Physical and functional interactions between Zic and Gli proteins.

Zic and Gli family proteins are transcription factors that share similar zinc finger domains. Recent studies indicate that Zic and Gli collaborate in neural and skeletal development. We provide evidence that the Zic and Gli proteins physically and functionally interact through their zinc finger domains. Moreover, Gli proteins were translocated to cell nuclei by coexpressed Zic proteins, and both proteins regulated each other's transcriptional activity. Our result suggests that the physical interaction between Zic and Gli is the molecular basis of their antagonistic or synergistic features in developmental contexts and that Zic proteins are potential modulators of the hedgehog-mediated signaling pathway.

Molecular properties of Zic proteins as transcriptional regulators and their relationship to GLI proteins.

Zic family genes encode zinc finger proteins, which play important roles in vertebrate development. The zinc finger domains are highly conserved between Zic proteins and show a notable homology to those of Gli family proteins. In this study, we investigated the functional properties of Zic proteins and their relationship to the GLI proteins. We first established an optimal binding sequence for Zic1, Zic2, and Zic3 proteins by electrophoretic mobility shift assay-based target selection and mutational analysis. The selected sequence was almost identical to the GLI binding sequence. However, the binding affinity was lower than that of GLI. Consistent results were obtained in reporter assays, in which transcriptional activation by Zic proteins was less dependent on the GLI binding sequence than GLI1. Moreover, Zic proteins activated a wide range of promoters irrespective of the presence of a GLI binding sequence. When Zic and GLI proteins were cotransfected into cultured cells, Zic proteins enhanced or suppressed sequence-dependent, GLI-mediated transactivation depending on cell type. Taken together, these results suggest that Zic proteins may act as transcriptional coactivators and that their function may be modulated by the GLI proteins and possibly by other cell type-specific cofactors.

Zic1 regulates the patterning of vertebral arches in cooperation with Gli3.

Skeletal abnormalities are described that appeared in Zic1-deficient mice. These mice show multiple abnormalities in the axial skeleton. The deformities are severe in the dorsal parts of the vertebrae, vertebral arches, but less so in the vertebral bodies (spina bifida occulta). The proximal ribs are deformed having ectopic processes. The abnormalities found in the vertebral arches can be traced back to disturbed segmental patterns of dorsal sclerotome. The Zic1/Gli3 double mutants showed severe abnormalities of vertebral arches not found in single mutants. The abnormalities in the vertebral arches were less severe in Zic1/Pax1 mutants than Zic1/Gli3 mutants, but significantly more pronounced than in Zic1 single mutants. The three genes may act synergistically in the development of the vertebral arches.

An AciI polymorphism in the 3' untranslated region of the human phosphomannomutase 2 (PMM2) gene.

We found an AciI polymorphism in the 3' untranslated region of the phosphomannomutase 2 (PMM2) gene located at 16p13. A G-to-C transition at nucleotide position 96 bp downstream from the PMM2 stop codon was detected in polymerase chain reaction (PCR) products after AciI digestion. The heterozygosity of the polymorphic alleles was 0.375 in a Japanese population. This polymorphism is useful for genetic analysis in patients with carbohydrate-deficient glycoprotein syndromes, of which there are four subtypes.

Missense mutations in the phosphomannomutase 2 gene of two Japanese siblings with carbohydrate-deficient glycoprotein syndrome type I.

Carbohydrate-deficient glycoprotein syndrome type I (CDG1) is an autosomal recessive disorder characterized by severe nervous system involvement and a carbohydrate moiety deficiency in N-linked glycoproteins. Clinical symptoms are psychomotor retardation, stroke-like episodes or hemorrhagic episodes, hepatic dysfunction, polyneuropathy, and cerebellar ataxia. Marked atrophy of the cerebellar hemispheres and pons is recognizable on CT scan or MRI. CDGI has been mapped to human chromosome 16p by linkage studies. Recently, missense mutations in the gene for phosphomannomutase (PMM2) have been detected in Caucasian patients with CDG1. We studied DNA mutations in PMM2 in a Japanese family with CDG1. DNA sequencing of PMM2 in the siblings showed missense mutations of maternal origin in exon 5 and of paternal origin in exon 8. No such mutations were detected in 50 unrelated healthy Japanese. These findings suggest that the PMM2 is responsible for CDG1 in the Japanese as well as in Caucasians, and CDG1 may be the diagnosis in OPCA of neonatal onset, more often than currently thought.

Missense mutations in phosphomannomutase 2 gene in two Japanese families with carbohydrate-deficient glycoprotein syndrome type 1.

Carbohydrate-deficient glycoprotein syndrome type 1 (CDG1) (MIM: 212065) is an autosomal recessive disorder with psychomotor retardation, strokelike episodes, ataxia, and olivopontocerebellar atrophy (OPCA) of neonatal onset. Recently, DNA substitutions in a gene for phosphomannomutase 2 (PMM2), mapped to 16p13, were identified in patients with CDG1. Biochemical findings in previously reported Japanese patients with CDG1 were slightly different from those of Caucasians, suggesting genetic heterogeneity of CDG1 in Japanese patients. We investigated the DNA sequence of PMM2 in two unrelated Japanese families with CDG1. Missense mutations in exon 5 (Phe144Leu) and exon 8 (Tyr229Ser, Arg238Pro) of the PMM2 gene were present in two families, but they were not present in 72 unrelated healthy Japanese individuals. One of the missense mutations, Phe144Leu in exon 5, was common to two families with CDG1. Our findings confirm that mutations in the PMM2 gene account for at least some Japanese patients with CDG1 similar to that seen in Caucasians and that exons 5 and 8 are hot spots of mutations of CDG1 caused by the PMM2 gene.

Interstitial deletion of chromosome 7q in a patient with Williams syndrome and infantile spasms.

Interstitial deletion of 7q11.23-q21.11 was identified by cytogenetic methods in a 4-year-old boy with Williams syndrome (WS) and infantile spasms. Deletion of the elastin (ELN) gene and the DNA polymorphic markers, D7S1870, D7S2490, D7S2518, and D7S2421, were identified in the patient, but the loci for D7S653 and D7S675 were not involved. Zackowski et al. (1990) reported that 6 of 16 patients with the interstitial deletion of 7q11.2-q22 had abnormal electro encephalograms, or seizures, or both, and that infantile spasms were present in 2 of the 6 patients. WS is a well defined developmental disorder characterized by distinct facial features, gregarious personality, and congenital heart defects. Seizures are not generally associated with this syndrome. WS commonly is characterized by deletion of the loci for ELN and D7S1870, but not those for D7S2490, D7S2518, or D7S2421. This suggests that a gene responsible for infantile spasms is located in the 2.7-cM interval between loci D7S1870 and D7S675.