A Trem2R47H mouse model without cryptic splicing drives age- and disease-dependent tissue damage and synaptic loss in response to plaques.

BACKGROUND: The TREM2 R47H variant is one of the strongest genetic risk factors for late-onset Alzheimer's Disease (AD). Unfortunately, many current Trem2 R47H mouse models are associated with cryptic mRNA splicing of the mutant allele that produces a confounding reduction in protein product. To overcome this issue, we developed the Trem2R47H NSS (Normal Splice Site) mouse model in which the Trem2 allele is expressed at a similar level to the wild-type Trem2 allele without evidence of cryptic splicing products. METHODS: Trem2R47H NSS mice were treated with the demyelinating agent cuprizone, or crossed with the 5xFAD mouse model of amyloidosis, to explore the impact of the TREM2 R47H variant on inflammatory responses to demyelination, plaque development, and the brain's response to plaques. RESULTS: Trem2R47H NSS mice display an appropriate inflammatory response to cuprizone challenge, and do not recapitulate the null allele in terms of impeded inflammatory responses to demyelination. Utilizing the 5xFAD mouse model, we report age- and disease-dependent changes in Trem2R47H NSS mice in response to development of AD-like pathology. At an early (4-month-old) disease stage, hemizygous 5xFAD/homozygous Trem2R47H NSS (5xFAD/Trem2R47H NSS) mice have reduced size and number of microglia that display impaired interaction with plaques compared to microglia in age-matched 5xFAD hemizygous controls. This is associated with a suppressed inflammatory response but increased dystrophic neurites and axonal damage as measured by plasma neurofilament light chain (NfL) level. Homozygosity for Trem2R47H NSS suppressed LTP deficits and loss of presynaptic puncta caused by the 5xFAD transgene array in 4-month-old mice. At a more advanced (12-month-old) disease stage 5xFAD/Trem2R47H NSS mice no longer display impaired plaque-microglia interaction or suppressed inflammatory gene expression, although NfL levels remain elevated, and a unique interferon-related gene expression signature is seen. Twelve-month old Trem2R47H NSS mice also display LTP deficits and postsynaptic loss. CONCLUSIONS: The Trem2R47H NSS mouse is a valuable model that can be used to investigate age-dependent effects of the AD-risk R47H mutation on TREM2 and microglial function including its effects on plaque development, microglial-plaque interaction, production of a unique interferon signature and associated tissue damage.

Hybridization and polyploidization effects on LTR-retrotransposon activation in potato genome.

Hybridization and polyploidization are major forces in plant evolution and potatoes are not an exception. It is proposed that the proliferation of Long Terminal Repeat-retrotransposons (LTR-RT) is related to genome reorganization caused by hybridization and/or polyploidization. The main purpose of the present work was to evaluate the effect of interspecific hybridization and polyploidization on the activation of LTR-RT. We evaluated the proliferation of putative active LTR-RT in a diploid hybrid between the cultivated potato Solanum tuberosum and the wild diploid potato species S. kurtzianum, allotetraploid lines derived from this interspecific hybrid and S. kurtzianum autotetraploid lines (ktz-autotetraploid) using the S-SAP (sequence-specific amplified polymorphism) technique and normalized copy number determination by qPCR. Twenty-nine LTR-RT copies were activated in the hybrid and present in the allotetraploid lines. Major LTR-RT activity was detected in Copia-27, Copia-12, Copia-14 and, Gypsy-22. According to our results, LTR-RT copies were activated principally in the hybrid, there was no activation in allotetraploid lines and only one copy was activated in the autotetraploid.

Genomic re-assessment of the transposable element landscape of the potato genome.

KEY MESSAGE: We provide a comprehensive and reliable potato TE landscape, based on a wide variety of identification tools and integrative approaches, producing clear and ready-to-use outputs for the scientific community. Transposable elements (TEs) are DNA sequences with the ability to autoreplicate and move throughout the host genome. TEs are major drivers in stress response and genome evolution. Given their significance, the development of clear and efficient TE annotation pipelines has become essential for many species. The latest de novo TE discovery tools, along with available TEs from Repbase and sRNA-seq data, allowed us to perform a reliable potato TEs detection, classification and annotation through an open-source and freely available pipeline ( https://github.com/DiegoZavallo/TE_Discovery ). Using a variety of tools, approaches and rules, we were able to provide a clearly annotated of characterized TEs landscape. Additionally, we described the distribution of the different types of TEs across the genome, where LTRs and MITEs present a clear clustering pattern in pericentromeric and subtelomeric/telomeric regions respectively. Finally, we analyzed the insertion age and distribution of LTR retrotransposon families which display a distinct pattern between the two major superfamilies. While older Gypsy elements concentrated around heterochromatic regions, younger Copia elements located predominantly on euchromatic regions. Overall, we delivered not only a reliable, ready-to-use potato TE annotation files, but also all the necessary steps to perform de novo detection for other species.

A novel recombinant variant of latent membrane protein 1 from Epstein Barr virus in Argentina denotes phylogeographical association.

AIM: To study LMP1 variants distribution among children with EBV+ malignant and benign conditions as well as in healthy carriers. METHODS: Oral secretions and blood cells from 31 children with IM, and biopsies from 14 EBV+ reactive lymphoid hyperplasia and 33 EBV+ lymphomas were included. LMP1 was amplified by nested PCR and sequenced. Phylogenetic reconstructions were made under Maximun Likelihood, Bayesian and coalescent algorithms. RESULTS: Six clades were defined (China1, China2, Med-, Alaskan, B95.8 and Argentine). Argentine variants, the most prevalent (46%), harbored 3 distinctive mutations and were a recombination between Raji and China1. Despite no pathology or compartment associations were observed for LMP1, the Argentine clade showed a phylogeographic association with our region. LMP1 estimated evolution rate was 8.591x10-5s/s/y and the estimated tMRCA for Raji and Argentine was 136ybp. CONCLUSIONS: An LMP1 Argentine clade was defined. LMP1 evolutionary rate was higher than expected for herpesviruses. The tMRCA for Raji and the Argentine agrees with African immigration and could explain the recombinant nature of the Argentine variant.

