Expression of wild-type and nuclear localization-deficient human lamin A in chick myogenic cells.
Previous analysis of chick embryonic muscle (CEM) differentiation in vivo and in ovo demonstrated that lamin A accumulation to steady-state levels preceded the accumulation of muscle-specific proteins. These observations have suggested the appearance of A-type lamins may be important for differentiation. To test this hypothesis, we have temporally and quantitatively altered the expression of A-type lamins in CEM cells by transient transfection of wild-type (wt; pHLA) or nuclear localization-deficient (NLd; pHLA-del) human lamin A expression plasmids. Transfected CEM cells synthesized the wt and NLd human lamin As to high levels, both of which were resistant to high-salt extraction. The wt human lamin A localized to the nucleus, whereas the NLd protein showed cytoplasmic staining patterns, as well as time-dependent nuclear localization. The presence of endogenous chicken lamins A and B2 in NLd human lamin A cytoplasmic structures suggested the interspecies lamin copolymerization. Thus, this approach may provide a possible method for analysis of lamin-lamin or lamin-lamina component interactions in vivo. With regard to muscle differentiation, CEM cells transfected with either pHLA or pHLA-del demonstrated moderate and transient increased levels of the muscle-specific myosin heavy chain and creatine kinase activity. These increases appeared temporally and quantitatively to reflect the transient accumulation of the human lamin As. In contrast, beta-tubulin and skeletal tropomyosin protein accumulations appeared unaffected. On the basis of these results, we suggest that nuclear lamina content and structure may play a limited, permissive and indirect role in the temporally regulated expression of the myogenic phenotype.
Lourim
D
D
Department of Biology, University of Iowa, Iowa City 52242.
Lin
J J
JJ
D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured / Q000378:metabolism; D002642:Chick Embryo; D003402:Creatine Kinase / Q000032:analysis; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D034904:Lamin Type A; D034882:Lamins; D009132:Muscles / Q000196:embryology*; D009687:Nuclear Proteins / Q000032:analysis / Q000096:biosynthesis*; D014162:Transfection
D034904:Lamin Type A; D034882:Lamins; D009687:Nuclear Proteins; D003402:Creatine Kinase