Prelamin A and lamin A appear to be dispensable in the nuclear lamina

J Clin Invest. 2006 Mar;116(3):743-52. doi: 10.1172/JCI27125.

Abstract

Lamin A and lamin C, both products of Lmna, are key components of the nuclear lamina. In the mouse, a deficiency in both lamin A and lamin C leads to slow growth, muscle weakness, and death by 6 weeks of age. Fibroblasts deficient in lamins A and C contain misshapen and structurally weakened nuclei, and emerin is mislocalized away from the nuclear envelope. The physiologic rationale for the existence of the 2 different Lmna products lamin A and lamin C is unclear, although several reports have suggested that lamin A may have particularly important functions, for example in the targeting of emerin and lamin C to the nuclear envelope. Here we report the development of lamin C-only mice (Lmna(LCO/LCO)), which produce lamin C but no lamin A or prelamin A (the precursor to lamin A). Lmna(LCO/LCO) mice were entirely healthy, and Lmna(LCO/LCO) cells displayed normal emerin targeting and exhibited only very minimal alterations in nuclear shape and nuclear deformability. Thus, at least in the mouse, prelamin A and lamin A appear to be dispensable. Nevertheless, an accumulation of farnesyl-prelamin A (as occurs with a deficiency in the prelamin A processing enzyme Zmpste24) caused dramatically misshapen nuclei and progeria-like disease phenotypes. The apparent dispensability of prelamin A suggested that lamin A-related progeroid syndromes might be treated with impunity by reducing prelamin A synthesis. Remarkably, the presence of a single Lmna(LCO) allele eliminated the nuclear shape abnormalities and progeria-like disease phenotypes in Zmpste24-/- mice. Moreover, treating Zmpste24-/- cells with a prelamin A-specific antisense oligonucleotide reduced prelamin A levels and significantly reduced the frequency of misshapen nuclei. These studies suggest a new therapeutic strategy for treating progeria and other lamin A diseases.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Transformed
  • Cells, Cultured
  • Female
  • Fibroblasts / metabolism
  • Lamin Type A / deficiency
  • Lamin Type A / genetics
  • Lamin Type A / metabolism
  • Lamin Type A / physiology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • Muscle Weakness / genetics
  • Nuclear Lamina / physiology*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / physiology*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Precursors / genetics
  • Protein Precursors / physiology*
  • RNA, Messenger / metabolism
  • Skull / abnormalities
  • Spine / abnormalities

Substances

  • Lamin Type A
  • Nuclear Proteins
  • Protein Isoforms
  • Protein Precursors
  • RNA, Messenger
  • lamin C
  • prelamin A