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1.
BMC Ecol Evol ; 24(1): 29, 2024 Mar 04.
Article in English | MEDLINE | ID: mdl-38433185

ABSTRACT

The African buffalo, Syncerus caffer, is a key species in African ecosystems. Like other large herbivores, it plays a fundamental role in its habitat acting as an ecosystem engineer. Over the last few centuries, African buffalo populations have declined because of range contraction and demographic decline caused by direct or indirect human activities. In Mozambique, historically home to large buffalo herds, the combined effect of colonialism and subsequent civil wars has created a critical situation that urgently needs to be addressed. In this study, we focused on the analysis of genetic diversity of Syncerus caffer caffer populations from six areas of Mozambique. Using genome-wide SNPs obtained from ddRAD sequencing, we examined the population structure across the country, estimated gene flow between areas under conservation management, including national reserves, and assessed the inbreeding coefficients. Our results indicate that all studied populations of Syncerus caffer caffer are genetically depauperate, with a high level of inbreeding. Moreover, buffaloes in Mozambique present a significant population differentiation between southern and central areas. We found an unexpected genotype in the Gorongosa National Park, where buffaloes experienced a dramatic population size reduction, that shares a common ancestry with southern populations of Catuane and Namaacha. This could suggest the past occurrence of a connection between southern and central Mozambique and that the observed population structuring could reflect recent events of anthropogenic origin. All the populations analysed showed high levels of homozygosity, likely due to extensive inbreeding over the last few decades, which could have increased the frequency of recessive deleterious alleles. Improving the resilience of Syncerus caffer caffer in Mozambique is essential for preserving the ecosystem integrity. The most viable approach appears to be facilitating translocations and re-establishing connectivity between isolated herds. However, our results also highlight the importance of assessing intraspecific genetic diversity when considering interventions aimed at enhancing population viability such as selecting suitable source populations.


Subject(s)
Bison , Buffaloes , Humans , Animals , Buffaloes/genetics , Ecosystem , Inbreeding , Mozambique
2.
Hum Mol Genet ; 25(21): 4686-4702, 2016 11 01.
Article in English | MEDLINE | ID: mdl-28173160

ABSTRACT

Progressive forms of multiple sclerosis lead to chronic disability, substantial decline in quality of life and reduced longevity. It is often suggested that they occur independently of inflammation. Here we investigated the disease progression in mouse models carrying PLP1 point mutations previously found in patients displaying clinical features of multiple sclerosis. These mouse models show loss-of-function of PLP1 associated with neuroinflammation; the latter leading to clinically relevant axonal degeneration, neuronal loss and brain atrophy as demonstrated by inactivation of the recombination activating gene 1. Moreover, these pathological hallmarks were substantially amplified when we attenuated immune regulation by inactivation of the programmed cell death-1 gene. Our observations support the view that primary oligodendroglial abnormalities can evoke pathogenically relevant neuroinflammation that drives neurodegeneration, as observed in some forms of multiple sclerosis but also in other, genetically-mediated neurodegenerative disorders of the human nervous system. As many potent immunomodulatory drugs have emerged during the last years, it is tempting to consider immunomodulation as a treatment option not only for multiple sclerosis, but also for so far non-treatable, genetically-mediated disorders of the nervous system accompanied by pathogenic neuroinflammation.


Subject(s)
Multiple Sclerosis/genetics , Mutation , Myelin Proteolipid Protein/genetics , Myelin Proteolipid Protein/metabolism , Animals , Disease Models, Animal , Disease Progression , Female , Humans , Immunologic Factors/genetics , Immunologic Factors/immunology , Inflammation/genetics , Inflammation/metabolism , Male , Mice , Mice, Transgenic , Multiple Sclerosis/immunology , Multiple Sclerosis/metabolism , Neurodegenerative Diseases/genetics , Neurodegenerative Diseases/immunology , Neurodegenerative Diseases/metabolism
3.
Nat Neurosci ; 16(4): 407-15, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23416450

ABSTRACT

The development of neuronal networks in the neocortex depends on control mechanisms for mitosis and migration that allow newborn neurons to find their accurate position. Multiple mitogens, neurotrophic factors, guidance molecules and their corresponding receptors are involved in this process, but the mechanisms by which these signals are integrated are only poorly understood. We found that TrkB and TrkC, the receptors for brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), are activated by epidermal growth factor receptor (EGFR) signaling rather than by BDNF or NT-3 in embryonic mouse cortical precursor cells. This transactivation event regulated migration of early neuronal cells to their final position in the developing cortex. Transactivation by EGF led to membrane translocation of TrkB, promoting its signaling responsiveness. Our results provide genetic evidence that TrkB and TrkC activation in early cortical neurons do not depend on BDNF and NT-3, but instead on transactivation by EGFR signaling.


