Hutchinson-Gilford Progeria Syndrome: Challenges at Bench and Bedside

Scaffold, mechanics and functions of nuclear lamins

Nuclear lamins are type-V intermediate filaments that are involved in many nuclear processes. In mammals, A- and B-type lamins assemble into separate physical meshwork underneath the inner nuclear membrane, the nuclear lamina, with some residual fraction localized within the nucleoplasm. Lamins are the major part of the nucleoskeleton, providing mechanical strength and flexibility to protect the genome and allow nuclear deformability, while also contributing to gene regulation via interactions with chromatin. While lamins are the evolutionary ancestors of all intermediate filament family proteins, their ultimate filamentous assembly is markedly different from their cytoplasmic counterparts. Interestingly, hundreds of genetic mutations in the lamina proteins have been causally linked with a broad range of human pathologies, termed laminopathies. These include muscular, neurological and metabolic disorders, as well as premature aging diseases. Recent technological advances have contributed to resolving the filamentous structure of lamins and the corresponding lamina organization. In this review, we revisit the multiscale lamin organization and discuss its implications on nuclear mechanics and chromatin organization within lamina-associated domains.

An infant with congenital micrognathia and upper airway obstruction was diagnosed as Hutchinson-Gilford progeria syndrome caused by a novel LMNA mutation: Case report and literature review

Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare disease characterized by appearance of premature aging, including the skin, bones, heart, and blood vessels caused by LMNA mutation. In this study, the patient presented with congenital micrognathia and progressively aggravated upper airway obstruction as the initial symptom, which required bilateral mandibular distraction osteogenesis (MDO) surgery intervention. This was not commonly described in the literature, and the primary clinical diagnosis of Pierre Robin sequence (PRS) was made. However, other clinical features included sclerotic skin, dry skin, growth failure, lipoatrophy, joint stiffness, prominent scalp veins, small ear lobes, hair loss, and craniofacial disproportion gradually emerged, the diagnosis of HGPS was preferred when the patient was 5 months old. The genetic testing result with a novel and de novo LMNA mutation (c.1968 + 3_1968+6delGAGT) further confirmed the diagnosis and expanded the clinical and mutational spectrum of HGPS. During the 12-month follow-up period after surgery, the patient no longer suffered dyspnea. Complications of other organs and systems have not happened at the moment. In addition, the pathogenesis, the role of LMNA gene mutation, the progress in clinical treatment, and breakthrough studies about genetic treatment in animals of HGPS are described in the literature review.

Hepatic hydrogen sulfide levels are reduced in mouse model of Hutchinson-Gilford progeria syndrome

Hutchinson-Gilford progeria syndrome (HGPS) is a rare human disease characterised by accelerated biological ageing. Current treatments are limited, and most patients die before 15 years of age. Hydrogen sulfide (H2S) is an important gaseous signalling molecule that it central to multiple cellular homeostasis mechanisms. Dysregulation of tissue H2S levels is thought to contribute to an ageing phenotype in many tissues across animal models. Whether H2S is altered in HGPS is unknown. We investigated hepatic H2S production capacity and transcript, protein and enzymatic activity of proteins that regulate hepatic H2S production and disposal in a mouse model of HGPS (G609G mice, mutated Lmna gene equivalent to a causative mutation in HGPS patients). G609G mice were maintained on either regular chow (RC) or high fat diet (HFD), as HFD has been previously shown to significantly extend lifespan of G609G mice, and compared to wild type (WT) mice maintained on RC. RC fed G609G mice had significantly reduced hepatic H2S production capacity relative to WT mice, with a compensatory elevation in mRNA transcripts associated with several H2S production enzymes, including cystathionine-γ-lyase (CSE). H2S levels and CSE protein were partially rescued in HFD fed G609G mice. As current treatments for patients with HGPS have failed to confer significant improvements to symptoms or longevity, the need for novel therapeutic targets is acute and the regulation of H2S through dietary or pharmacological means may be a promising new avenue for research.

