Astral microtubule cross-linking safeguards uniform nuclear distribution in the Drosophila syncytium

The early insect embryo develops as a multinucleated cell distributing the genome uniformly to the cell cortex. Mechanistic insight for nuclear positioning beyond cytoskeletal requirements is missing. Contemporary hypotheses propose actomyosin-driven cytoplasmic movement transporting nuclei or repulsion of neighbor nuclei driven by microtubule motors. Here, we show that microtubule cross-linking by Feo and Klp3A is essential for nuclear distribution and internuclear distance maintenance in Drosophila. Germline knockdown causes irregular, less-dense nuclear delivery to the cell cortex and smaller distribution in ex vivo embryo explants. A minimal internuclear distance is maintained in explants from control embryos but not from Feo-inhibited embryos, following micromanipulation-assisted repositioning. A dimerization-deficient Feo abolishes nuclear separation in embryo explants, while the full-length protein rescues the genetic knockdown. We conclude that Feo and Klp3A cross-linking of antiparallel microtubule overlap generates a length-regulated mechanical link between neighboring microtubule asters. Enabled by a novel experimental approach, our study illuminates an essential process of embryonic multicellularity.

Third phase formation behaviour of tris(2-methylbutyl) phosphate and tri-n-alkyl phosphates in the extraction of mineral acids and tetravalent metal ions

The formation of third phase is a detrimental phenomenon witnessed in the nuclear separation processes during the extraction of certain metal salts by an organic solution, which comprises of a neutral extractant, tri-n-butyl phosphate dispersed in a non-polar diluent, n-dodecane (n-C12H26). In the present work, a comparative analysis on the third phase formation behaviour of three trialkyl phosphates, TBP, its linear and branched higher homologues tri-n-amyl phosphate and tris(2-methylbutyl) phosphate (T2MBP), respectively, have been provided which will be useful for the identification of an extractant with minimum third phase formation tendency. The organic phase splitting behaviour during the extraction of three mineral acids (HClO4, HCl and HNO3) and two tetravalent metal nitrates (Th(IV) and Zr(IV)) by trialkyl phosphates has been investigated to understand the influence of anionic and cationic components, respectively, in third phase formation of trialkyl phosphates. The effect of structure of the alkyl groups of trialkyl phosphate and chain length of diluents on third phase formation during Zr(IV) extraction from HNO3 media have also been studied. Overall, the third phase formation behaviour of T2MBP was found to be lower both for the extraction of mineral acid and Zr(IV), thereby indicating its potentiality for applications in various solvent extraction processes.

Composite Ion Exchangers as New Age Photocatalyst

The innovation of different technologies and emphasis on development of new techniques is indispensable to improve the quality of water globally. Photocatalysis is one of the major techniques explored now a days for the exclusion of water impurities using solar light. Different types of photocatalysts have been employed for the removal of dyes, heavy metals, pesticides from aqueous system. During the last few years, nanocomposite ion exchangers were used as a photocatalyst for the removal of organic pollutants. This chapter includes detailed information about introduction of pollutants into the water system, nanocomposite ion exchangers and photocatalysis removal. Nanocomposite ion exchangers effectively degrade various pollutants present in the marine system. These nanocomposites have also been used in different areas such as fuel cell, sensor, nuclear separation and heavy metal removal etc. Therefore, nanocomposite ion exchangers are a new age photocatalyst with unique and effective properties.

CDK5RAP2 primary microcephaly is associated with hypothalamic, retinal and cochlear developmental defects

BackgroundPrimary hereditary microcephaly (MCPH) comprises a large group of autosomal recessive disorders mainly affecting cortical development and resulting in a congenital impairment of brain growth. Despite the identification of >25 causal genes so far, it remains a challenge to distinguish between different MCPH forms at the clinical level.Methods7 patients with newly identified mutations in CDK5RAP2 (MCPH3) were investigated by performing prospective, extensive and systematic clinical, MRI, psychomotor, neurosensory and cognitive examinations under similar conditions.ResultsAll patients displayed neurosensory defects in addition to microcephaly. Small cochlea with incomplete partition type II was found in all cases and was associated with progressive deafness in 4 of them. Furthermore, the CDK5RAP2 protein was specifically identified in the developing cochlea from human fetal tissues. Microphthalmia was also present in all patients along with retinal pigmentation changes and lipofuscin deposits. Finally, hypothalamic anomalies consisting of interhypothalamic adhesions, a congenital midline defect usually associated with holoprosencephaly, was detected in 5 cases.ConclusionThis is the first report indicating that CDK5RAP2 not only governs brain size but also plays a role in ocular and cochlear development and is necessary for hypothalamic nuclear separation at the midline. Our data indicate that CDK5RAP2 should be considered as a potential gene associated with deafness and forme fruste of holoprosencephaly. These children should be given neurosensory follow-up to prevent additional comorbidities and allow them reaching their full educational potential.Trial registration numberNCT01565005.

