Lamin A/C is a component of the nuclear lamina that contributes to nuclear integrity, chromatin organisation, gene transcription and DNA replication. Mutation of the LMNA gene, encoding lamin A/C, causes a number of diseases affecting different tissues, but the mechanism(s) by which this widely expressed protein causes tissue-specific disease remains unclear. Hutchinson-Gilford progeria syndrome (HGPS) is an early-onset premature aging disorder. The most common LMNA mutation (G608G) prevents complete posttranslational processing of lamin A, resulting in aberrant retention of a farnesyl group. In this study, a cohort of children with progeroid phenotypes were screened for genetic defects. The G608G mutation was identified in one patient with a classical phenotype. A second patient with mild progeria carried a rare T623S mutation, which also results in aberrant farnesylation of lamin A. In contrast, a severe progeroid phenotype resulted from homozygous mutation of ZMPSTE24, the key enzyme in lamin A processing. Studies of skin fibroblasts showed a correlation between farnesylated lamin A level and disease severity. FRAP studies revealed that retention of the farnsesyl group causes a 50% decrease in mobility of lamin A, irrespective of the exact mutation. Interestingly, one non-farnesylated mutant also had a 50% reduction in mobility, whilst other non-farnesylated mutants had normal mobility. The results of these studies indicate that incomplete processing of lamin A is an important contributor to severity of progeroid disorders but, in agreement with other reports, is not the only disease mechanism involved. Familial partial lipodystrophy (FPLD) is a fat wasting disorder also resulting from LMNA mutations. Preliminary analysis of the adipogenic potential of mesenchymal stem cells isolated from FPLD patients do not produce detectable levels of adipogenesis. Preliminary immunofluorescence and binding studies in FPLD and progeria tend to support existing evidence that mislocalisation of the adipogenic factor SREBP1 may underlie the lipodystrophy phenotype.

Universiẗat, Diss., 2006--Würzburg. / Erscheinungsjahr an der Haupttitelstelle: 2005.

Mammalian cells are known to respond to both extra- and intra- cellular forces as well as the physical properties of the surrounding tissue. There is increasing evidence to support the fundamental role of force, applied to or generated within cells, in maintaining proper tissue function. The mechanical integration from the exterior of a cell to the interior of the nucleus is crucial for cellular sensing of, and response to, the physical environment. Further, misregulation of this mechanosensitive ability can lead to the development or propagation of many diseases such as cancers, cardiovascular diseases, and tissue fibrosis. In this thesis, we investigate the role of various proteins in regulating the mechanical properties of mammalian cells. We also develop techniques to examine the propagation of forces through cells and multicell systems with the aim of elucidating critical biophysical factors involved in regulating cell function. The idea that the genome can be regulated through changes in forces applied to cells or changes in the propagation of forces through a cell, (i.e. mechanotransduction) is becoming widely accepted. The complex interplay between biochemical and biophysical mechanisms that ultimately control mechanotransduction are beginning to be uncovered; however, a true understanding of this remarkable cellular process has not yet been achieved. By investigating multiple factors which impact mechanosensitivity (such as protein expression, cell-cell and cell-environment connections, cell generated contractions, and physical connections through the cellular interior), we aim to further the understanding of potential pathways of mechanotransduction. Through novel studies and technological advances, the field of cellular biomechanics will continue to grow as we hope to uncover the physical mechanisms that regulate cell function or lead to disease.

