Marfan syndrome is an inherited disorder of connective tissue manifested in the ocular, skeletal and cardiovascular systems. It is inherited as an autosomal dominant with high penetrance, but has great clinical variability. Linkage studies have mapped the Marfan locus to chromosome 15q15-21.3. There have been no reports of genetic heterogeneity in the syndrome. Following the identification of fibrillin (a glycoprotein component of the extracellular microfibril), immunohistopathological quantification of the protein in skin and fibroblast culture, and examination of fibrillin synthesis, extracellular transport, and incorporation into the extracellular matrix (D. M. Milewicz, R.E.P., E. S. Crawford and P. H. Byers, manuscript in preparation) have demonstrated abnormalities of fibrillin metabolism in most patients. A portion of the complementary DNA encoding fibrillin has been cloned and mapped by in situ hybridization to chromosome 15. Here we report that the fibrillin gene is linked to the Marfan phenotype (theta = 0.00; logarithm of the odds (lod) = 3.9) and describe a de novo missense mutation in the fibrillin gene in two patients with sporadic disease. We thus implicate fibrillin as the protein defective in patients with the Marfan syndrome.

Variable in-frame skipping of exon 9 in cystic fibrosis transmembrane conductance regulator (CFTR) mRNA transcripts (exon 9-) occurs in the respiratory epithelium. To explore the genetic basis of this event, we evaluated respiratory epithelial cells and blood leukocytes from 124 individuals (38 with cystic fibrosis (CF), 86 without CF). We found an inverse relationship between the length of the polythymidine tract at the exon 9 splice branch/acceptor site and the proportion of exon 9- CFTR mRNA transcripts. These results strongly indicate a genetic basis in vivo modulating post-transcriptional processing of CFTR mRNA transcripts.

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene but the association between mutation (genotype) and disease presentation (phenotype) is not straightforward. We have been investigating whether variants in the CFTR gene that alter splicing efficiency of exon 9 can affect the phenotype produced by a mutation. A missense mutation, R117H, which has been observed in three phenotypes, was found to occur on two chromosome backgrounds with intron 8 variants that have profoundly different effects upon splicing efficiency. A close association is shown between chromosome background of the R117H mutation and phenotype. These findings demonstrate that the genetic context in which a mutation occurs can play a significant role in determining the type of illness produced.

73, 89, 90, and 92% CFTR transcripts with inframe deletion of exon 9, respectively, despite normal sweat Cl-and no clinical manifestation of CF. In the context that only 8% or less of bronchial CFTR transcripts need exon 9 to maintain normal airway function, these observations strongly suggest that either exon 9 is not necessary for CFTR structure and /or function or that only a very small fraction of bronchial epithelial cells need to express normal CFIR mRNA transcripts with exon 9 to perform the function of CFITR sufficient to maintain a normal phenotype in vivo. (J. Clin. Invest. 1992.

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Infants born prematurely risk significant life-long cognitive disability, representing a major pediatric health crisis. The neuropathology of this cohort is accurately modeled in mice subjected to sublethal postnatal hypoxia. Massively parallel transcriptome analysis using cDNA microchips (9,262 genes), combined with immunohistochemical and protein assays, reveals that sublethal hypoxia accentuates genes subserving presynaptic function, and it suppresses genes involved with synaptic maturation, postsynaptic function, and neurotransmission. Other significantly affected pathways include those involved with glial maturation, vasculogenesis, and components of the cortical and microtubular cytoskeleton. These patterns reveal a global dysynchrony in the maturation programs of the hypoxic developing brain, and offer insights into the vulnerabilities of processes that guide early postnatal cerebral maturation.

Two long terminal repeat (LTR) enhancer-binding proteins which may regulate high rates of avian leukosis virus (ALV) LTR-enhanced c-myc transcription during bursal lymphomagenesis have been identified (A.

The avian leukosis virus (ALV) long terminal repeat (LTR) contains a compact transcription enhancer that is active in many cell types. A major feature of the enhancer is multiple CCAAT/enhancer element motifs that could be important for the strong transcriptional activity of this unit. The contributions of the three CCAAT/ enhancer elements to LTR function were examined in B cells, as this cell type is targeted for ALV tumor induction following integration of LTR sequences next to the c-myc proto-oncogene. One CCAAT/enhancer element, termed a3, was found to be the most critical for LTR enhancement in transiently transfected B lymphoma cells, while in chicken embryo fibroblasts all three elements contributed equally to enhancement. Gel shift assays demonstrated that vitellogenin gene-binding protein (VBP), a member of the PAR subfamily of C/EBP factors, is a major component of the nuclear proteins binding to the a3 CCAAT/enhancer element. VBP activated transcription through the a3 CCAAT/enhancer element, supporting the idea that VBP is important for LTR enhancement in B cells. A member of the Rel family of proteins was also identified as a component of the a3 protein binding complex in B cells. Gel shift and immunoprecipitation assays indicatedthat this factor is RelA. Gel shift assays demonstrated that while RelA does not bind directly to the LTR CCAAT/enhancer elements, it does interact with VBP to potentiate VBP DNA binding activity. The synergistic interaction of VBP and RelA increased CCAAT/enhancer element-mediated transcription, indicating that both factors may be important for viral LTR regulation and also for expression of many cellular genes.