Abstract
Lysyl hydroxylase (EC 1.14.11.4, procollagen-lysine 2-oxoglutarate
5-dioxygenase, PLOD) catalyses the formation of hydroxylysine in
collagens and in the other collagen like proteins. Hydroxylysine
participates in the formation of cross-links between collagen molecules
and can bind to the carbohydrates, galactose and glucosylgalactose.
Patients with the type VIA Ehlers-Danlos syndrome (EDS) have characteristically
a deficiency in hydroxylysine of collagen in their skin that is caused
by reduced activity of lysyl hydroxylase 1. In this work the mutations
were studied in detail in four different Ehlers-Danlos VIA patients.
The first patient characterized in this study had a duplication
of seven exons in the lysyl hydroxylase gene 1. The mutation was
caused by homologous recombination of two identical 44-nucleotide
regions of Alu sequences in introns 9 and 16 in the gene. This study
also suggests that uniparental isodisomy does not explain the homozygosity
of the mutation.
The second patient was found to have two mutations in the
gene for lysyl hydroxylase 1 in a compound heterozygote state. The
study resulted in the discovery of the first deletion mutation in
the gene. The deletion was caused by an Alu-Alu recombination that
removes about 3 kb from the gene including all the exon 17 sequences.
The other mutation causes deletion of exon 16 from the mRNA. Deletion
of the penultimate nucleotide of intron 15 destroys the consensus
sequence of the intron/exon boundary and thus causes the
deletion.
The third patient was described to have a nonsense codon in
exon 14 of one allele which causes a reduction in the amount of
lysyl hydroxylase mRNA and leads to aberrant RNA splicing in the
cell. The other allele was concluded to be operationally null.
In the last work two novel null mutations were found in the
gene for lysyl hydroxylase 1. The first was a one nucleotide deletion
in the acceptor splice site of intron 4 and the other an insertion
of a C nucleotide in exon 2. The abnormal alleles lead to markedly
decreased lysyl hydroxylase mRNA levels. This work revealed many
exon deleted splicing variants of lysyl hydroxylase mRNA which were
first discovered in affected cells, but traces of similarly spliced
mRNA species were also found in the cytoplasm of normal human skin
fibroblasts. These data indicate that the splicing machinery of the
cell is leaky.
In this thesis, several types of stuctural mutations in the
DNA were found to be responsible for lysyl hydroxylase deficiency
in patients with type VIA variant of EDS. The different mechanisms causing
these mutations were also studied in detail.
| Identifer | oai:union.ndltd.org:oulo.fi/oai:oulu.fi:isbn951-42-5317-5 |
| Date | 24 June 1999 |
| Creators | Pousi, B. (Birgitta) |
| Publisher | University of Oulu |
| Source Sets | University of Oulu |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, © University of Oulu, 1999 |
| Relation | info:eu-repo/semantics/altIdentifier/pissn/0355-3221, info:eu-repo/semantics/altIdentifier/eissn/1796-2234 |
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