Point mutations throughout the GLI3 gene cause Greig cephalopolysyndactylysyndrome

Greig cephalopolysyndactyly syndrome, characterized by craniofacial and lim b anomalies (GCPS; MIM 175700), previously has been demonstrated to be asso ciated with translocations as well as point mutations affecting one allele of the zinc finger gene GLI3. In addition to GCPS, Pallister-Hall syndrome (PHS; MIM 146510) and past-axial polydactyly type A (PAP-A; MIM 174200), tw o other disorders of human development, are caused by GLI3 mutations. In or der to gain more insight into the mutational spectrum associated with a sin gle phenotype, we report here the extension of the GLI3 mutation analysis t o 24 new GCPS cases. We report the identification of 15 novel mutations pre sent in one of the patient's GLI3 alleles, The mutations map throughout the coding gene regions. The majority are truncating mutations (nine of 15) th at engender prematurely terminated protein products mostly but not exclusiv ely N-terminally to or within the central region encoding the DNA-binding d omain. Two missense and two splicing mutations mapping within the zinc fing er motifs presumably also interfere with DNA binding. The five mutations id entified within the protein regions C-terminal to the zinc fingers putative ly affect additional functional properties of GLI3, In cell transfection ex periments using fusions of the DNA-binding domain of yeast GAL4 to differen t segments of GLI3, transactivating capacity was assigned to two adjacent i ndependent domains (TA, and TA,) in the C-terminal third of GLI3. Since the se are the only functional domains affected by three C-terminally truncatin g mutations, we postulate that GCPS may be due either to haploinsufficiency resulting from the complete loss of one gene copy or to functional haploin sufficiency related to compromised properties of this transcription factor such as DNA binding and transactivation.