Cell micropatterning reveals the modulatory effect of cell shape on proliferation through intracellular calcium transients.

The mechanism by which cell shape regulates the function of the cell is one of the most important biological issues, but it remains unclear. Here, we investigated the effect of the regulation of cell shape on proliferation by using a micropatterning approach to confine MC3T3-E1 cells into specific shapes. Our results show that the proliferation rate for rectangle-, triangle-, square- and circle-shaped osteoblasts increased sequentially and was related to the nuclear shape index (NSI) but not the cell shape index (CSI). Interestingly, intracellular calcium transients also displayed different patterns, with the number of Ca2+ peaks increasing with the NSI in shaped cells. Further causal investigation revealed that the gene expression levels of the inositol 1,4,5-triphosphate receptor 1 (IP3R1) and sarco/endoplasmic reticulum Ca2+-ATPase 2 (SERCA2), two major calcium cycling proteins in the endoplasmic reticulum (ER), were increased with an increase in NSI as a result of nuclear volume changes. Moreover, the down-regulation of IP3R1 and/or SERCA2 using shRNAs in circle-shaped or control osteoblasts resulted in changes in intracellular calcium transient patterns and cell proliferation rates towards that of smaller-NSI-shaped cells. Our results indicate that changes in cell shape changed nuclear morphology and then the gene expression of IP3R1 and SERCA2, which produced different intracellular calcium transient patterns. The patterns of intracellular calcium transients then determined the proliferation rate of the shaped osteoblasts.

Nuclear envelope structural proteins facilitate nuclear shape changes accompanying embryonic differentiation and fidelity of gene expression.

BACKGROUND: Nuclear size and shape are specific to a cell type, function, and location, and can serve as indicators of disease and development. We previously found that lamin A/C and associated nuclear envelope structural proteins were upregulated when murine embryonic stem (ES) cells differentiated to primitive endoderm cells. Here we further investigated the morphological changes of nuclei that accompany this differentiation. RESULTS: The nuclei of undifferentiated wild type cells were found shaped as flattened, irregular ovals, whereas nuclei of Gata4-positive endoderm cells were more spherical, less flattened, and with a slightly reduced volume. The morphological change was confirmed in the trophectoderm and primitive endoderm lineages of E4.5 blastocysts, compared to larger and more irregularly shaped of the nuclei of the inner cell mass. We established ES cells genetically null for the nuclear lamina proteins lamin A/C or the inner nuclear envelope protein emerin, or compound mutant for both lamin A/C and emerin. ES cells deficient in lamin A/C differentiated to endoderm but less efficiently, and the nuclei remained flattened and failed to condense. The size and shape of emerin-deficient nuclei also remained uncondensed after treatment with RA. The emerin/lamin A/C double knockout ES cells failed to differentiate to endoderm cells, though the nuclei condensed but retained a generally flattened ellipsoid shape. Additionally, ES cells deficient for lamin A/C and/or emerin had compromised ability to undergo endoderm differentiation, where the differentiating cells often exhibited coexpression of pluripotent and differentiation markers, such as Oct3/4 and Gata4, respectively, indicating an infidelity of gene regulation. CONCLUSIONS: The results suggest that changes in nuclear size and shape, which are mediated by nuclear envelope structural proteins lamin A/C and/or emerin, also impact gene regulation and lineage differentiation in early embryos. Nevertheless, mice lacking both lamin A/C and emerin were born at the expected frequency, indicating their embryonic development is completed despite the observed protein deficiency.

Drosophila dany is essential for transcriptional control and nuclear architecture in spermatocytes.

