A planar polarized MYO6-DOCK7-RAC1 axis promotes tissue fluidification in mammary epithelia.

Tissue fluidification and collective motility are pivotal in regulating embryonic morphogenesis, wound healing, and tumor metastasis. These processes frequently require that each cell constituent of a tissue coordinates its migration activity and directed motion through the oriented extension of lamellipodium cell protrusions, promoted by RAC1 activity. While the upstream RAC1 regulators in individual migratory cells or leader cells during invasion or wound healing are well characterized, how RAC1 is controlled in follower cells remains unknown. Here, we identify a MYO6-DOCK7 axis essential for spatially restricting RAC1 activity in a planar polarized fashion in model tissue monolayers. The MYO6-DOCK7 axis specifically controls the extension of cryptic lamellipodia required to drive tissue fluidification and cooperative-mode motion in otherwise solid and static carcinoma cell collectives.

Recurrent Spliceosome Mutations in Cancer: Mechanisms and Consequences of Aberrant Splice Site Selection.

Splicing alterations have been widely documented in tumors where the proliferation and dissemination of cancer cells is supported by the expression of aberrant isoform variants. Splicing is catalyzed by the spliceosome, a ribonucleoprotein complex that orchestrates the complex process of intron removal and exon ligation. In recent years, recurrent hotspot mutations in the spliceosome components U1 snRNA, SF3B1, and U2AF1 have been identified across different tumor types. Such mutations in principle are highly detrimental for cells as all three spliceosome components are crucial for accurate splice site selection: the U1 snRNA is essential for 3' splice site recognition, and SF3B1 and U2AF1 are important for 5' splice site selection. Nonetheless, they appear to be selected to promote specific types of cancers. Here, we review the current molecular understanding of these mutations in cancer, focusing on how they influence splice site selection and impact on cancer development.

Myosin VI regulates ciliogenesis by promoting the turnover of the centrosomal/satellite protein OFD1.

The actin motor protein myosin VI is a multivalent protein with diverse functions. Here, we identified and characterised a myosin VI ubiquitous interactor, the oral-facial-digital syndrome 1 (OFD1) protein, whose mutations cause malformations of the face, oral cavity, digits and polycystic kidney disease. We found that myosin VI regulates the localisation of OFD1 at the centrioles and, as a consequence, the recruitment of the distal appendage protein Cep164. Myosin VI depletion in non-tumoural cell lines causes an aberrant localisation of OFD1 along the centriolar walls, which is due to a reduction in the OFD1 mobile fraction. Finally, loss of myosin VI triggers a severe defect in ciliogenesis that could be, at least partially, ascribed to an impairment in the autophagic removal of OFD1 from satellites. Altogether, our results highlight an unprecedent layer of regulation of OFD1 and a pivotal role of myosin VI in coordinating the formation of the distal appendages and primary cilium with important implications for the genetic disorders known as ciliopathies.

USP25 Regulates EGFR Fate by Modulating EGF-Induced Ubiquitylation Dynamics.

Deregulated epidermal growth factor receptor (EGFR) signaling is a key feature in different stages of oncogenesis. One important mechanism whereby cancer cells achieve increased and uncontrolled EGFR signaling is escaping down-modulation of the receptor. Ubiquitylation of the EGFR plays a decisive role in this process, as it regulates receptor internalization, trafficking and degradation. Deubiquitinating enzymes (DUBs) may oppose the ubiquitylation process, antagonizing or even promoting receptor degradation. Here, we use qualitative and quantitative assays to measure EGFR internalization and degradation after Ubiquitin Specific Peptidase 25 (USP25) depletion. We show that, by acting at the early steps of EGFR internalization, USP25 restrains the degradation of the EGFR by assisting in the association of the E3 ubiquitin ligase c-Cbl with EGFR, thereby modulating the amplitude of ubiquitylation on the receptor. This study establishes USP25 as a negative regulator of the EGFR down-modulation process and suggests that it is a promising target for pharmacological intervention to hamper oncogenic growth signals in tumors that depend on the EGFR.

Clathrin light chain A drives selective myosin VI recruitment to clathrin-coated pits under membrane tension.

