Short Gene Conversions in the Human Fetal Globin Gene Region: A by-Product of Chromosome Pairing during Meiosis?

DNA sequence comparisons of a 1200-base pair (bp) region in 14 human fetal globin genes in seven linked pairs reveal 31 nucleotide substitutions at positions where the fetal globin genes, G gamma and A gamma, usually differ. In each case, the newly substituted nucleotide is identical to the one found at the same position in the linked nonallelic gene. Most of these nucleotide substitutions are clearly the result of gene conversions, but 11 could be the result of either very short gene conversions or of point mutations. The unexpectedly frequent occurrence of these short gene conversions suggests that they may be the relics of some normal interaction between homologous but nonallelic DNA sequences, and we discuss the possibility that they result from interactions occurring between homologous sequences during the process of meiotic chromosome pairing.     

Interaction between the Sbcc Gene of Escherichia Coli and the Gam Gene of Phage λ

gam mutants of phage lambda carrying long palindromes fail to form plaques on wild-type Escherichia coli but do grow on strains that are mutant in the sbcC gene. gam + lambda carrying the same palindrome grow on both hosts and on a host deleted for the recB, C and D genes. These results suggest that the Gam protein of lambda, known to interact also with E. coli's recBCD protein, can interact with the product of the sbcC gene.     

Deletion Mapping of the λ REX Gene

Deletion mapping has been used to order 12 λ rex^- mutants. Correlation of recombination data with physically-determined positions of deletion end-points (Szybalski 1971; Blattner et al. 1972) suggests that the left-most rex^- mutation, rex209, is located about 260-300 nucleotide pairs from the p_L mutation sex1 and about 475 nucleotide pairs from the left end-point of the region of nonhomology with λimm434.     

Investigation of Gene Insertion–Deletion Polymorphism of the Gene for Angiotensin-Converting Enzyme in Populations of the Volga–Ural Region

Insertion–deletion polymorphism at the angiotensin I-converting enzyme (ACE) gene in populations of the Volga–Ural region was examined by means of polymerase chain reaction. The populations studied belong to the Finno-Ugric (Komis, Maris, Mordovians, and Udmurts), Turkic (Chuvashes, Tatars, and Bashkirs), and Eastern-Slavic (Russians) ethnic groups. Distribution patterns of allele and genotype frequencies of this polymorphic system in the examined region were characterized. Comparison of the obtained results with the literature data on the ACE gene polymorphism in other Caucasoid and Mongoloid populations revealed some trends in the ACE genotype frequency dynamics depending on the ethnicity of the populations.     

The Population Genetics of the α-2 Globin Locus of Orangutans (Pongo pygmaeus)

In this study, the molecular population genetics of the orangutans -2 globin (HBA2) gene were investigated in order to test for the action of natural selection. Haplotypes from 28 orangutan chromosomes were collected from a 1.46-kilobase region of the -2 globin locus. While many aspects of the data were consistent with neutrality, the observed heterogeneous distribution of polymorphisms was inconsistent with neutral expectations. Furthermore, a single amino acid variant, found in both the Bornean and the Sumatran orangutan subspecies, was associated with different alternative synonymous variants in each subspecies, suggesting that the allele may have spread separately through the two subspecies after two distinct origination events. This variant is not in Hardy–Weinberg equilibrium (HWE). These observations are consistent with neutral models that incorporate population structure and models that invoke selection. The orangutan Plasmodium parasite is a plausible selective agent that may underlie the variation at -2 globin in orangutans.This article contains electronic supplementary material.[Reviewing Editor: Dr. Deborah Charlesworth]Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession numbers AY372078–AY372110.     

