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Keywords:

  • nesprin;
  • SYNE;
  • MYNE;
  • NUANCE;
  • enaptin;
  • emerin;
  • lamin A/C;
  • nuclear lamina;
  • nuclear envelope;
  • nuclear membrane;
  • myogenesis;
  • muscle development;
  • NT-2;
  • Golgi;
  • nuclear positioning;
  • monoclonal antibody;
  • epitope mapping;
  • phage display

Abstract

Nesprins are a family of nuclear transmembrane proteins anchored via Sun proteins to the nuclear membrane. Analysis of nesprins during human muscle development revealed an increase in nesprin-1-giant during early myogenesis in vitro. During the transition from immature to mature muscle fibres in vivo, nesprin-2 partly replaced nesprin-1 at the nuclear envelope and short nesprin isoforms became dominant. Sun1 and Sun2 proteins remained unchanged during this fibre maturation. In emerin-negative skin fibroblasts, nesprin-2-giant was relocated from the nuclear envelope to the cytoplasm, not to the endoplasmic reticulum, while nesprin-1 remained at the nuclear envelope. In emerin-negative keratinocytes lacking nesprin-1, nesprin-2 remained at the nuclear envelope. HeLa cell nuclear envelopes lacked nesprin-1, which was the dominant form in myoblasts, while a novel 130-kD nesprin-2 isoform dominated Ntera-2 cells. The results suggest the possibility of isoform-specific and tissue-specific roles for nesprins in nuclear positioning. Developmental Dynamics 239:998–1009, 2010. © 2010 Wiley-Liss, Inc.