The terminal differentiation of adult stem cell progeny depends on transcriptional control. A dramatic change in gene expression programs accompanies the transition from proliferating spermatogonia to postmitotic spermatocytes, which prepare for meiosis and subsequent spermiogenesis. More than a thousand spermatocyte-specific genes are transcriptionally activated in early Drosophila spermatocytes. Here we describe the identification and initial characterization of dany, a gene required in spermatocytes for the large-scale change in gene expression. Similar to tMAC and tTAFs, the known major activators of spermatocyte-specific genes, dany has a recent evolutionary origin, but it functions independently. Like dan and danr, its primordial relatives with functions in somatic tissues, dany encodes a nuclear Psq domain protein. Dany associates preferentially with euchromatic genome regions. In dany mutant spermatocytes, activation of spermatocyte-specific genes and silencing of non-spermatocyte-specific genes are severely compromised and the chromatin no longer associates intimately with the nuclear envelope. Therefore, as suggested recently for Dan/Danr, we propose that Dany is essential for the coordination of change in cell type-specific expression programs and large-scale spatial chromatin reorganization.

Caracterização morfométrica de fêmeas, garanhões e castrados da raça Campolina baseada em índices / Morphometric characterization of Campolina mares, stallions and gelded horses using indexes

O presente estudo objetivou avaliar os índices morfométricos para garanhões, machos castrados e fêmeas da raça Campolina, bem como caracterizá-los morfologicamente. Para tanto, foram utilizadas as medidas lineares de 4.840 garanhões, 19.037 fêmeas e 1.371 machos castrados, obtidas no banco de dados do Serviço de Registro Genealógico da ABCCCampolina, com base nas quais nove índices morfométricos foram calculados utilizando-se seis medidas lineares. A análise de variância foi realizada para avaliar o efeito do sexo e da idade sobre os índices obtidos. Verificou-se que ambos os fatores influenciaram os índices morfométricos. Garanhões apresentaram peso calculado aproximado superior tanto às fêmeas quanto aos machos castrados. De acordo com o índice peitoral, todas as categorias foram classificadas como "longe do chão". Em relação aos valores médios dos índices corporal e dáctilo torácico, garanhões e castrados foram classificados como mediolíneos e eumétricos, respectivamente, enquanto as fêmeas foram classificadas como brevilíneas e hipométricas. Conclui-se que os machos castrados e os garanhões da raça Campolina enquadram-se no padrão da raça para animais tipo sela, mas as fêmeas não. Entretanto, os índices de compacidade 1 e 2 apresentam resultados contraditórios e precisam ser melhor avaliados para fins de uso em classificações. Para a maioria dos índices, os animais castrados apresentaram-se melhor proporcionados que as demais categorias.

The present study aimed to evaluate the morphometric indexes for Campolina stallions, gelded and mare horses, as well as morphologically characterizing them. For this purpose linear measurements from 4.840 stallions, 19.037 mares and 1371 gelded horses were used, obtained from ABCCCampolina's stud book database, from which nine morphometric indexes were calculated from six linear measurements. Analysis of variance was carried out to evaluate the effect of sex and age on the indexes obtained. We found that both factors influenced the morphometric index. Stallions have presented higher estimate body weight values than mares and gelded horses. According to the pectoral index values all categories were classified as far from the ground. According to body index and dactyl thoracic index average values, stallions and gelded horses were classified as medium lined and middleweight, respectively, once the mares were classified as more compact and overweight. It is concluded that Campolina stallions and gelded horses fall within the breed standard for saddle animals, but mares don't. However, the compact indexes 1 and 2 showed contradictory results and need to be better evaluated for its intended use in classifications. For most indexes gelded animals showed better proportion than the other categories.

Pan-cancer analysis of the extent and consequences of intratumor heterogeneity.

Intratumor heterogeneity (ITH) drives neoplastic progression and therapeutic resistance. We used the bioinformatics tools 'expanding ploidy and allele frequency on nested subpopulations' (EXPANDS) and PyClone to detect clones that are present at a ≥10% frequency in 1,165 exome sequences from tumors in The Cancer Genome Atlas. 86% of tumors across 12 cancer types had at least two clones. ITH in the morphology of nuclei was associated with genetic ITH (Spearman's correlation coefficient, ρ = 0.24-0.41; P < 0.001). Mutation of a driver gene that typically appears in smaller clones was a survival risk factor (hazard ratio (HR) = 2.15, 95% confidence interval (CI): 1.71-2.69). The risk of mortality also increased when >2 clones coexisted in the same tumor sample (HR = 1.49, 95% CI: 1.20-1.87). In two independent data sets, copy-number alterations affecting either <25% or >75% of a tumor's genome predicted reduced risk (HR = 0.15, 95% CI: 0.08-0.29). Mortality risk also declined when >4 clones coexisted in the sample, suggesting a trade-off between the costs and benefits of genomic instability. ITH and genomic instability thus have the potential to be useful measures that can universally be applied to all cancers.

