TRNT1 and Global developmental delay: In patients with sideroblastic anemia, B cell immunodeficiency, periodic fevers, and developmental delays (SIFD), mutations downstream of Met30—including premature stop codons, frameshifts, and catalytic region mutations—are predicted to disrupt both the mitochondrial and nuclear TRNT1 isoforms (Figure S7A).62,63 By contrast, our model predicts that nonsense or frameshift mutations upstream of the Met30 start codon would specifically impact the longer TRNT1 isoform.