Transforming growth factor-alpha (TGFA): genomic structure, boundary sequences, and mutation analysis in nonsyndromic cleft lip/palate and cleft palate only.

Transforming growth factor-alpha (TGFA) has been proposed as a candidate gene in the etiology of nonsyndromic cleft lip with or without cleft palate (NS-CL/P) and of nonsyndromic cleft palate only (NS-CPO). Biologic support for a role of TGFA arises from its presence at high levels in the epithelial tissue of the medial edge of the palatal shelves at the time of shelf fusion in mice. Genetic support for the role of TGFA in clefting comes from the reported association of TGFA alleles with human NS-CPO and NS-CL/P. In this study we report the sequence and structure of human genomic TGFA and the search for causal TGFA mutations in 250 individuals with NS-CL/P or NS-CPO by conformational analysis of the coding sequence, splice junctions, and a portion of the 3' untranslated region strongly homologous between human and mouse. We confirm that human TGFA is composed of six exons and here report several new sequence substitutions and their frequencies. Five variants in conserved segments may represent rare causes for clefting in humans and provide support for the role of TGFA in facial morphogenesis.

A novel homeobox gene PITX3 is mutated in families with autosomal-dominant cataracts and ASMD.

We report here the identification of a new human homeobox gene, PITX3, and its involvement in anterior segment mesenchymal dysgenesis (ASMD) and congenital cataracts in humans. The PITX3 gene is the human homologue of the mouse Pitx3 gene and is a member of the RIEG/PITX homeobox gene family. The protein encoded by PITX3 shows 99% amino-acid identity to the mouse protein, with 100% identity in the homeodomain and approximately 70% overall identity to other members of this family. We mapped the human PITX3 gene to 10q25 using a radiation-hybrid panel. A collection of 80 DNA samples from individuals with various eye anomalies was screened for mutations in the PITX3 gene. We identified two mutations in independent patients. A 17-bp insertion in the 3'-end of the coding sequence, resulting in a frame shift, occurred in a patient with ASMD and cataracts, and a G-->A substitution, changing a codon for serine into a codon for asparagine, in the 5'-end of the gene occurred in a patient with congenital cataracts. Both mutations cosegregate with the disease phenotype in families, and neither were found in up to 300 control individuals studied. Further expression analysis of Pitx3 in the mouse supports a unique role in early ocular development, with later expression extending to the midbrain, tongue, incisors, sternum, vertebrae and limbs. These data strongly suggest a role for PITX3 in ASMD and cataracts and provide new evidence of the contribution of the RIEG/PITX gene family to the developmental program underpinning normal eye formation.