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Chen Y, Geng A, Zhang W, Qian Z, Wan X, Jiang Y, Mao Z. Fight to the bitter end: DNA repair and aging. Ageing Res Rev 2020; 64:101154. [PMID: 32977059 DOI: 10.1016/j.arr.2020.101154] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/05/2020] [Accepted: 08/19/2020] [Indexed: 12/11/2022]
Abstract
DNA carries the genetic information that directs complex biological processes; thus, maintaining a stable genome is critical for individual growth and development and for human health. DNA repair is a fundamental and conserved mechanism responsible for mending damaged DNA and restoring genomic stability, while its deficiency is closely related to multiple human disorders. In recent years, remarkable progress has been made in the field of DNA repair and aging. Here, we will extensively discuss the relationship among DNA damage, DNA repair, aging and aging-associated diseases based on the latest research. In addition, the possible role of DNA repair in several potential rejuvenation strategies will be discussed. Finally, we will also review the emerging methods that may facilitate future research on DNA repair.
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Kumar V, Dickey AM, Seal DR, Shatters RG, Osborne LS, McKenzie CL. Unexpected High Intragenomic Variation in Two of Three Major Pest Thrips Species Does Not Affect Ribosomal Internal Transcribed Spacer 2 (ITS2) Utility for Thrips Identification. Int J Mol Sci 2017; 18:ijms18102100. [PMID: 28984819 PMCID: PMC5666782 DOI: 10.3390/ijms18102100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 09/28/2017] [Accepted: 09/30/2017] [Indexed: 11/16/2022] Open
Abstract
The mitochondrial cytochrome oxidase I gene (mtCO1) and the ribosomal internal transcribed spacer 2 region (ITS2) are among the most widely used molecular markers for insect taxonomic characterization. Three economically important species of thrips, Scirtothripsdorsalis, Thripspalmi, and Frankliniellaoccidentalis were selected to examine the extent of intragenomic variation within these two marker regions in the family Thripidae, and determine if this variation would affect the utility of markers in thrips molecular diagnostics. For each species, intragenomic (within individual) variation and intergenomic (among individuals) variation was assessed by cloning and sequencing PCR-amplified copies. Intergenomic variation was generally higher than intragenomic variation except in cases where intergenomic variation was very low, as in mtCO1 from S.dorsalis and F.occidentalis. Intragenomic variation was detected in both markers in all three of the thrips species, however, 2-3 times more intragenomic variation was observed for ITS2 than mtCO1 in both S.dorsalis and T.palmi. Furthermore, levels of intragenomic variation were low for both of the genes in F.occidentalis. In all of the three thrips species, no sex-based clustering of haplotypes was observed in either marker. Unexpected high intragenomic variation in ITS2 for two of three thrips species did not interfere with thrips diagnostics. However, caution should be taken in applying ITS2 to certain studies of S.dorsalis and T.palmi when high levels of intragenomic variation could be problematic or confounding. In such studies, mtCO1 may be a preferable marker. Possible reasons for discrepancies in intragenomic variation among genomic regions are discussed.
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Affiliation(s)
- Vivek Kumar
- Department of Entomology and Nematology, Mid-Florida Research and Education Center, University of Florida, Apopka, FL 32703, USA; (A.M.D.); (L.S.O.)
- U.S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, USA; (R.G.S.); (C.L.M.)
- Department of Entomology and Nematology, Tropical Research and Education Center, University of Florida, Homestead, FL 33031, USA;
- Correspondence: ; Tel.: +1-772-462-5978
| | - Aaron M. Dickey
- Department of Entomology and Nematology, Mid-Florida Research and Education Center, University of Florida, Apopka, FL 32703, USA; (A.M.D.); (L.S.O.)
- U.S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, USA; (R.G.S.); (C.L.M.)
- Present Address: U.S. Meat Animal Research Center, USDA-ARS, Clay Center, NE 68933, USA
| | - Dakshina R. Seal
- Department of Entomology and Nematology, Tropical Research and Education Center, University of Florida, Homestead, FL 33031, USA;
| | - Robert G. Shatters
- U.S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, USA; (R.G.S.); (C.L.M.)
| | - Lance S. Osborne
- Department of Entomology and Nematology, Mid-Florida Research and Education Center, University of Florida, Apopka, FL 32703, USA; (A.M.D.); (L.S.O.)
| | - Cindy L. McKenzie
- U.S. Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945, USA; (R.G.S.); (C.L.M.)
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Sun XQ, Li DH, Xue JY, Yang SH, Zhang YM, Li MM, Hang YY. Insertion DNA Accelerates Meiotic Interchromosomal Recombination in Arabidopsis thaliana. Mol Biol Evol 2016; 33:2044-53. [PMID: 27189569 DOI: 10.1093/molbev/msw087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Nucleotide insertions/deletions are ubiquitous in eukaryotic genomes, and the resulting hemizygous (unpaired) DNA has significant, heritable effects on adjacent DNA. However, little is known about the genetic behavior of insertion DNA. Here, we describe a binary transgenic system to study the behavior of insertion DNA during meiosis. Transgenic Arabidopsis lines were generated to carry two different defective reporter genes on nonhomologous chromosomes, designated as "recipient" and "donor" lines. Double hemizygous plants (harboring unpaired DNA) were produced by crossing between the recipient and the donor, and double homozygous lines (harboring paired DNA) via self-pollination. The transfer of the donor's unmutated sequence to the recipient generated a functional β-glucuronidase gene, which could be visualized by histochemical staining and corroborated by polymerase chain reaction amplification and sequencing. More than 673 million seedlings were screened, and the results showed that meiotic ectopic recombination in the hemizygous lines occurred at a frequency >6.49-fold higher than that in the homozygous lines. Gene conversion might have been exclusively or predominantly responsible for the gene correction events. The direct measurement of ectopic recombination events provided evidence that an insertion, in the absence of an allelic counterpart, could scan the entire genome for homologous counterparts with which to pair. Furthermore, the unpaired (hemizygous) architectures could accelerate ectopic recombination between itself and interchromosomal counterparts. We suggest that the ectopic recombination accelerated by hemizygous architectures may be a general mechanism for interchromosomal recombination through ubiquitously dispersed repeat sequences in plants, ultimately contributing to genetic renovation and eukaryotic evolution.
