Lack of miRNA Misregulation at Early Pathological Stages in Drosophila Neurodegenerative Disease Models
Résumé
Late onset neurodegenerative diseases represent a major public health concern as the population
in many countries ages. Both frequent diseases such as Alzheimer disease (AD,
14% incidence for 80–84 year-old Europeans) or Parkinson disease (PD, 1.4% prevalence
for >55 years old) share, with other low-incidence neurodegenerative pathologies such
as spinocerebellar ataxias (SCAs, 0.01% prevalence) and frontotemporal lobar degeneration
(FTLD, 0.02% prevalence), a lack of efficient treatment in spite of important research
efforts. Besides significant progress, studies with animal models have revealed unexpected
complexities in the degenerative process, emphasizing a need to better understand the
underlying pathological mechanisms. Recently, microRNAs (miRNAs), a class of small regulatory
non-coding RNAs, have been implicated in some neurodegenerative diseases.The
current data supporting a role of miRNAs in PD, tauopathies, dominant ataxias, and FTLD
will first be discussed to emphasize the different levels of the pathological processes which
may be affected by miRNAs.To investigate a potential involvement of miRNA dysregulation
in the early stages of these neurodegenerative diseases we have used Drosophila models
for seven diseases (PD, 3 FTLD, 3 dominant ataxias) that recapitulate many features of the
human diseases.We performed deep sequencing of head small RNAs after 3 days of pathological
protein expression in the fly head neurons.We found no evidence for a statistically
significant difference in miRNA expression in this early stage of the pathological process.
In addition, we could not identify small non-coding CAG repeat RNAs (sCAG) in polyQ disease
models. Thus our data suggest that transcriptional deregulation of miRNAs or sCAG
is unlikely to play a significant role in the initial stages of neurodegenerative diseases.
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