Clathrin light chains (CLCa and CLCb) are major constituents of clathrin-coated vesicles. Unique functions for these evolutionary conserved paralogs remain elusive, and their role in clathrin-mediated endocytosis in mammalian cells is debated. Here, we find and structurally characterize a direct and selective interaction between CLCa and the long isoform of the actin motor protein myosin VI, which is expressed exclusively in highly polarized tissues. Using genetically-reconstituted Caco-2 cysts as proxy for polarized epithelia, we provide evidence for coordinated action of myosin VI and CLCa at the apical surface where these proteins are essential for fission of clathrin-coated pits. We further find that myosin VI and Huntingtin-interacting protein 1-related protein (Hip1R) are mutually exclusive interactors with CLCa, and suggest a model for the sequential function of myosin VI and Hip1R in actin-mediated clathrin-coated vesicle budding.

SUMOylation of the nuclear pore complex basket is involved in sensing cellular stresses.

The nuclear pore complex (NPC) is the major conduit for nucleocytoplasmic transport and serves as a platform for gene regulation and DNA repair. Several nucleoporins undergo ubiquitylation and SUMOylation, and these modifications play an important role in nuclear pore dynamics and plasticity. Here, we perform a detailed analysis of these post-translational modifications of yeast nuclear basket proteins under normal growth conditions as well as upon cellular stresses, with a focus on SUMOylation. We find that the balance between the dynamics of SUMOylation and deSUMOylation of Nup60 and Nup2 at the NPC differs substantially, particularly in G1 and S phase. While Nup60 is the unique target of genotoxic stress within the nuclear basket that probably belongs to the SUMO-mediated DNA damage response pathway, both Nup2 and Nup60 show a dramatic increase in SUMOylation upon osmotic stress, with Nup2 SUMOylation being enhanced in Nup60 SUMO-deficient mutant yeast strains. Taken together, our data reveal that there are several levels of crosstalk between nucleoporins, and that the post-translational modifications of the NPC serve in sensing cellular stress signals.

When ubiquitin meets E-cadherin: Plasticity of the epithelial cellular barrier.

Cellular plasticity is, by definition, the ability of cells to adapt to a dynamic micro-environment by changing their phenotype. E-cadherin is the key organizer of the epithelial cell barrier, and it is required at the cell surface to preserve epithelial tissue integrity and homeostasis, since it not only organizes the adherens junctions, but also transfers intracellular signals that provide cues to regulate cell survival, morphology and polarity. As such, de-regulation of E-cadherin has deleterious effects on cells and whole tissues. The availability of cadherin at the cellular junctions is determined by the rates of new protein synthesis and degradation, as well as of internalization and recycling. Indeed, E-cadherin is subjected to a constant and a signal-mediated turnover due to trafficking and recycling between the cell surface and the cytoplasm. Importantly, the turnover of E-cadherin is required for both cell adhesion and cell plasticity within a tissue. Understanding the pathways and molecular mechanisms that E-cadherin undertakes to move in and out of adherens junctions, through which epithelial cells communicate with each other, has, thus, been a major research focus over the past decade, but several issues remain unresolved. Here, we review major advances and remaining open questions in the understanding of E-cadherin trafficking, with a particular focus on its ubiquitination.

Posttranslational marks control architectural and functional plasticity of the nuclear pore complex basket.

The nuclear pore complex (NPC) serves as both the unique gate between the nucleus and the cytoplasm and a major platform that coordinates nucleocytoplasmic exchanges, gene expression, and genome integrity. To understand how the NPC integrates these functional constraints, we dissected here the posttranslational modifications of the nuclear basket protein Nup60 and analyzed how they intervene to control the plasticity of the NPC. Combined approaches highlight the role of monoubiquitylation in regulating the association dynamics of Nup60 and its partner, Nup2, with the NPC through an interaction with Nup84, a component of the Y complex. Although major nuclear transport routes are not regulated by Nup60 modifications, monoubiquitylation of Nup60 is stimulated upon genotoxic stress and regulates the DNA-damage response and telomere repair. Together, these data reveal an original mechanism contributing to the plasticity of the NPC at a molecular-organization and functional level.

Ubiquitylation by the Ltn1 E3 ligase protects 60S ribosomes from starvation-induced selective autophagy.

