Imprinted genes display differential allelic expression in a manner that depends on the sex of the transmitting parent. The degree of imprinting is often tissue-specific and/or developmental stage-specific, and may be altered in some diseases including cancer. Here we applied Illumina/Solexa sequencing of the transcriptomes of reciprocal F1 mouse neonatal brains and identified 26 genes with parent-of-origin dependent differential allelic expression. Allele-specific Pyrosequencing verified 17 of them, including three novel imprinted genes. The known and novel imprinted genes all are found in proximity to previously reported differentially methylated regions (DMRs). Ten genes known to be imprinted in placenta had sufficient expression levels to attain a read depth that provided statistical power to detect imprinting, and yet all were consistent with non-imprinting in our transcript count data for neonatal brain. Three closely linked and reciprocally imprinted gene pairs were also discovered, and their pattern of expression suggests transcriptional interference. Despite the coverage of more than 5000 genes, this scan only identified three novel imprinted refseq genes in neonatal brain, suggesting that this tissue is nearly exhaustively characterized. This approach has the potential to yield an complete catalog of imprinted genes after application to multiple tissues and developmental stages, shedding light on the mechanism, bioinformatic prediction, and evolution of imprinted genes and diseases associated with genomic imprinting.

Rationale: Cardiac aging is an important contributing factor for heart failure which affects a large population but remains poorly understood. Objective: The purpose of this study is to investigate whether Klotho plays a role in cardiac aging. Methods and Results: Heart function declined in old mice (24 months), as evidenced by decreases in fractional shortening, ejection fraction, and cardiac output. Heart size and weight, cardiomyocyte size and cardiac fibrosis were increased in old mice, indicating that aging causes cardiac hypertrophy and remodeling. Circulating Klotho levels were dramatically decreased in old mice, which prompted us to investigate whether the Klotho decline may cause heart aging. We found that Klotho gene mutation (KL-/-) largely decreased serum klotho levels and impaired heart function. Interestingly, supplement of exogenous secreted Klotho prevented heart failure, hypertrophy, and remodeling in both old mice and KL (-/-) mice. Secreted Klotho treatment inhibited excessive cardiac oxidative stress, senescence and apoptosis in old mice and KL (-/-) mice. Serum phosphate levels in KL (-/-) mice were kept in the normal range, suggesting that Klotho deficiency-induced heart aging is independent of phosphate metabolism. Mechanistically, Klotho deficiency suppressed glutathione reductase (GR) expression and activity in the heart via inhibition of transcription factor Nrf2. Furthermore, cardiac-specific overexpression of GR prevented excessive oxidative stress, apoptosis, and heart failure in both old and KL (-/-) mice. Conclusions: Klotho deficiency causes cardiac aging via impairing the Nrf2-GR pathway. Supplement of exogenous secreted Klotho represents a promising therapeutic strategy for aging-associated cardiomyopathy and heart failure.

Genome-wide QTL analysis for bone density, structure, and biomechanical phenotypes was performed in 999 (B6xC3H)F2 mice. Multivariate phenotypes were also derived to test for pleiotropic QTL effects. Highly significant QTLs were detected with pleiotropic effects on many of these phenotypes, and QTLs with unique effects on specific phenotypes were found as well. Introduction:The inbred C57BL/6J (B6) and C3H/HeJ (C3H) mouse strains were previously shown to segregate quantitative trait loci (QTLs) for femoral bone density. Materials and Methods:The 999 s filial (F2) mouse progeny were further phenotyped for measures of femoral biomechanics (load to failure, F u ; work to failure, U; stiffness, S), structure (polar moment of inertia, I p ; moment of inertia ratio, I r ), and more specific femoral midshaft bone density measures (cortical and total vBMD). Two novel multivariate phenotypes were computed using principal component analysis, thus aiding in the exploration of pleiotropic effects of the QTLs detected. Results and Conclusions:Results of a genome-wide analysis provided strong evidence of pleiotropic QTL effects on chromosome 4, with six of the seven primary phenotypic measures, representing femoral biomechanics, density, and structure, producing LOD scores greater than 8. Chromosomes 1, 8, 13, and 14 were also identified as harboring QTLs that affect phenotypes in two of the three aspects of bone properties. QTLs uniquely contributing to variability in biomechanical measures were identified on chromosomes 10 and 12, whereas a QTL solely affecting structure was found on chromosome 17. Analysis of the evidence for pleiotropic effects using principal component analysis revealed pleiotropic QTLs on chromosomes 4 and 14, influencing nearly all the bone phenotypes measured and revealed QTLs on chromosomes 1, 8, 13, and 17 with pleiotropic effects restricted to either density or the structure and stiffness phenotypes. The use of multivariate phenotypes has allowed us to identify pleiotropic effects of several QTLs previously linked in studies of other mouse strains and in human studies of bone mineral density and femoral structure, which will provide important insight regarding the importance of allelic variation on the entire skeleton.