Taking the gene MMAB with the most MR discoveries as an example, its irQTL could be mapped in multiple tissues, leading to the downstream causal inference of its isoforms on multiple neuro-related phenotypes, such as sleep duration, insomnia, neuroticism, miserableness, and schizophrenia (results in the amygdala are illustrated in Fig. 2c). This evidence concerns the gene MMAB and insomnia measurement.