ABSTRACT
Genes subject to genomic imprinting generally occur in clusters of hundreds of kilobases. These domains exhibit several gamete of origin-dependent manifestations, including a pattern of asynchronous replication when studied by fluorescence in situ hybridization (FISH). We find a transition from asynchronous replication at the imprinted mouse H19 gene to synchronous replication at the downstream Rpl23 gene, the human homologue of which appears to be non-imprinted. Two-colour FISH demonstrates that this transition is due solely to a difference in replication timing between the upstream and downstream chromatin on the later-replicating (maternal) chromosome. This difference is lost in mice deleted for the H19 gene body and 9.9 kb of upstream DNA when this deletion is maternally inherited, with synchronous replication patterns extending over 110 kb upstream from the deleted area. No effect is seen when the deletion is paternally inherited. The presence of a boundary element in this region has been suggested by observations of position-independent expression of H19 -containing transgenes and the blocking of accessibility of downstream enhancers to the upstream Igf2 and Ins2 genes on the maternal chromosome. The FISH studies presented here demonstrate the insulation of replication patterns within the imprinted domain from downstream, non-imprinted chromatin, mediated by an element at the H19 locus which is subject to genomic imprinting.
Subject(s)
DNA Replication/genetics , Muscle Proteins/genetics , RNA, Untranslated , Animals , Chromosome Mapping , Genome , Humans , Mice , RNA, Long NoncodingABSTRACT
The plant enzyme phenylalanine ammonia lyase (PAL) will survive in the gut for long enough to deplete the phenylalanine derived from food protein and so reduce the rise in blood phenylalanine that otherwise occurs after a protein meal. This effect has been demonstrated in healthy adults and phenylketonuric (PKU) patients. When the enzyme was given to an untreated PKU patient for 12 consecutive days (three doses a day after food) his blood phenylalanine levels were reduced on average by a quarter. This enzyme preparation may have a place in the treatment of PKU.
Subject(s)
Ammonia-Lyases/metabolism , Phenylalanine Ammonia-Lyase/metabolism , Phenylalanine/blood , Phenylketonurias/blood , Adult , Dietary Proteins/administration & dosage , Humans , Phenylalanine/therapeutic use , Phenylketonurias/drug therapy , Phenylketonurias/enzymologyABSTRACT
Investigations were undertaken to discover the effect and importance of technical factors in the Guthrie test and to determine the most satisfactory materials available. These findings were used in setting up the screening service for phenylketonuria for the South West Metropolitan Region.
