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We have generated transgenic mouse lines that carry one of three different constructs in which the murine N-myc gene is expressed under the control of the immunoglobulin heavy chain transcriptional enhancer element (E mu-N-myc genes). High-level expression of the E mu-N-myc transgenes occurred in lymphoid tissues; correspondingly, many of these E mu-N-myc lines reproducibly developed pre-B- and B-lymphoid malignancies. The E mu-N-myc transgene also appeared to participate in the generation of a T cell malignancy that developed in one E mu-N-myc mouse. These tumors and cell lines adapted from them expressed exceptionally high levels of the E mu-N-myc transgene; the levels were comparable to those observed in human neuroblastomas with highly amplified N-myc genes. In contrast, all of the E mu-N-myc cell lines had exceptionally low or undetectable levels of the c-myc RNA sequences, consistent with the possibility that high-level N-myc expression can participate in the negative 'cross-regulation' of c-myc gene expression. Our findings demonstrate that deregulated expression of the N-myc gene has potent oncogenic potential within the B-lymphoid lineage despite the fact that the N-myc gene has never been implicated in naturally occurring B-lymphoid malignancies. Our results also are discussed in the context of differential myc gene activity in normal and transformed cells.

Three Puerto Rican siblings with the Hermansky-Pudlak syndrome are described, and the literature on this syndrome is reviewed with regard to clinical factors, pathology, pathophysiology, and management of the disorder. The three patients all manifested oculocutaneous albinism and platelet storage pool disease with a moderate bleeding tendency. The oldest sibling died from restrictive lung disease and another has evidence of reduced functional residual capacity, although he is asymptomatic. None of the patients had evidence of inflammatory bowel disease, which has been reported in some cases. All of the patients had an increased incidence of bacterial infections, and they were anergic. Whether their immunological defect(s) is related to the Hermansky-Pudlak syndrome is not known. Two of the patients were treated with oral vitamin E. Bleeding symptoms in both were markedly reduced, although major changes in platelet aggregation were not seen. Vitamin E therapy did not appear to affect the progression of lung disease in the patient with fatal restrictive lung disease.

We have demonstrated that the entire murine N-myc gene and the sequences necessary for its expression in human neuroblastoma cells are contained within a 7.4-kilobase murine genomic clone. The complete nucleotide sequence of this gene reveals a number of striking similarities and differences when compared to the related c-myc gene including the following: (i) each gene contains three exons of which the first encodes a long 5'-untranslated leader sequence; (ii) the coding regions of the N- and c-myc genes share regions of substantial nucleic acid homology, the putative N-myc protein shares substantial homology with the c-myc protein; (iii) as with c-myc, extensive nucleotide sequence homology exists between the untranslated regions of the human and murine N-myc gene transcripts; however, the N-myc and c-myc untranslated regions are totally divergent; (iv) the N-myc transcriptional promoter differs from that of c-myc and is more related to the promoter of the simian virus 40. We discuss these findings in the context of previously defined similarities and differences in the potential functional and regulatory aspects of these two myc-family members.

SummaryAtherosclerotic cardiovascular disease is the leading cause of death in insulin-resistant (type 2) diabetes. Vascular endothelial dysfunction paves the way for atherosclerosis through impaired nitric oxide availability, inflammation, and generation of superoxide. Surprisingly, we show that ablation of the three genes encoding isoforms of transcription factor FoxO in endothelial cells prevents atherosclerosis in low-density lipoprotein receptor knockout mice by reversing these subphenotypes. Paradoxically, the atheroprotective effect of FoxO deletion is associated with a marked decrease of insulin-dependent Akt phosphorylation in endothelial cells, owing to reduced FoxO-dependent expression of the insulin receptor adaptor proteins Irs1 and Irs2. These findings support a model in which FoxO is the shared effector of multiple atherogenic pathways in endothelial cells. FoxO ablation lowers the threshold of Akt activity required for protection from atherosclerosis. The data demonstrate that FoxO inhibition in endothelial cells has the potential to mediate wide-ranging therapeutic benefits for diabetes-associated cardiovascular disease.

