Table 1.

Mendelian Disorders that Exhibit Microcephaly and Growth Retardation Associated with Defective ATR-Pathway Function

Disorder	Mutant Gene	ATR-Dependent Cellular Features
Seckel syndrome	ATR, PCNT2 and unknown	Defective ATR-dependent G2-M arrest, supernumerary mitotic centrosomes, DFS expression
Nijmegen breakage syndrome	NBS1	Defective ATR-dependent G2-M arrest
Fanconi anaemia	FANC-A,B,C,D1,D2,E,F,G,H,M,J	Defective ATR-dependent G2-M arrest, DFS expression
MCPH1-dependent Primary Microcephaly	MCPH1	Defective ATR-dependent G2-M arrest, supernumerary mitotic centrosomes