title: Direct synthesis of lamin A, bypassing prelamin a processing, causes misshapen nuclei in fibroblasts but no detectable pathology in mice.
abstract: Lamin A, a key component of the nuclear lamina, is generated from prelamin A by four post-translational processing steps: farnesylation, endoproteolytic release of the last three amino acids of the protein, methylation of the C-terminal farnesylcysteine, and finally, endoproteolytic release of the last 15 amino acids of the protein (including the farnesylcysteine methyl ester). The last cleavage step, mediated by ZMPSTE24, releases mature lamin A. This processing scheme has been conserved through vertebrate evolution and is widely assumed to be crucial for targeting lamin A to the nuclear envelope. However, its physiologic importance has never been tested. To address this issue, we created mice with a "mature lamin A-only" allele (Lmna(LAO)), which contains a stop codon immediately after the last codon of mature lamin A. Thus, Lmna(LAO/LAO) mice synthesize mature lamin A directly, bypassing prelamin A synthesis and processing. The levels of mature lamin A in Lmna(LAO/LAO) mice were indistinguishable from those in "prelamin A-only" mice (Lmna(PLAO/PLAO)), where all of the lamin A is produced from prelamin A. Lmna(LAO/LAO) exhibited normal body weights and had no detectable disease phenotypes. A higher frequency of nuclear blebs was observed in Lmna(LAO/LAO) embryonic fibroblasts; however, the mature lamin A in the tissues of Lmna(LAO/LAO) mice was positioned normally at the nuclear rim. We conclude that prelamin A processing is dispensable in mice and that direct synthesis of mature lamin A has little if any effect on the targeting of lamin A to the nuclear rim in mouse tissues.
authors.affiliation: Department of Medicine, University of California, Los Angeles, CA 90095, USA. coffinie@ucla.edu
authors.forename: Catherine
authors.initials: C
authors.lastname: Coffinier
authors.forename: Hea-Jin
authors.initials: HJ
authors.lastname: Jung
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Li
authors.forename: Chika
authors.initials: C
authors.lastname: Nobumori
authors.forename: Ui Jeong
authors.initials: UJ
authors.lastname: Yun
authors.forename: Emily A
authors.initials: EA
authors.lastname: Farber
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Davies
authors.forename: Michael M
authors.initials: MM
authors.lastname: Weinstein
authors.forename: Shao H
authors.initials: SH
authors.lastname: Yang
authors.forename: Jan
authors.initials: J
authors.lastname: Lammerding
authors.forename: Javad N
authors.initials: JN
authors.lastname: Farahani
authors.forename: Laurent A
authors.initials: LA
authors.lastname: Bentolila
authors.forename: Loren G
authors.initials: LG
authors.lastname: Fong
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Young
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000473:pathology*; D017124:Conserved Sequence; D003433:Crosses, Genetic; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000473:pathology*; D007438:Introns; D034904:Lamin Type A / Q000096:biosynthesis* / Q000235:genetics; D008745:Methylation; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D046188:Protein Modification, Translational; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D014714:Vertebrates
chemical_list: D034904:Lamin Type A; D009687:Nuclear Proteins; D011498:Protein Precursors; C090764:prelamin A