Astral microtubule crosslinking by Feo safeguards uniform nuclear distribution in the Drosophila syncytium

The early insect embryo develops as a multinucleated cell distributing genome uniformly to the cell cortex. Mechanistic insight for nuclear positioning beyond cytoskeletal requirements is missing to date. Contemporary hypotheses propose actomyosin driven cytoplasmic movement transporting nuclei, or repulsion of neighbor nuclei driven by microtubule motors. Here, we show that microtubule crosslinking by Feo and Klp3A is essential for nuclear distribution and internuclear distance maintenance. Germline knockdown causes irregular, less dense nuclear delivery to the cell cortex and smaller distribution in ex vivo embryo explants. A minimal internuclear distance is maintained in explants from control embryos but not from Feo-depleted embryos, following micromanipulation assisted repositioning. A dimerization deficient Feo abolishes nuclear separation in embryo explants while the full-length protein rescues the genetic knockdown. We conclude that Feo and Klp3A crosslinking of antiparallel microtubule overlap generates a length-regulated mechanical link between neighboring microtubule asters. Enabled by a novel experimental approach, our study illuminates an essential process of embryonic multicellularity.

Nucleus-specific expression in the multinuclear mushroom-forming fungusAgaricus bisporusreveals different nuclear regulatory programs

Many fungi are polykaryotic, containing multiple nuclei per cell. In the case of heterokaryons, there are different nuclear types within a single cell. It is unknown what the different nuclear types contribute in terms of mRNA expression levels in fungal heterokaryons. Each cell of the mushroomAgaricus bisporuscontains two to 25 nuclei of two nuclear types originating from two parental strains. Using RNA-sequencing data, we assess the differential mRNA contribution of individual nuclear types and its functional impact. We studied differential expression between genes of the two nuclear types, P1 and P2, throughout mushroom development in various tissue types. P1 and P2 produced specific mRNA profiles that changed through mushroom development. Differential regulation occurred at the gene level, rather than at the locus, chromosomal, or nuclear level. P1 dominated mRNA production throughout development, and P2 showed more differentially up-regulated genes in important functional groups. In the vegetative mycelium, P2 up-regulated almost threefold more metabolism genes and carbohydrate active enzymes (cazymes) than P1, suggesting phenotypic differences in growth. We identified widespread transcriptomic variation between the nuclear types ofA. bisporus. Our method enables studying nucleus-specific expression, which likely influences the phenotype of a fungus in a polykaryotic stage. Our findings have a wider impact to better understand gene regulation in fungi in a heterokaryotic state. This work provides insight into the transcriptomic variation introduced by genomic nuclear separation.

Nucleus Specific expression in the multinucleated mushroom-forming fungusAgaricus bisporusreveals different nuclear regulatory programs

MotivationFungi are essential in nutrient recycling in nature. They also form symbiotic, commensal, parasitic and pathogenic interactions with other organisms including plants, animals and humans. Many fungi are polykaryotic, containing multiple nuclei per cell. In the case of heterokaryons, there are even different nuclear types within a cell. It is unknown what the different nuclear types contribute in terms of mRNA expression levels in fungal heterokaryons. Each cell of the cultivated, mushroom forming basidiomyceteAgaricus bisporuscontains 2 to 25 nuclei of two nuclear types,P1orP2,that originate from two parental strains. Using RNA-Seq data, we wish to assess the differential mRNA contribution of individual nuclear types in heterokaryotic cells and its functional impact.ResultsWe studied differential expression between genes of the two nuclear types throughout mushroom development ofA. bisporusin various tissue types. The two nuclear types, produced specific mRNA profiles which changed through development of the mushroom. The differential regulation occurred at a gene and multi-gene locus level, rather than the chromosomal or nuclear level. Although the P1 nuclear type dominates the mRNA production throughout development, the P2 type showed more differentially upregulated genes in important functional groups including genes involved in metabolism and genes encoding secreted proteins. Out of 5,090 karyolelle pairs, i.e. genes with different alleles in the two nuclear types, 411 were differentially expressed, of which 246 were up-regulated by the P2 type. In the vegetative mycelium, the P2 nucleus up-regulated almost three-fold more metabolic genes and cazymes than P1, suggesting phenotypic differences in growth. A total of 10% of the differential karyollele expression is associated with differential methylation states, indicating that epigenetic mechanisms may be partly responsible for nuclear specific expression.ConclusionWe have identified widespread transcriptomic variation between the two nuclear types ofA. bisporus. Our novel method enables studying karyollelle specific expression which likely influences the phenotype of a fungus in a polykaryotic stage. This is thus relevant for the performance of these fungi as a crop and for improving this species for breeding. Our findings could have a wider impact to better understand fungi as pathogens. This work provides the first insight into the transcriptomic variation introduced by genomic nuclear separation.