Summary Irs2-mediated insulin/IGF1 signaling in the CNS modulates energy balance and glucose homeostasis; however, the site for Irs2 function is unknown. The hormone leptin mediates energy balance by acting on leptin receptor (LepR-b)-expressing neurons. To determine whether LepR-b neurons mediate the metabolic actions of Irs2 in the brain, we utilized Lepr cre together with Irs2 L/L to ablate Irs2 expression in LepR-b neurons ( Lepr ΔIrs2 ). Lepr ΔIrs2 mice developed obesity, glucose intolerance, and insulin resistance. Leptin action was not altered in young Lepr ΔIrs2 mice, although insulin-stimulated FoxO1 nuclear exclusion was reduced in Lepr ΔIrs2 mice. Indeed, deletion of Foxo1 from LepR-b neurons in Lepr ΔIrs2 mice normalized energy balance, glucose homeostasis, and arcuate nucleus gene expression. Thus, Irs2 signaling in LepR-b neurons plays a crucial role in metabolic sensing and regulation. While not required for leptin action, Irs2 suppresses FoxO1 signaling in LepR-b neurons to promote energy balance and metabolism.

SummaryWe investigated the potential of in-depth quantitative proteomics to reveal plasma protein signatures that reflect lung tumor biology. We compared plasma protein profiles of four mouse models of lung cancer with profiles of models of pancreatic, ovarian, colon, prostate, and breast cancer and two models of inflammation. A protein signature for Titf1/Nkx2-1, a known lineage-survival oncogene in lung cancer, was found in plasmas of mouse models of lung adenocarcinoma. An EGFR signature was found in plasma of an EGFR mutant model, and a distinct plasma signature related to neuroendocrine development was uncovered in the small-cell lung cancer model. We demonstrate relevance to human lung cancer of the protein signatures identified on the basis of mouse models.

SummaryTo determine the role of telomere dysfunction and telomerase reactivation in generating pro-oncogenic genomic events and in carcinoma progression, an inducible telomerase reverse transcriptase (mTert) allele was crossed onto a prostate cancer-prone mouse model null for Pten and p53 tumor suppressors. Constitutive telomerase deficiency and associated telomere dysfunction constrained cancer progression. In contrast, telomerase reactivation in the setting of telomere dysfunction alleviated intratumoral DNA-damage signaling and generated aggressive cancers with rearranged genomes and new tumor biological properties (bone metastases). Comparative oncogenomic analysis revealed numerous recurrent amplifications and deletions of relevance to human prostate cancer. Murine tumors show enrichment of the TGF-β/SMAD4 network, and genetic validation studies confirmed the cooperative roles of Pten, p53, and Smad4 deficiencies in prostate cancer progression, including skeletal metastases. Thus, telomerase reactivation in tumor cells experiencing telomere dysfunction enables full malignant progression and provides a mechanism for acquisition of cancer-relevant genomic events endowing new tumor biological capabilities.

The telomere-stabilizing enzyme telomerase is induced in tumors and functionally associated with unlimited replicative potential. To further explore its necessity, transgenic mice expressing SV40 or HPV16 oncogenes, which elicit carcinomas in pancreas and skin, respectively, were rendered telomerase-deficient. Absence of telomerase had minimal impact on tumorigenesis, even in terc−/− generations (G5–7) exhibiting shortened telomeres and phenotypic abnormalities in multiple organs. Analyses of chromosomal aberrations were not indicative of telomere dysfunction or increased genomic instability in tumors. Quantitative image analysis of telomere repeat intensities comparing biopsies of skin hyperplasia, dysplasia, and carcinoma revealed that telomere numbers and relative lengths were maintained during progression, implicating a means for preserving telomere repeats and functionality in the absence of telomerase.

