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Spectrum of genetic alterations in patients with peroxisome biogenesis defects in the Iranian population: a case series study.

Peroxisomal disorders are a group of hereditary metabolic disorders that happen when peroxisomes are defective. Around 80% of individuals affected by peroxisomal disorders are classified within the spectrum of Zellweger syndromes with autosomal recessive inheritance pattern that results from mutations in one of the 13 PEX genes. Clinical exome sequencing plays a vital role in the diagnosis where the symptoms are atypical. In the current study, we used this technique to find the underlying genetic cause in 14 Iranian patients with peroxisomal disorders. PEX1 variants were detected in five patients. PEX2, PEX5, PEX6 and PEX7 variants were detected in three, one, one, and two cases, respectively. Finally, ACOX1 variants were identified in two cases. All cases except two cases were homozygote for the suspected variants in Zellweger syndrome-related genes. Two cases were compound heterozygote for variants in the PEX1 gene. In total, two novel variants were identified, including c.313 C > T (p.Gln105*) and c.961 A > T (p.Ile321Phe) in the PEX1 and ACOX1 genes, respectively. The present research expands the range of genetic variations observed in Iranian individuals diagnosed with various forms of Zellweger spectrum disorders.

Humans

Isolation of cDNA clones corresponding to the Mr = 150,000 subunit of chick type VI collagen.

Type VI collagen is a disulfide-bonded protein with an unusual structure in that the molecule contains three short triple-helical domains and very extended non-collagenous regions. The molecule is a heterotrimer composed in the chick of two polypeptides of similar apparent size in SDS-PAGE (Mr = 140- and 150,000) but different structure, and a third component that is much larger (Mr = 260,000) than the other two chains. We report here on the isolation of several overlapping cDNA clones from a chicken aorta mRNA expression library in the plasmid vector pEX1. Antibodies affinity purified onto the fusion proteins recognized the chick type VI collagen Mr = 150,000 subunit. Northern blots using the cDNA inserts from the above clones revealed a single RNA species of about 4,600 nucleotides sufficient to code for a protein with the size of the Mr = 150,000 subunit.

Animals

Construction of dystrophin fusion proteins to raise targeted antibodies to different epitopes.

For the study of the structure and function relationship of dystrophin, defective in DMD, and for diagnostic purposes it is important to dispose of antibodies against different parts of the protein. We have made five different constructs for the expression of fusion proteins containing parts of the four domains of dystrophin. Two different recombinant expression vectors, pATH2 and pEX1, were used. Rabbits were immunized with the fusion products and several polyclonal antibodies were raised. At a later stage, monoclonal antibodies were also raised to some of the fusion proteins. One polyclonal antibody, named P20 AB, is directed against the region covering amino acid sequence 1749-2248 or the nucleotide sequence 5456-6953 of the mRNA, which corresponds to the major deletion-prone region of the DMD gene. We show the particular value, sensitivity and specificity of the P20 AB in dystrophin analysis.

Antibody Formation

The MIC2 gene product: epitope mapping and structural prediction analysis define an integral membrane protein.

The MIC2 locus is located in the pseudoautosomal (pairing) region of human X and Y chromosomes (Goodfellow et al., Science 234, 740-743, 1986). Despite extensive molecular analysis of MIC2 (see Darling et al., Cold Spring Harb. Symp. quant. Biol. 51, 205-211, 1986), study of the gene product has been limited (Banting et al., EMBO J. 41, 1967-1972, 1985). Here we report the combined use of monoclonal antibodies, plasmid expression vectors and structural prediction analysis to define the MIC2 gene product as an integral membrane protein. Random overlapping fragments of a cDNA, corresponding to the MIC2 locus, were cloned into the plasmid expression vector pEX1 (Stanley and Luzio, EMBO J. 3, 1429-1434, 1984) to produce "epitope libraries". Six different monoclonal antibodies, known to recognize the extracellular region of the MIC2 gene product, were used to screen these libraries. Clones recognized by these antibodies were sequenced and their sequences aligned with one another and with the complete MIC2 cDNA sequence. All antibodies tested recognized adjacent and/or overlapping epitopes in the same region of the molecule. These results complement data from a hydropathy plot of a conceptual translation of the MIC2 sequence, which demonstrated the presence of a single long hydrophobic region in the mature protein. Since the antibodies recognize the extracellular portion of the molecule, we were able to determine the orientation in the plasma membrane. This method of analysis is generally applicable where antibodies and cloned cDNAs are available.

Amino Acid Sequence

Cloning and expression of Taenia ovis antigens in Escherichia coli.