Lamine bilden zusammen mit laminassoziierten Proteinen die nukleäre Lamina. Diese ist notwendig für die mechanische Stabilität von Zellen, die Organisation des Chromatins, der Genexpression, dem Fortgang des Zellzyklus und der Zellmigration. Die vielfältigen Funktionen der Lamine werden durch die Pathogenese von Laminopathien belegt. Zu diesen Erkrankungen, welche ihre Ursache in Mutationen innerhalb der laminkodierenden Gene, oder der Gene laminassoziierter bzw. laminprozessierender Proteine haben, zählen unter anderem das „Hutchinson-Gilford Progerie Syndrom“, die „Emery-Dreifuss“ Muskeldystrophie und die dilatierte Kardiomyopathie. Trotz der fundamentalen Bedeutung der Lamine, wurden diese bisher nur in Metazoen und nicht in einzelligen Organismen detektiert. Der amöbide Organismus Dictyostelium discoideum ist ein haploider Eukaryot, der häufig als Modellorganismus in den verschiedensten Bereichen der Zellbiologie eingesetzt wird. Mit der Entdeckung von NE81, einem Protein das mit der inneren Kernhülle von Dictyostelium discoideum assoziiert ist, wurde erstmals ein Protein identifiziert, dass man aufgrund seiner Eigenschaften als laminähnliches Protein in einem niederen Eukaryoten bezeichnen kann. Diese Merkmale umfassen die Existenz lamintypischer Sequenzen, wie die CDK1-Phosphorylierungsstelle, direkt gefolgt von einer zentralen „Rod“-Domäne, sowie eine typische NLS und die hoch konservierte CaaX-Box. Für die Etablierung des NE81 als „primitives“ Lamin, wurden im Rahmen dieser Arbeit verschiedene Experimente durchgeführt, die strukturelle und funktionelle Gemeinsamkeiten zu den Laminen in anderen Organismen aufzeigen konnten. Die Herstellung eines polyklonalen Antikörpers ermöglichte die Verifizierung der subzellulären Lokalisation des NE81 durch Elektronenmikroskopie und gab Einblicke in das Verhalten des endogenen Proteins innerhalb des Zellzyklus. Mit der Generierung von NE81-Nullmutanten konnte demonstriert werden, dass NE81 eine wichtige Rolle bei der nukleären Integrität und der Chromatinorganisation von Zellen spielt. Des Weiteren führte die Expression von zwei CaaX-Box deletierten NE81 - Varianten dazu, den Einfluss des Proteins auf die mechanische Stabilität der Zellen nachweisen zu können. Auch die Bedeutung der hochkonservierten CaaX-Box für die Lokalisation des Proteins wurde durch die erhaltenen Ergebnisse deutlich. Mit der Durchführung von FRAP-Experimente konnte außerdem die strukturgebende Funktion von NE81 innerhalb des Zellkerns bekräftigt werden. Zusätzlich wurde im Rahmen dieser Arbeit damit begonnen, den Einfluss der Isoprenylcysteincarboxylmethyltransferase auf die Lokalisation des Proteins aufzuklären. Die Entdeckung eines laminähnlichen Proteins in einem einzelligen Organismus, der an der Schwelle zu den Metazoen steht, ist für die evolutionäre Betrachtung der Entwicklung der sozialen Amöbe und für die Erforschung der molekularen Basis von Laminopathien in einem einfachen Modellorganismus sehr interessant. Die Arbeit mit Dictyostelium discoideum könnte daher Wege aufzeigen, dass Studium der Laminopathien am Tiermodell drastisch zu reduzieren. In den letzten Jahren hat die Erforschung unbekannter Bestandteile des Centrosoms in Dictyostelium discoideum große Fortschritte gemacht. Eine zu diesem Zwecke von unserer Arbeitsgruppe durchgeführte Proteomstudie, führte zur Identifizierung weiterer, potentiell centrosomaler Kandidatenproteine. Der zweite Teil dieser Arbeit beschäftigt sich mit der Charakterisierung eines solchen Kandidatenproteins, dem CP75. Es konnte gezeigt werden, dass CP75 einen echten, centrosomalen Bestandteil darstellt, der mikrotubuli-unabhängig mit der Core Struktur des Zellorganells assoziiert ist. Weiterhin wurde deutlich, dass die Lokalisation am Centrosom in Abhängigkeit vom Zellzyklus erfolgt und CP75 vermutlich mit CP39, einem weiteren centrosomalen Core Protein, interagiert. / Lamins build the nuclear lamina together with lamin-associated proteins. The latter is required for mechanical stabilization of cells, chromatin organization, gene expression, cell cycle progression and cell migration. This became evident by the pathogenesis of laminopathies. Laminopathies