Subject(s)
Cell Movement/physiology , Epidermal Growth Factor/physiology , Receptor, trkB/metabolism , Receptor, trkC/metabolism , Transcriptional Activation/physiology , Animals , Animals, Newborn , Cells, Cultured , Cerebral Cortex/cytology , Cerebral Cortex/metabolism , Female , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neurons/metabolism , Pregnancy , Receptor, trkB/genetics , Receptor, trkC/genetics , Signal Transduction/physiology
4.
Plant Physiol ; 146(4): 1786-96, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18310306

ABSTRACT

Rad5 is the key component in the Rad5-dependent error-free branch of postreplication repair in yeast (Saccharomyces cerevisiae). Rad5 is a member of the Snf2 ATPase/helicase family, possessing as a characteristic feature, a RING-finger domain embedded in the Snf2-helicase domain and a HIRAN domain. Yeast mutants are sensitive to DNA-damaging agents and reveal differences in homologous recombination. By sequence comparisons we were able to identify two homologs (AtRAD5a and AtRAD5b) in the Arabidopsis thaliana genome, sharing about 30% identity and 45% similarity to yeast Rad5. AtRad5a and AtRad5b have the same kind of domain organization with a higher degree of similarity to each other than to ScRad5. Surprisingly, both genes differ in function: whereas two independent mutants of Atrad5a are hypersensitive to the cross-linking agents mitomycin C and cis-platin and to a lesser extent to the methylating agent, methyl methane sulfonate, the Atrad5b mutants did not exhibit any sensitivity to all DNA-damaging agents tested. An Atrad5a/Atrad5b double mutant resembles the sensitivity phenotype of the Atrad5a single mutants. Moreover, in contrast to Atrad5b, the two Atrad5a mutants are deficient in homologous recombination after treatment with the double-strand break-inducing agent bleomycin. Our results suggest that the RAD5-dependent error-free branch of postreplication repair is conserved between yeast and plants, and that AtRad5a might be functionally homologous to ScRad5.


Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/genetics , DNA Repair/genetics , Genes, Plant , Recombination, Genetic , Amino Acid Sequence , Arabidopsis Proteins/chemistry , Molecular Sequence Data , Mutation , Polymerase Chain Reaction , Sequence Homology, Amino Acid
5.
Proc Natl Acad Sci U S A ; 104(43): 17210-5, 2007 Oct 23.
Article in English | MEDLINE | ID: mdl-17940030

ABSTRACT

Neurotrophins are potent survival factors for developing and injured neurons. However, they are not being used to treat neurodegenerative diseases because of difficulties in administration and numerous side effects that have been encountered in previous clinical trials. Their biological activities use Trk (tropomyosin-related kinase) transmembrane tyrosine kinases. Therefore, one alternative approach is to use transactivation pathways such as adenosine 2A receptor agonists, which can activate Trk receptor signaling independent of neurotrophin binding. However, the relevance in vivo and applicability of these transactivation events during neurodegenerative and injury conditions have never been extensively studied. Here we demonstrate that motoneuron survival after facial nerve lesioning is significantly enhanced by transactivation of Trk receptor tyrosine kinases by adenosine agonists. Moreover, survival of motoneurons directly required the activation of the BDNF receptor TrkB and an increase in Akt (AKT8 virus oncogene cellular homolog) activity. The ability of small molecules to activate a trophic response by using Trk signaling provides a unique mechanism to promote survival signals in motoneurons and suggests new strategies for using transactivation in neurodegenerative diseases.


