Disease relevance of Lam

• Null mutants of Drosophila B-type lamin Dm(0) show aberrant tissue differentiation rather than obvious nuclear shape distortion or specific defects during cell proliferation [1].
• Assembly of Drosophila lamin Dm0 and C mutant proteins studied with the baculovirus system [2].
• Second, in microinjection experiments we investigated whether fluorescently labeled lamins of Xenopus laevis (lamins A and LI) and Drosophila melanogaster (lamin Dmo) were able to associate in vivo with the Amoeba proteus honeycomb structure [3].
• Misrouted LN(v) projections and approximately 14% arrhythmia of mud flies were uncorrelated and attributed to pleiotropy rather than to specific effects of MB lesions [4].
• The insect cell lines Dm-1 (Drosophila melanogaster), AS-2 (Aceratagallia sanguinolenta) and AC-20 (Agallia constricta) were infected with spiroplasmas, mycoplasmas and Acholeplasma laidlawii [5].

High impact information on Lam

• Consistently, proximity of genomic regions to the nuclear lamina is partly conserved between cell types, and induction of gene expression or active histone marks reduces Lam binding [6].
• Lam target genes cluster in the genome, and these clusters are coordinately expressed during development [6].
• Antibodies directed against nuclear envelope lamin proteins have been used in conjunction with three-dimensional light and electron microscope methodologies to determine the spatial organization of lamins in diploid interphase nuclei and to relate this organization to the positions of chromatin in the nuclear periphery [7].
• Using Drosophila early embryos, Drosophila Kc cells, and human HeLa cells, it is qualitatively and quantitatively observed that lamins are organized as a highly discontinuous, apparently fibrillar network that leaves large voids in the nuclear periphery containing little or no lamin [7].
• The sequence organization and positions of the tRNA genes in a tRNA gene cluster at chromosomal region 42A of the D. melanogaster (Dm) genome have been studied by recombinant DNA methods [8].

Biological context of Lam

• These transgenic animals display a nuclear lamin aggregation phenotype remarkably similar to that observed when human mutant A-type lamins are expressed in mammalian cells [9].
• Substituting either of the threonine residues in the TRAT sequence with negatively charged residues decreases the binding of lamin Dm(0) to chromatin, indicating that this binding could be regulated by phosphorylation [10].
• Taken together, these results suggest that specific residues in lamin Dm(0) and histone H2A mediate the attachment of the nuclear lamina to chromosomes in vivo, which could have implications on the understanding of laminopathic diseases [10].
• Thus, our results suggest that the JIL-1 kinase is required to maintain nuclear morphology and integrity of nurse cells during oogenesis and that this function may be linked to molecular interactions with lamin Dm0 [11].
• Two isoforms of a single nuclear lamin, distinguishable on one-dimensional SDS-polyacrylamide gels, have previously been identified in Drosophila nuclei during interphase [12].

Anatomical context of Lam

• In agreement with this interaction, lamin and otefin can be coimmunoprecipitated from the vesicle fraction of Drosophila embryos and colocalize in nuclear envelopes of Drosophila larval salivary gland nuclei [13].
• The functions of Klarsicht and nuclear lamin in developmentally regulated nuclear migrations of photoreceptor cells in the Drosophila eye [14].
• We propose that nuclear migration requires linkage of the MTOC to the nucleus through an interaction between microtubules, Klarsicht, and lamin [14].
• The antibodies decorate the nuclear envelope in Drosophila Kc tissue culture cells as well as in salivary and accessory glands demonstrating that pG-IF encodes a nuclear lamin (lamin C) [15].
• Interconversion of Drosophila nuclear lamin isoforms during oogenesis, early embryogenesis, and upon entry of cultured cells into mitosis [12].

Associations of Lam with chemical compounds

• A lamin A mutant lacking this domain could be efficiently extracted from Sf9 cells with physiological buffers containing Triton X-100, demonstrating the importance of this domain for lamin assembly in vivo [16].
• Peptide competition experiments demonstrated directly that phosphorylation of serine 25 impedes lamin binding by ADL84 [17].
• Surprisingly, metaphase scaffolds isolated from Drosophila Kc cells contain both the lamin protein and a pore-complex protein, glycoprotein (gp) 188 [18].
• We studied this binding using Drosophila lamin Dm0-derived fragments containing either the NH2-terminal or COOH-terminal binding site with a combination of co-immunoprecipitation, yeast two-hybrid, analytical ultracentrifugation, and electron microscopic assays [19].
• Intron positions are conserved in other lamin genes from frogs, mice, and humans but different in lamin genes from Drosophila melanogaster and Caenorhabditis elegans [20].

Physical interactions of Lam

• The JIL-1 kinase interacts with lamin Dm0 and regulates nuclear lamina morphology of Drosophila nurse cells [11].
• Here, we show that C-terminal lamin-interacting region of YA is sufficient to target the heterologous soluble protein GFP-NLS to the nuclear periphery in Drosophila tissue culture cells [21].
• Fourth, the N-terminal domain of dLBR is sufficient for in vitro binding to sperm chromatin and lamin Dm0 [22].
• Interactions between coiled-coil proteins: Drosophila lamin Dm0 binds to the bicaudal-D protein [23].
• We show that the polymerized alpha-helical rod domain of lamin Dm0 provides by itself the specific binding to the ftz M/SAR [24].

Co-localisations of Lam

• With the exception of sperm cells, otefin colocalizes with lamin Dm0 derivatives in situ and presumably in vivo and is present in all somatic cells examined during the different stages of Drosophila development [25].
• SU(VAR)2-10 proteins colocalize with nuclear lamin in interphase, and little to no SU(VAR)2-10 is found on condensed mitotic chromosomes [26].

Regulatory relationships of Lam

• Kc cells contain products of both lamin genes, the lamin Dm0 gene encoding constitutive polypeptides expressed in almost all cell types and the developmentally regulated lamin C gene [27].
• Third, we mutated tailless lamin using two point mutations known to inhibit head-to-tail association of full-length lamin [28].

Other interactions of Lam

• The Klarsicht/lamin interaction provides a framework for understanding the mechanistic basis of human laminopathies [14].
• Expression of Drosophila lamin C is similar to that of vertebrate lamin A (plus C), which loses its CaaX motif during incorporation into the lamina [15].
• They also suggest that the need for both otefin and lamin in mediating association of vesicles with chromatin might reflect the function of a protein complex that includes these two proteins [13].
• The two-hybrid system was further used to map the domains of interaction among lamin, otefin, and YA [13].
• In contrast, when lamin DmO was reduced by RNAi the distribution of Bocksbeutel and otefin in the nuclear envelope of Kc167 cells was significantly altered [29].

Analytical, diagnostic and therapeutic context of Lam

• Southern blot analyses of genomic DNA are consistent with the notion that a single or only a few highly similar genes encoding Drosophila nuclear lamin Dm0 exist in the genome [30].
• In situ hybridization of lamin cDNA clones to Drosophila polytene chromosomes shows only a single locus of hybridization at or near position 25F on the left arm of chromosome 2 [30].
• Third, dLBR can be shown by co-immunoprecipitations and in vitro binding assays to bind to the Drosophila B-type lamin Dm0 [22].
• Immunoelectron microscopy of interphase nuclei indicates that otefin, like lamin, is not a component of nuclear pore complexes [31].
• Thirdly, immunoprecipitations with dMAN1-specific antibodies revealed that this Drosophila LEM-domain protein is contained in protein complexes together with lamins Dm0 and C. It has been previously shown that human MAN1 binds to A- and B-type lamins in vitro [32].

References