sirolimus and Dwarfism

Dermatologically, FGFR3 mutations can lead to acanthosis nigricans (AN), epidermal nevi, and seborrheic keratosis. A recent case report found that topical rapamycin (sirolimus) can improve FGFR3-induced epidermal nevi with AN features in children, specifically with Fitzpatrick skin type (FST) I/II, and we would like to expand these findings to skin plaques with extensive AN-like features in the FST IV/V adolescent population. An 18-year-old female with FST IV/V and FGFR3-induced hypochondroplasia presented to our clinic with extensive AN-like plaques. Significant improvement with lightening and thinning of the plaques was observed after applying 1% topical rapamycin cream twice daily. Topical rapamycin should be considered as a treatment option for AN, particularly in FST IV/V adolescents with FGFR3-induced AN.

Topics: Acanthosis Nigricans; Adolescent; Child; Dwarfism; Female; Humans; Nevus; Sirolimus; Skin Neoplasms

Human DNA-methylation data have been used to develop highly accurate biomarkers of aging ("epigenetic clocks"). Recent studies demonstrate that similar epigenetic clocks for mice (

Topics: Age Factors; Animals; Biological Clocks; Caloric Restriction; CpG Islands; Databases, Genetic; Disease Models, Animal; DNA Methylation; Dwarfism; Epigenesis, Genetic; Female; Genome-Wide Association Study; Longevity; Male; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Mice, Mutant Strains; Sirolimus; Species Specificity

Global but predictable changes impact the DNA methylome as we age, acting as a type of molecular clock. This clock can be hastened by conditions that decrease lifespan, raising the question of whether it can also be slowed, for example, by conditions that increase lifespan. Mice are particularly appealing organisms for studies of mammalian aging; however, epigenetic clocks have thus far been formulated only in humans.. We first examined whether mice and humans experience similar patterns of change in the methylome with age. We found moderate conservation of CpG sites for which methylation is altered with age, with both species showing an increase in methylome disorder during aging. Based on this analysis, we formulated an epigenetic-aging model in mice using the liver methylomes of 107 mice from 0.2 to 26.0 months old. To examine whether epigenetic aging signatures are slowed by longevity-promoting interventions, we analyzed 28 additional methylomes from mice subjected to lifespan-extending conditions, including Prop1. This study shows that lifespan-extending conditions can slow molecular changes associated with an epigenetic clock in mice livers.

Topics: Aging; Animals; Caloric Restriction; Cluster Analysis; CpG Islands; DNA Methylation; Dwarfism; Epigenesis, Genetic; Epigenomics; Female; Gene Expression Profiling; Humans; Liver; Longevity; Male; Mice; Sirolimus

SHORT syndrome is a rare, recognizable syndrome resulting from heterozygous mutations in PIK3R1 encoding a regulatory subunit of phosphoinositide-3-kinase (PI3K). The condition is characterized by short stature, intrauterine growth restriction, lipoatrophy and a facial gestalt involving a triangular face, deep set eyes, low hanging columella and small chin. PIK3R1 mutations in SHORT syndrome result in reduced signaling through the PI3K-AKT-mTOR pathway. We performed whole exome sequencing for an individual with clinical features of SHORT syndrome but negative for PIK3R1 mutation and her parents. A rare de novo variant in PRKCE was identified. The gene encodes PKCε and, as such, the AKT-mTOR pathway function was assessed using phospho-specific antibodies with patient lymphoblasts and following ectopic expression of the mutant in HEK293 cells. Kinase analysis showed that the variant resulted in a partial loss-of-function. Whilst interaction with PDK1 and the mTORC2 complex component SIN1 was preserved in the mutant PKCε, it bound to SIN1 with a higher affinity than wild-type PKCε and the dynamics of mTORC2-dependent priming of mutant PKCε was altered. Further, mutant PKCε caused impaired mTORC2-dependent pAKT-S473 following rapamycin treatment. Reduced pFOXO1-S256 and pS6-S240/244 levels were also observed in the patient LCLs. To date, mutations in PIK3R1 causing impaired PI3K-dependent AKT activation are the only known cause of SHORT syndrome. We identify a SHORT syndrome child with a novel partial loss-of-function defect in PKCε. This variant causes impaired AKT activation via compromised mTORC2 complex function.

