus erythematosus and found an apparent heavy-chain V (VH) gene deletion that was nearly restricted to the autoimmune patients. These data suggest that deletions of physiologically important VH genes may increase the risk of autoimmunity through indirect effects on the development and homeostasis of the B-cell repertoire.

Arthritis, Rheumatoid↗

PubMed1990

Rapid, nonradioactive detection of clonal T-cell receptor gene rearrangements in lymphoid neoplasms.

Southern blot hybridization analysis of clonal antigen receptor gene rearrangements has proved to be a valuable adjunct to conventional methods for diagnosing lymphoid neoplasia. However, Southern blot analysis suffers from a number of technical disadvantages, including the time necessary to obtain results, the use of radioactivity, and the susceptibility of the method to various artifacts. We have investigated an alternative approach for assessing the clonality of antigen receptor gene rearrangements in lymphoid tissue biopsy specimens. This approach involves the amplification of rearranged gamma T-cell receptor genes by the polymerase chain reaction and analysis of the polymerase chain reaction products by denaturing gradient gel electrophoresis. By use of this approach, clonal rearrangements from neoplastic lymphocytes constituting as little as 0.1-1% of the total cells in the tissue are detected as discrete bands in the denaturing gel after the gel is stained with ethidium bromide and viewed under ultraviolet light. In contrast, polyclonal rearrangements from reactive lymphocytes appear as a diffuse smear along the length of the gel. Our findings suggest that polymerase chain reaction combined with denaturing gradient gel electrophoresis may offer a rapid, nonradioactive, and sensitive alternative to Southern blot analysis for the diagnostic evaluation of lymphoid tissue biopsy specimens.

Base Sequence↗

PubMed1990

Characterization of a splicing mutation in group A xeroderma pigmentosum.

The molecular basis of group A xeroderma pigmentosum (XP) was investigated by comparison of the nucleotide sequences of multiple clones of the XP group A complementing gene (XPAC) from a patient with group A XP with that of a normal gene. The clones showed a G----C substitution at the 3' splice acceptor site of intron 3, which altered the obligatory AG acceptor dinucleotide to AC. Nucleotide sequencing of cDNAs amplified by the polymerase chain reaction revealed that this single base substitution abolishes the canonical 3' splice site, thus creating two abnormally spliced mRNA forms. The larger form is identical with normal mRNA except for a dinucleotide deletion at the 5' end of exon 4. This deletion results in a frameshift with premature translation termination in exon 4. The smaller form has a deletion of the entire exon 3 and the dinucleotide at the 5' end of exon 4. The result of a transfection study provided additional evidence that this single base substitution is the disease-causing mutation. This single base substitution creates a new cleavage site for the restriction nuclease AlwNI. Analysis of AlwNI restriction fragment length polymorphism showed a high frequency of this mutation in Japanese patients with group A XP: 16 of 21 unrelated Japanese patients were homozygous and 4 were heterozygous for this mutation. However, 11 Caucasians and 2 Blacks with group A XP did not have this mutant allele. The polymorphic AlwNI restriction fragments are concluded to be useful for diagnosis of group A XP in Japanese subjects, including prenatal cases and carriers.

Amino Acid Sequence↗

PubMed1990

An unusual insertion/deletion in the gene encoding the beta-subunit of propionyl-CoA carboxylase is a frequent mutation in Caucasian propionic acidemia.

