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Precise progerin targeting using RfxCas13d: A therapeutic avenue for Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome (HGPS), an extremely rare progressive genetic disorder, is caused by a point mutation in LMNA that induces progerin production, which disrupts cellular function and triggers premature aging and mortality. Despite extensive efforts, HPGS remains incurable. We successfully implemented a strategy using RfxCas13d to selectively target progerin mRNA at specific junction regions, without unintended cleavage and reduce its expression. This technique discriminated between normal lamin A and progerin, thus providing a safe and targeted therapeutic avenue to treat HGPS. Our approach effectively restored aberrant gene expression and progerin-induced cellular phenotypes, including senescence, mitochondrial dysfunction, and DNA damage in cells with HGPS and LMNAG608G/G608G mice. Notably, LMNAG608G/G608G mice exhibited improved progeroid phenotypes, suggesting a potential therapeutic application of this approach for other diseases resulting from abnormal RNA splicing.

Progeria

In Vivo Base Editing Partially Rescues Bone Dysplasia in a Mouse Model of Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder affecting tissues of mesenchymal origin. Most patients harbor a c.1824C>T/p.G608= variant, commonly described as G608G, in exon 11 of LMNA that leads to aberrant splicing and production of the toxic progerin protein. In addition to cardiovascular, dermal, and adipose tissue deterioration, HGPS mouse models also develop progressive bone dysplasia that occurs in patients. Here we characterize the efficacy of in&#xa0;vivo mutation correction with an adenine base editor (ABE) to rescue structural and functional defects in HGPS transgenic murine bone tissue. Treatment of double-copy transgenic osteoblast cultures with a lentiviral-delivered CRISPR-Cas9 ABE achieved nearly 40% gene correction in&#xa0;vitro, resulting in significant reduction of progerin transcripts and protein, in the absence of selective agents. Furthermore, gene correction improved progeroid osteoblasts' capacity to deposit and mineralize extracellular matrix compared to untreated cultures. In&#xa0;vivo, a single intravenous dose of AAV9-delivered ABE corrected the mutation, achieving ~14%, ~22%, ~10% and <&#x2009;1% correction in bone by six months of age when administered at P3, P14, 1 and 4&#x2009;months of age, respectively. Partially rescued bone structural and physical parameters were observed in P14-treated mice with concomitant normalization of gene transcriptional programs and intracellular signaling pathways involved in bone remodeling. This work demonstrates in&#xa0;vivo delivery of a locus-specific DNA base editor to bone tissue, delineates the timing of treatment required for maximum efficacy, and suggests that this system might be tailored for application to other monogenic bone disorders.

Animals

Transcriptional profiling of Hutchinson-Gilford Progeria patients identifies primary target pathways of progerin.

Hutchinson Gilford Progeria Syndrome (HGPS) is an ultra-rare pediatric premature aging disorder. The disease is caused by a point mutation in the LMNA gene leading to the production of the dominant-negative progerin isoform of the nuclear envelope protein lamin A. Disease severity and progression amongst the population of ~140 known patients is variable. Most of the mechanistic insights into the disease have come from studies using cellular or mouse models of HGPS. To probe the clinical relevance of previously implicated cellular pathways and to address the extent of gene expression heterogeneity between patients, we have performed transcriptomic analysis of a comprehensive set of HGPS patients. We find misexpression of several cellular pathways across the patient population, particularly of multiple signaling pathways as well as the Unfolded Protein Response (UPR) and mesodermal cell fate specification. Variability amongst individual patients was limited, with misregulation of the major pathways observed in most patients. Comparing the transcriptome of patients with an inducible HGPS cell model, we distinguished immediate-early cellular response pathways from secondary adaptive pathways and identified mTORC1, the UPR, UV response, apoptosis and TNF&#x3b1; signaling via NF-&#x3ba;B as primary targets of the disease-causing progerin protein.

Hutchinson-Gilford Progeria Syndrome

Pharmacologic activation of &#x394;133p53&#x3b1; reduces cellular senescence in progeria patients-derived cells.

BACKGROUND: Patients with Hutchinson-Gilford progeria syndrome (HGPS) show accelerated aging phenotypes and have shortened lifespan, with implications in physiological aging processes as well. While therapeutic approaches targeting the disease-causing abnormal protein, progerin, have been developed, further efforts to explore mechanistically distinct and complementary strategies are still critical to better treatment regimens. We previously showed that lentiviral vector-driven expression of &#x394;133p53&#x3b1;, a natural inhibitory isoform of p53, rescued HGPS patients-derived fibroblasts from early entry into cellular senescence, which is a downstream event of progerin-induced DNA damage. We also performed a quantitative high-throughput screen (qHTS) of approved drug and investigational agent libraries, leading to the identification of celastrol and AZD1981 as compounds that upregulate &#x394;133p53&#x3b1; protein levels. METHODS: To investigate whether celastrol and ADZ1981 upregulate endogenous &#x394;133p53&#x3b1; in HGPS-derived fibroblasts and reduce their senescence-associated phenotypes, we performed western blot assays (&#x394;133p53&#x3b1;, progerin, and p21WAF1, which mediates p53-induced senescence and is inhibited by &#x394;133p53&#x3b1;), senescence-associated &#x3b2;-galactosidase (SA-&#x3b2;-gal) staining, enzyme-linked immunosorbent assay (IL-6, which is a proinflammatory cytokine secreted from senescent cells), and qRT-PCR assays (p21WAF1 and IL-6). RESULTS: Treatment with celastrol (0.1 &#x3bc;M for 24 h) or AZD1981 (10 &#x3bc;M for 24 h) reproducibly increased &#x394;133p53&#x3b1; expression and decreased p21WAF1 expression in two strains of fibroblasts derived from HGPS patients. These compounds reduced the percentage of SA-&#x3b2;-gal-positive senescent cells and the secretion of IL-6 into culture medium in both of these fibroblast strains, irrespective of their different basal levels of senescence and IL-6 secretion. These compounds had no effect on the level of progerin. CONCLUSION: Celastrol and ADZ1981 upregulate endogenous &#x394;133p53&#x3b1; and, reproducing the effects of its vector-driven expression, inhibit cellular senescence and IL-6 secretion in HGPS-derived fibroblasts. Their progerin-independent action suggests that they may synergize with currently available progerin-targeting therapies. This study also warrants further investigation of these compounds for potential applications in other diseases and conditions in which &#x394;133p53&#x3b1;-regulated senescence plays a role.

