ABSTRACT
The Protection of telomeres 1 (POT1) protein is a single-stranded telomere binding protein that is essential for proper maintenance of telomere length. Disruption of POT1 function leads to chromosome instability and loss of cellular viability. Here, we show that targeted deletion of the mouse Pot1b gene results in increased apoptosis in highly proliferative tissues. In the setting of telomerase haploinsufficiency, loss of Pot1b results in depletion of germ cells and complete bone marrow failure due to increased apoptosis, culminating in premature death. Pot1b(-/-) mTR(+/-) hematopoietic progenitor and stem cells display markedly reduced survival potential in vitro. Accelerated telomere shortening, increased G overhang and elevated number of chromosome end-to-end fusions that initiate an ATR-dependent DNA damage response were also observed. These results indicate an essential role for Pot1b in the maintenance of genome integrity and the long-term viability of proliferative tissues in the setting of telomerase deficiency. Interestingly, these phenotypes closely resemble those found in the human disease dyskeratosis congenita (DC), an inherited syndrome characterized by bone marrow failure, hyperpigmentation, and nail dystrophy. We anticipate that this mouse will serve as a useful model to further understand the pathophysiology of DC.
Subject(s)
Cell Cycle Proteins/metabolism , DNA Damage , DNA-Binding Proteins/deficiency , Dyskeratosis Congenita/genetics , Gene Deletion , Haploidy , Protein Serine-Threonine Kinases/metabolism , Telomerase/deficiency , Animals , Ataxia Telangiectasia Mutated Proteins , Bone Marrow Cells/enzymology , Bone Marrow Cells/pathology , Cell Death , Cell Proliferation , Dyskeratosis Congenita/enzymology , Hematopoietic System/abnormalities , Hematopoietic System/enzymology , Hematopoietic System/pathology , Mice , Mice, Knockout , Nucleic Acid Conformation , Organ Specificity , Phenotype , Survival Analysis , Telomerase/metabolism , Telomere/chemistry , Telomere/metabolismABSTRACT
Xylella fastidiosa is the causative agent of Pierce's Disease of grape. No published record of X. fastidiosa genetics in Texas exists despite growing financial risk to the U.S. grape industry, a Texas population of the glassy-winged sharpshooter insect vector (Homalodisca vitripennis) now spreading in California, and evidence that the bacterium is ubiquitous to southern states. Using sequences of conserved gyrB and mopB genes, we have established at least two strains in Texas, grape strain and ragweed strain, corresponding genetically with subsp. piercei and multiplex, respectively. The grape strain in Texas is found in Vitis vinifera varieties, hybrid vines, and wild Vitis near vineyards, whereas the ragweed strain in Texas is found in annuals, shrubs, and trees near vineyards or other areas. RFLP and QRT PCR techniques were used to differentiate grape and ragweed strains with greater efficiency than sequencing and are practical for screening numerous X. fastidiosa isolates for clade identity.
