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https://science.sciencemag.org/content/364/6444/eaaw0726

The #Brain #Somatic Mosaicism Network
http://science.ScienceMag.org/content/356/6336/eaal1641 Long lifespan of neurons accentuates impact of individual somatic mutations

QT:{{”
Neuropsychiatric disorders have a complex genetic architecture. Human genetic population-based studies have identified numerous heritable sequence and structural genomic variants associated with
susceptibility to neuropsychiatric disease. However, these germline variants do not fully account for disease risk. During brain development, progenitor cells undergo billions of cell divisions to generate the ~80 billion neurons in the brain. The failure to accurately repair DNA damage arising during replication,
transcription, and cellular metabolism amid this dramatic cellular expansion can lead to somatic mutations. Somatic mutations that alter subsets of neuronal transcriptomes and proteomes can, in turn, affect cell proliferation and survival and lead to neurodevelopmental disorders. The long life span of individual neurons and the direct relationship between neural circuits and behavior suggest that somatic mutations in small populations of neurons can significantly affect individual neurodevelopment. The Brain Somatic Mosaicism Network has been founded to study somatic mosaicism both in neurotypical human brains and in the context of complex neuropsychiatric disorders.” “}}

Landscape of somatic retrotransposition in human cancers
http://science.sciencemag.org/content/337/6097/967.long 194 insertions in 43 WGS, mostly L1s w. ~50% near genes

Landscape of Somatic Retrotransposition in Human Cancers

Eunjung Lee1,2,
Rebecca Iskow3,
Lixing Yang1,
Omer Gokcumen3,
Psalm Haseley1,2,
Lovelace J. Luquette III1,
Jens G. Lohr4,5,
Christopher C. Harris6,
Li Ding6,
Richard K. Wilson6,
David A. Wheeler7,
Richard A. Gibbs7,
Raju Kucherlapati2,8,
Charles Lee3,
Peter V. Kharchenko1,9,*,
Peter J. Park1,2,9,*,
The Cancer Genome Atlas Research Network

Science 24 Aug 2012:
Vol. 337, Issue 6097, pp. 967-971
DOI: 10.1126/science.1222077

The paper describes the analysis of transposable elements (TE) insertions at single nucleotide resolution in 43 high coverage whole genome datasets from five cancer types. The authors developed a computational method that uses as input paired-end whole genome sequence data from tumor and normal sample aligned against a reference genome and a custom repeat assembly of TE sequences to detect the position and mechanism of TE insertion. The method identified 194 TE insertions (183 L1s, 10 Alus and 1 ERV). The diversity in the frequency of TE insertions in the same cancer type (ranging from 45-60 to 106 events per tumour) suggests the presence of tumour subtypes with respect to TE activity.

By intersecting the 194 TE with genome annotation, the authors found that 64 TE are in known genes (in UTRs and introns), most of which are implicated in tumour suppressor functions. Also, the TE events targeted genes that are frequently/recurrently mutated, suggesting that TE insertions can potentially contribute to cancer development. Gene expression analysis showed that TE insertion results in significantly decreasing the expression levels for the host gene. TE orientation also has an impact on the expression level, with antisense insertion being less disruptive.

Comparing the germline and somatic insertion sites shows notable differences. Germline L1s are significantly more depleted from genes compared to somatic L1s. Somatic L1s are significantly overrepresented within regions of DNA hypomethylation suggesting the DNA
hypomethylation promoted L1 integration.