Hutchinson-Gilford progeria syndrome

CK2&#x3b1; restriction of STING accumulation underlies systemic aging.

Chronic activation of the cGAS-STING pathway drives inflammaging and cellular senescence. Although nuclear envelope (NE) barrier failure leading to cytoplasmic chromatin leakage is a key trigger, the molecular mechanisms governing STING activity at the NE during aging remain poorly understood. Here, we identify lamin A/C (LMNA) as a critical NE scaffold that orchestrates STING regulation by recruiting both STING and Casein Kinase 2 (CK2&#x3b1;). We demonstrate that LMNA facilitates the phosphorylation of STING at Ser366 by CK2&#x3b1;, which promotes STING turnover and restricts its accumulation, thereby attenuating pathway activation and mitigating senescence in myeloid cells as well as systemic aging. Strikingly, pharmacologic STING inhibition in vivo robustly rescues progeroid phenotypes-including loss of bone density and multi-tissue senescence-and extends lifespan in progeroid mouse models. Moreover, H-151 treatment also ameliorates the premature aging phenotypes induced by myeloid-specific CK2&#x3b1; ablation. In contrast, constitutive STING ablation yields limited survival benefits, revealing that controlled attenuation of STING signaling, rather than complete elimination, drives therapeutic efficacy. Our findings establish the LMNA-CK2-STING axis as a key biochemical mechanism that suppresses innate immune activation at the NE, offering a promising strategy for ameliorating aging and progeroid pathologies.

Animals

Tissue specificity of senescent cell accumulation during physiologic and accelerated aging of mice.

Senescent cells accumulate with age in vertebrates and promote aging largely through their senescence-associated secretory phenotype (SASP). Many types of stress induce senescence, including genotoxic stress. ERCC1-XPF is a DNA repair endonuclease required for multiple DNA repair mechanisms that protect the nuclear genome. Humans or mice with reduced expression of this enzyme age rapidly due to increased levels of spontaneous, genotoxic stress. Here, we asked whether this corresponds to an increased level of senescent cells. p16Ink4a and p21Cip1 mRNA were increased ~15-fold in peripheral lymphocytes from 4- to 5-month-old Ercc1-/&#x2206; and 2.5-year-old wild-type (WT) mice, suggesting that these animals exhibit a similar biological age. p16Ink4a and p21Cip1 mRNA were elevated in 10 of 13 tissues analyzed from 4- to 5-month-old Ercc1-/&#x2206; mice, indicating where endogenous DNA damage drives senescence in vivo. Aged WT mice had similar increases of p16Ink4a and p21Cip1 mRNA in the same 10 tissues as the mutant mice. Senescence-associated &#x3b2;-galactosidase activity and p21Cip1 protein also were increased in tissues of the progeroid and aged mice, while Lamin B1 mRNA and protein levels were diminished. In Ercc1-/&#x394; mice with a p16Ink4a luciferase reporter, bioluminescence rose steadily with age, particularly in lung, thymus, and pancreas. These data illustrate where senescence occurs with natural and accelerated aging in mice and the relative extent of senescence among tissues. Interestingly, senescence was greater in male mice until the end of life. The similarities between Ercc1-/&#x2206; and aged WT&#xa0;mice support the conclusion that the DNA repair-deficient mice accurately model the&#xa0;age-related accumulation of senescent cells, albeit six-times faster.

Aging

The Ercc1-/&#x394; mouse model of XFE progeroid syndrome undergoes accelerated retinal degeneration.

Age-related macular degeneration (AMD) is a major cause of vision loss in older adults. AMD is caused by degeneration in the macula of the retina. The retina is the highest oxygen consuming tissue in our body and is prone to oxidative damage. DNA damage is one hallmark of aging implicated in loss of organ function. Genome instability has been associated with several disorders that result in premature vision loss. We hypothesized that endogenous DNA damage plays a causal role in age-related retinal changes. To address this, we used a genetic model of systemic depletion of expression of the DNA repair enzyme ERCC1-XPF. The neural retina and retinal pigment epithelium (RPE) from Ercc1-/&#x394; mice, which models a human progeroid syndrome, were compared to age-matched wild-type (WT) and old WT mice. By 3-months-of age, Ercc1-/&#x394; mice presented abnormal optokinetic and electroretinogram responses consistent with photoreceptor dysfunction and visual impairment. Ercc1-/&#x394; mice shared many ocular characteristics with old WT mice including morphological changes, elevated DNA damage markers (&#x3b3;-H2AX and 53BP1), and increased cellular senescence in the neural retinal and RPE, as well as pathological angiogenesis. The RPE is essential for the metabolic health of photoreceptors. The RPE from Ercc1-/&#x394; mice displayed mitochondrial dysfunction causing a compensatory glycolytic shift, a characteristic feature of aging RPE. Hence, our study suggests spontaneous endogenous DNA damage promotes the hallmarks of age-related retinal degeneration.

Animals