Diet-morphology relationship in the stream-dwelling characid Deuterodon stigmaturus (Gomes, 1947) (Characiformes: Characidae) is partially conditioned by ontogenetic development

We tested whether interindividual variations in diet composition within a population of Deuterodon stigmaturus can be explained by morphological differences between individuals, and whether diet-morphology relationships are dependent on the ontogenetic development. We analyzed diet of 75 specimens sampled in a coastal stream of Southern Brazil. Variation in stomach content was summarized with a Principal Coordinate Analysis (PCoA). The retained PCoA axes were tested as response to standard length (SL), and to values of intestine length (IL) and mouth length (ML) independent of body size, using linear mixed-effects models (LMM). The most consumed food items by D. stigmaturus were filamentous algae (41%), terrestrial plants (20.3%), detritus (12%), and aquatic invertebrates (8.8%). The LMMs showed that SL was positively related to consumption of terrestrial plants, whereas IL independent of SL was negatively related to aquatic invertebrates and positively related to filamentous algae. When body sized was held constant, ML was not related to diet variation. Interindividual diet differences conditioned to body size suggest that individuals shift their trophic niche and function in the ecosystem along the ontogenetic development. Relationships between intestine length and diet composition suggest interindividual differences in foraging ability and digestibility of distinct food items.

Nós testamos se variações na composição da dieta de uma população de Deuterodon stigmaturus podem ser explicadas por diferenças morfológicas entre indivíduos, e se as relações entre morfologia e dieta são dependentes do desenvolvimento ontogenético. A dieta de 75 indivíduos amostrados em um riacho costeiro do sul do Brasil foi analisada. Uma Análise de Coordenadas Principais (PCoA) foi utilizada para sumarizar variações individuais no conteúdo estomacal. Os eixos retidos da PCoA foram testados como resposta ao comprimento padrão (CP) e ao comprimentos do intestino (CI) e da boca (CB), independentes do tamanho corporal, usando modelos lineares mistos (LMMs). Os itens macroscópicos mais consumidos por D. stigmaturus foram algas filamentosas (41%), plantas terrestres (20,3%), detritos (12%), e invertebrados terrestres (8,8%). Os LMMs mostraram que o CP foi positivamente relacionado ao consumo de plantas terrestres, enquanto que valores de CI independentes de CP foram negativamente relacionados ao consumo de invertebrados aquáticos e positivamente relacionados ao consumo de algas filamentosas. Quando o CP foi mantido constante, CB não foi relacionado a composição da dieta. As diferenças na dieta condicionadas ao tamanho corporal sugerem que os indivíduos mudam seu nicho trófico e função no ecossistema ao longo do desenvolvimento ontogenético. As relações entre o tamanho do intestino e composição da dieta sugerem diferenças individuais na habilidade de forragear e digerir itens alimentares distintos.

Nuclear shape descriptors by automated morphometry may distinguish aggressive variants of squamous cell carcinoma from relatively benign skin proliferative lesions: a pilot study.

