Repressing PTBP1 is incapable to convert reactive astrocytes to dopaminergic neurons in a mouse model of Parkinson's disease

Abstract

Lineage reprograming of resident glia cells to induced dopaminergic neurons (iDAns) holds attractive prospect for cell-replacement therapy of Parkinsons disease (PD). Recently, whether repressing polypyrimidine tract binding protein 1 (PTBP1) could truly achieve efficient astrocyte-to-iDAn conversion in substantia nigra and striatum aroused widespread controversy. Although reporter positive iDAns were observed by two groups after delivering adeno-associated virus (AAV) expressing a reporter with shRNA or Crispr-CasRx to repress astroglial PTBP1, the possibility of AAV leaking into endogenous DAns could not be excluded without using a reliable lineage tracing method. By adopting stringent lineage tracing strategy, two other studies showed that neither knockdown nor genetic deletion of quiescent astroglial PTBP1 fails to obtain iDAns under physiological condition. However, the role of reactive astrocyte might be underestimated since upon brain injury, reactive astrocyte could acquire certain stem cell hallmarks which may facilitate the lineage conversion process. Therefore, whether reactive astrocytes could be genuinely converted to DAns after PTBP1 repression in a PD model needs further validation. In this study, we used Aldh1l1-CreERT2-mediated specific astrocyte-lineage tracing method to investigate whether reactive astrocytes could be converted to DAns in the 6-OHDA PD model. However, we found that no astrocyte-originated DAn was generated after effective knockdown of astroglial PTBP1 either in the substantia nigra or in the striatum, while AAV "leakage" to nearby neurons was observed. Our results further confirmed that repressing PTBP1 is unable to convert astrocytes to DAns no matter in physiological or PD-related pathological conditions. Graphic abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=69 SRC="FIGDIR/small/468309v2_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@fa2fa5org.highwire.dtl.DTLVardef@14e328eorg.highwire.dtl.DTLVardef@d93faborg.highwire.dtl.DTLVardef@e32225_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIAAV-shPtbp1 rapidly and efficiently induces viral-reporter-labeled DAns in mouse brain under physiological condition C_LIO_LIViral-reporter-positive DAns are not originated from PTBP1 repressed and lineage traced reactive astrocytes in a mouse PD model C_LI