Tet1 is dispensable for maintaining pluripotency and its loss is compatible with embryonic and postnatal development

The Tet family of enzymes (Tet1/2/3) converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Mouse embryonic stem cells (mESCs) highly express Tet1 and have an elevated level of 5hmC. Tet1 has been implicated in ESC maintenance and lineage specification in?vitro but its precise function in development is not well defined. To establish the role of Tet1 in pluripotency and development, we have generated Tet1 mutant mESCs and mice. Tet1(-/-) ESCs have reduced levels of 5hmC and subtle changes in global gene expression, and are pluripotent and support development of live-born mice in tetraploid complementation assay, but display skewed differentiation toward trophectoderm in?vitro. Tet1 mutant mice are viable, fertile, and grossly normal, though some mutant mice have a slightly smaller body size at birth. Our data suggest that Tet1 loss leading to a partial reduction in 5hmC levels does not affect pluripotency in ESCs and is compatible with embryonic and postnatal development.     

Microtubule End-Clustering Maintains a Steady-State Spindle Shape

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Gene targeting methods for studying nuclear transport factors in mice

Genetically engineered mice have been widely used to study gene function in a variety of life-science disciplines. However, the use of animal models in the field of nucleocytoplasmic transport has been limited, mainly because disruption of individual transport factors is expected to deregulate basic biological processes so severely that the embryo dies at an early stage in development. Early studies in which transport factors were knocked out in mice have confirmed this notion. Recent work has shown that hypomorphic alleles are very useful for studying essential genes at the organismal level. In combination with wild-type and knockout alleles, hypomorphic alleles can be used to generate a series of mice in which the expression of a protein is gradually reduced from normal to zero. Within this series, there is often an allelic combination that yields liveborn mice that develop overt phenotypes as they age, and that can be used to study the physiological relevance of the protein. In this article, we present an efficient method for generating an allelic series of mice. It involves the use of a multi-purpose gene-targeting vector that produces a hypomorphic allele that can also be converted into conditional and knockout alleles within the mouse. This method saves time and provides flexibility in terms of choosing the most appropriate model for studying components of the nucleocytoplasmic machinery at the organismal level.     

Resolution of sister centromeres requires RanBP2-mediated SUMOylation of topoisomerase IIalpha

RanBP2 is a nucleoporin with SUMO E3 ligase activity that functions in both nucleocytoplasmic transport and mitosis. However, the biological relevance of RanBP2 and the in vivo targets of its E3 ligase activity are unknown. Here we show that animals with low amounts of RanBP2 develop severe aneuploidy in the absence of overt transport defects. The main chromosome segregation defect in cells from these mice is anaphase-bridge formation. Topoisomerase IIalpha (Topo IIalpha), which decatenates sister centromeres prior to anaphase onset to prevent bridges, fails to accumulate at inner centromeres when RanBP2 levels are low. We find that RanBP2 sumoylates Topo IIalpha in mitosis and that this modification is required for its proper localization to inner centromeres. Furthermore, mice with low amounts of RanBP2 are highly sensitive to tumor formation. Together, these data identify RanBP2 as a chromosomal instability gene that regulates Topo IIalpha by sumoylation and suppresses tumorigenesis.     

Multitrophic interactions of entomopathogenic fungi in BioControl

BioControl - Biocontrol with hypocrealean entomopathogenic fungi (EF) is a key tool to develop Integrated Pest Management (IPM) programs for the progressive replacement of synthetic chemical...     

Field evaluation of the susceptibility of mill and table olive varieties to egg‐laying of olive fly

The susceptibility of 20 widely distributed mill and table olive varieties to Bactrocera oleae (Rossi) as affected by irrigation, and fruit diameter and oil content was evaluated in a 3‐year trial in Southern Spain. Bactrocera oleae was bivoltine life cycle in the experimental site, with significant differences among population size throughout the study. Even though the olive fruit fly damaged all varieties, significant differences in susceptibility were detected. Among the mill olive varieties “Nevadillo Blanco de Jaén” was the most susceptible, with average infestation levels ranging between 6.7% and 52.2% and between 10.3% and 69.2% under rainfed and irrigated conditions, respectively, and “Arbequina” was the least susceptible, with average infestation levels ranging between 0.6% and 12.7% and between 2.3% and 18.5% under rainfed and irrigated conditions, respectively. Among the table olive varieties, “Gordal Sevillana,” “Ascolana Tenera” and “Ocal” were the most susceptible (with average infestation levels reaching 39.7%, 36.5% and 33.3%, respectively), while “Callosina” was the least susceptible (with infestation levels of only 8.4%). Irrigation tended to promote both B. oleae infestation and its earlier occurrence compared to the rainfed condition. Even though the diameter and oil content were positively correlated with B. oleae fruit infestation (correlation coefficients ranged between 0.5 and 0.95), the present work reveals that other yet‐unknown factors may influence B. oleae oviposition preferences. The results of this study can be useful for breeding programmes to develop olive varieties resistant to B. oleae and provide key information for wide‐area olive fly pest management decisions.