Autophagy, the process by which proteins or organelles are engulfed by autophagosomes and delivered for vacuolar/lysosomal degradation, is induced to ensure survival under starvation and other stresses. A selective autophagic pathway for 60S ribosomal subunits elicited by nitrogen starvation in yeast-ribophagy-was recently described and requires the Ubp3-Bre5 deubiquitylating enzyme. This discovery implied that an E3 ligases act upstream, whether inhibiting the process or providing an initial required signal. In this paper, we show that Ltn1/Rkr1, a 60S ribosome-associated E3 implicated in translational surveillance, acts as an inhibitor of 60S ribosomal subunit ribophagy and is antagonized by Ubp3. The ribosomal protein Rpl25 is a relevant target. Its ubiquitylation is Ltn1 dependent and Ubp3 reversed, and mutation of its ubiquitylation site rendered ribophagy less dependent on Ubp3. Consistently, the expression of Ltn1-but not Ubp3-rapidly decreased after starvation, presumably to allow ribophagy to proceed. Thus, Ltn1 and Ubp3-Bre5 likely contribute to adapt ribophagy activity to both nutrient supply and protein translation.

Ubiquitination dynamics in the early-branching eukaryote Giardia intestinalis.

Ubiquitination is a highly dynamic and versatile posttranslational modification that regulates protein function, stability, and interactions. To investigate the roles of ubiquitination in a primitive eukaryotic lineage, we utilized the early-branching eukaryote Giardia intestinalis. Using a combination of biochemical, immunofluorescence-based, and proteomics approaches, we assessed the ubiquitination status during the process of differentiation in Giardia. We observed that different types of ubiquitin modifications present specific cellular and temporal distribution throughout the Giardia life cycle from trophozoites to cyst maturation. Ubiquitin signal was detected in the wall of mature cysts, and enzymes implicated in cyst wall biogenesis were identified as substrates for ubiquitination. Interestingly, inhibition of proteasome activity did not affect trophozoite replication and differentiation, while it caused a decrease in cyst viability, arguing for proteasome involvement in cyst wall maturation. Using a proteomics approach, we identified around 200 high-confidence ubiquitinated candidates that vary their ubiquitination status during differentiation. Our results indicate that ubiquitination is critical for several cellular processes in this primitive eukaryote.

Genetic parameters and breeding values for live weight using random regression models in a Bos taurus-Bos indicus multibreed cattle population in Colombia / Parámetros y valores genéticos para peso vivo empleando modelos de regresión aleatoria en una población bovina multirracial Bos taurus-Bos indicus en Colombia / Parâmetros genéticos e valores genéticos para peso vivo utilizando modelos de regressão aleatória em uma população multirracial Bos taurus - Bos índicos da Colômbia

Objective: the objective of this research was to estimate genetic parameters and to predict breeding values for live weight in a Colombian Bos taurus-Bos indicus multibreed beef cattle population using random regression models (RRM). Methods: the population included 352 offspring from 37 sires of nine breeds mated to Gray Brahman females. The sire breeds were Gray Brahman, Red Brahman, Guzerat, Blanco Orejinegro, Romosinuano, Simmental, Braunvieh, Normand and Limousin. A longitudinal structured data set comprising 1,090 records was used. First (LP1) and second (LP2) order Legendre polynomials were used to estimate the coefficients of covariance functions. The animal model used included animal age, parity, contemporary group (herd * year * season * sex), breed group, additive genetic and heterosis as fixed effects. Random effects were the direct and maternal additive genetic, and the maternal permanent environment. Residual variances were assumed to be constant along the trajectory (HOM) or to change trough different stages of the growth trajectory (HET). Thus, four RRM (i.e: LP1HOM, LP1HET, LP2HOM, and LP2HET) were compared via Schwartz's Bayesian information and Corrected Akaike's Information criteria. Results: the best RRM model was LP2HET. This model was used to obtain direct and maternal heritabilities (Dh and Mh), correlations, and breeding values. The estimated direct additive covariance function showed that additive genetic covariances increased with age. The Dh was 0.24 at birth, decreased to 0.02 at 132 days, then increased to 0.18 at 492 d. The Mh was negligible throughout the growth period. Direct additive correlation values were moderate (0.43) to high (0.99) and tended to decrease as difference between ages increased. Maternal permanent environmental correlations (MPEC) followed a similar trend. Conclusions: these results suggest that selection for additive direct genetic effects based on weight at an early age would be effective in obtaining heavier animals at advanced growth stages under Colombia's tropical pasture conditions.