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Affiliation(s)
- Xiao-Qin Sun
- Jiangsu Key Laboratory for the Research and Uti1ization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Ding-Hong Li
- Jiangsu Key Laboratory for the Research and Uti1ization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Jia-Yu Xue
- Jiangsu Key Laboratory for the Research and Uti1ization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Si-Hai Yang
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
| | - Yan-Mei Zhang
- Jiangsu Key Laboratory for the Research and Uti1ization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Mi-Mi Li
- Jiangsu Key Laboratory for the Research and Uti1ization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Yue-Yu Hang
- Jiangsu Key Laboratory for the Research and Uti1ization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
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The Rate and Tract Length of Gene Conversion between Duplicated Genes. Genes (Basel) 2011; 2:313-31. [PMID: 24710193 PMCID: PMC3924818 DOI: 10.3390/genes2020313] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 03/11/2011] [Accepted: 03/17/2011] [Indexed: 11/26/2022] Open
Abstract
Interlocus gene conversion occurs such that a certain length of DNA fragment is non-reciprocally transferred (copied and pasted) between paralogous regions. To understand the rate and tract length of gene conversion, there are two major approaches. One is based on mutation-accumulation experiments, and the other uses natural DNA sequence variation. In this review, we overview the two major approaches and discuss their advantages and disadvantages. In addition, to demonstrate the importance of statistical analysis of empirical and evolutionary data for estimating tract length, we apply a maximum likelihood method to several data sets.
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Hussain S, Livingston BT. Tracing misalignment and unequal crossing over during evolution of the repetitive region of the SM50 gene in sea urchins. ACTA ACUST UNITED AC 2009; 311:143-54. [PMID: 19048602 DOI: 10.1002/jez.511] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The location of misalignment and unequal crossover involved in concerted evolution of tandemly repetitive sequences is difficult to document owing to the homogeneity of sequences that are subject to this process. However, the repetitive domain of the SM50 gene in sea urchins contains variation, within the gene itself, between alleles, and between species that has allowed us to determine where misalignment and unequal crossing over occurred during evolution of this gene. We have therefore analyzed the SM50 repeat regions in a variety of species to determine where recent changes in repeat numbers have occurred, and from this have deduced the mechanisms that lead to these changes. We next tried to determine whether recent misalignment and unequal crossover has produced allelic variation in current populations of sea urchins. We found SM50 alleles within three species that have different numbers of repeats. This marks the first reported documentation of allelic variation in the number of repeats in the SM50 gene. We also show how a single unequal crossover event could have produced the allelic variation. We have found that substitutions and small deletions in the sequences within the repeats can substantially affect how misalignment occurs, resulting in different patterns of repeats after concerted evolution.
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Affiliation(s)
- Sofia Hussain
- Division of Cell Biology, Microbiology and Molecular Biology, Department of Biology, University of South Florida, Tampa, Florida, USA
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6
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Analysis of spontaneous gene conversion tracts within and between mammalian chromosomes. J Mol Biol 2008; 377:337-51. [PMID: 18262541 DOI: 10.1016/j.jmb.2008.01.036] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2007] [Revised: 01/04/2008] [Accepted: 01/15/2008] [Indexed: 11/24/2022]
Abstract
In the present study, we report the first characterization of gene conversion tract length, continuity and fidelity for pathways of gene targeting, ectopic and intrachromosomal homologous recombination using the same locus and mammalian somatic cell type. In this isogenic cell system, the vast majority of recombinants (>97%) are generated by homologous recombination and display a high degree of fidelity in the gene conversion process. Individual gene conversion tracts are highly likely to involve single, independent recombination events and proceed through a heteroduplex DNA intermediate. In all recombination pathways, gene conversion tracts are long, extending up to approximately 2 kb. Most gene conversion tracts are continuous in favor of donor region sequences, but in a small fraction of recombinants (15%), discontinuous gene conversion tracts are observed. In most cases, the recombination donor sequence is unaltered, although in two cases of intrachromosomal recombination, both recombination donor and recipient sequences bear gene conversion tracts. Overall, gene conversion events are similar, both qualitatively and quantitatively, for homologous recombination within and between mammalian chromosomes.
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7
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Hendricks CA, Engelward BP. "Recombomice": the past, present, and future of recombination-detection in mice. DNA Repair (Amst) 2005; 3:1255-61. [PMID: 15336621 DOI: 10.1016/j.dnarep.2004.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2004] [Indexed: 11/22/2022]
Abstract
Homology directed repair (HDR) provides an efficient strategy for repairing and tolerating many types of DNA lesions, such as strand breaks, base damage, and crosslinks. Recombinational repair and lesion avoidance pathways that involve homology searching are integral to normal DNA replication. Indeed, it is estimated that at least ten HDR events take place each time a mammalian cell divides. HDR is associated with the transfer and exchange of DNA sequences. Usually, homologous sequences are aligned perfectly and flanking sequences are not exchanged. However, those sequence misalignments and exchanges that do occur can lead to rearrangements that contribute to cancer (e.g. deletions, inversions, translocations or loss of heterozygosity (LOH)). In order to reveal genetic and environmental factors that modulate HDR in mammals, several approaches have been used to detect recombination events in vivo. Here, we briefly review three methods for detecting homologous recombination in mice, namely: sister chromatid exchange (SCE), LOH, and recombination at tandem repeats. We conclude with a more detailed description of the recently developed "Fluorescent Yellow Direct Repeat" (FYDR) mouse model, which exploits enhanced yellow fluorescent protein (EYFP) for detecting mitotic homologous recombination in vivo. Applications of the FYDR mice are described, as well as the broader potential for using fluorescent proteins to detect recombination in various tissues/cell types in vivo.
