SFPQ Condensates Help Neurons Transcribe Their Longest Genes

Neurons rely on an unusually large number of exceptionally long genes, some exceeding 2 Mb, to build synapses and wire neural circuits. Because transcription takes longer for these extended stretches of genetic code, and because gene expression must be regulated at multiple points along the way, neurons are thought to need specialized mechanisms for reading long genes accurately and keeping their expression stable. Until now, the details of how neurons manage this task have remained poorly understood.

Researchers from Ehime University examined SFPQ, an RNA-binding protein, to better understand this process. Using super-resolution microscopy and other techniques, the study found that SFPQ uses long RNA molecules as scaffolds to build meshwork-like structures known as condensates within the cell nucleus. Condensates are membraneless assemblies that form when specific molecules cluster together inside cells. 

The research, published in Cell Chemical Biology, further showed that these SFPQ condensates draw together numerous molecules involved in three separate processes: transcription itself, RNA splicing, and the regulation of chromatin. When the researchers prevented SFPQ condensates from forming, the consequences were substantial: extra-long genes were not read properly to the end, RNA splicing was impaired, and overall gene expression decreased.

Together, these findings point to SFPQ condensates functioning as a kind of shared workspace, one that brings together the several distinct processes exceptionally long genes need in order to function properly. The work offers physical insight into a concept previously proposed but not directly observed, the “transcriptional elongation condensate,” and it points to a new way of understanding gene regulation through the spatial organization of the nucleus.

The implications extend beyond basic cell biology. SFPQ and related proteins have already been linked to autism spectrum disorder and amyotrophic lateral sclerosis, both conditions tied to neuronal function. Because exceptionally long genes are especially important for synapse formation and neural circuitry, disruptions in how they are read and expressed could plausibly contribute to disease. Going forward, studying abnormal expression of these extra-long genes may help researchers better understand the mechanisms underlying neurodevelopmental and neurodegenerative disorders.