Telomere dysfunction and associated fusion-breakage in the mouse encourages epithelial carcinogenesis and a more humanized genomic profile that includes nonreciprocal translocations (NRTs). Here, array comparative genomic hybridization was used to determine the pathogenic significance of NRTs and to determine whether telomere dysfunction also drives amplifications and deletions of cancer-relevant loci. Compared to tumors arising in mice with intact telomeres, tumors with telomere dysfunction possessed higher levels of genomic instability and showed numerous amplifications and deletions in regions syntenic to human cancer hotspots. These observations suggest that telomere-based crisis provides a mechanism of chromosomal instability, including regional amplifications and deletions, that drives carcinogenesis. This model provides a platform for discovery of genes responsible for the major cancers affecting aged humans.

Activating mutations in the ras oncogene are not considered sufficient to induce abnormal cellular proliferation in the absence of cooperating oncogenes. We demonstrate that the conditional expression of an endogenous K-rasG12D allele in murine embryonic fibroblasts causes enhanced proliferation and partial transformation in the absence of further genetic abnormalities. Interestingly, K-rasG12D-expressing fibroblasts demonstrate attenuation and altered regulation of canonical Ras effector signaling pathways. Widespread expression of endogenous K-rasG12D is not tolerated during embryonic development, and directed expression in the lung and GI tract induces preneoplastic epithelial hyperplasias. Our results suggest that endogenous oncogenic ras is sufficient to initiate transformation by stimulating proliferation, while further genetic lesions may be necessary for progression to frank malignancy.

SummaryAging increases oxidative stress and osteoblast apoptosis and decreases bone mass, whereas forkhead box O (FoxO) transcription factors defend against oxidative stress by activating genes involved in free radical scavenging and apoptosis. Conditional deletion of FoxO1, FoxO3, and FoxO4 in 3-month-old mice resulted in an increase in oxidative stress in bone and osteoblast apoptosis and a decrease in the number of osteoblasts, the rate of bone formation, and bone mass at cancellous and cortical sites. The effect of the deletion on osteoblast apoptosis was cell autonomous and resulted from oxidative stress. Conversely, overexpression of a FoxO3 transgene in mature osteoblasts decreased oxidative stress and osteoblast apoptosis and increased osteoblast number, bone formation rate, and vertebral bone mass. We conclude that FoxO-dependent oxidative defense provides a mechanism to handle the oxygen free radicals constantly generated by the aerobic metabolism of osteoblasts and is thereby indispensable for bone mass homeostasis.

SummaryTo determine the role of the phosphatidylinositol 3-kinase (PI3-K) pathway in pancreas development, we generated a pancreas-specific knockout of Pten, a negative regulator of PI3-K signaling. Knockout mice display progressive replacement of the acinar pancreas with highly proliferative ductal structures that contain abundant mucins and express Pdx1 and Hes1, two markers of pancreatic progenitor cells. Moreover, a fraction of these mice develop ductal malignancy. We provide evidence that ductal metaplasia results from the expansion of centroacinar cells rather than transdifferentiation of acinar cells. These results indicate that Pten actively maintains the balance between different cell types in the adult pancreas and that misregulation of the PI3-K pathway in centroacinar cells may contribute to the initiation of pancreatic carcinoma in vivo.

Documented interactions among members of the Myc superfamily support a yin-yang model for the regulation of Myc-responsive genes in which transactivation-competent Myc-Max heterodimers are opposed by repressive Mxi1-Max or Mad-Max complexes. Analysis of mouse mxi1 has led to the identification of two mxi1 transcript forms possessing open reading frames that differ in their capacity to encode a short amino-terminal α-helical domain. The presence of this segment dramatically augments the suppressive potential of Mxil and allows for association with a mammalian protein that is structurally homologous to the yeast transcriptional repressor SIN3. These findings provide a mechanistic basis for the antagonistic actions of Mxi1 on Myc activity that appears to be mediated in part through the recruitment of a putative transcriptional repressor.

