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Neural stem/progenitor cells (NSCs) in the hippocampus produce new neurons throughout adult life. NSCs are maintained in a state of reversible quiescence and the failure to maintain the quiescent state can result in the premature depletion of the stem cell pool. The epigenetic mechanisms that maintain this quiescent state have not been identified. Using an inducible knockout mouse model, we show that the chromatin remodeling factor chromodomain-helicase-DNA-binding protein 7 (CHD7) is essential for maintaining NSC quiescence. CHD7 inactivation in adult NSCs results in a loss of stem cell quiescence in the hippocampus, a transient increase in cell divisions, followed by a significant decline in neurogenesis. This loss of NSC quiescence is associated with the premature loss of NSCs in middle-aged mice. We find that CHD7 represses the transcription of several positive regulators of cell cycle progression and is required for full induction of the Notch target gene Hes5 in quiescent NSCs. These findings directly link CHD7 to pathways involved in NSC quiescence and identify the first chromatin-remodeling factor with a role in NSC quiescence and maintenance. As CHD7 haplo-insufficiency is associated with a range of cognitive disabilities in CHARGE syndrome, our observations may have implications for understanding the basis of these deficits., (© 2014 AlphaMed Press.)

A library prepared from flow-sorted chromosomes was used to isolate single-copy sequences from chromosome seven. One such sequence 7C22 has been shown to be polymorphic for an EcoRI restriction site and to be informative for the study of CF in approximately 35% of matings. The segregation of the 7C22 alleles was followed through nineteen informative families with more than one child affected by cystic fibrosis. We report that the locus for 7C22 is linked to the locus for cystic fibrosis at a recombination fraction of 0.045. This marker will prove useful in improving the accuracy and informativeness of prenatal diagnosis and in constructing a fine genetic map around the cystic fibrosis gene.

The DNA probes met and pJ3.11 are derived from loci on chromosome seven that are closely linked to, and probably flanking, the gene mutation causing cystic fibrosis (CF). We have shown that mitotic chromosomes from the cell line MNNG-HOS, which contains an activated met oncogene, can induce morphological transformation of mouse NIH-3T3 cells. Southern analysis of isolated transfectant cell lines with cloned dispersed repetitive human DNA sequences as probes demonstrated that several lines of transformed NIH 3T3 cells had stabley incorporated large segments of chromosome seven DNA. Southern blot analysis also demonstrated the presence of met, pJ3.11 and several other single copy sequences that had been previously localised to chromosome 7 within the transgenomes. In this way a further four genetic markers were shown to be physically linked to met, and thus to CF. These probes may prove useful in confirming the order of loci around CF and in the prenatal diagnosis of this common autosomal recessive disease.

Cosmid libraries have been constructed from DNA of somatic cell hybrid cell lines, each containing a fragment of human chromosome seven and including sequences closely linked to cystic fibrosis (CF). Cosmids containing human DNA as insert were isolated from the library. Three cosmids, when used as probes to total genomic DNA, detected polymorphic loci, each of which was shown to be in strong linkage disequilibrium with CF. Restriction endonuclease digestion of cosmid clones and use of a new, rapid method of chromosome walking based on competitive hybridisation of cosmid inserts has allowed identification of several groups of overlapping cosmids ("contigs") from the vicinity of CF.