Objetivo: el objetivo de esta investigación fue estimar parámetros genéticos y predecir valores genéticos para peso vivo en una población bovina multirracial Bos taurus-Bos indicus empleando modelos de regresión aleatoria (RRM). Métodos: la población estuvo compuesta por 352 descendencias de 37 toros de nueve razas apareados con hembras Brahman gris. Las razas de los toros fueron: Brahman gris, Brahman rojo, Guzerat, Blanco Orejinegro, Romosinuano, Simmental, Braunvieh, Normando y Limousin. Se empleó una base de datos con estructura longitudinal de 1,090 registros. Para estimar los coeficientes de las funciones de covarianza se usaron Polinomios de Legendre de primero (LP1) y segundo orden (LP2). El modelo animal empleado consideró como efectos fijos la edad del animal, número de partos de la madre, grupo contemporáneo (hacienda * año * época * sexo), grupo racial genético aditivo, y heterosis. Los efectos aleatorios fueron genético aditivo directo y materno y ambiente permanente materno. Las varianzas residuales se asumieron constantes (HOM) o cambiantes a través de diferentes etapas de la trayectoria de crecimiento (HET). Así, se compararon cuatro modelos: LP1HOM, LP1HET, LP2HOM, LP2HET mediante los criterios de información Bayesiano de Schwartz y de Akaike corregido. Resultados: el mejor RRM fue LP2HET. Este modelo fue empleado para obtener heredabilidades directa (Dh) y materna (Mh), correlaciones, y valores genéticos. La función de covarianza aditiva directa estimada mostró que la covarianza aditiva directa aumentó conforme los animales crecieron. La Dh fue 0.24 al nacimiento, disminuyó a 0.02 a los 132 días y luego aumentó hasta 0.18 a los 492 días. La Mh fue despreciable a través del periodo de crecimiento. Los valores de correlación genética directa fueron moderados (0.43) a altos (0.99). Las correlaciones de ambiente permanente materno siguieron una tendencia similar. Conclusiones: estos resultados sugieren que la selección para efectos genéticos aditivos directos basada en el peso a edades tempranas sería efectiva para obtener animales más pesados en estadios de crecimiento posteriores bajo las condiciones tropicales de pastoreo en Colombia.

Objetivo: o objetivo deste trabalho foi à estimação de parâmetros genéticos e a predição dos valores genéticos para peso vivo em bovinos mestiços (Bos taurus-Bos indicus) utilizando modelos de regressão aleatória (RRM). Métodos: foram analisadas 1090 informações de 352 animais, filhos de 37 touros de nove raças diferentes, acasalados com fêmeas Brahman. As raças dos touros foram Brahman, Brahman Vermelho, Guzerá, Blanco Orejinegro, Romosinuano, Simental, Braunvieh, Normanda e Limousin. Para a estimação dos coeficientes das funções de covariância foram utilizados Polinômios de Legendre de primeiro (LP1) e segundo orden (LP2). O modelo animal empregado considerou como efeitos fixos a idade do animal, o numero de partos da vaca, o grupo contemporâneo (fazenda * ano * época * sexo da cria), a genética aditiva do grupo racial e a heterose. E como efeitos aleatórios: o efeito genético aditivo e materno e o ambiente permanente materno. As variâncias residuais assumiram se constantes ao longo da trajetória (HOM) ou com mudanças através das diferentes etapas do crescimento (HET). Assim, compararam se quatro modelos: LP1HOM, LP1HET, LP2HOM, LP2HET por médio de critérios de informação Bayesiano de Schwartz e pelo critério de informação Akaike corrigido. Resultados: o melhor modelo de RRM foi LP2HET. Este modelo foi usado para obter as herdabilidade direta e materna (Dh e Mh), e as correlações genéticas e os valores genéticos. A função de covariância aditiva direta mostrou que as covariâncias genéticas aditivas aumentaram com o crescimento do animal. A Dh foi de 0,24 ao nascimento, diminuiu até 0,02 aos 132 dias e após aumento até 0,18 aos 492 dias. A Mh foi insignificante durante todo o período de crescimento. Os valores de correlação direta aditiva foram de moderados (0,43) a altos (0,99) e tenderam a diminuir quando a idade aumentou. As correlações de ambiente permanente materno seguiram uma tendência similar. Conclusões: estes resultados sugerem que a seleção para os efeitos genéticos aditivos diretos nas idades iniciais seria eficiente na obtenção de animais com maiores pesos na idade adulta sob condições tropicais na Colômbia.