We evaluated whether degrees of dysplasia may be consistently accessed in an automatic fashion, using different kinds of non-melanoma skin cancer (NMSC) as a validatory model. Namely, we compared Bowen disease, actinic keratosis, basal cell carcinoma, low-grade squamous cell carcinoma, and invasive squamous cell carcinoma. We hypothesized that characterizing the shape of nuclei may be important to consistently diagnose the aggressiveness of a skin tumor. While basal cell carcinoma is comparatively relatively benign, management of squamous cell carcinoma is controversial because of its potential to recur and intraoperative dilemma regarding choice of the margin or the depth for the excision. We provide evidence here that progressive nuclear dysplasia may be automatically estimated through the thresholded images of skin cancer and quantitative parameters estimated to provide a quasi-quantitative data, which can thenceforth guide the management of the particular cancer. For circularity, averaging more than 2500 nuclei in each group estimated the means ± SD as 0.8 ± 0.007 vs. 0.78 ± 0.0063 vs. 0.42 ± 0.014 vs. 0.63 ± 0.02 vs. 0.51 ± 0.02 (F = 318063.56, p < 0.0001, one-way analyses of variance). The mean aspect ratios were (means ± SD) 0.97 ± 0.0014 vs. 0.95 ± 0.002 vs. 0.38 ± 0.018 vs. 0.84 ± 0.0035 vs. 0.74 ± 0.019 (F = 1022631.931, p < 0.0001, one-way analyses of variance). The Feret diameters averaged over 2500 nuclei in each group were the following: 1 ± 0.0001 vs. 0.9 ± 0.002 vs. 5 ± 0.031 vs. 1.5 ± 0.01 vs. 1.9 ± 0.004 (F = 33105614.194, p < 0.0001, one-way analyses of variance). Multivariate analyses of composite parameters potentially detect aggressive variants of squamous cell carcinoma as the most dysplastic form, in comparison to locally occurring squamous cell carcinoma and basal cell carcinoma, or benign skin lesions.

Spermatid head elongation with normal nuclear shaping requires ADP-ribosyltransferase PARP11 (ARTD11) in mice.

Sperm are highly differentiated cells characterized by their species-specific nuclear shapes and extremely condensed chromatin. Abnormal head shapes represent a form of teratozoospermia that can impair fertilization capacity. This study shows that poly(ADP-ribose) polymerase-11 (ARTD11/PARP11), a member of the ADP-ribosyltransferase (ARTD) family, is expressed preferentially in spermatids undergoing nuclear condensation and differentiation. Deletion of the Parp11 gene results in teratozoospermia and male infertility in mice due to the formation of abnormally shaped fertilization-incompetent sperm, despite normal testis weights and sperm counts. At the subcellular level, PARP11-deficient elongating spermatids reveal structural defects in the nuclear envelope and chromatin detachment associated with abnormal nuclear shaping, suggesting functional relevance of PARP11 for nuclear envelope stability and nuclear reorganization during spermiogenesis. In vitro, PARP11 exhibits mono(ADP-ribosyl)ation activity with the ability to ADP-ribosylate itself. In transfected somatic cells, PARP11 colocalizes with nuclear pore components, such as NUP153. Amino acids Y77, Q86, and R95 in the N-terminal WWE domain, as well as presence of the catalytic domain, are essential for colocalization of PARP11 with the nuclear envelope, but catalytic activity of the protein is not required for colocalization with NUP153. This study demonstrates that PARP11 is a novel enzyme important for proper sperm head shaping and identifies it as a potential factor involved in idiopathic mammalian teratozoospermia.

ParB spreading requires DNA bridging.

The parABS system is a widely employed mechanism for plasmid partitioning and chromosome segregation in bacteria. ParB binds to parS sites on plasmids and chromosomes and associates with broad regions of adjacent DNA, a phenomenon known as spreading. Although essential for ParB function, the mechanism of spreading remains poorly understood. Using single-molecule approaches, we discovered that Bacillus subtilis ParB (Spo0J) is able to trap DNA loops. Point mutants in Spo0J that disrupt DNA bridging are defective in spreading and recruitment of structural maintenance of chromosomes (SMC) condensin complexes in vivo. DNA bridging helps to explain how a limited number of Spo0J molecules per parS site (~20) can spread over many kilobases and suggests a mechanism by which ParB proteins could facilitate the loading of SMC complexes. We show that DNA bridging is a property of diverse ParB homologs, suggesting broad evolutionary conservation.

Tight coupling between nucleus and cell migration through the perinuclear actin cap.

