ERCC4 and Down syndrome: In addition to NER, the ERCC4/ERCC1 complex is suggested to play a role in removal of DNA interstrand cross-links (ICL), DNA double-strand breaks (DSB), and immunoglobulin class switch recombination (CSR) [11], [12], [13], [14] Germ-line mutations in ERCC4, among other XP genes in the NER pathway, are associated with some rare inherited human syndromes, such as Xeroderma pigmentosum (XP), Cockayne syndrome (CS) and Trichothiodystrophy (TTD) [15].