Lamin A and telomere maintenance in aging: Two to Tango.

Lamin proteins which constitute the nuclear lamina in almost all higher eukaryotes, are mainly of two types A & B encoded by LMNA and LMNB1/B2 genes respectively. While lamin A remains the principal product of LMNA gene, variants like lamin C, C2 and A∆10 are also formed as alternate splice products. Role of lamin A in aging has been highlighted in recent times due to its association with progeroid or premature aging syndromes which is classified as a type of laminopathy. Progeria caused by accelerated accumulation of lamin A Δ50 or progerin occurs due to a mutation in this LMNA gene leading to defects in post translational modification of lamin A. One of the most common and severe symptoms of progeroid laminopathy is accelerated cellular senescence or aging along with bone resorption, muscle weakness, lipodystrophy and cardiovascular disorders. On the other hand, progerin accumulation and telomere dysfunction merge as common traits in the process of chronological aging. Two major hallmarks of physiological aging in humans include loss of genomic integrity and telomere attrition which can result from defective laminar organization leading to deformed nuclear architecture and culminates into replicative senescence. This also adversely affects epigenetic landscape, mitochondrial dysfunction and several signalling pathways like DNA repair, mTOR, MAPK, TGFβ. In this review, we discuss the telomere-lamina interplay in the context of physiological aging and progeria.