Other putative CDKL5 substrates include trichothiodystrophy non‐photosensitive 1 (TTDN1), an uncharacterized protein mutated in a form of trichothiodystrophy (TTD), typically caused by failure in transcription‐coupled DNA repair (Heller et al, 2015). The gene discussed is CDKL5; the disease is trichothiodystrophy.