Lamins A and C appear during retinoic acid-induced differentiation of mouse embryonal carcinoma cells.

Abstract

Abstract. The lamin complement of nuclear matrix isolated from F9 embryonal carcinoma cells was studied during retinoic acid-induced differentiation in culture. Differentiation of the original cells into parietal endoderm-like cells was accompanied by the gradual appearance of lamins A and C while lamin B was present throughout all stages. Lamins were identified by their molecular masses, isoelectric points, recognition by a monoclonal antibody and a polyclonal antiserum, and by peptide mapping. The increase in the amounts of lamins A and C found in the matrix was due to de novo synthesis as no extranuclear pools of these lamins were detected in the undifferentiated cells. These results provide biochemical evidence that, as in amphibian embryogenesis, there are variations in nuclear lamina composition during mammalian development. THe peripheral lamina is a structural component of the nuclear envelope that interacts with peripheral chromatin and with the nucleoplasmic face of the inner nuclear membrane (for recent reviews see references 9, 10, 15). During mitosis, the lamina plays an important role in the process of nuclear envelope breakdown and reformation which is controlled by a phosphorylation-dephosphorylation cycle of its constituent proteins called lamins (9, 10). During interphase, the lamins associate to form the insoluble lamina in a manner similar to the interaction of intermediate filament (IF) 1 proteins: eDNA sequencing studies on lamins A and C (7, 25) and epitope mapping studies using mAbs on lamin B (18; Raymond, Y., and G. Gagnon, manuscript submitted for publication) have shown that lamins share important structural homologies with IF proteins.The parallel between lamins and IF proteins can be further extended to include differential expression during embryogenesis and differentiation. The lamins appear to constitute a family of proteins with major and minor species (19), the expression of which varies among cell types (reviewed in 15). In amphibians, the type and number of lamins vary during embryogenesis, gametogenesis, and in some adult somatic cells (15). In early Xenopus embryos, regulation of lamin expression seems to be at the level of translation (32). In mammalian cells, immunofluorescence studies have shown variations in the number and distribution of lamins during gametogenesis (24) and embryogenesis (28), but these results have not been confirmed by biochemical studies due to the lack of sufficient material. In all cases, changes in the composition of the lamina were correlated with changes in nuclear morphology.The requirements for more than one lamin type and the (5) while lamin B may provide the anchor to the inner nuclear membrane during both interphase and mitosis (10, 17). These rules are, however, tentative as preliminary results indicate the possibility of membrane interaction for lamins A and C (our unpublished results) and chromatin interaction for lamin B (4). Depletion of all three lamins by microinjection of an antibody prevented normal chromatin dispersion and nucle...

Expression of individual lamins in basal cell carcinomas of the skin

“…The lamin A gene has been mapped to 1q12.1-q23, a region of chromosome 1 that is commonly rearranged in tumours (Kamat et al, 1993). Gene deletion (Kamat et al, 1993) as well as transcriptional and post-transcriptional mechanisms (Lebel et al, 1987;Machiels et al, 1996) have all been implicated in the loss of lamin A or C expression. Therefore an important question is whether changes in lamin expression reflect de-differentiation within the tumour or is a requisite of tumour progression.…”

“…Pluripotent cells can be induced to express A-type lamins in culture by treatment that induces differentiation (Lebel et al, 1987) and in some instances the ectopic expression of lamin A can promote differentiation (Lourim and Lin, 1992). The correlation between A-type lamin expression and cell differentiation has led some workers to speculate that A-type lamins may facilitate differential gene expression, by anchoring chromatin at the nuclear envelope or by sequestering inhibitors (Nigg, 1989).…”

Dynamic and unique nucleolar microenvironment revealed by fluorescence correlation spectroscopy

“…GFP oligomers larger than GFP 5 might be unstable and degradable in expressed cells (19). In contrast, LA, known as a large and filamentous molecule, has near neutral isoelectric points (pIs) and is stable (31)(32)(33). Recently, it was demonstrated that plastic property and structure of the nucleolus were maintained after the depletion of LA, suggesting it may be physiologically nonfunctional in the nucleolus (34).…”

In vitro posttranslational modification of lamin B cloned from a human T-cell line.

“…Several studies have shown that there is differential expression of nuclear lamins A and C in lymphocyte and other cell lines, but that lamin B is always present (20,35,48,49,62). Since MOLT-4 cells are a T lymphocyte-derived cell line, we reasoned that they may contain only lamin B. Immunofluorescence studies with whole-cell preparations (not shown) and Western blot analysis with whole-cell extracts showed the absence of lamins A and C in MOLT-4 cells (Fig.…”