Impact of a genetic diagnosis of a mitochondrial disorder 5-17 years after the death of an affected child.

This study used in-depth interviews to explore the experiences of parents who were re-contacted with new genetic results many years after the death of a child with a mitochondrial disorder. At the time of their child's illness, parents had consented to a tissue sample being taken to help with diagnosis of a suspected mitochondrial disorder, and subsequently further DNA testing identified the genetic cause. Parents did not express negative feelings about being re-contacted with new information, and hoped that continuing research might help other families. Positive aspects included relief from feelings of guilt over the cause of the child's disorder, and having accurate genetic information available for surviving children. Difficult emotional and psychosocial implications included contradictions to previous beliefs about inheritance, deciding how and when to communicate information to surviving children, and coping with new fears for the mother's health if a gene located in the mitochondrial DNA was identified. In half of the families the new results significantly altered the parents' understanding of the inheritance pattern. This study highlights the impact of new genetic information offered after a delay of several years, which has the potential to re-open feelings of grief and uncertainty and can present a new inheritance scenario for which research participants or their families are unprepared. Health professionals involved in conveying genetic research results can help to support families through this process.

Characterisation of a cyanide hydratase gene in the phytopathogenic fungus Leptosphaeria maculans.

A gene encoding a cyanide hydratase was cloned from an aggressive isolate of Leptosphaeria maculans, the fungus which causes blackleg disease of oilseed Brassica spp. This enzyme catalyses the breakdown of hydrogen cyanide to a less toxic compound, formamide. The predicted amino acid sequence of cyanide hydratase in L. maculans is 77% and 82% identical to cyanide hydratases from two other ascomycetes, Gloeocercospora sorghi and Fusarium lateritium, respectively. The gene is present as a single copy in the L. maculans genome, in both aggressive and non-aggressive isolates, although there is a restriction fragment length polymorphism between these two isolate groups for this gene. The cyanide hydratase promoter contains four putative target sites for GATA transcription factors, proteins that regulate nitrogen metabolism and other processes. Transcription of cyanide hydratase in an aggressive L. maculans isolate is induced strongly by potassium cyanide. Transcription of the gene is detectable in cotyledons of Brassica juncea and B. napus during infection. L. maculans can utilise the reaction product, formamide, as a sole source of nitrogen.

Cloning, characterization and chromosomal location of three genes encoding host-cell-wall-degrading enzymes in Leptosphaeria maculans, a fungal pathogen of Brassica spp.

The ascomycete, Leptosphaeria maculans, causes blackleg disease of oilseed Brassica spp. such as canola (Brassica napus). We have cloned a gene encoding endopolygalacturonase, pg1, and two genes encoding cellulases, cel1 and cel2, in L. maculans. These genes are not clustered in the genome, as they are located on different chromosomes. The deduced amino acid sequences of all three genes predict an N-terminal signal sequence, as is common for secreted fungal enzymes that degrade plant cell walls. The endopolygalacturonase encoded by pg1 shows the highest similarity (54% amino acid identity) to endopolygalacturonase 4 from Botrytis cinerea. Both cel1 and cel2 appear to encode cellobiohydrolase, and neither gene encodes a recognizable cellulose-binding domain or linker region. Transcription of pg1 is induced in cultures containing 1% polygalacturonic acid or pectin, and cel1 is induced in 1% cellulose or carboxymethylcellulose, as shown by Northern analysis. Glucose represses the induction of cel1 caused by cellulose and carboxymethylcellulose, but does affect transcription of pg1. Transcription of cel2 (but not cel1 or pg1) is detectable during infection of B. napus and B. juncea cotyledons and leaves using reverse transcription-PCR.