Genetic affinities of inbred mouse strains of uncertain origin

Phylogenetic analyses of genetic data arising from 144 gene loci are used to describe the interrelationships among 24 widely used inbred strains of mice. An unordered-parsimony analysis gives a cladogram that is virtually identical to the known genealogy of the mouse strains. A loss-parsimony analysis is used to evaluate the hypothesis that the observed patterns of genetic divergence among these 24 strains can be explained by the segregation of residual heterozygosity arising from a small population of highly heterozygous mice. The loss-parsimony cladogram is very similar to both the unordered-parsimony cladogram and the known genealogy of the mice. The phylogenetic analyses of these 144 loci are integrated with data on the type and origin of the Y chromosome. Inclusion of the Y-chromosome data provides additional insights into the genetic composition of several of the original stocks used to produce the current inbred strains of mice. Ten strains of uncertain origin are contained in these analyses, including AKR, BUB, CE, I, NZB, P, RF, SJL, ST, and SWR. SJL is hypothesized to have been derived from the same Swiss albino stock previously used to produce SWR. The BUB strain appears to have had a complex origin and shows closest genetic similarity to SWR and ST. AKR and RF are shown to be closely related, while the I strain shows greatest genetic similarity to DBA/2 for the 144 loci. However, I and DBA possess different types of Y chromosome. The NZB strain shows genetic similarity to several stocks of both U.S. and European origins. The power of the genetic data used in these analyses reiterates that inbred strains of mice can be a valuable paradigm for studies in evolutionary biology.      

Liver cell death and anemia in Wilson disease involve acid sphingomyelinase and ceramide

Wilson disease is caused by accumulation of Cu(2+) in cells, which results in liver cirrhosis and, occasionally, anemia. Here, we show that Cu(2+) triggers hepatocyte apoptosis through activation of acid sphingomyelinase (Asm) and release of ceramide. Genetic deficiency or pharmacological inhibition of Asm prevented Cu(2+)-induced hepatocyte apoptosis and protected rats, genetically prone to develop Wilson disease, from acute hepatocyte death, liver failure and early death. Cu(2+) induced the secretion of activated Asm from leukocytes, leading to ceramide release in and phosphatidylserine exposure on erythrocytes, events also prevented by inhibition of Asm. Phosphatidylserine exposure resulted in immediate clearance of affected erythrocytes from the blood in mice. Accordingly, individuals with Wilson disease showed elevated plasma levels of Asm, and displayed a constitutive increase of ceramide- and phosphatidylserine-positive erythrocytes. Our data suggest a previously unidentified mechanism for liver cirrhosis and anemia in Wilson disease.     

Enhanced suicidal death of erythrocytes from gene-targeted mice lacking the Cl-/HCO(3)(-) exchanger AE1

Genetic defects of anion exchanger 1 (AE1) may lead to spherocytic erythrocyte morphology, severe hemolytic anemia, and/or cation leak. In normal erythrocytes, osmotic shock, Cl^– removal, and energy depletion activate Ca²⁺-permeable cation channels with Ca²⁺-induced suicidal erythrocyte death, i.e., surface exposure of phosphatidylserine, cell shrinkage, and membrane blebbing, all features typical for apoptosis of nucleated cells. The present experiments explored whether AE1 deficiency favors suicidal erythrocyte death. Peripheral blood erythrocyte numbers were significantly smaller in gene-targeted mice lacking AE1 (AE1^–/– mice) than in their wild-type littermates (AE1^+/+ mice) despite increased percentages of reticulocytes (AE1^–/–: 49%, AE1^+/+: 2%), an indicator of enhanced erythropoiesis. Annexin binding, reflecting phosphatidylserine exposure, was significantly larger in AE1^–/–erythrocytes/reticulocytes (10%) than in AE1^+/+ erythrocytes (1%). Osmotic shock (addition of 400 mM sucrose), Cl^– removal (replacement with gluconate), or energy depletion (removal of glucose) led to significantly stronger annexin binding in AE1^–/– erythrocytes/reticulocytes than in AE1^+/+ erythrocytes. The increase of annexin binding following exposure to the Ca²⁺ ionophore ionomycin (1 µM) was, however, similar in AE1^–/– and in AE1^+/+ erythrocytes. Fluo3 fluorescence revealed markedly increased cytosolic Ca²⁺ permeability in AE1^–/– erythrocytes/reticulocytes. Clearance of carboxyfluorescein diacetate succinimidyl ester-labeled erythrocytes/reticulocytes from circulating blood was more rapid in AE1^–/– mice than in AE1^+/+ mice and was accelerated by ionomycin treatment in both genotypes. In conclusion, lack of AE1 is associated with enhanced Ca²⁺ entry and subsequent scrambling of cell membrane phospholipids. annexin; cell volume; osmolarity; phosphatidylserine; energy depletion     

FLOWERING PHENOLOGY AT BIG RUN BOG,WEST VIRGINIA

In each of four major plant communities at Big Run Bog, a 15-ha Sphagnum-dominated wetland in the Appalachian Mountains of West Virginia, the flowering phenology of 21 species was measured by counting the number of flowering stems at frequent intervals throughout the growing season. The four plant communities exhibited no consistent differences with regard to the patterns of flowering phenology. Mean flowering duration was 30 days for all species, and was 32 and 31 days for wind- and insect-pollinated species, respectively. Peak flowering times for the 21 species were randomly distributed throughout the growing season. Results from Big Run Bog are not markedly different from those reported for other bogs in North America.     

PGE2-induced apoptotic cell death in K562 human leukaemia cells.

Prostaglandin-E2 (PGE2) is known to trigger suicidal death of nucleated cells (apoptosis) and enucleated erythrocytes (eryptosis). In erythrocytes PGE2 induced suicidal cell death involves activation of nonselective cation channels leading to Ca2+ entry followed by cell shrinkage and triggering of Ca2+ sensitive cell membrane scrambling with phosphatidylserine (PS) exposure at the cell surface. The present study was performed to explore whether PGE2 induces apoptosis of nucleated cells similarly through cation channel activation and to possibly disclose the molecular identity of the cation channels involved. To this end, Ca2+ activity was estimated from Fluo3 fluorescence, mitochondrial potential from DePsipher fluorescence, phosphatidylserine exposure from annexin binding, caspase activation from caspAce fluorescence, cell volume from FACS forward scatter, and DNA fragmentation utilizing a photometric enzyme immunoassay. Stimulation of K562 human leukaemia cells with PGE2 (50 microM) increased cytosolic Ca2+ activity, decreased forward scatter, depolarized the mitochondrial potential, increased annexin binding, led to caspase activation and resulted in DNA fragmentation. Gene silencing of the Ca2+-permeable transient receptor potential cation channel TRPC7 significantly blunted PGE2-induced triggering of PS exposure and DNA fragmentation. In conclusion, K562 cells express Ca2+-permeable TRPC7 channels, which are activated by PGE2 and participate in the triggering of apoptosis.