Finaurini, S. | Search bioRxiv

bioRxiv2021

Identification of LINE retrotransposons and long non-coding RNAs expressed in the octopus brain

BackgroundTransposable elements (TEs) widely contributed to the evolution of genomes allowing genomic innovations, generating germinal and somatic heterogeneity and giving birth to long non-coding RNAs (lncRNAs). These features have been associated to the evolution, functioning and complexity of the nervous system at such a level that somatic retrotransposition of long interspersed element (LINE) L1 has been proposed to be associated to human cognition. Among invertebrates, octopuses are fascinating animals whose nervous system reaches a high level of complexity achieving sophisticated cognitive abilities. The sequencing of the genome of the Octopus bimaculoides revealed a striking expansion of TEs which were proposed to have contributed to the evolution of its complex nervous system. We recently found a similar expansion also in the genome of Octopus vulgaris. However a specific search for the existence of full-length transpositionally competent TEs has not been performed in this genus. ResultsHere we report the identification of LINE elements competent for retrotransposition in Octopus vulgaris and Octopus bimaculoides and show evidence suggesting that they might be active driving germline polymorphisms among individuals and somatic polymorphisms in the brain. Transcription and translation measured for one of these elements resulted in specific signals in neurons belonging to areas associated with behavioral plasticity. We also report the transcription of thousands of lncRNAs and the pervasive inclusion of TE fragments in the transcriptomes of both Octopus species, further testifying the crucial activity of TEs in the evolution of the octopus genomes. ConclusionsThe neural transcriptome of the octopus shows the transcription of thousands of putative lncRNAs and of a full lenght LINE element belonging to the RTE class. We speculate that a convergent evolutionary process involving retrotransposons activity in the brain has been important for the evolution of sophisticated cognitive abilities in this genus.

genomics↗

bioRxiv2020

Transposable Element activation promotes neurodegeneration in a Drosophila model of Huntington's disease

Huntingtons disease (HD) is a late-onset, autosomal dominant disorder characterized by progressive motor dysfunction, cognitive decline and psychiatric disturbances. The most prominent pathological manifestation is a selective loss of medium-sized spiny neurons of the striatum. The disease is caused by a CAG repeat expansion in the IT15 gene, which elongates a stretch of polyglutamine at the amino-terminal of the HD protein, Huntingtin (Htt). Despite the accumulation of an impressive amount of data on the molecular basis of neurodegeneration, no therapeutic treatments are available and new pharmacological targets are needed. Transposable Elements (TEs) are mobile genetic elements that constitute a large fraction of eukaryotic genomes. Retrotransposons (RTEs) replicate through an RNA intermediate and represent approximately 40% and 30% of the human and Drosophila genomes. Mounting evidence suggests that mammalian RTEs are normally active during neurogenesis and may be involved in diseases of the nervous system. Here we show that TE expression and mobilization are increased in a Drosophila melanogaster HD model. By inhibiting TE mobilization with Reverse Transcriptase inhibitors, polyQ-dependent eye neurodegeneration and genome instability in larval brains are rescued and fly lifespan is increased. These results suggest that TE activation may be involved in polyQ-induced neurotoxicity and a potential pharmacological target.

neuroscience↗