Functional consequences of all KARS1 missense variants (p.(Ala2Val), p.(Ala57Pro), p.(Arg108Cys), p.(Arg205Cys), p.(Phe291Val), p.(Ile346Thr), p.(Arg348Cys), p.(His402Tyr), p.(Pro499Leu), p.(Pro533Arg), and p.(Phe585Cys)) plus the p.(Asn591Ile) variant recently found in a patient with microcephaly (Boonsawat et al., 2019), were investigated in Saccharomyces cerevisiae. The gene discussed is KARS1; the disease is microcephaly.