Subject(s)
Motor Neurons/cytology , Motor Neurons/enzymology , Receptor, trkB/genetics , Receptors, Adenosine A2/metabolism , Transcriptional Activation/genetics , Adenosine/analogs & derivatives , Adenosine/pharmacology , Adenosine A2 Receptor Agonists , Animals , Axotomy , Cell Separation , Cell Survival/drug effects , Cells, Cultured , Embryo, Mammalian/cytology , Embryo, Mammalian/drug effects , Embryo, Mammalian/enzymology , Enzyme Activation/drug effects , Facial Nerve/drug effects , Facial Nerve/pathology , Mice , Motor Neurons/drug effects , Phenethylamines/pharmacology , Transcriptional Activation/drug effects
6.
Histochem Cell Biol ; 127(4): 439-48, 2007 Apr.
Article in English | MEDLINE | ID: mdl-17102992

ABSTRACT

Primary neurons are a common tool for investigating gene function for survival and morphological and functional differentiation. Gene transfer techniques play an important role in this context. However, the efficacy of conventional gene transfer techniques, in particular for primary motoneurons is low so that it is not possible to distinguish whether the observed effects are representative for all neurons or only for the small subpopulation that expresses the transfected cDNA. In order to develop techniques that allow high gene transfer rates, we have optimized lentiviral-based gene transfer for cultured motoneurons by using a replication-defective viral vector system. These techniques result in transduction efficacies higher than 50%, as judged by EGFP expression under the control of SFFV or CMV promoters. Under the same conditions, survival and morphology of the cultured motoneurons was not altered, at least not when virus titers did not exceed a multiplicity of infection of 100. Under the same cell culture conditions, electroporation resulted in less than 5% transfected motoneurons and reduced survival. Therefore we consider this lentivirus-based gene transfer protocol as a suitable tool to study the effects of gene transfer on motoneuron survival, differentiation and function.


Subject(s)
Lentivirus/genetics , Motor Neurons/metabolism , Transfection/methods , Animals , Cell Line , Cells, Cultured , Cytomegalovirus/genetics , Defective Viruses/genetics , Electroporation/methods , Genetic Vectors/genetics , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Humans , Immunohistochemistry , Mice , Mice, Inbred C57BL , Microscopy, Confocal , Motor Neurons/cytology , Promoter Regions, Genetic/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Spleen Focus-Forming Viruses/genetics , Time Factors
7.
Plant J ; 38(6): 954-68, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15165187

ABSTRACT

Rad17 is involved in DNA checkpoint control in yeast and human cells. A homologue of this gene as well as other genes of the pathway (the 9-1-1 complex) are present in Arabidopsis and share conserved sequence domains with their yeast and human counterparts. DNA-damaging agents induce AtRAD17 transcriptionally. AtRAD17 mutants show increased sensitivity to the DNA-damaging chemicals bleomycin and mitomycin C (MMC), which can be reversed by complementation, suggesting that the loss of function of Rad17 disturbs DNA repair in plant cells. Our results are further confirmed by the phenotype of a mutant of the 9-1-1 complex (Rad9), which is also sensitive to the same chemicals. AtRAD9 and AtRAD17 seem to be epistatic as the double mutant is not more sensitive to the chemicals than the single mutants. The mutants show a delay in the general repair of double-strand breaks (DSBs). However, frequencies of intrachromosomal homologous recombination (HR) are enhanced. Nevertheless, the mutants are proficient for a further induction of HR by genotoxic stresses. Our results indicate that a mutant Rad17 pathway is associated with a general deregulation of DNA repair, which seems to be correlated with a deficiency in non-homologous DSB repair.


Subject(s)
Arabidopsis/genetics , Cell Cycle Proteins/physiology , DNA Damage/physiology , DNA Repair/physiology , DNA-Binding Proteins , Amino Acid Sequence , Arabidopsis Proteins , Cell Cycle Proteins/chemistry , Cell Cycle Proteins/isolation & purification , DNA, Complementary/analysis , Endonucleases/isolation & purification , Molecular Sequence Data , Recombination, Genetic , Schizosaccharomyces pombe Proteins , Sequence Homology, Amino Acid
8.
Methods Mol Biol ; 262: 25-34, 2004.
Article in English | MEDLINE | ID: mdl-14769954

ABSTRACT

Because of the availability of the complete sequence of the genome of the model plant Arabidopsis and of insertion mutants for most genes in public mutant collections, the elucidation of the particular role of different factors involved in DNA recombination and repair processes, an important task for plant biology, is becoming feasible. An assay system based on transgenes harboring homologous overlaps of the beta-glucuronidase (uidA) gene is available to determine recombination behavior in various mutant backgrounds. Restoration of the marker gene by homologous recombination can be detected by histochemical staining in planta. Inclusion of a site of the rare cutting restriction enzyme I-SceI in the transgene construct enables the determination of recombination frequencies after induction of double-strand breaks. In this chapter we describe how the respective transgene is transferred by transformation or crossing into the mutant background, how recombination frequencies are determined, and, if necessary, how cells carrying a restored uidA gene can be isolated and propagated for molecular analysis of the particular recombination event.