Propionic acidemia is an inherited disorder of organic acid metabolism that is caused by deficiency of propionyl-CoA carboxylase (PCC; EC 6.4.1.3). Affected patients fall into two complementation groups, pccA and pccBC (subgroups B, C, and BC), resulting from deficiency of the nonidentical alpha and beta subunits of PCC, respectively. We have detected an unusual insertion/deletion in the DNA of patients from the pccBC and pccC subgroups that replaces 14 nucleotides in the coding sequence of the beta subunit with 12 nucleotides unrelated to this region of the gene. This results in elimination of an Msp I restriction site, a 2-base-pair (bp) deletion, a frameshift, and a stop codon in the new frame approximately 100 amino acid residues proximal to the normal carboxyl terminus. Among 14 unrelated Caucasian patients in the pccBC complementation group, this unique mutation was found in 8 of 28 mutant alleles examined. Mutant allele-specific oligonucleotide hybridization to amplified genomic DNAs revealed that the inserted 12 nucleotides do not originate in an approximately 1000-bp region around the mutation. In the course of our investigation, we identified another mutation in the same exon: a 3-bp in-frame deletion that eliminates one of two isoleucine codons immediately preceding the Msp I site. Two unrelated patients were compound heterozygotes for this single-codon deletion and for the insertion/deletion described above. We conclude that either there is a propensity for the PCC beta-subunit gene to undergo mutations of this sort at this position or, more likely, the mutations in all of the involved Caucasian patients have a common origin in preceding generations.

Alleles↗

PubMed1990

Lipoprotein lipaseBethesda: a single amino acid substitution (Ala-176----Thr) leads to abnormal heparin binding and loss of enzymic activity.

The molecular defect that leads to a deficiency of lipoprotein lipase (LPL) activity in the proband from a Bethesda kindred has been identified. The pre- and post-heparin plasma LPL mass in the proband was elevated when compared to controls; however, there was no detectable LPL activity, indicating the presence of a defective enzyme (termed LPLBethesda). Analysis of the patient's post-heparin plasma by heparin-Sepharose affinity chromatography demonstrated that the mutant LPL had an altered affinity for heparin. Southern blot hybridization of the gene for LPLBethesda revealed no major rearrangements. Northern blot analysis of LPLBethesda mRNA from patient monocyte-derived macrophages revealed normal-sized mRNAs (3.4 and 3.7 kilobases) as well as normal cellular mRNA levels when compared to control macrophages. Sequence analysis of polymerase chain reaction-amplified LPL cDNA revealed a G----A substitution at position 781 of the normal LPL gene that resulted in the substitution of an alanine for a threonine at residue 176 and the loss of an SfaNI site present in the normal LPL gene. Amplification of cDNA by the PCR followed by digestion with SfaNI established that the patient was a true homozygote for the mutation. Expression of LPL cDNA in COS-7 cells resulted in the synthesis of a nonfunctional LPL enzyme establishing that the Ala----Thr substitution was the mutation responsible for the inactive LPL. The identification of this mutation in the LPL gene defines a region of the LPL enzyme, at Ala-176, that is essential for normal heparin-binding and catalytic activity. We propose that an amino acid substitution in this critical region of LPLBethesda results in the synthesis of a nonfunctional enzyme that leads to the chylomicronemia syndrome expressed in this proband.

Adult↗

PubMed1991

Two types of abnormal genes for plasminogen in families with a predisposition for thrombosis.

The gene coding for plasminogen has been compared with several abnormal genes from Japanese patients by the polymerase chain reaction and DNA sequence analysis. Two types of abnormal genes coding for plasminogen were identified in these patients. In the type I mutation, a guanosine in GCT coding for Ala-601 near the active-site histidine was replaced by an adenosine resulting in ACT coding for threonine. This mutation was also shown by the loss of a cleavage site for Fnu4HI endonuclease, a restriction enzyme that recognizes GCTGC but not ACTGC. In the type II mutation, a guanosine in GTC coding for Val-355 was replaced by a thymidine resulting in TTC coding for phenylalanine. This change was readily shown by digestion with Ava II endonuclease, a restriction enzyme that recognizes GGTCC and not GTTCC. The type I mutation has been found to be identical to a plasminogen variant identified in Japanese patients by amino acid sequence analysis and also detected by isoelectric focusing, whereas the type II mutation is a unique amino acid substitution in the connecting region between the third and fourth kringles in plasminogen. DNA sequence analysis also revealed that the abnormal genes carry several silent nucleotide substitutions located primarily within introns and 5' and 3' flanking regions.

