-TEFb, 7SK, 7SK non-coding RNA, 7SK small nuclear ribonucleoprotein, 7SK snRNA, 7SK snRNP, Alazami syndrome, Arg518, C, Cyclin-T1, Flavopiridol, HEXIM1, HEXIM1/2, ID2, ID3, LARP7, LARP7 loss-of-function variants, MEPCE, MEPCE nonsense variant, MEPCE protein, MRPL11, P, P-TEFb, RNA polymerase II, RNAP II, RNAP II C-terminal domain, RNAP II-, RNAP II-sensitive genes, U1, U2, U4, boy, c, c.1552C>T, cyclin-dependent kinase 9, eukaryotes, fibroblasts, global developmental delay, growth retardation, intellectual disability, mRNA, neurodevelopmental disorder, patient, patient cells, seizures, snRNAs, specific genes, transcription elongation factor b