Additive genetic group and heterosis effects on growth and corporal composition of crossbred cattle in southern Cesar (Colombia) / Efectos aditivos de grupo genético y heterosis sobre crecimiento y composición corporal en bovinos cruzados en el sur del Cesar (Colombia) / Efeitos aditivos do grupo genético e de heterose para crescimento e composição corporal de bovinos mestiços no sul do Cesar (Colômbia)

Objective: given the need to evaluate several cattle breeds for growth and body composition traits in Colombia, the objective of this study was to obtain the best linear unbiased estimators of heterosis and breed group effects for these traits. Methods: live weight was evaluated at birth (PN), and aproximately at 4 months (P4), weaning (PD), first year (PA), and 15 months of age (P15). Body composition traits evaluated were rib eye area (AOL) and back fat thickness (GD) measured at the same ages as live weight, except at birth: AOL4 and GD4, AOLD and GDD, AOLA and GDA, AOL15 and GD15. The evaluated population consisted of 352 offspring from 37 bulls representing 9 breeds (Gray Brahman, Red Brahman, Guzerat, Blanco Orejinegro, Romosinuano, Normando, Braunvieh, Limousin, and Simmental), and Gray Brahman females. The farms were located in southern Cesar, Colombia. Univariate animal models were used. Models included contemporary group, dam parity, age of the animal, expected fraction of breed group in the animal, and proportion of heterozygosis as fixed effects, with direct additive and maternal as random effects. Results: the highest additive genetic values for PN, P4, PD, PA, P15 were found in Guzerat (6.31 kg), Normando (12.67 kg), Normando (8.28 kg), Braunvieh (24.80 kg) and Normando (42.20 kg), respectively. Those for AOL4, AOLD, AOLA and AOL15 in Limousin (20.87 cm²), Limousin (12.60 cm²), Simmental (10.94 cm²) and Limousin (16.09 cm²). And those for GD4, GDD, GDA and GD15 in Limousin (0.27 mm), Guzerat (0.21 mm), Blanco Orejinegro (1.05 mm) and Romosinuano (0.71 mm), respectively. The heterosis values for live weight ranged from -3.22 (PA) to 7.43 kg (P15), for AOL from 0.12 (AOL4) to 4.39 mm² (AOLA) and for GD from 0.01 (GDD and GD15) to 0.09 mm (GDA). Conclusion: results indicated that Normando was generally superior for live weight and Limousin was superior for AOL among the animals sampled from each breed in the study.

Objetivo: dada la necesidad de evaluar varias razas bovinas en Colombia para caracteres de crecimiento y composición corporal, el objetivo de este estudio fue obtener mejores estimadores lineales insesgados para efectos de heterosis y grupo racial para tales caracteres. Métodos: las características de crecimiento evaluadas fueron el peso a diferentes edades: nacimiento (PN), y aproximadamente a los 4 meses (P4), destete (PD), año (PA), y 15 meses (P15). Las caracteristicas de composición corporal fueron área de ojo del lomo (AOL) y grasa dorsal (GD) medidas a las mismas edades que el peso, excepto al nacimiento: AOL4 y GD4, AOLD y GDD, AOLA y GDA, AOL15 y GD15. La población estuvo conformada por 352 progenies de 37 toros representando 9 razas (Brahman Gris, Brahman Rojo, Guzerat, Blanco Orejinegro, Romosinuano, Normando, Braunvieh, Limousin y Simmental) y hembras Brahman Gris. Se emplearon modelos animales uni-varidos con los efectos de: grupo contemporáneo, número de partos de la madre, edad del animal, fracción esperada de grupo racial en el animal, y proporción de heterocigosis como efectos fijos y aditivos directo y materno como aleatorios. Resultados: los mayores valores genéticos aditivos para PN, P4, PD, PA y P15 se encontraron en animales de la raza Guzerat (6.31 kg), Normando (12.67 kg), Normando (8.28 kg), Braunvieh (24.80 kg) y Normando (42.20 kg), respectivamente. Para AOL4, AOLD, AOLA y AOL15 se encontraron en animales de la raza Limousin (20.87 cm²), Limousin (12.60 cm²), Simmental (10.94 cm²) y Limousin (16.09 cm²), respectivamente. Y para GD4, GDD, GDA y GD15 se encontraron en animales de la raza Limousin (0.27 mm), Guzerat (0.21 mm), Blanco Orejinegro (1.05 mm) y Romosinuano (0.71 mm). Los valores de heterosis para peso variaron entre -3.22 kg (PA) y 7.43 kg (P15), para AOL entre 0.12 cm² (AOL4) y 4.39 cm² (AOLA) y para GD entre 0.01 (GDD y GD15) y 0.09 mm (GDA). Conclusiones: los resultados indicaron que en general Normando fue superior para peso vivo, y Limousin para AOL entre los animales de cada raza en el estudio.