Base Sequence↗

PubMed1991

Recombinant fusion protein identified by lepromatous sera mimics native Mycobacterium leprae in T-cell responses across the leprosy spectrum.

Pooled polyvalent sera from lepromatous leprosy patients were used to screen a lambda gt11 recombinant DNA expression library of Mycobacterium leprae in order to identify the relevant antigens recognized by the human immune response. Of the 300,000 phages screened, 4 clones were identified that coded for fusion proteins of the same molecular mass. The fusion protein from clone LSR2 was tested for immunoreactivity in assays using peripheral blood cells and sera from 11 laboratory personnel and 105 patients across the leprosy spectrum. LSR2 protein appears to be predominantly a T-cell antigen. It evokes similar lymphoproliferative responses as the native bacillus both at the individual level and in the leprosy spectrum as a whole. Though only 50% of patient sera with anti-M. leprae antibodies reacted with the fusion protein, the pattern of reactivity in the antibody responses was also similar for the various clinical types. The coding regions of clones LSR1 and LSR2 are identical. They show no homology with sequences stored in data banks and encode a protein of 89 amino acids with a calculated molecular mass of approximately 10 kDa.

Amino Acid Sequence↗

PubMed1991

Apolipoprotein A-I deficiency due to a codon 84 nonsense mutation of the apolipoprotein A-I gene.

The molecular genetic defect of a female patient with apolipoprotein A-I (apoA-I) deficiency and premature atherosclerosis was examined. Her parents were first cousins. Her plasma density fraction from 1.063 to 1.21 g/ml contained no apoA-I on SDS/PAGE and no measurable high density lipoprotein cholesterol. Southern blot hybridization showed no gross abnormality to be present in the patient's apoA-I gene and homozygosity for a haplotype of restriction fragment length polymorphisms in the apoA-I gene region. Sequencing after amplification by PCR revealed a codon 84 nonsense mutation (CAG----TAG, Gln----stop) of exon 4 and a codon 67 missense mutation (GCC----ACC, Ala----Thr) of exon 3 in the patient's apoA-I gene. The data from dot-blot hybridization with allele-specific oligonucleotide probes indicated that she was homozygous for the apoA-I gene with regard to the two mutations. The codon 37 missense mutation was also detected in the apoA-I gene of 6 out of 60 controls, who all had normal levels of apoA-I and high density lipoprotein cholesterol, suggesting that the missense mutation is polymorphic and not associated with apoA-I deficiency. These findings indicate that homozygosity for the apoA-I gene with codon 84 nonsense mutation causes the deficiency of apoA-I and of high density lipoprotein cholesterol in the patient.

Adult↗

PubMed1992

Two mutations in the beta-globin polyadenylylation signal reveal extended transcripts and new RNA polyadenylylation sites.

Two mutations in the beta-globin poly(A) signal were identified in Israeli patients with beta +-thalassemia by sequence analysis following PCR. One is a point mutation (AATAAA----AATAAG) and the other is a 5-base-pair deletion (AATAAA----A----). The mutant genes were used to investigate the function of the poly(A) signal in vivo and to evaluate the mechanism whereby these mutations lead to a thalassemic phenotype. Analysis of RNA derived from peripheral blood demonstrated the presence of elongated RNA species in patients carrying either mutation. Other aspects of RNA processing (initiation, splicing) were unimpaired. RNA obtained from the patients carrying the point mutation contained four discrete, extended RNA species, 1500-2900 nucleotides long, which were found to be polyadenylated. Some normal cleavage-polyadenylylation was also observed. The 5-base-pair deletion completely abolished cleavage at the normal site. This deletion mutation resulted in a phenotype of beta +-thalassemia, thus providing evidence that the extended mRNAs are translatable in vivo. Furthermore, additional transcripts, greater than 5 kilobases, presumably mRNA precursors, were found in all RNA samples, including those of nonthalassemic controls. The extended transcripts of the poly(A) mutants, together with the high molecular weight precursors, suggest that the human beta-globin gene transcription unit is significantly longer than previously recognized.