Polymorphism and Linkage of the αa-Crystallin Gene in t-Haplotypes of the Mouse

Restriction fragment polymorphisms were used to order the alpha A-crystallin locus (Crya-1) relative to other genes in mouse t-chromatin and to investigate the relatedness of alpha-A-crystallin sequences among different t-haplotypes. Analysis of DNA from t-recombinant mice mapped Crya-1 to the K end of the H-2 complex and within the distal inverted region characteristic of t-haplotypes. Hybridization with Crya-1 cDNA revealed three distinct phenotypic groups among the 17 different t-haplotypes studied. A majority (9 of 17) of the t-haplotypes were classified into a novel group (Crya-1t) characterized by restriction fragments apparently unique to t-chromosomes and therefore thought to contain alpha A-crystallin sequences descended from the original t-chromosome. A second group of t-haplotypes had restriction fragment patterns indistinguishable from those observed among many common inbred strains of mice of the Crya-1a type, and a third restriction fragment pattern, observed only in the tw121 haplotype, was indistinguishable from the fragment pattern for C3H/DiSn (Crya-1b) and several other inbred strains of mice. Thus, with respect to sequences around the Crya-1 locus, different t-haplotypes show restriction fragment polymorphisms, some of which are comparable to those found in wild-type chromosomes and provide further evidence for genetic heterogeneity in DNA from the distal region of t-haplotypes.     

Cloning of the Xuhuai Goat PPARγ Gene and the Preparation of Transgenic Sheep

This study aimed to clone the peroxisome proliferator-activated receptor γ (PPARγ) gene of the Xuhuai goat and to make transgenic sheep using intratesticular injection, so as to improve the meat quality and flavor by increasing the intramuscular fat content. The coding sequence of the goat PPARγ gene was 1,428 bp, encoding 475 amino acids. Its similarity with other species was 81 (chicken), 89 (mouse), 92 (pig), 98 (cow), and 99% (sheep). The similarity of the corresponding amino acid sequences was 92.9, 97.3, 98.3, 99.6, and 99.8%, respectively. The signal peptide region of the PPARγ protein was not found in this study, demonstrating that the protein is not secreted. RT-PCR and western blot revealed that PPARγ was expressed in vitro, and the protein was localized in the cytoplasm. The PPARγ gene was expressed in F₁ transgenic sheep at both the mRNA and the protein levels; the positive ratio was 13.7%.     

Genetic Characterization of the Drosophila Birt-Hogg-Dubé Syndrome Gene

Folliculin (FLCN) is a conserved tumor suppressor gene whose loss is associated with the human Birt-Hogg-Dubé (BHD) syndrome. However, its molecular functions remain largely unknown. In this work, we generated a Drosophila BHD model through genomic deletion of the FLCN gene (DBHD⁻). The DBHD mutant larvae grew slowly and stopped development before pupation, displaying various characteristics of malnutrition. We found the growth delay was sensitive to the nutrient supplies. It became more severe upon restrictions of the dietary yeast; while high levels of yeast significantly restored the normal growth, but not viability. We further demonstrated that leucine was able to substitute for yeast to provide similar rescues. Moreover, the human FLCN could partially rescue the DBHD⁻ phenotypes, indicating the two genes are involved in certain common mechanisms. Our work provides a new animal model of the BHD syndrome and suggests that modulation of the local nutrient condition might be a potential treatment of the BHD lesions.     

Characterization of Mutant Alleles of Myospheroid, the Gene Encoding the β Subunit of the Drosophila PS Integrins

This paper presents the characterization of nine alleles of myospheroid, which encodes the beta PS subunit of the Drosophila PS integrins. On Southern blots, the mysXB87, mysXN101 and mysXR04 genes yield restriction digest patterns similar to that seen for wild-type chromosomes, however the mys1 and mysXG43 genes contain detectable deletions. mys1, mysXB87 and mysXG43 make little or no stable protein product, and genetically behave as strong lethal alleles. For the mysXN101 mutation, protein product is seen on immunoblots and a reduced amount of beta PS protein is seen at muscle attachment sites of embryos; this mutant protein retains some wild-type function, as revealed by complementation tests with weak alleles. Protein is also seen on immunoblots from mysXR04 embryos, and this allele behaves as an antimorph, being more deleterious in some crosses than the complete deficiency for the locus. mysts2 and mysnj42 are typically lethal in various combinations with other alleles at high temperatures only, but even at high physiological temperatures, neither appears to eliminate gene function completely. The complementation behaviors of mysts1 and mysts3 are quite unusual and suggest that these mutations involve regulatory phenomena. For mysts3, the data are most easily explained by postulating transvection effects at the locus. The results for mysts1 are less straightforward, but point to the possibility of a chromosome pairing-dependent negative interaction.     