Objetivo: em virtude da necessidade de avaliar diversas raças de bovinos na Colômbia para características de crescimento e composição corporal, o objetivo deste estudo foi determinar o melhor estimador linear não-viciado para obter os efeitos de heterose e grupo racial para essas características. Métodos: as características de crescimento foram os pesos a diferentes idades: nascimento (PN), y aproximadamente aos quatro meses (P4), desmame (PD), ano (PA) e 15 meses (P15). Características de composição corporal como a área de olho de lombo (AOL) e espessura de gordura subcutânea (GD) foram mensuradas nas mesmas idades, exceto ao peso ao nascimento (AOL4 e GD4; AOLD e GDD; AOLA e GDA; AOL15 e GD15). A população estava conformada por 352 progênies de 37 touros pertencentes a nove raças (Brahman Cinza, Brahman Vermelho, Guzerá, Blanco Orejinegro, Romosinuano, Normando, Braunvieh, Limuosin e Simental) acasalados com fêmeas da raça Brahman Cinza. Foram empregados modelos animais univariados considerando: efeito de grupo de contemporâneos, número de partos da mãe, idade do animal, fração esperada do grupo racial no animal e proporção da heterozigose como efeitos fixos, e como aleatórios o efeito aditivo direto e o efeito materno. Resultados: os maiores valores genéticos aditivos para PN, P4, PD, PA e P15 foram encontrados em animais da raça Guzerá (6.31 kg), Normando (12.67 kg), Normando (8.28 kg), Braunvieh (24.80 kg) e Normando (42.20 kg) respectivamente. Para AOL4, AOLD, AOLA e AOL15 os maiores valores foram encontrados em animais da raça Limousin (20.87 cm²), Limousin (12.60 cm²), Simental (10.94 cm²) e Limousin (16.09 cm²), respectivamente. E para GD4, GDD, GDA e GD15 os maiores valores foram encontrados na raça Limousin (0.27 mm), Guzerá (0.21 mm), Blanco Orejinegro (1.05 mm) e Romosinuano (0.71 mm). Os valores de heterose para peso variaram de -3.22 kg (PA) ate 7.43 kg (P15), para AOL entre 0.12 cm² (AOL4) e 4.39 cm² (AOLA) e para GD entre 0.01 mm (GDD e GD15) e 0.09 mm (GDA). Conclusões: os resultados indicam que em geral animais da raça Normando foram superiores para peso vivo quando se compararam com as outras raças, e para a AOL animais da raça Limousin apresentaram os maiores valores.

Cattle genetic evaluation: a historical perception / La evaluación genética de vacunos: una percepción histórica / A avaliação genética de bovinos: uma percepçã

Mixed model methodology has been the main statistical tool for unbiased genetic animal evaluation and selection of domestic animals, such as bovines, for over thirty years. Since the use of linear mixed models to obtain the best linear unbiased prediction of the breeding value of the individuals in a population was proposed, there have been scientific advances at the statistical and computational level that have led to implement more complex models describing different biological situations and data structures. This work briefly reviews the history of genetic evaluation in cattle emphasizing on the mixed model methodology in which these evaluations are based. The following topics are discussed in this paper: The unibreed animal model, the derivation of the mixed model equations, some extensions of the unibreed animal model (additive direct and maternal effects, random environmental effects, multiple traits model), the mutibreed animal model, models for the genetic evaluation of longitudinal data and, finally, a brief description of genomic evaluation.

La metodología de modelos mixtos ha sido la principal herramienta estadística para la evaluación y la selección de animales domésticos tales como el vacuno durante más de 30 años. Desde que se propuso el uso de modelos lineales mixtos para obtener los mejores predictores lineales insesgados de los valores genéticos de los individuos en una población se han dado avances científicos a nivel estadístico y computacional que han permitido implementar modelos más complejos, los cuales describen diferentes situaciones biológicas y estructuras de datos. En el presente trabajo se hace una breve revisión de la historia de las evaluaciones genéticas en vacunos haciendo énfasis en la metodología de modelos mixtos en la cual se han basado dichas evaluaciones. Los siguientes tópicos son descritos en este documento: El modelo animal unirracial, la derivación de las ecuaciones de modelos mixtos, algunas extensiones del modelo animal unirracial (efectos aditivos directos y maternos, efectos ambientales aleatorios, modelo para múltiples caracteres), el modelo animal multirracial, modelos para la evaluación genética de datos longitudinales y finalmente una breve descripción de la evaluación genómica.

