IFN-I signaling and inflammasome activation are two innate pathways important for combatting a variety of pathogens. Swanson et al. show that cGAMP activates the inflammasome in addition to IFN-I, and that the activation of both is needed to control infection by a DNA virus.

Given the multiple differences between mice and men, it was once thought that mice could not be used to model atherosclerosis, principally a human disease. Apolipoprotein E-deficient (apoEKO) mice have convincingly changed this view, and the ability to model human-like plaques in these mice has provided scientists a platform to study multiple facets of atherogenesis and to explore potential therapeutic interventions. In addition to its well-established role in lipoprotein metabolism, recent observations of reduced adiposity and improved glucose homeostasis in apoEKO mice suggest that apoE may also play a key role in energy metabolism in peripheral organs, including adipose tissue. Finally, along with apoEKO mice, knockin mice expressing human apoE isoforms in place of endogenous mouse apoE have provided insights into how quantitative and qualitative genetic alterations interact with the environment in the pathogenesis of complex human diseases.-Pendse, A. A., J. M. Arbones-Mainar, L. A. Johnson, M. K. Altenburg, and N. Maeda. Apolipoprotein E knock-out and knock-in mice: atherosclerosis, metabolic syndrome, and beyond. J. Lipid Res. 2009. 50: S178-S182.Supplementary key words apolipoprotein E isoforms • diabetes • adipose tissue Apolipoprotein E (apoE) plays a central role in lipoprotein metabolism and is required for the efficient clearance of diet-derived chylomicrons and liver-derived VLDL remnants by the liver (1). Consequently, mice lacking apoE (apoEKO) provided the first practical model of hyperlipidemia and atherosclerosis. In this review, we revisit the primary features of lipoprotein metabolism and atherosclerosis in apoEKO mice and the contributions of human apoE isoforms using the apoE knock-in mice. We then extend our discussion to more recent observations that suggest an important role for apoE in peripheral energy metabolism and consequently in metabolic syndrome (MetS) and its components, mainly obesity and diabetes. LIPOPROTEIN METABOLISM IN APOEKO MICEPlasma cholesterol in wild-type mice on a regular chow diet is ?80 mg/dl, primarily carried in HDL particles. Mice have a small amount of LDL and other atherogenic lipoproteins, such as VLDL remnants. This high HDL-to-

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OBJECTIVEWe investigated the differential roles of apolipoprotein E (apoE) isoforms in modulating diabetic dyslipidemia—a potential cause of the increased cardiovascular disease risk of patients with diabetes.RESEARCH DESIGN AND METHODSDiabetes was induced using streptozotocin (STZ) in human apoE3 (E3) or human apoE4 (E4) mice deficient in the LDL receptor (LDLR−/−).RESULTSDiabetic E3LDLR−/− and E4LDLR−/− mice have indistinguishable levels of plasma glucose and insulin. Despite this, diabetes increased VLDL triglycerides and LDL cholesterol in E4LDLR−/− mice twice as much as in E3LDLR−/− mice. Diabetic E4LDLR−/− mice had similar lipoprotein fractional catabolic rates compared with diabetic E3LDLR−/− mice but had larger hepatic fat stores and increased VLDL secretion. Diabetic E4LDLR−/− mice demonstrated a decreased reliance on lipid as an energy source based on indirect calorimetry. Lower phosphorylated acetyl-CoA carboxylase content and higher gene expression of fatty acid synthase in the liver indicated reduced fatty acid oxidation and increased fatty acid synthesis. E4LDLR−/− primary hepatocytes cultured in high glucose accumulated more intracellular lipid than E3LDLR−/− hepatocytes concomitant with a 60% reduction in fatty acid oxidation. Finally, the exaggerated dyslipidemia in diabetic E4LDLR−/− mice was accompanied by a dramatic increase in atherosclerosis.CONCLUSIONSApoE4 causes severe dyslipidemia and atherosclerosis independent of its interaction with LDLR in a model of STZ-induced diabetes. ApoE4-expressing livers have reduced fatty acid oxidation, which contributes to the accumulation of tissue and plasma lipids.

