Genetic integration of a nuclear -encoded mitochondrial gene with cardiac function

Cardiovascular disease (CVD) is the leading cause of death in the United States. One manifestation of CVD known to increase mortality is an enlarged, or hypertrophic heart. Hypertrophic cardiomyocytes adapt to increased contractile demand at the genetic level with a re-emergence of the fetal gene program and a downregulation of fatty acid oxidation genes with concomitant increased reliance on glucose-based metabolism. To understand the transcriptional regulatory pathways that implement hypertrophic directives we analyzed the upstream promoter region of the muscle specific isoform of the nuclear-encoded mitochondrial gene, carnitine palmitoyltransferase-1β (CPT-1β) in cultured rat neonatal cardiac myocytes. This enzyme catalyzes the rate-limiting step of fatty acid entry into β-oxidation and is downregulated in cardiac hypertrophy and failure, making it an attractive model for the study of hypertrophic gene regulation and metabolic adaptations. We demonstrate that the muscle-enriched transcription factors GATA-4 and SRF synergistically activate CPT-1β; moreover, DNA binding to cognate sites and intact protein structure are required. This mechanism coordinates upregulation of energy generating processes with activation of the energy consuming contractile promoter for cardiac α-actin. We hypothesized that fatty acid or glucose responsive transcription factors may also regulate CPT-1β. Oleate weakly stimulates CPT-1β activity; in contrast, the glucose responsive Upstream Stimulatory Factors (USF) dramatically depresses the CPT-1β reporter. USF regulates CPT-1β through a novel physical interaction with the cofactor PGC-1 and abrogation of MEF2A/PGC-1 synergistic stimulation. In this way, USF can inversely regulate metabolic gene programs and may play a role in the shift of metabolic substrate preference seen in hypertrophy. Failing hearts have elevated expression of the nuclear hormone receptor COUP-TF. We report that COUP-TF significantly suppresses reporter transcription independent of DNA binding and specific interactions with GATA-4, Nkx2.5 or USF. In summary, CPT-1β transcriptional regulation integrates mitochondrial gene expression with two essential cardiac functions: contraction and metabolic substrate oxidation. ^

The contributions of the hippocampal formation, perirhinal cortex and areas TH/TF to object, spatial and contextual recognition memory in primates

Adult monkeys (Macaca mulatta) with lesions of the hippocampal formation, perirhinal cortex, areas TH/TF, as well as controls were tested on tasks of object, spatial and contextual recognition memory. ^ Using a visual paired-comparison (VPC) task, all experimental groups showed a lack of object recognition relative to controls, although this impairment emerged at 10 sec with perirhinal lesions, 30 sec with areas TH/TF lesions and 60 sec with hippocampal lesions. In contrast, only perirhinal lesions impaired performance on delayed nonmatching-to-sample (DNMS), another task of object recognition memory. All groups were tested on DNMS with distraction (dDNMS) to examine whether the use of active cognitive strategies during the delay period could enable good performance on DNMS in spite of impaired recognition memory (revealed by the VPC task). Distractors affected performance of animals with perirhinal lesions at the 10-sec delay (the only delay in which their DNMS performance was above chance). They did not affect performance of animals with areas TH/TF lesions. Hippocampectomized animals were impaired at the 600-sec delay (the only delay at which prevention of active strategies would likely affect their behavior). ^ While lesions of areas TH/TF impaired spatial location memory and object-in-place memory, hippocampal lesions impaired only object-in-place memory. The pattern of results for perirhinal cortex lesions on the different task conditions indicated that this cortical area is not critical for spatial memory. ^ Finally, all three lesions impaired contextual recognition memory processes. The pattern of impairment appeared to result from the formation of only a global representation of the object and background, and suggests that all three areas are recruited for associating information across sources. ^ These results support the view that (1) the perirhinal cortex maintains storage of information about object and the context in which it is learned for a brief period of time, (2) areas TH/TF maintain information about spatial location and form associations between objects and their spatial relationship (a process that likely requires additional time) and (3) the hippocampal formation mediates associations between objects, their spatial relationship and the general context in which these associations are formed (an integrative function that requires additional time). ^