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Affiliation(s)
- Carrie A Hendricks
- Division of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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8
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Würtele H, Gusew N, Lussier R, Chartrand P. Characterization of in vivo recombination activities in the mouse embryo. Mol Genet Genomics 2005; 273:252-63. [PMID: 15902491 DOI: 10.1007/s00438-005-1112-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Accepted: 12/20/2004] [Indexed: 10/25/2022]
Abstract
Homologous recombination makes use of sequence homology to repair DNA and to rearrange genetic material. In mammals, these processes have mainly been characterized using cultured cell systems. We have developed an assay that allows us to quantitatively analyze homologous recombination in vivo in the mouse embryo. Transgenic mouse lines were generated by microinjection into a fertilized mouse ovum of a vector containing two homologous LINE-1 (L1) sequences arranged as a direct repeat: these sequences can recombine with each other and with endogenous L1 sequences before, during or after integration of the vector into the genome. Using a plasmid rescue procedure, we determined the composition of the integrated vector array in several transgenic mice and their descendants. Homologous recombination frequencies were found to be strikingly high, involving 70% of integrated vectors in some arrays, with homologous deletions being five times more frequent than gene conversion without crossing-over. Interestingly, non-homologous recombination was found to be much less frequent. We also found that endogenous L1 sequences could be involved in homologous recombination events in the mouse embryo, and that the integrated arrays could be modified from generation to generation by homologous recombination between the integrated L1 sequences.
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Affiliation(s)
- Hugo Würtele
- Institute of Research in Immunology and Cancer, Université de Montréal, Pavillon Roger-Gaudry, 2900 Edouard-Montpetit, Montreal, Quebec, Canada H3T 1J4
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9
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Maggi A, Ottobrini L, Biserni A, Lucignani G, Ciana P. Techniques: Reporter mice – a new way to look at drug action. Trends Pharmacol Sci 2004; 25:337-42. [PMID: 15165750 DOI: 10.1016/j.tips.2004.04.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
During the past decade remarkable progress in molecular genetics and the possibility of manipulating cells so that the expression of genes can directly 'report' on drug activity has produced major changes in drug development strategies. The recent description and pharmacological validation of reporter mice for in vivo analysis of hormone receptor activity opens new horizons for drug discovery. These novel animal models, in association with in vivo imaging technologies, provide a global view of the target tissues of drug action following acute and repeated drug treatment, thus enabling the prediction of potential side-effects in the early phase of preclinical studies. It is anticipated that further improvements of transgene architecture will lead to models that combine pharmacokinetic, pharmacodynamic and toxicological studies in a single step, which should provide a tremendous saving in time and, paradoxically, the number of animals to be sacrificed in the development of novel pharmacologically active molecules.
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Affiliation(s)
- Adriana Maggi
- Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133 Milan, Italy.
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10
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Rozen S, Skaletsky H, Marszalek JD, Minx PJ, Cordum HS, Waterston RH, Wilson RK, Page DC. Abundant gene conversion between arms of palindromes in human and ape Y chromosomes. Nature 2003; 423:873-6. [PMID: 12815433 DOI: 10.1038/nature01723] [Citation(s) in RCA: 388] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2003] [Accepted: 04/07/2003] [Indexed: 11/09/2022]
Abstract
Eight palindromes comprise one-quarter of the euchromatic DNA of the male-specific region of the human Y chromosome, the MSY. They contain many testis-specific genes and typically exhibit 99.97% intra-palindromic (arm-to-arm) sequence identity. This high degree of identity could be interpreted as evidence that the palindromes arose through duplication events that occurred about 100,000 years ago. Using comparative sequencing in great apes, we demonstrate here that at least six of these MSY palindromes predate the divergence of the human and chimpanzee lineages, which occurred about 5 million years ago. The arms of these palindromes must have subsequently engaged in gene conversion, driving the paired arms to evolve in concert. Indeed, analysis of MSY palindrome sequence variation in existing human populations provides evidence of recurrent arm-to-arm gene conversion in our species. We conclude that during recent evolution, an average of approximately 600 nucleotides per newborn male have undergone Y-Y gene conversion, which has had an important role in the evolution of multi-copy testis gene families in the MSY.
