Large deletion of androsterone UDP-glucuronosyltransferase gene in the inherited deficient strain of Wistar rats

LA Wistar rats have a deficiency of androsterone UDP-glucuronosyltransferase (UDPGT) and are present in Wistar rat colonies around the world. In order to clarify the molecular mechanism of the deficiency, androsterone UDPGT cDNA clone, pGT2 was isolated from rat liver cDNA library and was digested with restriction enzymes to afford three probes for Northern and Southern blot analyses in HA (normal), heterozygous LA and LA Wistar rats. In Northern blot analysis, androsterone UDPGT mRNA was totally absent in LA Wistar rat liver. Southern blot analysis suggested a large deletion of androsterone UDPGT gene in the rats. Genomic DNA amplifications with synthetic primers which have nucleotide sequences corresponding to the 5′-region of androsterone UDPGT cDNA, suggested that androsterone UDPGT gene has exon 1 with a length of some 700 bp and that this exon is deleted in LA Wistar rats. Based on these lines of evidence, it is concluded that the large portion of androsterone UDPGT gene is deleted in LA Wistar rats, which results in the absence of androsterone UDPGT mRNA and consequently the corresponding enzyme protein.     

The molecular basis of the inherited deficiency of androsterone UDP-glucuronyltransferase in Wistar rats

A major UDP-glucuronyltransferase isoenzyme in rat liver (51 kDa), corresponding to androsterone glucuronidating activity, has been identified by immunoblot analysis. This isoenzyme is absent from Wistar rats exhibiting the low androsterone (LA) UDP-glucuronyltransferase activity exhibiting the low androsterone (LA) UDP-glucuronyltransferase activity phenotype. Northern blot analysis of total RNA from normal and androsterone glucuronidation deficient Wistar rats demonstrated that the mRNA encoding this protein was not synthesised. Differences in restriction fragment length observed on Southern blotting of genomic DNA from LA Wistar rats indicate that this inherited deficiency is the result of a deletion in the androsterone UDP-glucuronyltransferase gene.     

The 3-methylcholanthrene-inducible UDP-glucuronosyltransferase deficiency in the hyperbilirubinemic rat (Gunn rat) is caused by a -1 frameshift mutation

The Gunn rat is a mutant strain of Wistar rat which has unconjugated hyperbilirubinemia as a result of the absence of hepatic UDP-glucuronosyltransferase (UDPGT) activity toward bilirubin. The Gunn rat is also deficient in a 3-methylcholanthrene (MC)-inducible UDPGT isoenzyme that has high activity toward phenolic substrates. We have isolated and sequenced a cDNA, designated 4-NP UDPGT, which encodes an MC-inducible UDPGT from normal Wistar rat livers (Iyanagi, T., Haniu, M., Sogawa, F., Fujii-Kuriyama, Y., Watanabe, S., Shively, J.E., and Anan, K.F. (1986) J. Biol. Chem. 261, 15607-15614). In the present study, we found that this cDNA detected MC-inducible UDPGT mRNA in the MC-treated homozygous Gunn rat liver. The level of this mRNA, however, was significantly lower than that of normal Wistar livers. The size of mRNA in Gunn rats was identical to that of the functionally mature UDPGT mRNA in Wistar rats, but the MC-inducible UDPGT protein was absent from homozygous Gunn rat microsomes. We therefore made a cDNA library from MC-treated Gunn rat liver mRNA and isolated cDNA clones, using the 4-NP UDPGT cDNA as a probe. Sequencing analysis of these cDNA clones revealed a single base deletion in the coding region. Northern blot analysis of mRNAs from normal Wistar and heterozygous and homozygous Gunn rats livers was performed using specific oligonucleotide probes, and the results confirmed the presence of mRNA containing the single base deletion in heterozygous and homozygous Gunn rats. These data suggested that the defect of the MC-inducible isoenzyme in Gunn rats arises from a -1 frameshift mutation that removes 115 amino acids from the COOH terminus.     

The full length coding sequence of rat liver androsterone UDP-glucuronyltransferase cDNA and comparison with other members of this gene family.

