Tissue-specific control of brain-enriched miR-7 biogenesis

Area of Science:

• Molecular Biology
• Genetics
• Neuroscience

Background:

• MicroRNA (miRNA) biogenesis is tightly regulated in eukaryotes.
• Tissue-specific miRNA expression patterns suggest post-transcriptional regulation.
• The brain-enriched miR-7 originates from a ubiquitous primary transcript.

Purpose of the Study:

• To elucidate the post-transcriptional mechanisms controlling brain-specific miR-7 expression.
• To identify factors responsible for inhibiting miR-7 biogenesis in non-neural tissues.
• To investigate the role of MSI2 and HuR in miR-7 processing.

Main Methods:

• Stable isotope labeling by amino acids in cell culture (SILAC) mass spectrometry.
• RNase-assisted RNA pull-down assays.
• Electrophoretic mobility shift assays (EMSA) and footprinting analysis.
• Neuronal differentiation studies in SH-SY5Y cells.
• Analysis of miR-7 levels in MSI2 knockout mice.

Main Results:

• Musashi homolog 2 (MSI2) and Hu antigen R (HuR) were identified as inhibitors of miR-7 processing in non-neural cells.
• HuR mediates MSI2 binding to pri-miR-7, stabilizing its structure and inhibiting processing.
• This inhibitory mechanism was confirmed in a neuronal differentiation model.
• MSI2 knockout mice exhibit elevated miR-7 levels without changes in pri-miR-7 transcript abundance.

Conclusions:

• The study reveals a novel mechanism for regulating brain-enriched miRNA processing.
• MSI2 and HuR act as tissue-specific factors controlling miR-7 biogenesis.
• This provides the first insight into defined factors regulating brain-specific miRNA processing.