Transcriptional map of the Treacher Collins candidate gene region

Clinical spectrum of Treacher Collins syndrome

Treacher Collins syndrome (TCS) is the most common of the human mandibulofacial dysostosis disorders. It is an autosomal-dominant disorder of the craniofacial development occurring between the fifth and the eighth weeks of embryonic development with an incidence of 1/50,000 live births, range between 1-40,000 and 1-70,000. We present here the various clinical, radiographical and other diagnostic findings of the TCS to correlate the clinical assessment with the diagnostic imaging and review the various investigations and management options being carried out to improve their facial deformity.

TCOF1 gene encodes a putative nucleolar phosphoprotein that exhibits mutations in Treacher Collins Syndrome throughout its coding region

Treacher Collins Syndrome (TCS) is the most common of the human mandibulofacial dysostosis disorders. Recently, a partial TCOF1 cDNA was identified and shown to contain mutations in TCS families. Here we present the entire exon/intron genomic structure and the complete coding sequence of TCOF1. TCOF1 encodes a low complexity protein of 1,411 amino acids, whose predicted protein structure reveals repeated motifs that mirror the organization of its exons. These motifs are shared with nucleolar trafficking proteins in other species and are predicted to be highly phosphorylated by casein kinase. Consistent with this, the full-length TCOF1 protein sequence also contains putative nuclear and nucleolar localization signals. Throughout the open reading frame, we detected an additional eight mutations in TCS families and several polymorphisms. We postulate that TCS results from defects in a nucleolar trafficking protein that is critically required during human craniofacial development.

Identification of the complete coding sequence and genomic organization of the Treacher Collins syndrome gene

Treacher Collins syndrome (TCS) is an autosomal dominant disorder of craniofacial development, the features of which include conductive hearing loss and cleft palate. Recently, the demonstration of a series of 10 mutations within a partial-length cDNA clone have indicated that the TCS gene (TCOF1) has been positionally cloned. Although it has been shown that the gene is expressed in a wide variety of fetal and adult tissues, database sequence comparisons have failed to provide significant information on the function of the gene. In the current investigation, a combination of cDNA library screening and rapid amplification of cDNA ends has permitted the isolation of the complete coding sequence of TCOF1, which is encoded by 26 exons and predicts a low complexity, serine/alanine-rich protein of approximately 144 kD. The use of a variety of bioinformatics tools has resulted in the identification of repeated units within the gene, each of which maps onto an individual exon. The predicted protein Treacle contains numerous potential phosphorylaiton sites, a number of which map to similar positions within the repeated units, and shows weak but significant homology to the nucleolar phosphoproteins. Although the precise function of Treacle remains unknown, these observations suggest that phosphorylation may be important for its role in early embryonic development and that it may play a role in nucleolar-cytoplasmic shuttling. The information presented in this study will allow continued mutation analysis in families with a history of TCS and should facilitate continued experimentation to shed further light on the function of the gene/protein during development of the craniofacial complex.

Treacher Collins syndrome

Treacher Collins syndrome is an autosomal dominant disorder of craniofacial development, the features of which include conductive hearing loss and cleft palate. In the absence of a candidate gene, a positional cloning approach has been used to isolate the mutated gene which maps to chromosome 5q31.3-32. Flanking markers were identified and a yeast artificial chromosome and cosmid contig of the region defined by these markers was created as a prelude to the creation of a transcript map of the region. Analysis of genes isolated using this approach resulted in the identification of the mutated gene. While the function of the gene remains unknown, the identification of 20 mutations spread throughout the gene, all of which would result in the insertion of a premature termination codon into the reading frame, suggests that the mechanism underlying the disease is haploinsufficiency.

Prenatal diagnosis in Treacher Collins syndrome using combined linkage analysis and ultrasound imaging

Treacher Collins syndrome is an autosomal dominant disorder of facial development, the features of which include conductive hearing loss and cleft palate. In the current investigation, linkage analysis has been used to make first trimester diagnostic predictions in a pregnancy at high risk of producing an affected child. The results of this analysis predicted that the child would be affected. As predictions of the severity of the disease were not possible, the pregnancy was also assessed by ultrasound imaging. This confirmed the affected diagnosis and predicted that the child would be severely affected.

Positional cloning of a gene involved in the pathogenesis of Treacher Collins syndrome. The Treacher Collins Syndrome Collaborative Group

Treacher Collins syndrome is an autosomal dominant disorder of craniofacial development, which has been localized to chromosome 5q32-33.1. In the present study, the isolation of new polymorphic markers has allowed the identification of overlapping recombination events in two affected individuals. Extension of the transcription map of the critical region proximally has resulted in the isolation of a new gene (which has been named Treacle) of unknown function. The identification of different mutations in five unrelated families, all of which would result in premature termination of the predicted protein, indicates that the Treacher Collins syndrome gene has been positionally cloned.