Topics: Adaptor Proteins, Signal Transducing; Adolescent; Dwarfism; Female; Growth Disorders; HEK293 Cells; Humans; Hypercalcemia; Mechanistic Target of Rapamycin Complex 2; Metabolic Diseases; Mutation; Nephrocalcinosis; Phosphatidylinositol 3-Kinases; Phosphorylation; Protein Kinase C-epsilon; Proto-Oncogene Proteins c-akt; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Studies of the mTOR pathway have prompted speculation that diminished mTOR complex-1 (mTORC1) function may be involved in controlling the aging process. Our previous studies have shown diminished mTORC1 activity in tissues of three long-lived mutant mice: Snell dwarf mice, growth hormone receptor gene disrupted mice (GHRKO), and in this article, mice deficient in the pregnancy-associated protein-A (PAPPA-KO). The ways in which lower mTOR signals slow aging and age-related diseases are, however, not well characterized. Here, we show that Snell, GHKRO, and PAPPA-KO mice express high levels of two proteins involved in DNA repair, O-6-methylguanine-DNA methyltransferase (MGMT) and N-myc downstream-regulated gene 1 (NDRG1). Furthermore, we report that lowering mTOR enhances MGMT and NDRG1 protein expression via post-transcriptional mechanisms. We show that the CCR4-NOT complex, a post-transcriptional regulator of gene expression, is downstream of the mTORC1 pathway and may be responsible for the upregulation of MGMT and NDRG1 in all three varieties of long-lived mice. Our data thus suggest a novel link between DNA repair and mTOR signaling via post-transcriptional regulation involving specific alteration in the CCR4-NOT complex, whose modulation could control multiple aspects of the aging process.

Topics: Animals; Cell Cycle Proteins; DNA Damage; DNA Modification Methylases; DNA Repair Enzymes; Down-Regulation; Dwarfism; Female; Intracellular Signaling Peptides and Proteins; Liver; Longevity; Male; Mice, Knockout; Models, Biological; Pregnancy-Associated Plasma Protein-A; Receptors, CCR4; Receptors, Somatotropin; RNA, Messenger; Sirolimus; TOR Serine-Threonine Kinases; Transcription Factors; Tumor Suppressor Proteins

There is large variation in lifespan among different species, and there is evidence that modulation of proteasome function may contribute to longevity determination. Comparative biology provides a powerful tool for identifying genes and pathways that control the rate of aging. Here, we evaluated skin-derived fibroblasts and demonstrate that among primate species, longevity correlated with an elevation in proteasomal activity as well as immunoproteasome expression at both the mRNA and protein levels. Immunoproteasome enhancement occurred with a concurrent increase in other elements involved in MHC class I antigen presentation, including β-2 microglobulin, (TAP1), and TAP2. Fibroblasts from long-lived primates also appeared more responsive to IFN-γ than cells from short-lived primate species, and this increase in IFN-γ responsiveness correlated with elevated expression of the IFN-γ receptor protein IFNGR2. Elevation of immunoproteasome and proteasome activity was also observed in the livers of long-lived Snell dwarf mice and in mice exposed to drugs that have been shown to extend lifespan, including rapamycin, 17-α-estradiol, and nordihydroguaiaretic acid. This work suggests that augmented immunoproteasome function may contribute to lifespan differences in mice and among primate species.

Topics: Animals; Antigen Presentation; ATP Binding Cassette Transporter, Subfamily B, Member 2; ATP Binding Cassette Transporter, Subfamily B, Member 3; ATP-Binding Cassette Transporters; beta 2-Microglobulin; Cells, Cultured; Dwarfism; Estradiol; Female; Fibroblasts; Gene Expression Regulation; Histocompatibility Antigens Class I; Interferon gamma Receptor; Interferon-gamma; Janus Kinases; Longevity; Male; Masoprocol; Mice; Mice, Inbred C3H; Mice, Mutant Strains; Oxidative Stress; Primates; Proteasome Endopeptidase Complex; Protein Subunits; Receptors, Interferon; RNA, Messenger; Signal Transduction; Sirolimus; Species Specificity; STAT Transcription Factors; Up-Regulation

How growth hormone (GH) stimulates protein synthesis is unknown. Phosphoinositide 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathways balance anabolic and catabolic activities in response to nutrients and growth factor signaling. As a test of GH signaling, immunoassays of two downstream translation regulatory proteins were compared in ad libitum-fed 2-month-old normal and Ames (Prop1df) dwarf mice. Phosphorylation of the p70 and p85 isoforms of S6 kinase 1 in liver and the p70 isoform in gastrocnemius muscle were significantly decreased in dwarfs. Messenger RNA (mRNA) Cap-binding demonstrated significantly higher levels of translation repressor 4E-BP1/eukaryotic initiation factor 4E (eIF4E) (coprecipitates) from dwarf livers, but not muscle. Consistent with these binding data, significantly less phosphorylation of 4E-BP1 was documented in dwarf liver. These data suggest a link between GH signaling and translation control in a model of extended longevity.

Topics: 1-Phosphatidylinositol 4-Kinase; Aging; Animals; Disease Models, Animal; Down-Regulation; Dwarfism; Female; Genetic Markers; Growth Hormone; Immunoblotting; Liver; Mice; Mice, Inbred Strains; Muscle, Skeletal; Phosphorylation; Signal Transduction; Sirolimus; Tissue Culture Techniques