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Affiliation(s)
- Steve Rozen
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA
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11
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Pittman DL, Schimenti KJ, Hanneman WH, Schimenti JC. Transgenic and mutational analyses of meiotic recombination in mice. Ann N Y Acad Sci 1999; 870:220-2. [PMID: 10415485 DOI: 10.1111/j.1749-6632.1999.tb08882.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D L Pittman
- Jackson Laboratory, Bar Harbor, Maine 04609, USA
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12
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Lambert S, Saintigny Y, Delacote F, Amiot F, Chaput B, Lecomte M, Huck S, Bertrand P, Lopez BS. Analysis of intrachromosomal homologous recombination in mammalian cell, using tandem repeat sequences. Mutat Res 1999; 433:159-68. [PMID: 10343649 DOI: 10.1016/s0921-8777(99)00004-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In all the organisms, homologous recombination (HR) is involved in fundamental processes such as genome diversification and DNA repair. Several strategies can be devised to measure homologous recombination in mammalian cells. We present here the interest of using intrachromosomal tandem repeat sequences to measure HR in mammalian cells and we discuss the differences with the ectopic plasmids recombination. The present review focuses on the molecular mechanisms of HR between tandem repeats in mammalian cells. The possibility to use two different orientations of tandem repeats (direct or inverted repeats) in parallel constitutes also an advantage. While inverted repeats measure only events arising by strand exchange (gene conversion and crossing over), direct repeats monitor strand exchange events and also non-conservative processes such as single strand annealing or replication slippage. In yeast, these processes depend on different pathways, most of them also existing in mammalian cells. These data permit to devise substrates adapted to specific questions about HR in mammalian cells. The effect of substrate structures (heterologies, insertions/deletions, GT repeats, transcription) and consequences of DNA double strand breaks induced by ionizing radiation or endonuclease (especially the rare-cutting endonuclease ISce-I) on HR are discussed. Finally, transgenic mouse models using tandem repeats are briefly presented.
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Affiliation(s)
- S Lambert
- UMR 217 CNRS, CEA, DSV, DRR, Fontenay aux Roses, France
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13
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Abstract
It is possible to measure gene conversion of MHC genes with the help of a semi-nested PCR assay. Several considerations are of utmost importance when such an assay is set up. Using this assay, we have found that gene conversion occurs in MHC class II genes in mouse sperm, but not in somatic cells tested. Although this gene conversion occurs in germline cells, it is already completed in spermatogonia, and consequently is mitotic event unlinked to meiosis. The frequency of gene conversion events in MHC class II genes varies strongly from one allele to another, with the highest detected frequencies as high as 1/40,000 for an individual heterozygous for both donor and acceptor sequences. Deletions or insertions in one gene relative to the other seem to lower the efficiency of gene conversion considerably. Stretches within MHC genes amenable to gene conversion are located in CpG clusters, whereas MHC genes not involved in gene conversion have background CpG levels. DNA damage, either chemical or radiation induced, increases the frequency of gene conversion of MHC class II genes in cultured cells of the fibroblastoid lineage. The effect of chemical DNA damage seems roughly dose dependent, whereas irradiation has a maximal effect at low doses.
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Affiliation(s)
- K Högstrand
- Department of Immunology, Stockholm University, Sweden
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14
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Högstrand K, Böhme J. DNA damage caused by etoposide and gamma-irradiation induces gene conversion of the MHC in a mouse non-germline testis cell line. Mutat Res 1999; 423:155-69. [PMID: 10029693 DOI: 10.1016/s0027-5107(98)00239-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have explored the effects of gamma-irradiation and etoposide on the gene conversion frequency between the endogenous major histocompatibility complex class II genes Abk and Ebd in a mouse testis cell line of non-germline origin with a polymerase chain reaction assay. Both gamma-rays and etoposide were shown to increase the gene conversion frequency with up to 15-fold compared to untreated cells. Etoposide, which is an agent that stabilise a cleavable complex between DNA and DNA topoisomerase II, shows an increased induction of gene conversion events with increased dose of etoposide. Cells treated with gamma-rays, which induce strand breaks, had an increased gene conversion frequency when they were subjected to low doses of irradiation, but increasing doses of irradiation did not lead to an increase of gene conversion events, which might reflect differences in the repair process depending on the extent and nature of the DNA damage. These results where DNA damage was shown to be able to induce gene conversion of endogenous genes in mouse testis cells suggests that the DNA repair system could be involved in the molecular genetic mechanism that results in gene conversion in higher eukaryotes like mammals.
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Affiliation(s)
- K Högstrand
- Department of Immunology, The Wenner-Gren Institute, University of Stockholm, S-10691, Stockholm, Sweden.
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15
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Schimenti JC. Mice and the role of unequal recombination in gene-family evolution. Am J Hum Genet 1999; 64:40-5. [PMID: 9915941 PMCID: PMC1377700 DOI: 10.1086/302220] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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16
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Affiliation(s)
- D Liao
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
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17
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Abstract
Duplicated genes and repetitive sequences are distributed throughout the genomes of complex organisms. The homology between related sequences can promote nonallelic (ectopic) recombination, including gene conversion and reciprocal exchange. Resolution of these events can result in translocations, deletions, or other harmful rearrangements. In yeast, ectopic recombination between sequences on nonhomologous chromosomes occurs at high frequency. Because the mammalian genome is replete with duplicated sequences and repetitive elements, high levels of ectopic exchange would cause aneuploidy and genome instability. To understand the factors regulating ectopic recombination in mice, we evaluated the effects of homology length on gene conversion between unlinked sequences in the male germline. Previously, we found high levels of gene conversion between lacZ transgenes containing 2557 bp of homology. We report here that genetic background can play a major role in ectopic recombination; frequency of gene conversion was reduced by more than an order of magnitude by transferring the transgenes from a CF1 strain background to C57BL/6J. Additionally, conversion rates decreased as the homology length decreased. Sequences sharing 1214 bp of sequence identity underwent ectopic conversion less frequently than a pair sharing 2557 bp of identity, while 624 bp was insufficient to catalyze gene conversion at significant levels. These results suggest that the germline recombination machinery in mammals has evolved in a way that prevents high levels of ectopic recombination between smaller classes of repetitive sequences, such as the Alu family. Additionally, genomic location appeared to influence the availability of sequences for ectopic recombination.
