• dyrk1aa KO zebrafish embryos (Kim et al., 2017): microcephaly, increased apoptosis in the brain, anxiety behavior and impaired social skills in adult fish• human COs overexpressing mutant PTEN (Dhaliwal et al., 2021): reduced size due to impaired neural precursor proliferation and premature neuronal differentiation mediated by a decrease in AKT activation• MO-mediated mfsd2a KD in zebrafish embryos (Guemez-Gamboa et al., 2015): early postnatal lethality and microcephaly with brain-blood barrier disruption. The gene discussed is MFSD2A; the disease is microcephaly.