A deep hybrid learning pipeline for accurate diagnosis of ovarian cancer based on nuclear morphology

Nuclear morphological features are potent determining factors for clinical diagnostic approaches adopted by pathologists to analyze the malignant potential of cancer cells. Considering the structural alteration of the nucleus in cancer cells, various groups have developed machine learning techniques based on variation in nuclear morphometric information like nuclear shape, size, nucleus-cytoplasm ratio and various non-parametric methods like deep learning have also been tested for analyzing immunohistochemistry images of tissue samples for diagnosing various cancers. We aim to correlate the morphometric features of the nucleus along with the distribution of nuclear lamin proteins with classical machine learning to differentiate between normal and ovarian cancer tissues. It has already been elucidated that in ovarian cancer, the extent of alteration in nuclear shape and morphology can modulate genetic changes and thus can be utilized to predict the outcome of low to a high form of serous carcinoma. In this work, we have performed exhaustive imaging of ovarian cancer versus normal tissue and developed a dual pipeline architecture that combines the matrices of morphometric parameters with deep learning techniques of auto feature extraction from pre-processed images. This novel Deep Hybrid Learning model, though derived from classical machine learning algorithms and standard CNN, showed a training and validation AUC score of 0.99 whereas the test AUC score turned out to be 1.00. The improved feature engineering enabled us to differentiate between cancerous and non-cancerous samples successfully from this pilot study.

The role of inner nuclear membrane proteins in tumourigenesis and as potential targets for cancer therapy

Despite significant advances in our understanding of tumourigenesis and cancer therapeutics, cancer continues to account for 30% of worldwide deaths. Therefore, there remains an unmet need for the development of cancer therapies to improve patient quality of life and survival outcomes. The inner nuclear membrane has an essential role in cell division, cell signalling, transcription, cell cycle progression, chromosome tethering, cell migration and mitosis. Furthermore, expression of several inner nuclear membrane proteins has been shown to be frequently altered in tumour cells, resulting in the dysregulation of cellular pathways to promote tumourigenesis. However, to date, minimal research has been conducted to investigate how targeting these dysregulated and variably expressed proteins may provide a novel avenue for cancer therapies. In this review, we present an overview of the involvement of the inner nuclear membrane proteins within the hallmarks of cancer and how they may be exploited as potent anti-cancer therapeutics.

Hydrogen sulfide in ageing, longevity and disease

Hydrogen sulfide (H₂S) modulates many biological processes, including ageing. Initially considered a hazardous toxic gas, it is now recognised that H₂S is produced endogenously across taxa and is a key mediator of processes that promote longevity and improve late-life health. In this review, we consider the key developments in our understanding of this gaseous signalling molecule in the context of health and disease, discuss potential mechanisms through which H₂S can influence processes central to ageing and highlight the emergence of novel H₂S-based therapeutics. We also consider the major challenges that may potentially hinder the development of such therapies.

Hutchinson-Gilford Progeria Syndrome: An Overview of the Molecular Mechanism, Pathophysiology and Therapeutic Approach

Lamin A/C encoded by the LMNA gene is an essential component for maintaining the nuclear structure. Mutation in the lamin A/C leads to a group of inherited disorders is known as laminopathies. In the human body, there are several mutations in the LMNA gene that have been identified. It can affect diverse organs or tissues or can be systemic, causing different diseases. In this review, we mainly focused on one of the most severe laminopathies, Hutchinson-Gilford progeria syndrome (HGPS). HGPS is an immensely uncommon, deadly, metameric ill-timed laminopathies caused by the abnormal splicing of the LMNA gene and production of an aberrant protein known as progerin. Here, we also presented the currently available data on the molecular mechanism, pathophysiology, available treatment, and future approaches to this deadly disease. Due to the production of progerin, an abnormal protein leads to an abnormality in nuclear structure, defects in DNA repair, shortening of telomere, and impairment in gene regulation which ultimately results in aging in the early stage of life. Now some treatment options are available for this disease, but a proper understanding of the molecular mechanism of this disease will help to develop a more appropriate treatment which makes it an emerging area of research.