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Affiliation(s)
- D M Cooper
- The Jackson Laboratory, Bar Harbor, Maine 04609, USA
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18
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Pittman DL, Cobb J, Schimenti KJ, Wilson LA, Cooper DM, Brignull E, Handel MA, Schimenti JC. Meiotic prophase arrest with failure of chromosome synapsis in mice deficient for Dmc1, a germline-specific RecA homolog. Mol Cell 1998; 1:697-705. [PMID: 9660953 DOI: 10.1016/s1097-2765(00)80069-6] [Citation(s) in RCA: 463] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
DMC1 is a meiosis-specific gene first discovered in yeast that encodes a protein with homology to RecA and may be component of recombination nodules. Yeast dmc1 mutants are defective in crossing over and synaptonemal complex (SC) formation, and arrest in late prophase of meiosis I. We have generated a null mutation in the Dmc1 gene in mice and show that homozygous mutant males and females are sterile with arrest of gametogenesis in the first meiotic prophase. Chromosomes in mutant spermatocytes fail to synapse, despite the formation of axial elements that are the precursor to the SC. The strong similarity of phenotypes in Dmc1-deficient mice and yeast suggests that meiotic mechanisms have been highly conserved through evolution.
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Affiliation(s)
- D L Pittman
- Jackson Laboratory, Bar Harbor, Maine 04609, USA
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19
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Böhme J, Högstrand K. Timing and effects of template number for gene conversion of major histocompatibility complex genes in the mouse. Hereditas 1998; 127:11-8. [PMID: 9420465 DOI: 10.1111/j.1601-5223.1997.00011.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Pachytene spermatocytes and haploid spermatocytes from adult mice, as well as testis cells from prepubescent mice were analysed for the presence of gene conversion products resulting from the transfer between the MHC class II genes Ebd and Abk in a PCR assay. Gene conversion products were detected in testis cells as early as in 8 days old mice, where the only existing spermatogenic cells are spermatogonia. The frequency of gene conversion products remains the same as the cells reach meiosis in 18 days old mice or in pachytene cells, and is unchanged after meiosis is completed in haploid spermatocytes, thus indicating that gene conversion is largely completed already in the mitotically dividing spermatogonia. We have furthermore analysed the frequency of gene conversion between the Eb and Ab loci within the same MHC haplotype, the k haplotype. The frequency of such events is the same in animals with one and two copies of the same haplotype, and consequently seems to be independent of template number.
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Affiliation(s)
- J Böhme
- Department of Immunology, Wenner-Gren Institute, Stockholm University, Sweden
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20
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Högstrand K, Böhme J. Gene conversion of major histocompatibility complex genes in the mouse spermatogenesis is a premeiotic event. Mol Biol Cell 1997; 8:2511-7. [PMID: 9398672 PMCID: PMC25724 DOI: 10.1091/mbc.8.12.2511] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The molecular genetic mechanism of gene conversion in higher eukaryotes remains unknown. We find it of considerable interest to determine when during spermatogenesis gene conversion occurs. We have therefore purified pachytene spermatocytes and haploid spermatocytes from adult mice and analyzed these fractions for the presence of gene conversion products resulting from the transfer between the major histocompatibility complex class II genes Ebd and Abk in a polymerase chain reaction assay. We have further isolated spermatogenic cells from prepubescent mice and analyzed them for the presence of the same gene conversion products. We can detect gene conversion products in testis cells as early as in 8-d-old mice where the only existing spermatogenic cells are spermatogonia. The frequency of gene conversion products remains the same as the cells reach meiosis in 18-d-old mice, and is unchanged after meiosis is completed in haploid spermatocytes. Gene conversion of this specific fragment therefore appears to be a premeiotic event and, consequently, relies on genetic mechanisms other than normal meiotic recombination.
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Affiliation(s)
- K Högstrand
- Department of Immunology, The Wenner-Gren Institute, Stockholm University, Sweden
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21
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Abstract
Transgenic and knockout mice have been proposed as substitutes for one of the standard 2-yr rodent assays. The advantages of using genetically engineered mouse models is that fewer mice are needed, the time to develop disease is greatly reduced, and the mice are predisposed to developing cancer by virtue of gain or loss of functions. The models currently being used have yielded a large amount of data and have proved to be informative for risk assessment; however, they are still far from ideal. In fact, they inherently do not reflect the complexity of mutation and carcinogenesis in humans. Recent advances in technology and the creation of new knockout mice may produce more useful and more sensitive models. This review covers two recent advances in technology--inducible and regulatable gene expression and targeted genetic modifications in the genome--that will allow us to make better models. I also discuss new gene deletion and transgenic mouse models and their potential impact on risk-assessment assays. These models are presented in the context of four basic components or events that occur in the multistep process leading to cancer: maintenance of gene expression patterns, genome stability and DNA repair, cell-cell communication and signaling, and cell-cycle regulation. Finally, surrogate markers and utility in risk assessment are also discussed. This review is meant to stimulate further discussion in the field and to generate excitement about working toward the next generation of risk-assessment models.
