High-resolution maps of the murine Chromosome 2 region containing the cholesterol gallstone locus, Lith1

The Lith1 region on Chromosome (Chr) 2 contains a gene that markedly affects the prevalence of cholesterol gallstones in inbred mice. We report the high-resolution genetic and radiation hybrid maps of the chromosomal region surrounding Lith1, using three resources: a DNA panel from 188 progeny from two reciprocal backcrosses between C57BL/6 and Mus spretus inbred strains; 423 progeny of an N4 generation from backcrossing the susceptible C57L/J alleles at Lith1 into the resistant AKR/J strain; and the newly developed hamster–mouse T31 radiation hybrid panel. We mapped 17 microsatellite markers in the D2Mit182 to D2Mit14 region and two candidate genes for Lith1, the canalicular bile salt export pump (Bsep) also known as sister of P-glycoprotein (Spgp) and the low-density-lipoprotein-receptor-related gene megalin (Gp330). Both genetic maps were in agreement and ordered the microsatellite markers into a 10.4 ± 1.5 cM region. The high-resolution physical map revealed ordering of microsatellite markers and relative distances between markers in almost complete agreement with the genetic maps. Mapping of Bsep revealed its location on Chr 2, homologous to the human chromosomal position (Nature Genet 20, 233–238, 1998). The radiation hybrid results also provided the highest resolution of the area containing the two candidate genes, which both mapped in the Lith1 region with close linkage, being separated by a distance of only 15 cR₃₀₀₀. The total radiation hybrid map length of the region between D2Mit182 and D2Mit14 was 326 cR₃₀₀₀, suggesting that 31 cR₃₀₀₀ is equivalent to 1 cM in this region of Chr 2. Received: 29 April 1999 / Accepted: 21 July 1999     

Group D Adenoviruses Infect Primary Central Nervous System Cells More Efficiently than Those from Group C

Group C adenovirus-mediated gene transfer to central nervous system cells is inefficient. We found that wild-type group D viruses, or recombinant adenovirus type 2 (Ad2) (group C) modified to contain Ad17 (group D) fiber, were more efficient in infecting primary cultures of neurons. Together with studies on primary vascular endothelial cells and tissue culture cell lines, our results indicate that there is not a universally applicable adenovirus serotype for use as a gene transfer vector.     

The heart of autophagy: deconstructing cardiac proteotoxicity

The heart is capable of robust structural remodeling, sometimes improving performance and sometimes leading to failure. Recent studies have uncovered a critical role for autophagy in disease-related remodeling of the cardiomyocyte. We have shown previously that hemodynamic load elicits a maladaptive autophagic response in cardiomyocytes which contributes to disease progression. In a recent study, we went on to demonstrate that protein aggregation is a proximal event triggering autophagic clearance mechanisms. The ubiquitin-proteasome-dependent pathways of protein clearance are similarly activated in parallel with processing of stress-induced protein aggregates into aggresomes and clearance through autophagy. These findings in the setting of pressure overload contrast with protein aggregation occurring in a model of protein chaperone malfunction in myocytes, where activation of autophagy is beneficial, antagonizing disease progression. Our findings situate heart disease stemming from environmental stress in the category of proteinopathy and raise important new questions regarding molecular events that elicit adaptive and maladaptive autophagy.     

Age and gender affect DNMT3a and DNMT3b expression in human liver

DNA methylation is catalyzed by a family of DNA methyltransferases (DNMTs) including the maintenance enzyme DNMT 1 and de novo methyltransferases DNMT 3a and DNMT 3b. Elevated levels of DNMTs have been found in cancer cells and in several types of human tumors. A polymorphism found in DNMT3b has been associated with increased risk for several cancers. The factors influencing DNMT expression in human tissues have not been clearly determined. he present study examined TDNMT3a and DNMT3b levels in human liver tissue samples and compared the effect of ageing, cigarette smoking, and gender. DNMT3a and DNMT3b expression levels in the samples from older individuals (56–78 years, n = 28) were both significantly higher than those of the younger group (16–48 years, n = 27) (73.2 ± 3.4 vs 8.3 ± 2.8 and 56.1 ± 1.9 vs 17.5 ± 5.7, respectively; p < 0.05). Levels of DNMT3b in females were significantly higher than those in males (75.4 ± 2.2 vs 16.3 ± 4.7; p < 0.05); however, DNMT3a levels were similar for females and males (52.7 ± 2.7 vs 48.4 ± 2.0). Expression levels of DNMT3a and DNMT3b were similar in smokers and nonsmokers (58.1 ± 3.5 vs 60.8 ± 3.1 and 54.5 ± 2.3 vs 48.3 ± 1.8, respectively). Genotyping for DNMT3b (C→T) variant in this sample pool showed a frequency distribution of CC (41%), CT (50%), and TT (9%). The findings from this study suggest that ageing and gender may be important factors influencing DNA methylation status.