A Mouse Model with Widespread Expression of the C9orf72-Linked Glycine-Arginine Dipeptide Displays Non-Lethal ALS/FTD-Like Phenotypes

Background: Translation of the hexanucleotide G4C2 expansion associated with C9orf72 Amyotrophic Lateral Sclerosis and Frontotemporal Dementia (ALS/FTD) produces five different dipeptide repeat protein (DPR) species that can confer toxicity. Yet, there is much to learn about the contribution of DPRs to disease pathogenesis, as not all DPRs function and localize within cells in the same manner, nor are they all the same repeat length. These phenomena create a heterogeneity that confounds the study of their toxic consequences. Methods: In vitro transfection of different lengths of the toxic DPR glycine-arginine (poly-GR) was used to determine a relevant pathogenic length for in vivo assessment. We then generated a novel transgenic mouse expressing poly-GR under a ubiquitous promoter for histological characterization and assessment of motor and cognitive behaviors. Results: We identify a short repeat length in vitro that, when expressed, correlates with a reduction in cell survival over an extended period. In vivo, we observe sex-specific chronic ALS/FTD-like phenotypes in our transgenic mice expressing the same short-length DPR, including mild motor neuron loss, but no TDP-43 mis-localization, as well as motor and cognitive impairments. Despite the chronic phenotype, survival of these animals is not affected over 12 months. Conclusions: We show that a short repeat length is sufficient for the DPR poly-GR to confer neurotoxicity in vitro, a phenomenon previously unobserved. This toxicity is reported in vivo in our novel knock-in mouse model characterized by widespread central nervous system (CNS) expression of the short-length poly-GR. We conclude that this short length poly-GR induces a chronic, but non-lethal phenotype in our mouse model and suggest that this model can serve as the foundation for phenotypic exacerbation through second-hit forms of stress.

A highly mutable GST is essential for bract colouration in Euphorbia pulcherrima Willd. Ex Klotsch

BackgroundMutation breeding is an extraordinary tool in plant breeding to increase the genetic variability, where mutations in anthocyanin biosynthesis are targets to generate distinctive phenotypes in ornamental species. In poinsettia, ionizing radiation is routinely applied in breeding programs to obtaining a range of colours, with nearly all pink and white varieties being obtained after γ- or X-ray mutagenesis of red varieties. In the present study we performed a thorough characterization of a potential mutagenesis target gene as the main responsible for the ‘white paradox’ in poinsettia.ResultsWe identified aGSTgene in poinsettia (Bract1) as an essential factor for the expression of anthocyanin-based red colouration of bracts, which presents a high phylogenetic similarity to known anthocyanin-related GSTs. Red poinsettia varieties and white mutants generated from these varieties by X-ray were analysed for polymorphisms related to the ‘white paradox’ in the species. A 4 bp mutation in a short repeat within the coding region ofBract1is most likely responsible for the appearance of white phenotypes upon irradiation treatment. The polymorphism between wild-type and mutant alleles co-segregates with the phenotype in progeny from heterozygous red and white parents. Moreover, overexpression ofBract1wild-type allele in Arabidopsistt19mutants restored the anthocyanin phenotype, while theBract1mutated allele showed to be non-functional.ConclusionsThe identified repeat seems to be highly unstable, since mutated plants can be easily detected among fewer than 200 shoots derived from 10 mutated plants. Our data indicate that particular short repeat sequences, similar to microsatellite sequences or so-called dynamic mutations, might be hot spots for genetic variability. Moreover, the identification of theBract1mutation fills a gap on the understanding on the molecular mechanism of colour formation in poinsettia.

A Highly Mutable GST is Essential for Bract Colouration in Euphorbia Pulcherrima Willd. Ex Klotsch

Background: Mutation breeding is an extraordinary tool in plant breeding to increase the genetic variability, where mutations in anthocyanin biosynthesis are targets to generate distinctive phenotypes in ornamental species. In poinsettia, ionizing radiation is routinely applied in breeding programs to obtaining a range of colours, with nearly all pink and white varieties being obtained after γ- or X-ray mutagenesis of red varieties. In the present study we performed a thorough characterization of a potential mutagenesis target gene as the main responsible for the ‘white paradox’ in poinsettiaResults: We identified a GST gene in poinsettia (Bract1) as an essential factor for the expression of anthocyanin-based red colouration of bracts, which presents a high phylogenetic similarity to known anthocyanin-related GSTs. Red poinsettia varieties and white mutants generated from these varieties by X-ray were analysed for polymorphisms related to the ‘white paradox’ in the species. A 4 bp mutation in a short repeat within the coding region of Bract1 is most likely responsible for the appearance of white phenotypes upon irradiation treatment. The polymorphism between wild-type and mutant alleles co-segregates with the phenotype in progeny from heterozygous red and white parents. Moreover, overexpression of Bract1 wild-type allele in Arabidopsis tt19 mutants restored the anthocyanin phenotype, while the Bract1 mutated allele showed to be non-functional. Conclusions: The identified repeat seems to be highly unstable, since mutated plants can be easily detected among fewer than 200 shoots derived from 10 mutated plants. Our data indicate that particular short repeat sequences, similar to microsatellite sequences or so-called dynamic mutations, might be hot spots for genetic variability. Moreover, the identification of the Bract1 mutation fills a gap on the understanding on the molecular mechanism of colour formation in poinsettia