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Affiliation(s)
- M P Rosenberg
- Department of Genomics, Glaxo Wellcome Research, Inc., Research Triangle Park, North Carolina
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22
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Hanneman WH, Schimenti KJ, Schimenti JC. Molecular analysis of gene conversion in spermatids from transgenic mice. Gene 1997; 200:185-92. [PMID: 9373154 DOI: 10.1016/s0378-1119(97)00416-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Investigations into the mechanisms and properties of gene conversion in mammals are greatly restricted by the inability to recover all the products of a meiosis. Additionally, the study of this process has been hampered by the lack of visible markers to detect gene conversion, especially when the events are rare. In previous work, we developed a transgenic system for detection and quantitation of gene conversion events in the germline of mice (Murti, J.R., Bumbulis, M., Schimenti, J.C., 1992. High frequency germline gene conversion in transgenic mice. Mol. Cell. Biol. 12, 2545-2552) that could be exploited as an assay for recombinogenic chemicals (Murti, J.R, Schimenti, K.J., Schimenti, J.C., 1994. A recombination-based transgenic mouse system for genotoxicity testing. Mutat. Res. 307, 583-595). A specific intrachromosomal gene conversion event between two complementarily defective lacZ genes resulted in the production of beta-galactosidase in spermatids, enabling a measurement of conversion frequency. Here, we report that the anticancer drug, cisplatin, increased gene conversion in meiotic stage cells in these transgenic mice. Furthermore, a method was developed for direct molecular analysis of transgene conversion events in single or pooled lacZ-positive spermatids. The ability to identify gametes that have undergone a rare gene conversion event, followed by molecular amplification of the recombinant gene, should make it possible to investigate the mechanisms of genetic recombination in mammals in greater detail than previously possible.
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Affiliation(s)
- W H Hanneman
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
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23
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Ewulonu UK, Schimenti JC. Function of untranslated regions in the mouse spermatogenesis-specific gene Tcp10 evaluated in transgenic mice. DNA Cell Biol 1997; 16:645-51. [PMID: 9174169 DOI: 10.1089/dna.1997.16.645] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The mouse Tcp10 genes are transcribed exclusively in male germ cells and display multiple 5' and 3' untranslated variations generated by alternative splicing and polyadenylation signal usage. To investigate the possible role of untranslated sequences in the regulation of these genes, chimeric expression constructs with or without endogenous 5' and 3' untranslated sequences were generated and used to make transgenic mice. Analysis of these animals showed that the untranslated sequences have no effect on the transcription or translation of an attached lacZ reporter gene, thereby implying these sequences are dispensible. However, the endogenous pattern of polyadenylation site usage was altered when Tcp10 3' untranslated sequences were linked to lacZ, indicating that internal coding sequence can influence recognition of polyadenylation signals in testis. The characteristics of alternative splicing and polyadenylation signal variability reflects a common theme of promiscuity in testicular gene expression.
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Affiliation(s)
- U K Ewulonu
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
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24
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Abstract
The function of meiotic recombination has remained controversial, despite recent inroads into mechanisms. Ideas concerning a possible role of recombination in the elimination or efficient incorporation of mutations have been backed by theoretical studies but have lacked empirical support. Recent investigations into the basis for local variations in recombination frequency in yeast have uncovered a strong association between recombination initiation sites and transcriptional regulatory sequences. Other recent studies indicate a strong correlation between transcription and mutation rates in yeast genes. Taken together, these data imply that distributions of recombination and mutation frequencies may be strongly correlated. This suggests that recombination may be targeted to genomic sites of high mutation frequency; such a 'mutation-tracking' function would clearly aid in the shuffling of mutations to break up unfavorable and create favorable allelic combinations. Moreover, recent insights into the mechanism of gene conversion in yeast reveal a very strong inherent bias in favor of alleles on the non-initiating homolog. Combined with mutation tracking, these findings suggest a novel and general mechanism by which allelic gene conversion may act to eliminate mutations.
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Affiliation(s)
- B D McKee
- Department of Biochemistry and Molecular and Cellular Biology, University of Tennessee, Knoxville 37996, USA.
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25
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26
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Zangenberg G, Huang MM, Arnheim N, Erlich H. New HLA-DPB1 alleles generated by interallelic gene conversion detected by analysis of sperm. Nat Genet 1995; 10:407-14. [PMID: 7670490 DOI: 10.1038/ng0895-407] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The rate at which allelic diversity at the HLA loci evolves has been the subject of considerable controversy. The patchwork pattern of sequence polymorphism within the second exon of the HLA class II loci, particularly in the DPB1 locus, may have been generated by segmental exchange (gene conversion). We have analysed the frequency of variant DPB1 sequences that have been created by interallelic gene conversion in the germline by screening pools of sperm using PCR amplification and oligonucleotide probe typing. Our results indicate that about 1/10,000 sperm represents a new DPB1 sequence generated by short tracts of segmental exchange (gene conversion) within the second exon, suggesting that interallelic gene conversion may have an important role in generating the extensive allelic diversity at the HLA loci.
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Affiliation(s)
- G Zangenberg
- Department of Human Genetics, Roche Molecular Systems, Alameda, California 94501, USA
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Murti JR, Schimenti KJ, Schimenti JC. A recombination-based transgenic mouse system for genotoxicity testing. Mutat Res 1994; 307:583-95. [PMID: 7514731 DOI: 10.1016/0027-5107(94)90268-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
It is well established that mutagens induce recombination in cultured cells and experimental organisms. Presumably, this is a consequence of the DNA-damage-triggering cellular-repair mechanisms. The relationship between recombination and mutagenicity has been exploited in submammalian organisms, such as yeast, to assay the ability of chemical agents and radiation to induce a form of recombination called gene conversion--the non-reciprocal transfer of genetic information. This work has demonstrated the efficacy of predicting mutagenicity on the basis of recombination induction. Here, we describe the utilization of a transgenic mouse system for efficient detection of germ-line gene-conversion events as a mutagen-screening tool. These mice contain two mutually defective reporter (lacZ) genes under the regulatory control of a spermatogenesis-specific promoter. A particular intrachromosomal gene conversion event must occur for the generation of functional lacZ activity. Conversion events are visualized by histochemical staining or flow cytometric analysis of transgenic spermatids. The highly mutagenic compound chlorambucil induced a several fold percentage-wise increase of lacZ-positive spermatids, whereas acrylamide, a weak genotoxin, produced no marked increase in converted spermatids. The results indicate that recombination-based transgenic mouse models for genotoxin screening present a viable option for inexpensive and rapid whole-animal mutagen testing. The particular mice we describe may ultimately prove to be a useful tool for identifying agents which can cause heritable genetic mutations in humans.