Cloned cDNAs coding for hepatic UDP-glucuronyltransferase (UDPGT) have been isolated from a rat liver cDNA library in the expression vector bacteriophage lambda gt11 using anti-UDPGT antibodies. Four different mRNAs have been identified by sequencing of 15 UDPGT cDNA clones. The sequences of the four classes of cDNA were determined to be 85-95% homologous. Restriction fragments were isolated from the cDNA in each class and used as class specific probes. Hybridisation of these probes to northern blots of total RNA prepared from the livers of normal and genetically deficient Wistar rats identified the cDNA in class 4 with androsterone UDPGT. Translation of the cDNA sequence of clone rlug 23, the longest member of class 4, allowed determination of the complete amino acid sequence of androsterone UDPGT.     

Cloning and sequence analysis of a cDNA encoding the Rieske iron-sulfur protein of rat mitochondrial cytochrome bc1 complex

We have isolated a cDNA clone for the Rieske iron-sulfur protein of rat cytochrome bc1 complex, by screening a rat liver cDNA expression library using antiserum directed against the corresponding protein of bovine. The amino acid sequence deduced from the nucleotide sequence of the cDNA indicated that the mature polypeptide of the rat protein consists of 196 amino acid residues with a molecular weight of 21,465, and that it is formed as a precursor with an amino-terminal extension. Northern blot analysis indicated that rat liver possibly contains different sizes of mRNAs for the Rieske iron-sulfur protein, and Southern blot analysis demonstrated that rats and mice possess a single gene for this protein.     

Defective splicing of thyroglobulin gene transcripts in the congenital goitre of the Afrikander cattle

The structure of thyroglobulin mRNA was analyzed in an inbred herd of Afrikander cattle with hereditary goitre. Northern transfer of RNA from affected animals revealed both a shorter (approximately 7100 bases) and a normal-sized (approximately 8200 bases) thyroglobulin mRNA when hybridized to bovine thyroglobulin cDNA clones. S1 nuclease mapping experiments established that 1100 bases are deleted in the 5' region of the smaller mRNA. Electron microscopy of RNA from animals with goitre hybridized to a bovine genomic DNA clone showed that the region deleted corresponds to exon 9 of the thyroglobulin gene. Southern blot analysis of the exon 9 region revealed differences between affected and control animals with the enzymes PstI and TaqI. Although they could reflect a linkage disequilibrium between the mutation and restriction fragment length polymorphism, it is noteworthy that these differences map in the region of the exon 9/intron 9 junction. Our results show that a genetic lesion in the thyroglobulin gene causes aberrant splicing of the pre-mRNA, and suggest that the responsible mutation is at the exon 9/intron 9 junction.     

Rat cholesterol side-chain cleavage enzyme (P-450scc): use of a cDNA probe to study the hormonal regulation of P-450scc mRNA levels in ovarian granulosa cells

A rat ovarian cDNA library was constructed and screened by differential colony hybridization to detect cDNA clones specific for mRNA induced by follicle-stimulating hormone (FSH). The cDNA clone which demonstrated the greatest degree of induction contained a 766-bp insert which was characterized and sequenced. We conclude that this cDNA is specific for the rat gene coding for cholesterol side-chain cleavage enzyme (P-450scc) by virtue of nucleotide sequence homology to the bovine and human P-450scc cDNA sequences. Southern blotting of rat genomic DNA suggests the presence of a single P-450scc gene. Northern blot analysis indicates that P-450scc mRNA is present in steroidogenic tissues (ovary, adrenal, testis), but not in brain, kidney, liver, lung, or heart. The rat P-450scc mRNA is induced by FSH or pregnant mare's serum gonadotropin in ovaries of estrogen-treated immature rats in vivo. In cultured granulosa cells, estradiol treatment alone did not increase P-450scc mRNA levels, but in combination with FSH or 8-Br-cAMP resulted in three- to four-fold increase in this mRNA.     

Specific species and tissue differences for the gene expression of calcium-binding protein regucalcin

The existence and expression of gene encoding the Ca²⁺-binding protein regucalcin in various species and tissues were investigated with Southern and Northern hybridization analyses using regucalcin cDNA (0.9 kb of open reading frame). Genomic Southern hybridization analysis demonstrated that regucalcin gene was widely conserved among higher animals including human, monkey, rat, mouse, dog, bovine, rabbit and chicken. The gene was not found in yeast. The Northern blot analysis of poly (A)⁺RNAs extracted from the liver of various species showed that regucalcin mRNA was predominantly expressed in rat and mouse, although the expression was also seen in human, bovine and chicken. Furthermore, the enzyme-linked immunoadsorbent assay (ELISA) with rabbit-anti-regucalcin IgG indicated that hepatic regucalcin concentration was most pronounced in rat as compared with that of guinea pig, mouse and chicken. These observations show that the gene expression of regucalcin and its protein synthesis is unique in the liver of rats, suggesting the existence of a specific mechanism in demonstrating regucalcin synthesis from gene.     

