ATR and microcephalic primordial dwarfism: Mutations in five loci have been linked with Seckel syndrome: SCKL1 and SCKL2 are due to mutation of the genes for the DNA damage response proteins ATR and CtIP (RBBP8), respectively; SCKL4 and SCKL5 are due to mutation of the genes for the centrosomal proteins CENPJ (Centromere protein J, or centrosomal P4.1-associated protein, CPAP; Figure 1A) and CEP152; while the gene responsible for SCKL3 is currently unknown [4], [5], [6], [7].