Premature aging disorders: A clinical and genetic compendium

Progeroid disorders make up a heterogeneous group of very rare hereditary diseases characterized by clinical signs that often mimic physiological aging in a premature manner. Apart from Hutchinson-Gilford progeria syndrome, one of the best-investigated progeroid disorders, a wide spectrum of other premature aging phenotypes exist, which differ significantly in their clinical presentation and molecular pathogenesis. Next-generation sequencing (NGS)-based approaches have made it feasible to determine the molecular diagnosis in the early stages of a disease. Nevertheless, a broad clinical knowledge on these disorders and their associated symptoms is still fundamental for a comprehensive patient management and for the interpretation of variants of unknown significance from NGS data sets. This review provides a detailed overview on characteristic clinical features and underlying molecular genetics of well-known as well as only recently identified premature aging disorders and also highlights novel findings towards future therapeutic options.

The Putative Type III Secreted Chlamydia abortus Virulence-Associated Protein CAB063 Targets Lamin and Induces Apoptosis

Since intracellular survival of all chlamydiae depends on the manipulation of the host cell through type III secreted effector proteins, their characterization is crucial for the understanding of chlamydial pathogenesis. We functionally characterized the putative type III secreted Chlamydia abortus protein CAB063, describe its intracellular localization and identified pro- and eukaryotic binding partners. Based on an experimental infection model and plasmid transfections, we investigated the subcellular localization of CAB063 by immunofluorescence microscopy, immunoelectron microscopy, and Western blot analysis. Pro- and eukaryotic targets were identified by co-immunofluorescence, co-immunoprecipitation, and mass spectrometry. Transmission electron microscopy and flow cytometry were used for morphological and functional investigations on host cell apoptosis. CAB063 localized in the nuclear membrane of the host cell nucleus and we identified the chaperone HSP70 and lamin A/C as pro- and eukaryotic targets, respectively. CAB063-dependent morphological alterations of the host cell nucleus correlated with increased apoptosis rates of infected and CAB063-transfected cells. We provide evidence that CAB063 is a chaperone-folded type III secreted C. abortus virulence factor that targets lamin thereby altering the host cell nuclear membrane structure. This process may be responsible for an increased apoptosis rate at the end of the chlamydial developmental cycle, at which CAB063 is physiologically expressed.

Calcitriol Prevents RAD51 Loss and cGAS-STING-IFN Response Triggered by Progerin

Hutchinson Gilford progeria syndrome (HGPS) is a devastating accelerated aging disease caused by LMNA gene mutation. The truncated lamin A protein produced "progerin" has a dominant toxic effect in cells, causing disruption of nuclear architecture and chromatin structure, genomic instability, gene expression changes, oxidative stress, and premature senescence. It was previously shown that progerin-induced genomic instability involves replication stress (RS), characterized by replication fork stalling and nuclease-mediated degradation of stalled forks. RS is accompanied by activation of cGAS/STING cytosolic DNA sensing pathway and STAT1-regulated interferon (IFN)-like response. It is also found that calcitriol, the active hormonal form of vitamin D, rescues RS and represses the cGAS/STING/IFN cascade. Here, the mechanisms underlying RS in progerin-expressing cells and the rescue by calcitriol are explored. It is found that progerin elicits a marked downregulation of RAD51, concomitant with increased levels of phosphorylated-RPA, a marker of RS. Interestingly, calcitriol prevents RS and activation of the cGAS/STING/IFN response in part through maintenance of RAD51 levels in progerin-expressing cells. Thus, loss of RAD51 is one of the consequences of progerin expression that can contribute to RS and activation of the IFN response. Stabilization of RAD51 helps explain the beneficial effects of calcitriol in these processes.

Metabolic Dysfunction in Hutchinson-Gilford Progeria Syndrome

Hutchinson–Gilford Progeria Syndrome (HGPS) is a segmental premature aging disease causing patient death by early teenage years from cardiovascular dysfunction. Although HGPS does not totally recapitulate normal aging, it does harbor many similarities to the normal aging process, with patients also developing cardiovascular disease, alopecia, bone and joint abnormalities, and adipose changes. It is unsurprising, then, that as physicians and scientists have searched for treatments for HGPS, they have targeted many pathways known to be involved in normal aging, including inflammation, DNA damage, epigenetic changes, and stem cell exhaustion. Although less studied at a mechanistic level, severe metabolic problems are observed in HGPS patients. Interestingly, new research in animal models of HGPS has demonstrated impressive lifespan improvements secondary to metabolic interventions. As such, further understanding metabolism, its contribution to HGPS, and its therapeutic potential has far-reaching ramifications for this disease still lacking a robust treatment strategy.