The known T-cell receptors (TCRs) involved in the recognition of antigen and major histocompatibility complex (MHC) molecules are glycoproteins comprised of polymorphic disulphide-linked alpha- and beta-chains. The genes encoding these chains are homologous to immunoglobulin genes and consist of V (variable), J (joining) and C (constant) regions that rearrange during development. TCRs are expressed relatively late in thymocyte development and only in association with an invariant molecular complex of proteins termed T3. Immature thymocytes do not express the TCR-T3 complex but do express messenger RNA encoding a third rearranging T-cell receptor-like gene, termed T gamma. Here we report a clone of normal immature T4-T8- human thymocytes, designated CII, which does not express mature mRNA for T alpha or T beta genes, but does express high levels of T gamma mRNA. This clone also expresses high levels of surface T3, and antibodies to T3 induce immunologically relevant functions in CII cells. Immunoprecipitation of CII surface-labelled proteins with anti-T3 co-precipitates a T3 molecular complex together with two additional and novel peptides of relative molecular mass (Mr), 44,000 (44K) and 62,000 (62K).

N-myc, a cellular gene related to the c-myc proto-oncogene1–4, was originally identified on the basis of its very frequent amplification and overexpression in a restricted set of tumours, most notably human neuroblastomas1,2. That N-myc may have a causal role in the genesis of these tumours is suggested by the observation that in the rat embryo fibroblast co-transformation assay5,6 it has a transforming potential similar to that of c-myc7,8. The apparent structural and functional homology of N-myc and c-myc suggests that they may be members of the same proto-oncogene family. However, despite these apparent similarities, expression of the two genes appears to be dramatically different with respect to tumour specificity, as well as tissue and developmental stage specificity9,10. To further elucidate the common and unique aspects of N-myc and c-myc gene structure and function in normal and transformed cells, we have determined the organization of human N-myc and the nucleotide sequence of its messenger product, and we report here that N-myc and c-myc have a similar intron/exon structure and that their protein products share regions of significant homology.

The myc-family of cellular oncogenes is a dispersed multi-gene family that includes the c-, N- and L-myc genes (For review see Alt et al., 1986). The human and murine c-, N, and L-myc genes encode related but distinct nuclear proteins and have a similar overall organization (Kohl et al., 1986; DePinho et al., 1986, Stanton et al., 1986; DePinho et al., 1987; Legouy et al., 1987; Kay et al., 1988); all have three exons with the first encoding a potentially untranslated leader sequence. All three genes also cooperate similarly with an activated Ha-Ras oncogene to transform primary rat embryo fibroblasts (REFs) (Yancopoulos et al., 1985; DePinho et al., 1987). Despite striking similarities of regions of the myc proteins and the in vitro transforming activities, the three genes are conserved as distinct sequences throughout vertebrate species suggesting unique functional roles. This possibility is supported by findings that the genes are differentially expressed in a stage-and tissue-specific manner during human and murine differentiation (Zimmerman et al., 1986). In addition, deregulated c-myc expression has been causally implicated in the genesis of a wide variety of different tumor types and occurs by a variety of different mechanisms; deregulation of the N- and L-myc genes has been clearly implicated only in a few naturally occurring tumors (eg. human neuroblastomas and small cell lung carcinomas) and only by the mechanism of gene amplification (reviewed by Alt et al., 1986).

The hybridoma technology has made it possible to sample the B-cell repertoire and to generate monoclonal antibodies which can be analyzed for their specificity and idiotypy. Using the recombinant DNA technology, the structure of the genes which encode those antibodies can be analyzed. The knowledge gained from the application of these techniques has made it possible to pose specific questions about the origins of autoantibodies.