are diseases which arise from mutations in genes encoding lamins, lamin-associated-or lamin-processing proteins. Prominent examples are the „Hutchinson-Gilford progeria syndrome“, the „Emery-Dreifuss“muscular dystrophy and dilated cardiomyopathy. Despite their universal importance, lamins have only been found in metazoans, but not in unicellular organisms so far. The amoeboid organism Dictyostelium discoideum is a haploid eukaryote widely used in different fields of cell biology. With the discovery of NE81, a protein associated with the inner nuclear membrane of Dictyostelium discoideum, for the first time a protein was identified, whose properties jutify denomination as a lamin-like protein in a lower eukaryote. This is based on the presence of lamin-typical sequences such as a CDK1 phosphorylation consensus sequence, followed by a central rod domain, a typical nuclear localization sequence and the highly conserved CaaX box. For the verification of NE81 as a primitive lamin, various different experiments were conducted in the frame of this work, which revealed structural and functional similarities to lamins of other organisms. Analysis of the behavior of the endogenous protein in cell cycle and the verification of the subcellular localization with electron microscopy was done with the generation of a polyclonal antibody. With a NE81 null mutant, it could be shown, that NE81 plays an important role in nuclear integrity and chromatin organization. The expression of two CaaX-box deleted protein variants confirmed the influence of NE81 on the mechanical stability of cells. These results furthermore underlined the importance of the presence of the highly conserved CaaX-box. FRAP-experiments further emphasized the structural function of NE81 in the nucleus. Furthermore, first steps were undertaken to determine the influence of the Isoprenylcysteinecarboxylmethyltransferase on the localization of NE81. In the light of evolution the discovery of a lamin-like protein in a unicellular organism is very interesting and could provide a simple experimental system for studies of the molecular basis of laminopathies. Hence, the study on laminopathies in animal models could be reduced dramatically. The identification of unknown centrosomal components in Dictyostelium discoideum has made significant proceedings in the last years. A proteomic approach which was accomplished for this purpose, yielded several potential centrosomal candidate proteins. The second part of this work focuses on the characterization of one of these proteins, CP75. It could be shown that CP75 is a genuine, centrosomal component, which is associated with the centrosomal core structure independently of microtubules. Furthermore, it could be demonstrated, that the localization of CP75 is cell cycle-dependent and that it presumably interacts with the core protein CP39.

In this study, we focused on interactions of structural proteins of mouse polyomavirus (MPyV) and BK virus (BKV) with the nuclear lamina. Our goal was to examine whether and how can the virus, hence viral structural proteins, interact with the nuclear lamina and how would these interactions affect its properties. We supposed, that the expression of viral proteins would induce disintegration of the structure of nuclear lamina, thus enabling nuclear egress of virions in the late phase of infection. Viral structural proteins were expressed transiently in cells transfected with an expression vector pMPyV LATE. In these cells, VP1 was localized in a likewise manner as it shows in infected cells - mostly in a perinuclear area. Concurrently, defects in staining of nuclear lamina were observed in these cells, similarly to infected cells. Also, another expression vector was used in our experiments, the pMPyV mut3 VP1 encoding for a mutated protein VP1. When transiently expressed in cells, the mutated VP1 protein showed mostly diffuse nuclear localization. However, we observed significant morphological deformations and defective staining of the nuclear lamina. These observations imply an important role of VP1 in mechanical and biochemical properties alterations of the nuclear lamina in transfected and...