Subject(s)
Arabidopsis/genetics , Chromosomes, Plant/genetics , Recombination, Genetic/genetics , Agrobacterium tumefaciens/genetics , Crosses, Genetic , DNA Repair/genetics , DNA, Plant/genetics , Genome, Plant , Glucuronidase/genetics , Mutagenesis, Insertional/methods , Transformation, Genetic/genetics
9.
Plant J ; 35(5): 604-12, 2003 Sep.
Article in English | MEDLINE | ID: mdl-12940953

ABSTRACT

Different DNA repair pathways that use homologous sequences in close proximity to genomic double-strand breaks (DSBs) result in either an internal deletion or a gene conversion. We determined the efficiency of these pathways in somatic plant cells of transgenic Arabidopsis lines by monitoring the restoration of the beta-glucuronidase (GUS) marker gene. The transgenes contain a recognition site for the restriction endonuclease I-SceI either between direct GUS repeats to detect deletion formation (DGU.US), or within the GUS gene to detect gene conversion using a nearby donor sequence in direct or inverted orientation (DU.GUS and IU.GUS). Without expression of I-SceI, the frequency of homologous recombination (HR) was low and similar for all three constructs. By crossing the different lines with an I-SceI expressing line, DSB repair was induced, and resulted in one to two orders of magnitude higher recombination frequency. The frequencies obtained with the DGU.US construct were about five times higher than those obtained with DU.GUS and IU.GUS, irrespective of the orientation of the donor sequence. Our results indicate that recombination associated with deletions is the most efficient pathway of homologous DSB repair in plants. However, DSB-induced gene conversion seems to be frequent enough to play a significant role in the evolution of tandemly arranged gene families like resistance genes.


Subject(s)
Arabidopsis/genetics , DNA Repair , Genome, Plant , Recombination, Genetic/genetics , Tandem Repeat Sequences/genetics , Deoxyribonucleases, Type II Site-Specific/genetics , Deoxyribonucleases, Type II Site-Specific/metabolism , Glucuronidase/genetics , Glucuronidase/metabolism , Plants, Genetically Modified , Saccharomyces cerevisiae Proteins
10.
Plant Mol Biol ; 51(4): 523-31, 2003 Mar.
Article in English | MEDLINE | ID: mdl-12650618

ABSTRACT

Surprising species-specific differences in non-homologous end-joining (NHEJ) of genomic double-strand breaks (DSBs) have been reported for the two dicotyledonous plants Arabidopsis thaliana and Nicotiana tabacum. In Arabidopsis deletions were, on average, larger than in tobacco and not associated with insertions. To establish the molecular basis of the phenomenon we analysed the fate of free DNA ends in both plant species by biolistic transformation of leaf tissue with linearized plasmid molecules. Southern blotting indicated that, irrespective of the nature of the ends (blunt, 5' or 3' overhangs), linearized full-length DNA molecules were, on average, more stable in tobacco than in Arabidopsis. The relative expression of a beta-glucuronidase gene encoded by the plasmid was similar in both plant species when the break was distant from the marker gene. However, if a DSB was introduced between the promoter and the open reading frame of the marker, transient expression was halved in Arabidopsis as compared to tobacco. These results indicate that free DNA ends are more stable in tobacco than in Arabidopsis, either due to lower DNA exonuclease activity or due to a better protection of DNA break ends or both. Exonucleolytic degradation of DNA ends might be a driving force in the evolution of genome size as the Arabidopsis genome is more than twenty times smaller than the tobacco genome.


Subject(s)
Arabidopsis/genetics , DNA Repair , Nicotiana/genetics , Recombination, Genetic/genetics , Evolution, Molecular , Gene Expression Regulation, Enzymologic , Genome, Plant , Glucuronidase/genetics , Glucuronidase/metabolism , Mutagenesis, Insertional , Plants, Genetically Modified , Plasmids/genetics , Promoter Regions, Genetic/genetics
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