Estudio de microcefalia en recién nacidos de Argentina: su relación con virus Zika y otras etiologías / Study of microcephaly in newborns from Argentina: its relationship with Zika virus and other etiologies

INTRODUCCIÓN El virus Zika (ZIKV) es un flavivirus. La transmisión vertical puede provocar microcefalia y/u otras anomalías congénitas. En Argentina el vector Aedes Aegypti tiene amplia distribución y desde 2016 hay brotes de ZIKV. OBNETIVOS Conocer la situación epidemiológica de la microcefalia y/o anomalías cerebrales seleccionadas en la red de maternidades de la Red Nacional de Anomalías Congénitas (RENAC). MÉTODOS Se incluyeron recién nacidos de la RENAC desde 4/ 2016 a 3/2017. Caso; recién nacidos con perímetro cefálico menor al percentilo 3 según edad gestacional y sexo. Se analizó sangre y orina de madre y recién nacido. Para ZIKV se realizó PCR, ELISA IgM y neutralización por reducción de placas (PRNT). Se evaluó infección por toxoplasmosis, rubéola, herpes simple, lúes, citomegalovirus (CMV). RESULTADOS Se detectaron 104 casos, prevalencia 6,9 por 10.000 (IC95%;5,7-8,4), resultando un incremento significativo al comparar con el año 2015, RP 1,7 (IC 95%;1,2-2,3). Las jurisdicciones con transmisión sostenida de dengue no mostraron diferencias significativas con aquellas sin transmisión, RP 1,06 (IC 95% 0,6-2,0). Se detectó una causa conocida específica 25%, microcefalia por una malformación cerebral específica 9,6% y sin causa definida 65,4%. En 4 casos se detectó serología positiva para ZIKV, 2 fueron autóctonos y 2 importados. Los 4 casos presentaron microcefalia con desproporción craneofacial y en un caso artrogriposis. Además se detectaron; 4 casos de infección por CMV, 3 por toxoplasmosis, 2 por herpes simple y 1 lúes congénita. No hubo casos de rubéola. DISCUSIÓN La prevalencia fue significativamente mayor a la detectada en la RENAC en el período previo. Esta situación podría estar indicando un aumento real en la prevalencia o bien puede explicarse por el efecto del conocimiento. El sistema permitió detectar cuatro casos con síndrome de ZIKV congénito, en un país que ha tenido brotes aislados de esta enfermedad

LMP1 promoter sequence analysis in Epstein Barr virus pediatric infection reveals preferential circulation of B95.8 related variants in Argentina.

The Epstein Barr virus (EBV) is associated with several lymphoid and epithelial malignancies such as Hodgkin and Burkitt lymphoma or nasopharyngeal carcinoma and it is also the etiological agent of infectious mononucleosis (IM). Transcriptional regulation of the viral oncoprotein LMP1, remains yet not fully understood. LMP1 expression can be initiated in an EBNA2 dependent or independent manner from ED-L1 or LT-R1 promoters. It has been proposed that sequence variation at ED-L1 region could be an important factor concerning LMP1 expression. In order to characterize the natural sequence variation of the ED-L1 promoter, and its relationship with neoplasia, 44 pediatric patients, 17 IM and 27 EBV-associated lymphoma cases from Argentina, were studied. Phylogenetic analysis showed 4 main clusters, namely B95.8, Raji, Cao and P3HR1. Most isolates, 80.3%, conformed the B95.8 group. Co-infection with more than one viral variant was detected in 5/17 IM cases, but no co-infections were detected among lymphoma cases. Moreover, co-infected IM cases exhibited differences between the ED-L1 sequences obtained from different anatomical compartments. Mutations confined to transcription factor binding sites such as SP1/SP3, CRE, AP2, C/EBP were found in similar proportions in 23 isolates from both benign and malignant samples, rendering the distribution of these mutations not significant among malignant samples.

Distinctive Epstein-Barr virus variants associated with benign and malignant pediatric pathologies: LMP1 sequence characterization and linkage with other viral gene polymorphisms.

The ubiquitous Epstein-Barr virus (EBV) is related to the development of lymphoma and is also the etiological agent for infectious mononucleosis (IM). Sequence variations in the gene encoding LMP1 have been deeply studied in different pathologies and geographic regions. Controversial results propose the existence of tumor-related variants, while others argued in favor of a geographical distribution of these variants. Reports assessing EBV variants in IM were performed in adult patients who displayed multiple variant infections. In the present study, LMP1 variants in 15 pediatric patients with IM and 20 pediatric patients with EBV-associated lymphomas from Argentina were analyzed as representatives of benign and malignant infections in children, respectively. A 3-month follow-up study of LMP1 variants in peripheral blood cells and in oral secretions of patients with IM was performed. Moreover, an integrated linkage analysis was performed with variants of EBNA1 and the promoter region of BZLF1. Similar sequence polymorphisms were detected in both pathological conditions, IM and lymphoma, but these differ from those previously described in healthy donors from Argentina and Brazil. The results suggest that certain LMP1 polymorphisms, namely, the 30-bp deletion and high copy number of the 33-bp repeats, are associated with EBV-related pathologies, either benign or malignant, instead of just being tumor related. Additionally, this is the first study to describe the Alaskan variant in EBV-related lymphomas that previously was restricted to nasopharyngeal carcinomas from North America.