Author(s) : Heather N Yeowell, Linda C Walker, Luitgard M Neumann , Div of Dermatology, Duke Univ Medical Centre, Durham, NC, USA Fax: (+1) 919-684-3002., Institute of Human Genetics, Charité Campus Virchow-Klinikum, Berlin, Germany.
Summary : We have characterized a patient with the phenotype of Ehlers-Danlos syndrome type VIA (EDS VIA: kyphoscoliotic form), accompanied by the unique feature of cystic malformations of the meninges, to be homozygous for a large duplication of 8.9kb in the lysyl hydroxylase 1 (LH1) gene that is the cause of severely decreased levels of LH activity in her skin fibroblasts. Electrophoresis of full length cDNA for LH1, prepared from the patient’s fibroblasts and amplified by PCR, showed an abnormally large DNA fragment indicative of a duplication mutation\; this mutation was confirmed in genomic DNA by PCR using duplication-specific primers and sequence analysis of the duplication junction. The homozygosity of this mutation was confirmed by analysis of DNA from the unaffected parents which showed them to be carriers of this duplication. This seven exon duplication is the most common mutation in the LH1 gene in patients with EDS VIA and occurs via a homologous recombination of Alu sequences in introns 9 and 16. Using the data from this study and other recent reports, we have updated the allele frequency for this mutation, based on 19 duplicated alleles out of a total of 104 genetically independent alleles from 53 EDS VIA families, to be 18.3%.
Keywords : collagen disorder, Ehlers-Danlos syndrome type VIA, kyphoscoliosis, lysyl hydroxylase deficiency, duplication mutation, skin fibroblasts, cystic malformation of meninges, allelic mutation frequency
Pictures
Figure 1 Pedigree of three generations of the
family. The single affected member of the family (patient 1276),
shown by the arrow, is from a consanguineous marriage. This study
has shown that her parents, although clinically unaffected, are
carriers for the disorder. Her three brothers are clinically
unaffected and they have not been tested to determine whether they
are carriers for the disorder.
Figure 2 Patient at the age of ten years (with
permission). A. Left lateral view: kyphoscoliosis and
prominent abdomen, hypoplasia of left arm due to upper brachial
plexus palsy; B. Right lateral view: kyphoscoliosis and
prominent abdomen; C. Forehead with cigarette paper-type
scars after minimal trauma that are characteristic of EDS.
Figure 3(A) The rapid PCR detection and
(B) location and sequence analysis of the duplication
junction in the LH1 gene (not shown to scale).A. Using
primers JH71 and JH44 (as shown in (B)), PCR amplification of a
960bp DNA fragment provides a rapid detection method for the
duplication mutation in genomic DNA isolated from the proband and
her parents. The lanes are identified in the following order: 1)
blank; 2) negative control (no duplication); 3) proband; 4) father;
5) mother and 6) positive control (a patient previously identified
with the duplication mutation). M represents the 1kb ladder. The
father and mother are carriers of the mutation, confirming the
homozygosity of the mutation in their daughter.B. Diagram of
the duplication junction that is present in the proband (line 3)
and, in lines 1 and 2, the corresponding normal introns: introns 9
and 16, respectively. The location of forward primer JH71 and
reverse primers JH55 and JH44 is shown. The hatched box represents
the identical 44 bp Alu sequence present in introns 9 and 16.
The location and sequence of the region sequenced across the
duplication junction in the LH1 gene from the proband is shown.
This sequence includes the 44bp Alu sequence (boxed in bold)
flanked by intron 16 and intron 9. The underlined t (in bold) in
intron 16 differs from the reported LH1 sequence (obtained from the
UCSC Genome Browser (http://genome.ucsc.edu) using the BLAT
program), but is identical to a previously reported sequence from a
different EDS VIA patient with this mutation [5].
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