A metodologia dos modelos mistos tem sido a principal ferramenta estatística para a avaliação e seleção de animais domésticos, como ocorreu em bovinos há mais de trinta anos. Desde sua proposta, o uso de modelos lineares mistos, para obter os melhores preditores lineares imparciais dos valores genéticos de indivíduos de uma população, têm sofrendo avanços científicos a nível estatístico e computacional, tornando-se possível implementar modelos mais complexos que descrevem diferentes situações biológicas e estruturas de dados. No presente trabalho, é feita uma breve revisão histórica sobre as avaliações genéticas em bovinos, com ênfase na metodologia de modelos mistos, na qual estas avaliações são baseadas. Os seguintes tópicos são descritos neste documento: o modelo animal unirracial, a derivação das equações de modelos mistos, algumas extensões do modelo animal unirracial (efeitos aditivos direto e materno, efeitos aleatórios ambientais, modelos multicaracterísticas), o modelo animal multirracial, modelos para a avaliação genética de dados longitudinais e, finalmente, uma breve descrição da avaliação genômica.

Mapping ubiquitin modifications reveals new functions for the yeast nuclear pore complex.

Covalent attachment of ubiquitin to target proteins, or ubiquitylation, has emerged as one of the most prevalent posttranslational modifications (PTMs), regulating nearly every cellular pathway. The diversity of functions associated with this particular PTM stems from the myriad ways in which a target protein can be modified by ubiquitin, e.g., monoubiquitin, multi-monoubiquitin, and polyubiquitin linkages. In the current study, we took a systematic approach to analyze the ubiquitylation profiles of the yeast Saccharomyces cerevisiae nuclear pore complex (NPC) proteins or nucleoporins. We found the yeast NPC to be extensively modified by ubiquitin with highly variable ubiquitylation profiles, suggesting that dissection of these modifications may provide new insights into the regulation of NPC functions and reveal additional roles for nucleoporins beyond nuclear transport.

The ubiquitin-activating enzyme (E1) of the early-branching eukaryote Giardia intestinalis shows unusual proteolytic modifications and play important roles during encystation.

Giardia intestinalis is considered an early-branching eukaryote and is therefore a valuable model for studying primordial cellular processes. This work reports the characterization of the ubiquitin-activating enzyme (E1) during growth and different stages of trophozoite differentiation into cysts. We found that in Giardia E1 expression (both at mRNA and protein levels) is regulated during encystation. The enzyme is proteolytically processed mainly into two fragments of 68kDa (N-terminal) and 47kDa (C-terminal). This phenomenon has not been described for any other E1. In trophozoites, this enzyme localized at spots within the cytoplasm as detected by using polyclonal antibodies against either E1 N- or C-terminal fragments. This pattern changed during encystation into a diffuse localization throughout the cytoplasm of encysting cells. E1 localizes in mature cysts at cytoplasmic spots and in the cyst wall. Our antisense silencing experiments suggested that E1 is an essential gene for parasite viability. On the other hand, E1 over-expression greatly increased the encystation rate, indicating a relationship between E1 and Giardia differentiation.

Transcription of metabolic enzyme genes during the excystation of Giardia lamblia.

The present study evaluates the expression of genes of Giardia lamblia, one of the most simple and most early diverging eukaryotes, that encode the metabolic enzymes pyruvate: ferredoxin oxidoreductase (PFOR), acetyl-CoA synthetase (ACS), alcohol dehydrogenase E (ADHE) and glutamate dehydrogenase (GDH) and the cyst wall protein (CWP1) gene in trophozoites, cysts and during the excystation process. Primers were designed to amplify mRNA fragments through quantitative reverse-transcriptase-polymerase-chain-reaction. In trophozoites, all transcripts of the enzymes studied were present. In cysts, three of the transcripts were detected: CWP1, GDH and ACS; but the relative levels of the mRNA of GDH and ACS were very different between trophozoites and cysts. During excystation, PFOR and ADHE transcripts appeared after the first induction phase, and the mRNAs of ACS and GDH increased throughout the process.