Review of How Genetic Research on Segmental Progeroid Syndromes Has Documented Genomic Instability as a Hallmark of Aging But Let Us Now Pursue Antigeroid Syndromes!

The purpose of this early contribution to the new Fellows Forum of this pioneering journal for what is now called Geroscience is to provide an example of how the author’s interest in using the emerging tools of human genetics has led to strong support for one of the hallmarks of aging—Genomic Instability. We shall also briefly review our emerging interests in the genetic analysis of what we have called Antigeroid Syndromes. While there has been significant progress in that direction via genetic studies of centenarians, the search for genetic pathways that make individuals unusually resistant or resilient to the ravages of specific geriatric disorders has been comparatively neglected. We refer to these disorders as Unimodal Antigeroid Syndromes. It is our hope that our young colleagues will consider research efforts in that direction.

METTL3 counteracts premature aging via m6A-dependent stabilization of MIS12 mRNA

N6-Methyladenosine (m6A) messenger RNA methylation is a well-known epitranscriptional regulatory mechanism affecting central biological processes, but its function in human cellular senescence remains uninvestigated. Here, we found that levels of both m6A RNA methylation and the methyltransferase METTL3 were reduced in prematurely senescent human mesenchymal stem cell (hMSC) models of progeroid syndromes. Transcriptional profiling of m6A modifications further identified MIS12, for which m6A modifications were reduced in both prematurely senescent hMSCs and METTL3-deficient hMSCs. Knockout of METTL3 accelerated hMSC senescence whereas overexpression of METTL3 rescued the senescent phenotypes. Mechanistically, loss of m6A modifications accelerated the turnover and decreased the expression of MIS12 mRNA while knockout of MIS12 accelerated cellular senescence. Furthermore, m6A reader IGF2BP2 was identified as a key player in recognizing and stabilizing m6A-modified MIS12 mRNA. Taken together, we discovered that METTL3 alleviates hMSC senescence through m6A modification-dependent stabilization of the MIS12 transcript, representing a novel epitranscriptional mechanism in premature stem cell senescence.

A Novel Syndrome With Short Stature, Mandibular Hypoplasia, and Osteoporosis May Be Associated With a PRRT3 Variant

Context Despite considerable progress in elucidating the molecular basis of various progeroid syndromes, some rare patients remain unexplained. Objective To elucidate molecular genetic basis of a novel autosomal recessive progeroid syndrome. Participants A 24-year-old male and his 18-year-old sister with short stature, mandibular hypoplasia, pointed nose, shrill voice, severe osteoporosis, and short eyebrows and their unaffected siblings and parents belonging to a consanguineous Arab family. Results Using exome and Sanger sequencing, we report a novel homozygous p.Glu394Lys disease-causing variant in proline-rich transmembrane protein 3 (PRRT3). PRRT3 belongs to the family of proline-rich proteins containing several repeats of a short proline-rich sequence, but its function remains to be determined. Preliminary observations showing colocalization of Prrt3 and synaptophysin support its role in vesicle exocytosis. Consistent with the highest messenger ribonucleic acid expression of PRRT3 in the pituitary, both the patients had mild growth hormone deficiency but had near normal reproductive development. Conclusions We conclude that the homozygous p.Glu394Lys variant in PRRT3 may be associated with a novel autosomal recessive, progeroid syndrome with short stature, mandibular hypoplasia, osteoporosis, short eyebrows, and mild growth hormone (GH) deficiency. Our findings extend the spectrum of progeroid syndromes and elucidate important functions of PRRT3 in human biology, including secretion of GH from the pituitary.

Progeroid Syndrome with Mitral Regurgitation: A Rare Case Report

Progeroid syndromes (PS) involve the disorder of early aging. Although survival of progeria syndrome patients is nearly 15 years as per literature, the adult onset progeroid starts manifesting in the third decade. Here, we are presenting a rare case of progeroid at the age of 45 years with mitral regurgitation (MR). The patient has alopecia, dry skin, frontal bossing, up staring eyes with bilateral corneal opacities, prominent nose with parrot beak appearance, thin upper lip, large, low-set ears, periorbital hyperpigmentation, micrognathia, retrognathia, and hyperpigmentation over lower abdomen/both feet and hands. Facial and skeletal manifestation are the major clinical features of the PS; along with the characteristics mentioned above, the patient also had severe eccentric MR. This patient has PS with mitral valve prolapse and severe MR. Most of the features of progeria exist in this patient, which manifested at a younger age. However, the progression of the external features and survival up to 45 years favors PS instead of progeria. Therefore, genetic analysis is mandatory to confirm. We are reporting this case due to the rarity of onset of symptoms within a younger age group; however, the progression of the disease was very slow, which may be a another variant of progeria/PS.

Hereditary syndromes with signs of premature aging

Aging is a multi-factor biological process that inevitably affects everyone. Degenerative processes, starting at the cellular and molecular levels, gradually influence the change in the functional capabilities of all organs and systems. Progeroid syndromes (from Greek. progērōs prematurely old), or premature aging syndromes, represent clinically and genetically heterogeneous group of rare hereditary diseases characterized by accelerated aging of the body. Progeria and segmental progeroid syndromes include more than a dozen diseases, but the most clear signs of premature aging are evident in Hutchinson-Guilford Progeria Syndrome and Werner Syndrome. This review summarizes the latest scientific data reflecting the etiology and clinical picture of progeria and segmental progeroid syndromes in humans. Molecular mechanisms of aging are considered, using the example of progeroid syndromes. Modern possibilities and potential ways of influencing the mechanisms of the development of age-related changes are discussed. Further study of genetic causes, as well as the development of treatment for progeria and segmental progeroid syndromes, may be a promising direction for correcting age-related changes and increasing life expectancy.

Looking at New Unexpected Disease Targets in LMNA-Linked Lipodystrophies in the Light of Complex Cardiovascular Phenotypes: Implications for Clinical Practice

Variants in LMNA, encoding A-type lamins, are responsible for laminopathies including muscular dystrophies, lipodystrophies, and progeroid syndromes. Cardiovascular laminopathic involvement is classically described as cardiomyopathy in striated muscle laminopathies, and arterial wall dysfunction and/or valvulopathy in lipodystrophic and/or progeroid laminopathies. We report unexpected cardiovascular phenotypes in patients with LMNA-associated lipodystrophies, illustrating the complex multitissular pathophysiology of the disease and the need for specific cardiovascular investigations in affected patients. A 33-year-old woman was diagnosed with generalized lipodystrophy and atypical progeroid syndrome due to the newly identified heterozygous LMNA p.(Asp136Val) variant. Her complex cardiovascular phenotype was associated with atherosclerosis, aortic valvular disease and left ventricular hypertrophy with rhythm and conduction defects. A 29-year-old woman presented with a partial lipodystrophy syndrome and a severe coronary atherosclerosis which required a triple coronary artery bypass grafting. She carried the novel heterozygous p.(Arg60Pro) LMNA variant inherited from her mother, affected with partial lipodystrophy and dilated cardiomyopathy. Different lipodystrophy-associated LMNA pathogenic variants could target cardiac vasculature and/or muscle, leading to complex overlapping phenotypes. Unifying pathophysiological hypotheses should be explored in several cell models including adipocytes, cardiomyocytes and vascular cells. Patients with LMNA-associated lipodystrophy should be systematically investigated with 24-h ECG monitoring, echocardiography and non-invasive coronary function testing.