We have isolated a 12 kb clone from the murine genome which we show by DNA transfection studies to contain an entire functional L-myc gene and the transcriptional promoter sequences necessary for its expression. We have also isolated a 3.1 kb cDNA sequence from a murine brain cDNA library which corresponds to most of the L-myc mRNA. We have identified the L-myc coding region within the genomic clone by a combination of S1 nuclease analyses. Northern blotting analyses and comparative nucleotide sequence analyses with the cDNA clone. The L-myc gene appears to be organized similarly to the other well-characterized myc-family genes, c-myc and N-myc. The predicted amino acid coding sequence of the L-myc gene indicates that the L-myc protein is significantly smaller than c- and N-myc, but is highly related. In particular, comparison of the N- and c-myc protein sequences reveals seven relatively conserved regions interspersed among non-conserved regions; the L-myc gene retains five of these conserved regions but lacks two others. In addition, a portion of one highly conserved region is encoded within a different region of the L-myc gene but, due to changes in the size of L-myc exons relative to those of N- and c-myc, maintains its overall position in the peptide backbone with respect to other conserved regions. We discuss these findings in the context of potential functional domains and the possibility of overlapping and distinct activities of myc-family proteins.

Analyses of A-MuLV transformed cell lines have provided fundamental insights into the molecular mechanisms which control the rearrangement events leading to the expression of specific antigen receptor genes. These studies have clearly indicated that tissue-specific, developmental stage-specific, and allelically excluded assembly of Ig H and L chain and TCR variable region genes are very strictly regulated processes and, furthermore, that this regulation probably is effected at the level of the accessibility of the individual sets of V gene segments to a common recombinase. More preliminary studies have also suggested that accessibility targeting may be involved in the regulation of directed Ig H chain class-switch recombination events. Currently, we do not understand the nature of "accessible" DNA sequences and we have little understanding of the molecular mechanisms by which Ig (and potentially TCR) chains mediate the regulation of specific recombination events by signaling changes in the accessibility of the various loci. However, an ideal model system for the analysis of these questions is currently available in the form of A-MuLV transformed pre-B cell lines which, in a properly regulated fashion, undergo all of the various recombination events associated with the pre-B stage of B cell differentiation.

To elucidate further the general mechanisms which control the assembly and expression of Immunoglobulin variable region gene segments and heavy-chain class switching, we have exploited Abelson murine leukemia virus (A-MuLV) transformed pre-B cells as a model system. The Abelson virus is a replication defective retrovirus which is unique in its capacity to transform very early B-lineage cells in vitro (1). A-MuLV transformants generated from murine fetal liver or adult bone marrow have provided both a static representation of various pre-B cell differentiation stages, as well as a dynamic view of pre-B cell immunodifferentiation events (2,3). Our analyses of these lines have provided a variety of new and sometimes surprising findings regarding the early stages of B cell differentiation; and importantly, all of these novel aspects first observed in A-MuLV transformants were found to reflect events that occur early in normal B lineage cells in vitro. Furthermore, we have utilized gene transfer technology to gain additional insight into the molecular events involved with the regulation of immunogloblin and T cell receptor variable region (V) gene assembly (3).

The editorial board of Aging reviews research papers published in 2009,which they believe have or will have a significant impact on aging research. Among many others, the topics include genes that accelerate aging or incontrast promote longevity in model organisms, DNA damage responsesand telomeres, molecular mechanisms of life span extension by calorierestriction and pharmacologic interventions into aging. The emergingmessage in 2009 is that aging is not random but determined by agenetically-regulated longevity network and can be decelerated bothgenetically and pharmacologically. © Blagosklonny et al.

International audience; The International Cancer Genome Consortium (ICGC) was launched to coordinate large-scale cancer genome studies in tumors from 50 different cancer types and/or subtypes that are of clinical and societal importance across the globe. Systematic studies of over 25,000 cancer genomes at the genomic, epigenomic, and transcriptomic levels will reveal the repertoire of oncogenic mutations, uncover traces of the mutagenic influences, define clinically-relevant subtypes for prognosis and therapeutic management, and enable the development of new cancer therapies.

Monoclonal antibodies, potentially powerful diagnostic and therapeutic reagents, are having a significant impact in basic and clinical research. Some persisting problems must be solved, however, in order to realize the potential of this technology. We review the basic biology of antibody molecules and the genes that encode them, and discuss how this knowledge can be applied to make more effective monoclonal antibodies.