Structure and organization of the microsomal xenobiotic epoxide hydrolase gene

The gene for the microsomal xenobiotic rat liver epoxide hydrolase has been isolated and characterized. Clones were obtained from a Wistar Furth Charon 35 genomic library by hybridization with a full-length epoxide hydrolase cDNA. The gene for the xenobiotic epoxide hydrolase is approximately 16 kilobases in length and consists of 9 exons ranging in size from 109 to 420 base pairs and 8 intervening sequences, the largest of which is 3.2 kilobases. S1-nuclease mapping, primer extension studies, and sequence analysis were used to determine the 5' cap site and the size of the first exon (170 base pairs). Regulatory sequences analogous to TATA, CCAAT, and core enhancer sequences were noted in the 5'-flanking region of the gene. The cDNA and gene for epoxide hydrolase displayed nucleotide sequence identity although they were isolated from different rat strains. Also, Southern blot analysis of restricted liver DNA from inbred Fischer 344 and Wistar Furth rat strains, and outbred Sprague-Dawley rats indicated a high degree of structural similarity for the epoxide hydrolase gene within these three strains. Only a single functional epoxide hydrolase gene was identified and no evidence of hybridization to the genes for the microsomal cholesterol epoxide hydrolase or the cytosolic epoxide hydrolase was observed. However, a pseudogene for the microsomal xenobiotic epoxide hydrolase was isolated and characterized from the genomic library.     

Characterization of the gene encoding the major rat liver asialoglycoprotein receptor

A cloned cDNA encoding the major rat liver asialoglycoprotein receptor has been used to analyze the gene for this protein. Genomic Southern blot analysis reveals that the gene is contained on a single EcoRI restriction fragment and is unique. A clone containing the gene (isolated from a rat liver genomic library) has been characterized by sequence analysis. The mRNA for the receptor is encoded by nine exons separated by eight introns. The first exon is confined to the 5'-untranslated region of the mRNA, the second exon encodes most of the cytoplasmic NH2-terminal domain of the receptor polypeptide, the third exon corresponds to the hydrophobic transmembrane portion of the polypeptide, and the remaining exons encode the extracellular parts of the receptor. Some, but not all, of the divisions between exons correspond to boundaries between functional domains of the polypeptide.     

On the cDNA's for two types of rat pancreatic secretory trypsin inhibitor

Two types of cDNA, which code for the two types of rat pancreatic secretory trypsin inhibitors (PSTIs), were cloned and sequenced. Both predicted amino acid sequences consisting of 79 amino acids, with the secretion signal peptide consisting of 18 and 23 amino acids for PSTI-I and PSTI-II, respectively. The nucleotide sequences were 91% homologous between the two cDNAs, but 68% and 65% homologous, respectively, when compared with human PSTI cDNA. Northern blot analyses showed that PSTI-I is expressed in the pancreas, whereas PSTI-II is expressed in the pancreas and the liver using the same promoter. Southern blot analyses suggested that both PSTI-I and PSTI-II genes are single copy genes per haploid genome. Duplication of rat PSTI gene seems to have occurred recently, after the divergence of humans and rats.     

脂肪酸合成酶基因片段克隆以及胰岛素诱导时该酶mRNA含量的变化

采用高效的由mRNA合成cDNA的方法,我们得到了含有3.7kb的脂肪酸合成酶基因片段的克隆pFAS_(203)。它具有限制内切酶PstⅠ、BamH Ⅰ、HineⅡ、PvuⅡ、Ava Ⅰ以及Pvu Ⅰ酶切位点,与已经得到的经杂交选择的mRNA离体翻译产物鉴定的cDNA克隆pFAS_(15)有部分重叠。对饥饿的糖尿病大鼠注射胰岛素并饲以无脂食物,肝中FAS mRNA以及其前体RNA含量增加,当注射后再饲无脂食物达12小对,肝中FASmRNA及其前体RNA约为糖尿病鼠的30倍。Poly(A)~+ RNA的Northern分析表明诱导期间FASmRNA含量增加而其分子大小不变。这些结果表明胰岛素对FAS基因的转录有调节作用。胰岛素诱导后的脂肪酸合成酶活性升高是在转录水平上调节的。