Mutations and polymorphisms in PPARG have been linked to adiposity and partial lipodystrophy in humans. However, how disturbances in PPARG lead to depot-specific effects on adipose tissue, as shown by the characteristic aberrant fat distribution in patients, remains unclear. By manipulating the 3'-untranslated region of the Pparg gene, we have generated mice with peroxisome proliferator-activated receptor gamma (PPAR gamma) gene expression ranging from 25% to 100% normal. Basal levels of PPAR gamma transcripts between 50% and approximately 100% had no significant effect on body weight, fat mass, and insulin sensitivity. In contrast, mice with 25% normal PPAR gamma expression exhibited reduced body weight and total fat mass, insulin resistance, and dyslipidemia. Interestingly, fat mass was selectively reduced in perigonadal depot without significant changes in inguinal and other depots. Expression of adipogenic factor CCAAT enhancer binding protein-alpha and some other metabolic genes containing peroxisome proliferator response element were reduced in a perigonadal depot-specific fashion. This was further associated with depot-specific reduction in the expression of adipokines, increased expression of TNFalpha, and increased ectopic lipid deposition in muscles. Together, these results underscore the differential sensitivity of the individual fat depots on PPAR gamma availability as an underlying mechanism of partial lipodystrophy.

We observed severe ataxia in mice homozygous for modification of the Pparg locus. Genetic analysis and nucleotide sequencing revealed that ataxia is caused by a T692K substitution in plasma membrane calcium ATPase 2 (Pmca2), which is tightly linked to Pparg, but not by modified PPARgamma itself. We traced this mutation and found that it arose spontaneously during clonal expansion of the targeted embryonic stem (ES) cells. Consistent with the deafwaddler phenotype in other Pmca2 mutants, homozygous T692K Pmca2 mutants exhibit severe balance disorder, impaired neurologic reflexes, and motor coordination, and have profound hearing loss. Heterozygous mutants have normal movement and motor function but are severely deficient in hearing. Our findings represent a cautionary example since, although rare, spontaneous mutations do arise in ES cells during culture and hitchhike onto the targeted gene mutation.

Recent evidence has implicated EFL1 in a phenotype overlapping Shwachman–Diamond syndrome (SDS), with the functional interplay between EFL1 and the previously known causative gene SBDS accounting for the similarity in clinical features. Relatively little is known about the phenotypes associated with pathogenic variants in the EFL1 gene, but the initial indication was that phenotypes may be more severe, when compared with SDS. We report a pediatric patient who presented with a metaphyseal dysplasia and was found to have biallelic variants in EFL1 on reanalysis of trio whole-exome sequencing data. The variant had not been initially reported because of the research laboratory's focus on de novo variants. Subsequent phenotyping revealed variability in her manifestations. Although her metaphyseal abnormalities were more severe than in the original reported cohort with EFL1 variants, the bone marrow abnormalities were generally mild, and there was equivocal evidence for pancreatic insufficiency. Despite the limited number of reported patients, variants in EFL1 appear to cause a broader spectrum of symptoms that overlap with those seen in SDS. Our report adds to the evidence of EFL1 being associated with an SDS-like phenotype and provides information adding to our understanding of the phenotypic variability of this disorder. Our report also highlights the value of exome data reanalysis when a diagnosis is not initially apparent.

Epithelioid sarcoma is a rare mesenchymal neoplasm, with an as yet unidentified cell of origin. Two subtypes of epithelioid sarcoma, distal/classic and proximal/large cell type, are recognized in the literature; with the proximal-type having a lower incidence amongst the two. Here, we present a case of proximal-type epithelioid sarcoma in a previously healthy young man. Fine-needle-aspiration of a large axillary mass was performed for diagnosis. The cytologic findings included a dispersed population of large epithelioid to polyhedral cells with abundant cytoplasm. Immunohistochemical staining showed coexpression of keratin and vimentin, as well as loss of INI1 staining, consistent with an epithelioid sarcoma, proximal subtype.