SNAI2 and Werner syndrome: WS is clinically and genetically heterogeneous and is classified into four types (WS1–4) caused by mutations of paired box 3 (PAX3), melanogenesis-associated transcription factor (MITF), endothelin 3 (EDN3), endothelin receptor type B (EDNRB), snail-family transcriptional repressor 2 (SNAI2), and SRY-box 10 (SOX10)3, 4.