Die Lamine gehören zu einer Familie von Proteinen, die als strukturelle Hauptelemente die Kernlamina ausbilden, einen wesentlichen Bestandteil der Kernhülle eukaryontischer Zellen. In Säugern exprimieren differenzierte somatische Zellen die Lamine A, C, B1 und B2. Die Kernhülle in Keimzellen unterscheidet sich in Bezug auf Struktur und Proteinzusammensetzung deutlich von der einer somatischen Zelle. So exprimieren Keimzellen Lamin B1 als einziges der somatischen Lamine und zwei kurze keimbahnspezifische Spleißvarianten, die Lamine C2 und B3. Die vorliegende Arbeit enthält eine detaillierte Analyse des Expressionsmusters und der zellulären Verteilung von Lamin B3 im Verlauf der Spermatogenese der Maus. Die Daten aus RT-PCR, Western Blot und Immunfluoreszenz belegen eindeutig, dass Lamin B3 ausschließlich in postmeiotischen Stadien während der Spermiogenese exprimiert wird. In runden Spermatiden konnte das Protein an der Kernhülle und überraschenderweise auch im Nukleoplasma nachgewiesen werden. Im weiteren Verlauf der Spermiogenese kommt es zu einer Umverteilung des Proteins, es konzentriert sich zunehmend am posterioren Pol des Spermatidenkerns. Damit ist die Lamina während der Säuger-Spermiogenese nur aus B-Typ-Laminen aufgebaut und Lamin B3 ist in Säugern das erste Beispiel für ein Lamin, das selektiv nur in postmeiotischen Stadien der Spermatogenese exprimiert wird. Die ektopische Expression von Lamin B3 in Kulturzellen führt zu einer Deformation der Zellkerne, die eine hakenförmige Gestalt annehmen. Mit Hilfe von Transfektionsexperimenten in COS-7-Zellen konnte eindeutig gezeigt werden, dass die auftretenden morphologischen Veränderungen der Kerne transfizierter Zellen auf die trunkierte zentrale Stäbchendomäne in Lamin B3 zurückzuführen ist. Darüber hinaus zeigte das Protein eine stark erhöhte Löslichkeit im Vergleich zu Lamin B2 und die Analyse transfizierter Kulturzellen mit „fluorescence recovery after photobleaching“ (FRAP) und „fluorescence loss in photobleaching“ (FLIP) ergab, dass ein erheblicher Anteil der Lamin-B3-Moleküle eine hohe Mobilität aufweist, die ebenfalls ausschließlich durch die kurze Stäbchendomäne begründet ist. Die Ergebnisse führen zu dem Schluss, dass Lamin B3 die Kernhülle in Keimzellen flexibler macht, was eine Voraussetzung für einige Vorgänge in der Spermiogenese sein könnte. Mit einem Fusionsprotein aus GST und dem 84 Aminosäuren umfassenden N-Terminus von Lamin B3 wurde über einen „Pull-Down-Assay“ nach möglichen Interaktionspartnern in Keimzellen gesucht. Mit MSY2, MSY2a und MSY4 wurden drei hoch interessante Kandidaten identifiziert. Sie gehören zu den Y-Box-Proteinen, DNA- und RNA-bindende Proteine, die bei der Speicherung und späteren Translation von mRNAs beteiligt sind, u.a. die mRNA von Protamin 1 (diese Form der Regulation von Genexpression hat in der Spermatogenese große Bedeutung). Die Interaktion von Lamin B3 mit diesen Proteinen muss noch überprüft werden, würde aber einen weiteren Bezug zwischen Kernhülle und Chromatinreorganisation in der Spermiogenese herstellen, wie es für die Kernhüllenproteine GCL und LBR bereits gezeigt werden konnte. Außerdem wäre es ein erster Hinweis auf eine funktionelle Bedeutung der N-terminalen Domäne von Lamin B3. / Lamins are members of a protein family that are the main structural elements of the nuclear envelope in eukaryotic cells. Differentiated mammalian somatic cells express lamins A, C, B1 and B2. The composition and structural organisation of the nuclear lamina in spermatogenic cells differ significantly from that of somatic cells: among the somatic lamins they only express lamin B1 but, additionally, two germ line-specific isoforms could be found, namely lamins C2 and B3. This study contains a detailed investigation of the expression pattern and localisation of lamin B3 during mouse spermatogenesis. By combining RT-PCR, immunoblotting, and immunofluorescence microscopy, it turned out, that lamin B3 is selectively expressed in postmeiotic stages during spermiogenesis. In round spermatids, lamin B3 is distributed in the nuclear periphery and, notably, also in the nucleoplasm. In the course of spermiogenesis, lamin B3 becomes redistributed as it concentrates progressively to the posterior pole of spermatid nuclei. The results show that during mammalian spermiogenesis the nuclear lamina is composed of B-type isoforms only, namely lamin B1 and the germ line-specific lamin B3. Lamin B3 is the first example of a mammalian lamin that is selectively expressed during postmeiotic stages of spermatogenesis. When ectopically expressed in culture cells, lamin B3 causes severe deformation of nuclei which adopt a hook-like configuration. Transfection experiments in COS-7 cells could prove that the observed nuclear deformations are due to the shortened rod domain of lamin B3. Cell fractionation experiments revealed that lamin B3 can be solubilised more easily than lamin B2. In addition, fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) analyses of transfected COS-7 cells showed that considerable amounts of lamin B3 molecules exhibit a significantly increased mobility compared to lamin B2. The increased solubility of lamin B3 compared to lamin B2 as well as the mobility of that protein is only determined by its shortened rod domain. Taken together, these data lead to the conclusion that lamin B3 reduces the stability of the nuclear periphery, what might be an important prerequisite for some reorganisation processes during spermiogenesis to occur. Via a pull-down assay using a fusion protein containing GST and the 84 amino acid long N-terminal domain of lamin B3 a screen for interaction partners of lamin B3 was performed. With MSY2, MSY2a and MSY4 three interesting candidates were found. These proteins belong to the large family of Y-box containing proteins, which are DNA and RNA binding proteins. They are involved in storage and subsequent translation of various mRNAs, e.g. the mRNA of protamine 1 (this mechanism for regulation of gene expression is a major principle in spermatogenesis). The interaction between lamin B3 and the Y-box proteins has to be verified but it would provide an additional link between reorganisation of chromatin and the nuclear envelope as it has already been reported for other proteins of the nuclear envelope like GCL or LBR. Besides that it could be a first evidence for a specific function of the lamin B3 N-terminal domain.