Comparative mitogenomics of the zoonotic parasite Echinostoma revolutum resolves taxonomic relationships within the ‘E. revolutum’ species group and the Echinostomata (Platyhelminthes: Digenea)

The complete mitochondrial sequence of 17,030 bp was obtained from Echinostoma revolutum and characterized with those of previously reported members of the superfamily Echinostomatoidea, i.e. six echinostomatids, one echinochasmid, five fasciolids, one himasthlid, and two cyclocoelids. Relationship within suborders and between superfamilies, such as Echinostomata, Pronocephalata, Troglotremata, Opisthorchiata, and Xiphiditata, are also considered. It contained 12 protein-coding, two ribosomal RNA, 22 transfer RNA genes and a tandem repetitive consisting non-coding region (NCR). The gene order, one way-positive transcription, the absence of atp8 and the overlapped region by 40 bp between nad4L and nad4 genes were similar as in common trematodes. The NCR located between tRNAGlu (trnE) and cox3 contained 11 long (LRUs) and short repeat units (SRUs) (seven LRUs of 317 bp, four SRUs of 207 bp each), and an internal spacer sequence between LRU7 and SRU4 specifying high-level polymorphism. Special DHU-arm missing tRNAs for Serine were found for both tRNAS1(AGN) and tRNAS2(UCN). Echinostoma revolutum indicated the lowest divergence rate to E. miyagawai and the highest to Tracheophilus cymbius and Echinochasmus japonicus. The usage of ATG/GTG start and TAG/TAA stop codons, the AT composition bias, the negative AT-skewness, and the most for Phe/Leu/Val and the least for Arg/Asn/Asp codons were noted. Topology indicated the monophyletic position of E. revolutum to E. miyagawai. Monophyly of Echinostomatidae and Fasciolidae was clearly solved with respect to Echinochasmidae, Himasthlidae, and Cyclocoelidae which were rendered paraphyletic in the suborder Echinostomata.

Brief Communication: Twelve-year cyclic surging episodes at Donjek Glacier in Yukon, Canada

Surge-type glaciers repeat their short active phase and their much longer quiescent phase usually every several decades or longer, but detailed observations of the evolution cycles have been limited to only a few glaciers. Here we report three surging episodes in 1989, 2001, and 2013 at Donjek Glacier in the Yukon, Canada, indicating remarkably regular and short repeat cycles of 12 years. The surging area is limited within the ∼ 20 km section from the terminus, originating in an area where the flow width significantly narrows downstream, suggesting a strong control of the valley constriction on the surge dynamics.

Detection of simple sequence repeats in the chloroplast genome of Tetraphis pellucida Hedw.

Simple sequence repeats (SSRs) consist of short repeat motifs of 1-6 nucleotides and are found in DNA sequences.The present study was conducted to detect SSRs in chloroplast genome of Tetraphis pellucida (Accession number: NC_024291), downloaded from the National Center for Biotechnology Information (NCBI). The sequence was mined with the help of MISA, a Perl script, to detect SSRs. The length of SSRs defined as ≥12 for mono, di, tri and tetranucleotide, ≥15 for pentanucleotide and ≥18 for hexanucleotide repeats. In total, 41 perfect microsatellites were identified in 127.489 kb sequence mined. An average length of 13.56 bp was calculated for mined SSRs with a density of 1 SSR/3.04 kb. Depending on the repeat units, the length of SSRs ranged from 12 to 20 nt. Dinucleotides (14, 34.15%) were the most frequent repeat type, followed by tetranucleotides (10, 24.39%), trinucleotides (7, 17.07%), mononucleotides (6, 14.63%) and pentanucleotide (4, 9.76%) repeats. Hexanucleotide repeats were completely absent in chloroplast genome of Tetraphis pellucida. The mined SSRs can be used to develop molecular markers and genetic diversity studies in Tetraphis species.

Brief Communication: Twelve-year cyclic surging episode at Donjek Glacier in Yukon, Canada

Surge-type glaciers repeat their short active phase and much longer quiescent phase usually every several decades or longer, but detailed observations of the evolution cycles have been limited to a few glaciers. Here we report three surging episodes in 1989, 2001, and 2013 at Donjek Glacier in the Yukon, indicating remarkably regular and short repeat cycles of 12 years. The surging area is limited within the ~ 20 km section from the terminus, where the flow width significantly narrows than upstream, suggesting a strong control of the valley constriction on the surge dynamics.