Spatial proteomics reveals distinct protein patterns in cortical migration disorders caused by LIN28A overexpression and WNT activation.

Abstract

Developmental signalling pathways act in stage and tissue dependent relation and mis-activation can drive tumour formation. The RNA-binding protein LIN28A binds to mRNA and miRNA and thereby affects the protein turnover and maintains stemness. LIN28A is overexpressed in embryonal brain tumours which show low correlation between transcriptome and proteome signatures. Additionally, stabilising CTNNB1 mutations activating the WNT pathway have been reported in brain tumours with LIN28A overexpression. The aim of this study was to co-activate these oncogenic proteins during embryonal brain development and investigate the histomorphology of the cerebral cortex in relation to proteome levels with spatial resolution using the nanosecond infrared laser (NIRL) system for nano-volume sampling. The combination of both oncogenic factors in in vivo model did not lead to brain tumour formation during embryonal development but resulted in disturbed lamination and impaired cell migration in the cerebral cortex. Spatially resolved proteome analysis of the cortices reveal unique layer signatures across ablated layers. Moreover, the extracellular matrix receptors RPSA and ITGB1 were spatially disturbed comparing the mouse models and accompanied by a porous pial border and overmigration of neural cells. Cajal-Retzius cells were misplaced in deeper cortex regions without affecting general REELIN levels. Additionally, the glycosylated levels of α-DYSTROGLYCAN were reduced in this model. Taken together, the interplay of LIN28A and CTNNB1 resulted in a cortical migration disorder showing histomorphological and molecular similarities to human Cobblestone lissencephaly (type 2) disorder. This highlights novel implications of the oncogene LIN28A in extracellular matrix integrity.