Although eukaryotic cells are known to alternate between 'advancing' episodes of fast and persistent movement and 'hesitation' episodes of low speed and low persistence, the molecular mechanism that controls the dynamic changes in morphology, speed and persistence of eukaryotic migratory cells remains unclear. Here, we show that the movement of the interphase nucleus during random cell migration switches intermittently between two distinct modes - rotation and translocation - that follow with high fidelity the sequential rounded and elongated morphologies of the nucleus and cell body, respectively. Nuclear rotation and translocation mediate the stop-and-go motion of the cell through the dynamic formation and dissolution, respectively, of the contractile perinuclear actin cap, which is dynamically coupled to the nuclear lamina and the nuclear envelope through LINC complexes. A persistent cell movement and nuclear translocation driven by the actin cap are halted following the disruption of the actin cap, which in turn allows the cell to repolarize for its next persistent move owing to nuclear rotation mediated by cytoplasmic dynein light intermediate chain 2.

Association of cup-like nuclei in blasts with FLT3 and NPM1 mutations in acute myeloid leukemia.

The purpose of this study was to investigate the correlation of mutations of the fms-like tyrosine kinase (FLT3) and nucleophosmin (NPM1) genes with the cup-like nuclear morphology of blasts in patients with acute myeloid leukemia (AML). We retrospectively reviewed peripheral blood (PB) and bone marrow (BM) slides of 208 patients prepared at the time of diagnosis of AML based on the results of testing for mutations of both NPM1 exon 12 and FLT3. We investigated the association between this phenotype and hematologic findings, disease markers, and mutations in NPM1 exon 12, FLT3-internal tandem duplication (ITD), and tyrosine kinase domain (TKD) genes. Cup-like nuclei were found in 44 patients (21.2 %) diagnosed with AML. This morphology was associated with high blast counts in the PB and BM; AML type, especially AML M1 (FAB classification); low CD34 expression; and mutation of FLT3-ITD, -TKD, NPM1 regardless of other mutations (p < 0.05 for all). However, FLT3-ITD or TKD mutation alone (nine cases, p = 0.228) was not associated, and NPM1 mutation alone (14 cases, p = 0.036) was weakly associated with cup-like nuclei. Mutation of both NPM1 and FLT3-ITD or TKD (17 cases, p < 0.001) was strongly correlated with the cup-like nuclear morphology. AML with cup-like nuclei is strongly associated with co-occurring mutations of both NPM1 and FLT3-ITD or TKD. Therefore, testing for both mutations is recommended for patients with the cup-like nuclear morphology.

Role of actin dependent nuclear deformation in regulating early gene expression.

The nucleus of a living cell is constantly undergoing changes in shape and size as a result of various mechanical forces in physiology. These changes correlate with alterations in gene expression, however it is unclear whether nuclear deformation alone is sufficient to elicit these alterations. We used T-cell activation as a model system to test the coupling between nuclear deformation (elongation) and gene expression. Naïve T-cell activation with surrogate antigens resulted in actin dependent nuclear elongation. This was accompanied with Erk and NF-κB signaling to the nucleus to induce CD69 expression. Importantly, inhibiting actin polymerization abolished both nuclear elongation and CD69 expression, while inhibiting Erk, NF-κB or microtubule depolymerization only abolished expression but not elongation. Immobilization of antigen-coated beads, under conditions where actin polymerization was inhibited, rescued both nuclear elongation and CD69 expression. In addition, fibroblast cells plated on fibronectin micropatterns of different sizes showed correlation between nuclear shape index and tenascin C expression. Upon inhibiting the signaling intermediate Erk, tenascin C expression was down regulated although the nuclear shape index remained unaltered. Our results highlight the importance of specific signaling intermediates accompanied with nuclear deformation in the modulation of cellular genomic programs.

Neural Wiskott-Aldrich syndrome protein is required for accurate chromosome congression and segregation.