Cloning and Molecular Characterization of the First Innexin of the Phylum Annelida—Expression of the Gene During Development

A novel member of the innexin family (cv-inx) has been isolated from the annelid polychaete worm Chaetopterus variopedatus using a PCR approach on genomic DNA and sequence analysis on genomic DNA clones. The gene is present in a HindIII-HindIII segment of 2250 bp containing an uninterrupted open reading frame of 1196 bp encoding a protein of 399 amino acids. The predicted protein shows the typical structural features of innexins and consensus sites for phosphorylation. Analyses on genomic DNA demonstrate that cv-inx is a single copy gene with no introns in the coding region, exactly corresponding to the cDNA sequence. The gene expression is regulated during development as shown by Northern blots analyses of the RNA and by immunoreaction with antibodies against the protein at several embryonic stages. The finding of an innexin in the phylum Annelida, outside of the Ecdysozoa clade, and its peculiar gene structure suggest the necessity to reconsider the current hypothesis on the origin and evolution of gap junctional proteins. Received: 15 December 2000 / Accepted: 27 August 2001     

Do Deletions of Mos1-Like Elements Occur Randomly in the Drosophilidae Family?

We compared deleted copies of the seven mauritiana subfamilies of mariner transposable elements in species of the Drosophilidae. All elements were detected by PCR using the inverted terminal repeats of the Mos1 element of Drosophila mauritiana as primers. A higher frequency of breakpoints in the 5′ part of the element compared to the 3′ part was observed. Of the 27 deletions, 9 (33%) occurred between short direct repeats (SDR) of 5 to 8 bp. The SDRs can be at or close to the breakpoints of the deletion. A deleted copy of D. simulans (St. Martin population) had three repeats of a motif present only once in the complete consensus sequence. The high frequency of SDRs at or near the breakpoints of the deletions strongly suggests that some of them do not occur at random. Mechanisms that might explain these deletions, such as unequal crossing-over, ectopic recombination, and abortive gap repair, are discussed. Received: 22 December 2000 / Accepted: 12 July 2001     

Functional Identification of a Putative β-Galactosidase Gene in the Special lac Gene Cluster of Lactobacillus acidophilus

The putative β-galactosidase gene (lacZ) of Lactobacillus acidophilus has a very low degree of homology to the Escherichia coli β-galactosidase gene (lacZ) and locates in a special lac gene cluster which contains two β-galactosidase genes. No functional characteristic of the putative β-galactosidase has been described so far. In this study, the lacZ gene of L. acidophilus was hetero-expressed in E. coli and the recombinant protein was purified by a three-step procedure. The product of the lacZ gene was also extracted from L. acidophilus ATCC 4356 and active staining was carried out. The enzymatic properties of the purified recombinant LacZ were assayed. The results of hetero-expression showed the recombinant LacZ without tag had β-galactosidase activity. The purified recombinant LacZ had a specific activity of 43.2 U/mg protein. The result of active staining showed that the functional product of the lacZ gene did exist in L. acidophilus. The L. acidophilus β-galactosidase (LacZ) had an optimal pH of 6, an optimal temperature of 37°C and could hydrolyze 73% of lactose in milk in 30 h at 10°C. The L. acidophilus β-galactosidase (LacZ) was identified as cold-adapted β-galactosidase in this study for the first time, and may be useful for lactose removal from dairy products at low temperatures.     

Polymorphism of Human Glutatione S-Transferase Gene in the Populations of the Volga–Ural Region

The frequency of the GstM1 gene deletion homozygotes in eight populations of the Volga–Ural region belonging according to linguistic classification to Turkic (Bashkirs, Tatars, and Chuvashs), Finno–Ugric (Maris, Komis, Mordovians, and Udmurts), and Eastern–Slavic (Russians) ethnic groups, was examined by means of PCR technique. The frequency of the deletion homozygotes varied from 41.4% in Bashkirs to 61.3% in Mordovians. The mean deletion frequency comprised 50.1%, which was consistent with the data for European populations (²= 0.009).