Compact Calm1 promoter enables AAV mediated neuron-targeted expression in human iPSC-derived brain organoids

Compact neuron-specific promoters enable targeted gene expression in the brain, especially when using size-limited adeno-associated virus (AAV) vectors. The human synapsin 1 gene promoter (hSyn) promoter is widely used, but the recently described Calm1 promoter (120 bp long) offers a smaller alternative with demonstrated excitatory and inhibitory neuron-specificity in animal models. Here, we compared the commonly used hSyn promoter and the compact Calm1 promoter in human iPSC-derived brain organoids using AAV reporter constructs. Our study evaluating reporter gene expression and immunohistology showed comparable performance in human neurons. Our findings suggest that the compact Calm1 promoter could be used for future central nervous system-targeted human gene therapies.