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Affiliation(s)
- J R Murti
- Jackson Laboratory, Bar Harbor, ME 04609
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28
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Gerson SL, Zaidi NH, Dumenco LL, Allay E, Fan CY, Liu L, O'Connor PJ. Alkyltransferase transgenic mice: probes of chemical carcinogenesis. Mutat Res 1994; 307:541-55. [PMID: 7514728 DOI: 10.1016/0027-5107(94)90265-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Transgenic mice expressing DNA-repair genes are an instructive model with which to study the protective role of DNA-repair pathways in both spontaneous and chemical carcinogenesis. Of particular interest in chemical carcinogenesis is the DNA-repair protein O6-alkylguanine-DNA alkyltransferase (alkyltransferase) which repairs O6-alkylguanine-DNA adducts. Transgenic mice carrying expression constructs for the alkyltransferase gene--either the human MGMT cDNA or the bacterial ada gene--express increased levels of alkyltransferase and have increased capacity to remove O6-methylguanine-DNA adducts. Protection from the DNA damaging effects of N-nitroso compounds occurs specifically in the cells and tissues in which the alkyltransferase transgene is expressed. For instance, mice carrying the PEPCKada construct have increased alkyltransferase in the liver and more rapid removal of O6methylguanine-DNA adducts. The protective effect is noted in hepatocytes, which express PEPCK-linked genes, not in nonparenchymal cells of the liver, which do not. Other tissues that express the transgene in the various models include the thymus, spleen, testes, muscle, stomach and brain. Mice expressing the human alkyltransferase in the thymus have a reduced incidence of thymic lymphomas following exposure to methyl nitrosourea (MNU), evidence of a role for this DNA-repair protein in protection from carcinogenesis due to N-nitroso compounds. Protection has also been observed in the induction of hepatic tumors by N-nitroso-dimethylamine (NDMA). These models will be used to identify whether overexpression of a single DNA-repair gene can block the carcinogenic process of N-nitroso compounds in many different tissues.
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Affiliation(s)
- S L Gerson
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4937
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29
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Jansen G, Willems P, Coerwinkel M, Nillesen W, Smeets H, Vits L, Höweler C, Brunner H, Wieringa B. Gonosomal mosaicism in myotonic dystrophy patients: involvement of mitotic events in (CTG)n repeat variation and selection against extreme expansion in sperm. Am J Hum Genet 1994; 54:575-85. [PMID: 8128954 PMCID: PMC1918095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Myotonic dystrophy (DM) is caused by abnormal expansion of a polymorphic (CTG)n repeat, located in the DM protein kinase gene. We determined the (CTG)n repeat lengths in a broad range of tissue DNAs from patients with mild, classical, or congenital manifestation of DM. Differences in the repeat length were seen in somatic tissues from single DM individuals and twins. Repeats appeared to expand to a similar extent in tissues originating from the same embryonal origin. In most male patients carrying intermediate- or small-sized expansions in blood, the repeat lengths covered a markedly wider range in sperm. In contrast, male patients with large allele expansions in blood (> 700 CTGs) had similar or smaller repeats in sperm, when detectable. Sperm alleles with > 1,000 CTGs were not seen. We conclude that DM patients can be considered gonosomal mosaics, i.e., combined somatic and germ-line tissue mosaics. Most remarkably, we observed multiple cases where the length distributions of intermediate- or small-sized alleles in fathers' sperm were significantly different from that in their offspring's blood. Our combined findings indicate that intergenerational length changes in the unstable CTG repeat are most likely to occur during early embryonic mitotic divisions in both somatic and germ-line tissue formation. Both the initial CTG length, the overall number of cell divisions involved in tissue formation, and perhaps a specific selection process in spermatogenesis may influence the dynamics of this process. A model explaining mitotic instability and sex-dependent segregation phenomena in DM manifestation is discussed.
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Affiliation(s)
- G Jansen
- Department of Cell Biology and Histology, Faculty of Medical Sciences, University of Nijmegen, The Netherlands
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30
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Garey CE, Schwarzman AL, Rise ML, Seyfried TN. Ceruloplasmin gene defect associated with epilepsy in EL mice. Nat Genet 1994; 6:426-31. [PMID: 7914452 DOI: 10.1038/ng0494-426] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Epilepsy is a dominant trait in EL mice, a model for human complex partial seizures. We recently mapped the major gene, El-1, to chromosome 9 near the predicted location for the ceruloplasmin (Cp) gene. We now present evidence for a partial duplication in the Cp gene in EL mice. This Cp duplication is coinherited with seizures in backcross generations and is associated with enhanced expression of Cp mRNA and increased Cp oxidase activity. Moreover, the duplication is associated with an enhanced frequency of double recombinants, simulating negative interference. The findings are relevant to the basic mechanisms of epilepsy and to theories of genetic recombination and gene mapping.
