PubMed · 11691897
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Z A Khan, J R Novell. 2001. A missing vas.. https://doi.org/10.1177/014107680109401108
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Tracheal cartilaginous sleeve (TCS) is a congenital malformation characterized by fusion of the tracheal arches that may be isolated to a few tracheal arches, include the entire trachea, or extend beyond the carina into the bronchi. TCS has been reported only in children with craniosynostosis. Seven cases of TCS and Crouzon syndrome (CS) are mentioned in the literature. In addition to our case study, a review of the literature on TCS in CS, a classification of TCS and treatment options will be provided. Tracheotomy and frequent airway endoscopy coupled with a keen understanding of the shifting sites of obstruction will permit longterm survival in patients with TCS and CS.
ICF syndrome (immunodeficiency, centromere instability and facial anomalies) is a recessive human genetic disorder resulting from mutations in the DNA methyltransferase 3B (DNMT3B) gene. Patients with this disease exhibit numerous chromosomal abnormalities, including anomalous decondensation, pairing, separation and breakage, primarily involving the pericentromeric regions of chromosomes 1 and 16. Global levels of DNA methylation in ICF cells are only slightly reduced; however, certain repetitive sequences and genes on the inactive X chromosome of female ICF patients are significantly hypomethylated. In the present report, we analyze the molecular defect of de novo methylation in ICF cells in greater detail by making use of a model Epstein-Barr virus (EBV)-based system and three members of the unique cellular cancer-testis (C-T) gene family. Results with the EBV-based system indicate that de novo methylation of newly introduced viral sequences is defective in ICF syndrome. Limited de novo methylation capacity is retained in ICF cells, indicating that the mutations in DNMT3B are not complete loss-of-function mutations or that other DNMTs cooperate with DNMT3B. Analysis of three C-T genes (two on the X chromosome and one autosomal) revealed that loss of methylation from cellular gene sequences is heterogeneous, with both autosomal and X chromosome-based genes demonstrating sensitivity to mutations in DNMT3B. Aberrant hypomethylation at a number of loci examined correlated with altered gene expression levels. Lastly, no consistent changes in the protein levels of the DNA methyltransferases were noted when normal and ICF cell lines were compared.