Now that the functioning of microtubules and the actin cytoskeleton has been worked out in enormous detail, the next important task is defining the structure of intermediate filaments that are far behind the other two major skeletal networks due to their inherent resistance to most structural techniques. The evolution of novel structural approaches for flexible proteins is making this possible now. In my thesis I will aim to elucidate the structure and assembly principles of lamin A nuclear intermediate filament protein. To study lamin A, I principally employed chemical cross-linking that allows the capturing of full-length protein structures in solution. I combined this with mass spectrometry approaches to identify cross-linked residues at the various stages of lamin A assembly that were additionally tracked with SILAC labelling and rotary metal shadowing TEM. Unlike previous cross-linking studies on intermediate filaments I use a zero-length self-excluding cross-linking agent EDC that is better tailored for investigation of the polar interactions between multiple unstructured or otherwise flexible charged sequences of lamins. Using this composite approach I interrogated lamin A dimeric and tetrameric assemblies. I elucidated hinge-like properties of the L12 and found indications that L1 and the region containing coil 2A and L2 and the beginning of coil 2B possess properties of linker-like flexibility and of predicted linear α-helical bundle and could act as molecular springs or compression buffers for the nuclear intermediate filaments. Further I confirm the role of the N-terminal unstructured region in lamin A assembly and for the first time show similar role for the C-terminal unstructured region flanking the rod domain of lamin A. Collected data strongly supports the model where both positively charged unstructured regions participate in extensive interaction with acidic rod termini and act as molecular bridges between these in the head-to-tail interface, confirming the uniformity of this principle between cytoplasmic and nuclear intermediate filaments. Formation of these bridges requires conformational change likely happening due to proline residues in the mitotic phosphorylation sites. Finally I suggest a mechanism of regulation of the order of assembly unique to the nuclear intermediate filament where C-terminal unstructured region blocks lateral interactions until it is tethered to the head-to-tail interface. Collected data on the dynamic behaviour of the C-terminal unstructured region and its ability to tether lamin A Ig domain may have far reaching implications for filament assembly and regulation of binding of hundreds of lamin A partner proteins presenting an important step in our understanding of relationship between lamin A structure and function and how altering the former could lead to disease.

Proteins of the nuclear lamina provide structural support to the nuclear envelope and participate in a variety of cellular functions, such as chromatin organization and transcriptional regulation. One of these proteins, Lamin A (72kDa), is synthesized as a 74 kDa precursor protein, Prelamin A, which undergoes an unusual maturation pathway that requires two farnesylation-dependent endoproteolytic cleavages. The second cleavage is unique to lamin A in higher vertebrates and is specifically carried out by the endoprotease zmpste24. Although most previous studies have focused mainly on the function of mature Lamin A, recent evidence from our laboratory shows important biological functions for Prelamin A as well. Prelamin A concentration in proliferating cells is very low or undetectable. Conversely, during quiescence induced by mitogen withdrawal or contact inhibition, Prelamin A levels increase dramatically. These variations are directly regulated by changes in expression and enzymatic activity of zmpste24. The central hypothesis of this dissertation is that full-length farnesylated and carboxymethylated prelamin A (FC-PreA) antagonizes both proliferation and apoptosis, therefore playing a role in cellular quiescence/senescence. To accomplish this goal, we studied the transcriptional regulation of zmpste24 and the interaction of FC-preA with proteins that participate in cell cycle control. 1) We identified and characterized a functional site for the E2F1 transcription factor (involved in the control of cell cycle) in the proximal 5’ UTR region of zmpste24. 2) By using proximity-labeling and co-immunoprecipitation-mass spectrometry techniques, we identified a set of proteins that interact preferentially with L467R-Prelamin A (uncleavable mutant) but not with mature Lamin A. Many of these proteins function to regulate progression through cell cycle.