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MESH Headings
- Animals
- Ceruloplasmin/biosynthesis
- Ceruloplasmin/genetics
- Chromosome Mapping
- Copper/physiology
- Crosses, Genetic
- Crossing Over, Genetic
- Disease Models, Animal
- Epilepsy, Complex Partial/enzymology
- Epilepsy, Complex Partial/genetics
- Gene Expression Regulation, Enzymologic
- Humans
- Liver/enzymology
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Inbred Strains/genetics
- Mice, Neurologic Mutants/genetics
- Multigene Family
- Nerve Tissue Proteins/biosynthesis
- Nerve Tissue Proteins/genetics
- Polymerase Chain Reaction
- Polymorphism, Restriction Fragment Length
- Recombination, Genetic
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Affiliation(s)
- C E Garey
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02167
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31
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Abstract
We have constructed two sets of Escherichia coli lacZ-based vectors for use in studies of general mitotic recombination, both in somatic mammalian cells grown in culture and in transgenic animals. The vectors use two mutant copies of the E. coli lacZ gene as their recombination substrates and contain a neo gene for selection of stable transformants. In one vector, pLrec, an SV40 promoter drives lacZ, while the other vector, pArec, utilizes a human non-muscle beta-actin promoter for lacZ expression. Gene conversions, unequal sister chromatid exchanges and reciprocal exchanges between the two lacZ genes result in expression of beta-galactosidase, which can be detected in situ by histochemical staining. These vectors yield rates and frequencies of mitotic intrachromosomal recombination in human and rodent cell lines which are similar to rates reported using conventional recombination vectors. Molecular analysis of recombinational events involving the lacZ-based vectors can be carried out on genomic DNA isolated from clonally expanded populations and individual LacZ+ cells and cell clusters can be analyzed using PCR amplification. These reporter gene-based vectors may facilitate the study of recombination in cells with limited proliferative capacities, allow for analysis of both products of an unequal sister chromatid exchange, and permit in situ detection of recombination in the tissues of transgenic animals.
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Affiliation(s)
- L B Herzing
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510
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32
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Rassoulzadegan M, Paquis-Flucklinger V, Bertino B, Sage J, Jasin M, Miyagawa K, van Heyningen V, Besmer P, Cuzin F. Transmeiotic differentiation of male germ cells in culture. Cell 1993; 75:997-1006. [PMID: 7504588 DOI: 10.1016/0092-8674(93)90543-y] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A cell culture system that supports the differentiation of male germ cells through meiosis is described. It takes advantage of the properties of a cell line, 15P-1, established from testicular cells of transgenic mice that express the large T protein of polyoma virus in the seminiferous epithelium. This line exhibits features characteristics of Sertoli cells, including transcription of the Wilms' tumor (WT1) and Steel genes. Cells of the 15P-1 type support the meiotic and postmeiotic differentiation in cocultures of diploid premeiotic germ cells into haploid spermatids expressing the protamine (Prm-1) gene. When cocultured with 15P-1 cells, testicular cells explanted from immature 9-day-old animals, before the onset of the first meiosis, generated tetrads of haploid cells with the morphology of round spermatids and initiated protamine transcription.
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Affiliation(s)
- M Rassoulzadegan
- Unité 273 de l'Institut National de la Santé, Université de Nice, France
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33
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Trezise AE, Linder CC, Grieger D, Thompson EW, Meunier H, Griswold MD, Buchwald M. CFTR expression is regulated during both the cycle of the seminiferous epithelium and the oestrous cycle of rodents. Nat Genet 1993; 3:157-64. [PMID: 7684647 DOI: 10.1038/ng0293-157] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Severely reduced fertility is a common finding in cystic fibrosis (CF). We used in situ hybridization to examine the cell-specific expression of CFTR in the reproductive organs of rodents. In males CFTR mRNA is found in the round spermatids (spermatogenic stages V-X) and in the principal cells that line the initial segment of the epididymis. In both the testis and the epididymis, CFTR expression is developmentally regulated suggesting that the defect in the genital tract of male CF patients is of developmental origin. CFTR expression in the luminal and glandular epithelium of the uterus is regulated during the oestrous cycle and is maximal at pro-oestrus. Our results provide a biological rationale for the reduced fertility of CF patients, and suggest a possible cause for the comparatively poorer prognosis for women with CF.
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Affiliation(s)
- A E Trezise
- Department of Genetics, Hospital for Sick Children, Toronto, Ontario, Canada
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34
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Bullard DC, Ticknor C, Schimenti JC. Functional analysis of a t complex responder locus transgene in mice. Mamm Genome 1992; 3:579-87. [PMID: 1421767 DOI: 10.1007/bf00350625] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Transmission ratio distortion (TRD) of mouse t haplotypes occurs through the interaction of multiple distorter loci with the t complex responder (Tcr) locus. Males heterozygous for a t haplotype will transmit the t-bearing chromosome to nearly all of their offspring. This process is mediated by the production of functionally inequivalent gametes: wild-type meiotic partners of t spermatozoa are rendered functionally inactive. The Tcr locus, which is required for TRD to occur, is thought to somehow protect its host spermatid from the sperm-inactivating effects of linked distorter genes (Lyon 1984). In previous work, Tcr was mapped to a small genetic interval in t haplotypes, and a candidate gene from this region was isolated (Tcp-10bt). In this work, we further localize Tcr to a 40-kb region that contains the 21-kb Tcp-10bt gene. A cloned genomic copy of Tcp-10bt was used to generate transgenic mice. The transgene was bred into a variety of genetic backgrounds to test for non-Mendelian segregation. Abberrant segregation was observed in some mice carrying either a complete t haplotype or a combination of certain partial t haplotypes. These observations, coupled with those of Snyder and colleagues (in this issue), provide genetic and functional evidence that the Tcp-10bt gene is Tcr. However, other genotypes that were predicted to produce distortion did not. The unexpected data from a variety of crosses in this work and those of our colleagues suggest that elements to the TRD system and the Tcr locus remain to be identified.
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Affiliation(s)
- D C Bullard
- Baylor College of Medicine, Institute for Molecular Genetics, Houston, Texas 77030
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