Hutchinson-Gilford Progeria Syndrome (HGPS) Cell Models for Research

Hutchinson-Gilford Progeria Syndrome (HGPS) is an extremely rare genetic disorder with an estimated incidence of 1 in 4 million live births worldwide. According to the Progeria Research Foundation, there are approximately 130 known cases globally, but the actual number may be higher due to underdiagnosis. The disease is characterized by accelerated aging in children, leading to death at a median age of 14.6 years, primarily from cardiovascular complications such as myocardial infarction or stroke. There is no cure, and current treatments (e.g., lonafarnib) only extend life by about 1.6 years on average. The clinical impact is profound, affecting multiple organ systems including skin, bone, and cardiovascular system. The rarity of the disease makes it a challenge for clinical trials, but also highlights the importance of preclinical models for understanding mechanisms and testing therapies.

HGPS serves as an exceptional model for studying the biology of normal aging and age-related diseases. The disease is caused by a single point mutation in the LMNA gene, providing a clear genotype-phenotype correlation. This simplicity allows for precise genetic manipulation in cell models to dissect molecular pathways. HGPS also offers insights into nuclear architecture, DNA damage repair, and cellular senescence, which are relevant to cancer and other age-related pathologies. Public datasets, such as those from the NCBI Gene Expression Omnibus (GEO), provide transcriptomic and epigenetic profiles of HGPS patient cells, enabling bioinformatic analyses. Open questions include the role of progerin in non-nuclear functions, the interplay between mechanical stress and nuclear fragility, and the development of targeted therapies that reverse or delay the aging phenotype.

HGPS is not a cancer predisposition syndrome, but the molecular pathways involved in HGPS overlap with those implicated in cancer and aging. The primary pathway is the accumulation of progerin, a truncated form of lamin A, which disrupts nuclear structure and function. This leads to:

• • Genomic instability: Progerin causes defects in DNA repair, leading to accumulation of DNA damage and mutations.
• • Cellular senescence: Progerin activates p53 and RB pathways, inducing premature senescence.
• • Epigenetic alterations: Progerin affects histone modifications and DNA methylation, altering gene expression.
• • Mitochondrial dysfunction: Progerin induces oxidative stress and mitochondrial damage.

These pathways contribute to the accelerated aging phenotype and may also influence cancer development in HGPS patients, although cancer is rare in HGPS due to early death.

The primary genetic alteration in HGPS is a de novo point mutation in the LMNA gene (c.1824C>T; p.G608G) that activates a cryptic splice site, resulting in a 50-amino acid deletion in prelamin A. This mutation is present in about 90% of HGPS cases. Other rare mutations include c.1822G>A (p.G608S) and c.1821G>A (p.G608D), which also affect splicing. The mutation is autosomal dominant and occurs sporadically. In terms of somatic mutations, HGPS patients do not show increased cancer mutations, but the genomic instability may predispose to mutations in other genes. The following table summarizes the key genetic alterations:

Data from ClinVar and NCBI Gene.

Progerin disrupts multiple signaling networks:

• • Wnt/β-catenin pathway: Progerin alters β-catenin localization, affecting cell proliferation and differentiation.
• • MAPK/ERK pathway: Hyperactivation of ERK1/2 is observed in HGPS cells, contributing to senescence.
• • PI3K/AKT pathway: Reduced AKT phosphorylation leads to increased apoptosis.
• • NF-κB pathway: Progerin activates NF-κB, promoting inflammation.
• • p53 pathway: Upregulation of p53 and its target genes, leading to cell cycle arrest.

These networks are interconnected and contribute to the aging phenotype. Targeting these pathways may offer therapeutic opportunities.

Several cell lines are used to study HGPS:

Induced pluripotent stem cells (iPSCs) derived from HGPS patients can be differentiated into various cell types, including mesenchymal stem cells, endothelial cells, and smooth muscle cells, providing more physiologically relevant models. Organoids, such as vascular organoids, are emerging as powerful tools to study tissue-specific effects of progerin.

Animal models for HGPS include:

• • Zmpste24 knockout mouse: This mouse lacks the metalloproteinase ZMPSTE24, which is required for lamin A processing, leading to accumulation of prelamin A and progeroid features.
• • Lmna G609G knock-in mouse: This mouse carries the equivalent of the human G608G mutation and exhibits accelerated aging phenotypes.
• • BAC transgenic mouse: Expresses human progerin under a β-actin promoter, showing vascular and bone abnormalities.
• • Induced models: In vitro models using CRISPR to introduce the mutation in mouse embryonic fibroblasts.

These models are valuable for studying disease mechanisms and testing therapies, but they have limitations in recapitulating all aspects of the human disease.

CRISPR-based gene editing has enabled the creation of isogenic cell models for HGPS. These models are generated by introducing the specific LMNA mutation (e.g., G608G) into a normal cell line, such as HEK293 or HFF, or by correcting the mutation in patient-derived cells. This allows for direct comparison of mutant and wild-type cells with identical genetic backgrounds, eliminating confounding factors.

Examples of gene-edited models:

• • LMNA G608G knock-in in HEK293 cells: These cells express progerin and recapitulate nuclear abnormalities.
• • LMNA knockout in HFF cells: These cells lack lamin A, providing a model for understanding the loss-of-function effects.
• • Reporter cell lines: Cells with a fluorescent reporter under the control of progerin-responsive promoters, useful for high-content screening.

These gene-edited cell models are commercially available from various sources and are sequence-verified for accuracy. They are essential for drug discovery, functional genomics, and target validation. Using isogenic pairs, researchers can identify compounds that specifically target progerin toxicity without affecting normal lamin A function.

Gene-edited cell models are used to validate the function of genes involved in HGPS. For example, knocking out LMNA in normal cells can reveal the role of lamin A in nuclear stability and gene regulation. Conversely, introducing the G608G mutation into cells allows for the study of progerin's gain-of-function effects. CRISPR screens using these models can identify genetic modifiers that suppress or enhance progerin toxicity, providing new therapeutic targets.

Isogenic pairs (wild-type vs. mutant) are ideal for high-throughput drug screening. Compounds that selectively reduce progerin levels or mitigate its effects can be identified by comparing viability or senescence markers between the two cell lines. These models are also used to test resistance mechanisms, such as the development of resistance to farnesyltransferase inhibitors (e.g., lonafarnib). By generating resistant cell lines, researchers can study the underlying mechanisms and develop combination therapies.

CRISPR-based synthetic lethality screens in HGPS cell models can identify genes that, when knocked out, selectively kill progerin-expressing cells but not normal cells. This approach can reveal novel biomarkers and therapeutic targets. Additionally, gene-edited cells can be used to validate candidate biomarkers by measuring their expression levels in response to progerin modulation.

The following databases provide valuable data for HGPS research:

These resources allow researchers to access genomic, transcriptomic, and proteomic data to support their studies.