Base Sequence↗

PubMed1992

Deposition of beta/A4 immunoreactivity and neuronal pathology in transgenic mice expressing the carboxyl-terminal fragment of the Alzheimer amyloid precursor in the brain.

The deposition of amyloid in senile plaques and along the walls of the cerebral vasculature is a characteristic feature of Alzheimer disease. The peptide comprising the carboxyl-terminal 100 amino acids of the beta-amyloid precursor protein (beta APP) has been shown to aggregate into amyloid-like fibrils in vitro and to be neurotoxic, suggesting that this fragment may play a role in the etiology of Alzheimer disease. To address this question, we expressed this carboxyl-terminal 100-amino acid peptide of beta APP in transgenic mice under the control of the brain dystrophin promoter. We used an antibody to the principal component of amyloid, beta/A4, to demonstrate cell-body and neuropil accumulation of beta/A4 immunoreactivity in the brains of 4- and 6-month-old transgenic mice. Only light cytoplasmic staining with this antibody was visible in control mice. In addition, immunocytochemical analysis of the brains with an antibody to the carboxyl terminus of beta APP revealed abnormal aggregation of this epitope of beta APP within vesicular structures in the cytoplasm and in abnormal-appearing neurites in the CA2/3 region of the hippocampus in transgenic mice, similar to its aggregation in the cells of Alzheimer disease brains. Thioflavin S histochemistry suggested accumulations of amyloid in the cerebrovasculature of transgenic mice with the highest expression of the beta APP-C100 transgene. These observations suggest that expression of abnormal carboxyl-terminal subfragments of beta APP in vivo may cause amyloidogenesis and specific neuropathology.

Amyloid beta-Protein Precursor↗

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↗

PubMed1993

Molecular characterization of the 128-kDa immunodominant antigen of Helicobacter pylori associated with cytotoxicity and duodenal ulcer.

Helicobacter pylori has been associated with gastritis, peptic ulcer, and gastric adenocarcinoma. We report the nucleotide sequence and expression of an immunodominant antigen of H. pylori and the immune response to the antigen during disease. The antigen, named CagA (cytotoxin-associated gene A), is a hydrophilic, surface-exposed protein of 128 kDa produced by most clinical isolates. The size of the cagA gene and its protein varies in different strains by a mechanism that involves duplication of regions within the gene. Clinical isolates that do not produce the antigen do not have the gene and are unable to produce an active vacuolating cytotoxin. An ELISA to detect the immune response against a recombinant fragment of this protein detects 75.3% of patients with gastroduodenal diseases and 100% of patients with duodenal ulcer (P < 0.0005), suggesting that only bacteria harboring this protein are associated with disease.

Amino Acid Sequence↗

PubMed1994

Targeted mutation in the neurotrophin-3 gene results in loss of muscle sensory neurons.

Neurotrophin 3 (NT-3) is one of four related polypeptide growth factors that share structural and functional homology to nerve growth factor (NGF). NT-3 and its receptor, called neurotrophic tyrosine kinase receptor type 3 (Ntrk3; also called TrkC), are expressed early and throughout embryogenesis. We have inactivated the NT-3 gene in embryonic stem (ES) cells by homologous recombination. The mutated allele has been transmitted through the mouse germ line, and heterozygote intercrosses have yielded homozygous mutant newborn pups. The NT-3-deficient mutants fail to thrive and exhibit severe neurological dysfunction. Analysis of mutant embryos uncovers loss of Ntrk3/TrkC-expressing sensory neurons and abnormalities at early stages of sensory neuronal development. NT-3-deficient mice will permit further study of the role of this neurotrophin in neural development.

Animals↗

PubMed1994

CD40-deficient mice generated by recombination-activating gene-2-deficient blastocyst complementation.