The accurate distribution and segregation of replicated chromosomes through mitosis is crucial for cellular viability and development of organisms. Kinetochores are responsible for the proper congression and segregation of chromosomes. Here, we show that neural Wiskott-Aldrich syndrome protein (N-WASP) localizes to and forms a complex with kinetochores in mitotic cells. Depletion of NWASP by RNA interference causes chromosome misalignment, prolonged mitosis, and abnormal chromosomal segregation, which is associated with decreased proliferation of N-WASP-deficient cells. N-WASP-deficient cells display defects in the kinetochores recruitment of inner and outer kinetochore components, CENP-A, CENP-E, and Mad2. Live-cell imaging analysis of GFP-α-tubulin revealed that depletion of N-WASP impairs microtubule attachment to chromosomes in mitotic cells. All these results indicate that N-WASP plays a role in efficient assembly of kinetochores and attachment of microtubules to chromosomes, which is essential for accurate chromosome congression and segregation.

Diverse miRNA spatial expression patterns suggest important roles in homeostasis and regeneration in planarians.

miRNAs are an important class of non-protein coding small RNAs whose specific functions in animals are rapidly being elucidated. It is clear that miRNAs can play crucial roles in stem cell maintenance, cell fate determination and differentiation. We use planarians, which possess a large population of pluripotent somatic stem cells, as a powerful model system to study many aspects of stem cell biology and regeneration. In particular we wish to investigate the regulatory role miRNAs may have in planarian stem cell self renewal, proliferation and differentiation. Here, we characterized the differential spatial patterns of expression of miRNAs in whole and regenerating planarians by in situ hybridization to nascent miRNA transcripts. These miRNA expression patterns are the first which have been determined for a Lophotrocozoan animal. We have characterized the expression patterns of 42 miRNAs in adult planarians, constituting a complete range of tissue specific expression patterns. We also followed miRNA expression during planarian regeneration. The majority of planarian miRNAs were expressed either in areas where stem cells (neoblasts) are located and/or in the nervous system. Some miRNAs were definitively expressed in stem cells and dividing cells as confirmed by in situ hybridisation after irradiation. We also found miRNAs to be expressed in germ stem cells of the sexual strain. Together, these data suggest an important role for miRNAs in stem cell regulation and in neural cell differentiation in planarians.

Tumores estromales gastrointestinales: parámetros morfologicos e histogenéticos de valor pronostico / Tumors estromal gastrointestinal: morphologic parameters and histogenéticos of value I predict

INTRODUCCION: Los tumores estromales gastrintestinales (GISTs) constituyen la categoría más amplia de neoplasias no epiteliales primarias del tracto gastrointestinal. Son más frecuentes en estómago y en intestino delgado, pero también pueden comprometer esófago, colon, recto y ano. Han sido encontrados, además, en mesenterio, retroperitoneo, omento y tejidos blandos (EGIST-Tumor estromal extragastrointestinal). Martín los reconoció como entidad clínico -patológica y Stout los denominó Leinomioblastomas. Mazur y Clark acuñaron el término tumor estromal gastrointesitnal y sugierieron que podían originarse del sistema nervioso mioentérico. Hubo, además, algunos casos con evidencias de diferenciacion neural, y fue introducido el término "Tumor autonómico gastrointestinal" (GANT). Kindblom y col., sugirieron que esta neoplasias presentan un inmunofenotipo similar a células intersticiales de Cajal (Células marcapsos del tracto gastrointestinal). OBJETIVOS: -Correlacionar tamaño tumoral, patrón microscopico e inmunofenotipo con el comportamiento biológico. - Determinar formas macro y microscopicas y analizar la forma de preesentación clínica. - Relacionar topografia, tamaño y grado con la agresividad tumoral. - Confirmar el valor del protooncogen (CD-117) como marcador de CIC y de GISTs.

Mouse neutrophils lacking lamin B-receptor expression exhibit aberrant development and lack critical functional responses.