Multiple sclerosis (MS), a demyelinating disorder of the central nervous system (CNS), affects approximately 400,000 individuals in the United States, and 2.5 million people worldwide. It is a leading cause of disability in young adults. Current treatments for MS target the inflammatory aspects of the disease, but do not aid in remyelination. To address remyelination as a therapeutic strategy, it is imperative to identify mechanisms that regulate myelin formation, including epigenetic targets. In this study, we investigate the role of the LMNA, a gene encoding Lamins A and C, intermediate filaments of the nuclear lamina, in regulating oligodendrocyte development and myelination in the CNS. Using electron microscopic analyses, I examined levels of heterochromatin and its distribution in the oligodendrocyte nucleus as an indicator of gene expression, oligodendrocyte maturity, and myelin formation in the absence of A type lamins.. While overall levels of heterochromatin in oligodendrocytes were not altered in the absence of A type lamins, peripherally located heterochromatin was reduced and thinner myelin was observed in the spinal cord. My observations present novel findings for the role of LMNA in oligodendrocytes and myelination.

<p><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:HyphenationZone>21</w:HyphenationZone> <w:PunctuationKerning /> <w:ValidateAgainstSchemas /> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables /> <w:SnapToGridInCell /> <w:WrapTextWithPunct /> <w:UseAsianBreakRules /> <w:DontGrowAutofit /> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; line-height:150%; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US;} p.Standardmedluft, li.Standardmedluft, div.Standardmedluft {mso-style-name:"Standard med luft"; margin-top:14.0pt; margin-right:0cm; margin-bottom:0cm; margin-left:0cm; margin-bottom:.0001pt; text-align:justify; line-height:150%; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 70.85pt 2.0cm 70.85pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!--[if gte mso 10]><mce:style><! /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} --><!--[endif]--></p><p>Transvection is a widespread phenomenon affecting chromosomal and gene function. There are many examples of epigenetic machineries controlling gene regulation. Nuclear Lamin proteins could have this function. This project shows <em>zeste</em> dependent transvection<strong> </strong>in loss-of-function<strong> </strong><em>lamin</em> mutants in <em>Drosophila melanogaster</em>.<strong> </strong>The <em>zeste</em> locus<strong> </strong>encodes a regulatory gene product affecting the expression of other loci, e.g. <em>white</em>. No transvection effect in loss-of-function <em>lamin </em>mutants has so far been shown. The effect of homozygosity versus heterozygosity of <em>lamin</em> on <em>zeste</em>-dependent transvection at paired <em>white</em> loci was analysed by crossing fruit flies to get homozygous<em> </em><em>z¹</em>; <em>lam</em>^D395 individuals. Whether or not the <em>zeste (z¹</em>) transvection effect on <em>white</em> was affected by <em>lam</em> ^D395 loss-of-function mutation was determined by comparing the eye colour phenotypes of double mutant <em>z¹</em>; <em>lam</em>^D395 females to that of <em>z¹/Y</em>; <em>lam</em>^D395 males, which were used as an internal negative control since they are hemizygous for <em>zeste</em> that is located on the X chromosome. Females homozygous for <em>z¹</em> and <em>lam</em>^D395 displayed the <em>z¹</em>-characteristic yellow eye colour. The conclusion is that <em>zeste</em>-dependent transvection effect at <em>white</em> also occurs in <em>lamin</em> mutants. Future research on transvection is needed in order to understand the exact mechanisms of gene regulation. Even gene therapies for some human diseases can take advantage of <em>trans</em>-acting sequences to correct gene expression.</p><p> </p>