To study the role of B-cell antigen CD40 in immune responses, mouse embryonic stem (ES) cells in which both copies of the gene encoding CD40 had been disrupted by homologous recombination were injected in RAG-2 (recombination-activating gene-2)-deficient blastocysts to generate chimeras in which all mature lymphocytes are derived from the CD40-deficient ES cells. T- and B-cell number and phenotype were normal in the CD40-/- chimeras. However, B cells failed to proliferate and undergo isotype switching in vitro in response to soluble CD40 ligand (sCD40L) with interleukin 4 (IL-4) but responded normally to lipopolysaccharide (LPS) with IL-4. CD40-/- chimeras completely failed to mount an antigen-specific antibody response or to develop germinal centers following immunization with the T cell-dependent (TD) antigen keyhole limpet hemocyanin. In contrast, CD40-/- mutant mice responded normally to the T cell-independent (TI) antigens, 2,4,6-trinitrophenyl (TNP)-LPS and TNP-Ficoll. The most noticeable alteration in the serum immunoglobulin levels of young (6-8 weeks old) CD40-/- animals was absence of IgE and severe decrease of IgG1 and IgG2a. These results confirm the essential role of CD40- CD40L interactions in the antibody response to TD antigens and in isotype switching.

Animals↗

PubMed1995

Partial rescue of human carbonic anhydrase II frameshift mutation by ribosomal frameshift.

A single-base-pair deletion in exon 7 of the human carbonic anhydrase II gene was found to be the molecular defect in a group of independently ascertained, clinically heterogeneous, Hispanic carbonic anhydrase II-deficient patients, all of whom had ancestors from the Caribbean islands. This mutation predicts a +1 frameshift at codon 227 and incorporation of 12 missense amino acids before an early stop codon at position 239 produces a 27-kDa truncated carbonic anhydrase II. Expression of the Hispanic mutant cDNA in bacteria produced predominantly the 27-kDa protein, which was inactive. However, a minor 29-kDa polypeptide species was also produced that had 10% the specific activity of the wild-type enzyme after affinity purification. Amino acid sequencing showed that the 29-kDa mutant protein was produced by two frameshift events: a +1 frameshift at codon 227 due to the single-base deletion and a -1 ribosomal frameshift at codon 237 that restored the original reading frame after 11 missense amino acids were incorporated. Antibody against the 11-amino acid frameshift peptide detected the 29-kDa mutant protein in lysates of transfected COS cells. These results indicate that ribosomal frameshift can partially rescue the human carbonic anhydrase II frameshift mutation and suggest a mechanism whereby a compensatory ribosomal frameshift can ameliorate the consequences of certain frameshift mutations. Whether individual differences in efficiency of ribosomal frameshift contribute to clinical heterogeneity in patients with such mutations deserves further study.

Amino Acid Sequence↗

PubMed1996

Impaired locomotor activity and exploratory behavior in mice lacking histamine H1 receptors.

From pharmacological studies using histamine antagonists and agonists, it has been demonstrated that histamine modulates many physiological functions of the hypothalamus, such as arousal state, locomotor activity, feeding, and drinking. Three kinds of receptors (H1, H2, and H3) mediate these actions. To define the contribution of the histamine H1 receptors (H1R) to behavior, mutant mice lacking the H1R were generated by homologous recombination. In brains of homozygous mutant mice, no specific binding of [3H]pyrilamine was seen. [3H]Doxepin has two saturable binding sites with higher and lower affinities in brains of wild-type mice, but H1R-deficient mice showed only the weak labeling of [3H]doxepin that corresponds to lower-affinity binding sites. Mutant mice develop normally, but absence of H1R significantly increased the ratio of ambulation during the light period to the total ambulation for 24 hr in an accustomed environment. In addition, mutant mice significantly reduced exploratory behavior of ambulation and rearings in a new environment. These results indicate that through H1R, histamine is involved in circadian rhythm of locomotor activity and exploratory behavior as a neurotransmitter.

Animals↗