OBJECTIVE: The capacity of neutrophils to eradicate bacterial infections is dependent on normal development and activation of functional responses, which include chemotaxis and generation of oxygen radicals during the respiratory burst. A unique feature of the neutrophil is its highly lobulated nucleus, which is thought to facilitate chemotaxis, but may also play a role in other critical neutrophil functions. Nuclear lobulation is dependent on expression of the inner nuclear envelope protein, the lamin B receptor (LBR), mutations of which cause hypolobulated neutrophil nuclei in human Pelger-Huët anomaly and the "ichthyosis" (ic) phenotype in mice. In this study, we have investigated roles for LBR in mediating neutrophil development and activation of multiple neutrophil functions, including chemotaxis and the respiratory burst. MATERIALS AND METHODS: A progenitor EML cell line was generated from an ic/ic mouse, and derived cells that lacked LBR expression were induced to mature neutrophils and then examined for abnormal morphology and functional responses. RESULTS: Neutrophils derived from EML-ic/ic cells exhibited nuclear hypolobulation identical to that observed in ichthyosis mice. The ic/ic neutrophils also displayed abnormal chemotaxis, supporting the notion that nuclear segmentation augments neutrophil extravasation. Furthermore, promyelocytic forms of ic/ic cells displayed decreased proliferative responses and produced a deficient respiratory burst upon terminal maturation. CONCLUSIONS: Our studies of promyelocytes that lack LBR expression have identified roles for LBR in regulating not only the morphologic maturation of the neutrophil nucleus, but also proliferative and functional responses that are critical to innate immunity.

Epidermal expression of the truncated prelamin A causing Hutchinson-Gilford progeria syndrome: effects on keratinocytes, hair and skin.

Hutchinson-Gilford progeria syndrome (HGPS) is an accelerated aging disorder caused by point mutation in LMNA encoding A-type nuclear lamins. The mutations in LMNA activate a cryptic splice donor site, resulting in expression of a truncated, prenylated prelamin A called progerin. Expression of progerin leads to alterations in nuclear morphology, which may underlie pathology in HGPS. We generated transgenic mice expressing progerin in epidermis under control of a keratin 14 promoter. The mice had severe abnormalities in morphology of skin keratinocyte nuclei, including nuclear envelope lobulation and decreased nuclear circularity not present in transgenic mice expressing wild-type human lamin A. Primary keratinocytes isolated from these mice had a higher frequency of nuclei with abnormal shape compared to those from transgenic mice expressing wild-type human lamin A. Treatment with a farnesyltransferase inhibitor significantly improved nuclear shape abnormalities and induced the formation of intranuclear foci in the primary keratinocytes expressing progerin. Similarly, spontaneous immortalization of progerin-expressing cultured keratinocytes selected for cells with normal nuclear morphology. Despite morphological alterations in keratinocyte nuclei, mice expressing progerin in epidermis had normal hair grown and wound healing. Hair and skin thickness were normal even after crossing to Lmna null mice to reduce or eliminate expression of normal A-type lamins. Although progerin induces significant alterations in keratinocyte nuclear morphology that are reversed by inhibition of farnesyltransferasae, epidermal expression does not lead to alopecia or other skin abnormalities typically seen in human subjects with HGPS.

The granulocyte nucleus and lamin B receptor: avoiding the ovoid.

The major human blood granulocyte, the neutrophil, is an essential component of the innate immunity system, emigrating from blood vessels and migrating through tight tissue spaces to the site of bacterial or fungal infection where they kill and phagocytose invading microbes. Since the late nineteenth century, it has been recognized that the human neutrophil nucleus is distinctly not ovoid as in other cell types, but possesses a lobulated (segmented) shape. This deformable nucleus enhances rapid migration. Recent studies have demonstrated that lamin B receptor (LBR) is necessary for the non-ovoid shape. LBR is an integral membrane protein of the nuclear envelope. A single dominant mutation in humans leads to neutrophils with hypolobulated nuclei (Pelger-Huet anomaly); homozygosity leads to ovoid granulocyte nuclei. Interestingly, LBR is also an enzyme involved in cholesterol metabolism. Homozygosity for null mutations is frequently lethal and associated with severe skeletal deformities. In addition to the necessity for LBR, formation of the mature granulocyte nucleus also depends upon lamin composition and microtubule integrity. These observations are part of a larger question on the relationships between nuclear shape and cellular function.