Double stranded DNA complementary to poly(A)+ mRNA from the tapeworm Taenia ovis was cut with Sau 3A to an average length of about 300 bp and inserted into the Bam HI site of the expression plasmids pEX1, pEX2 and pEX3. These plasmids express a hybrid protein derived from a fusion of the cro gene with the lac Z gene (truncated at its 5' end by 53 bp) of phage lambda. Cloning sites lie downstream from the gene fusion. Escherichia coli infected with another plasmid (pCI857) bearing the temperature sensitive repressor of phage lambda was transformed with the pEX plasmids into which T. ovis DNA had been inserted; recombinants were selected by growth at 30 degrees C in the presence of ampicillin at 100 micrograms ml-1. Replicas were made and hybrid protein expression induced in recombinants by transferring them to 42 degrees C. Several recombinants expressing antigenic determinants of T. ovis were detected with T. ovis infected sheep serum that had been absorbed to remove antibodies to E. coli. Of five selected for further study, three expressed hybrid proteins of between 165 and 170 kDa of which the T. ovis component contributed between 48 and 55 kDa; in the other two, the tapeworm contribution was between 0.5 and 1.5 kDa. These antigenic determinants may be of some interest with respect to vaccine development since they are expressed during the normal course of T. ovis infection in sheep, and they are also present in the oncosphere - the infective larva of the parasite which stimulates immunity in sheep. The native antigens in adult worms and oncospheres that correspond to the antigenic determinants produced by the recombinant clones comprise a number of species ranging from 92.5 to 180 kDa. Tests with affinity purified antibodies indicate that the expressed products of the clones represent different epitopes on the same subset of polypeptides in both adult worms and oncospheres.

Animals

P-glycoprotein genes in the winter flounder, Pleuronectes americanus: isolation of two types of genomic clones carrying 3' terminal exons.

In mammals, P-glycoprotein (P-gp) is encoded by two or more highly conserved genes that differ in their abilities to transport drugs. One isoform class (class I) is consistently associated with the multidrug resistance phenotype, while the other (class III) is not. This study was designed to enumerate the P-gp genes in fish and determine how they are related to the two functional classes already defined in mammals. Southern blot analysis using a conserved single exon from the 3' terminal region of hamster P-gp cDNA (pEX1-172) as a probe indicated that there were two P-gp genes in right-eye flounders. Subsequently, two sets of clones were isolated from a winter flounder genomic library that correspond to the 3' ends of the two flounder P-gp genes. Sequence analysis was done on two key areas: the 3' ATP binding site and the 3' terminal exon, both of which were found to be homologous with their mammalian counterparts. Despite high levels of sequence identity in the predicted coding regions of the gene fragments it has not been possible to use these sequences to relate the homologs to particular mammalian classes of P-gp genes, perhaps because of gene conversion between mammalian P-gp genes. These cloned sequences are the first set of P-gp genes reported in lower vertebrates and will be useful for delineating the expression of P-gp genes in fish and understanding the role of P-gp in fish physiology.

ATP Binding Cassette Transporter, Subfamily B, Mem

Characterization of native and recombinant 75-kilodalton immunogens from Chlamydia trachomatis serovar L2.

A 75-kilodalton (kDa) immunogen from Chlamydia trachomatis serovar L2 was characterized. The 75-kDa protein was localized in the cytoplasm of chlamydiae and was shown to be a protein synthesized early in the developmental cycle of chlamydiae. A gene library was made by the recombinant DNA technique, using the expression vectors pEX1, pEX2, and pEX3. From this library one clone was found which reacted with a monoclonal antibody against the 75-kDa immunogen of C. trachomatis. The 75-kDa protein produced by the recombinant Escherichia coli was expressed independently of the promoter for the hybrid protein cro-betagalactosidase. Thus it is not produced as a fusion protein. Epitope mapping of the 75-kDa protein from C. trachomatis L2 and from the recombinant E. coli performed by Staphylococcus aureus V8 protease digestion showed that the two proteins are identical. Furthermore, patient sera reacted with both proteins.

Animals

Cloning of Mycoplasma pneumoniae DNA and expression of P1-epitopes in Escherichia coli.

A genomic library of Mycoplasma pneumoniae was constructed by cloning partial Sau3A-digested genomic DNA into the expression plasmids pEX1 to pEX3. The recombinant clones were screened for production of M. pneumoniae P1-antigen by an in situ colony enzyme-linked immunosorbent assay (ELISA) blot method with a monospecific rabbit antiserum raised against the surface protein P1. The length of the translated P1-sequence and the size of the inserted DNA were determined. By comparison it was shown that six clones contained DNA fragments coding for an internal part of the P1-protein and eight clones code for the C-terminal part of terminated P1-protein. In reactions against sera from patients suffering from M. pneumoniae infection and sera from healthy persons, one of the internal clones and five of the C-terminal clones reacted with one or two of the patient sera, but only one clone reacted with all patient sera.

Antibodies, Bacterial