RNA-based mutation screening in German families with Sjögren-Larsson syndrome

Abstract

Sjögren-Larsson syndrome (SLS) is a rare autosomal recessively inherited disorder characterised by mental retardation, spasticity and ichthyosis. SLS patients have a profound deficiency in fatty aldehyde dehydrogenase (FALDH) activity. The human cDNA of FALDH has been shown to map to the SLS locus on chromosome 17p11.2. Here we describe a method based on reverse transcriptase-polymerase chain reaction (RT-PCR) and protein truncation test to identify mutations in the FALDH gene in nine German SLS families. Using this detection system both disease-causing mutations were found in eight of the nine SLS families examined (17/18 chromosomes). Seven different mutations were identified: an exon 2 skipping due to exon 2 splice donor mutation; two different exon 3 splice donor mutations resulting in combined exon 2 and 3 skipping; a 906delT deletion in exon 6; a genomic deletion of about 6 kb including exon 9; a 1277T > G transversion resulting in a Leu426Ter nonsense mutation; and a 1297delGA deletion. Two of the mutations identified, the genomic exon 9 deletion and the 906delT in exon 6 affected five out of seven SLS patients from a small region of Northern Bavaria. Therefore these two mutations accounted for 71% (10/14 chromosomes) of Bavarian SLS alleles and so far have not been described in SLS families from other countries. Our findings do not support our 'historical' hypothesis, that a possible region clustering in Northern Bavaria could be due to the presence of Swedish soldiers during the 30 Years War (1618-1648), but suggest that two mutations causing SLS syndrome originated in Northern Bavaria.

Sjögren–Larsson syndrome: Molecular genetics and biochemical pathogenesis of fatty aldehyde dehydrogenase deficiency

“…A variety of mutations have been identified including deletions, insertions, missense mutations, splicing defects and complex rearrangements. Most mutations are private, but several common mutations have been found in patients from Europe [23][24][25][26][27][28], the Mideast [26] and Brazil [29]. For example, the c. 943C>T mutation is responsible for SLS in most of the Swedish patients [23;24] and a c. 1297_1298delGA allele is carried by many other European patients [25].…”

“…Nucleotide deletions and insertions of various sizes have been found in the ALDH3A2 gene. The largest reported deletion is 6kb and results in complete loss of exon 9 [27,28]. Several complex ALDH3A2 alleles containing multiple nucleotide changes have also been seen [22].…”

Sjögren–Larsson syndrome: Novel mutations in the ALDH3A2 gene in a French cohort

“…The c.471+ 1delG splice site mutation was found at the homozygous state in patient 1 and at the heterozygous state in patient 3, native to France. This mutation, associated with haplotype 2 (with regard to haplotype constructed with four intragenic SNPs as described by Rizzo et al [7]) causes the loss of exons 2 and 3, predicting a protein with a loss of 106 amino acids (AA) [7,8]. Surprisingly, the analysis of patient 1's ALDH3A2 mRNA revealed three different transcripts: the shorter one (1.4 kb) shows exon 2 and 3 skipping, the intermediate one (1.5 kb) only exon 3 skipping and the longest one (1.6 kb) corresponds to a deletion of the last 3′ guanidine of exon 3 due to its use to replace the deleted guanidine of the splice donor site (Fig.…”

“…Total RNAs were isolated from cultured fibroblasts using Trizol reagent (Invitrogen). Reverse transcription reactions were performed using conditions previously described by Kraus et al [8]. ALDH3A2 cDNAs were amplified from exons 1 to 10 and 3 to 6 by PCR using the following primers: Ex1F 5′ GTGGGTTGACGGTGGAGAC3′, Ex10R 5′GGTTCATTAACCATTTAAAA-GAGGA3′, Ex3F 5′GGCAAAGCTTCTCCCTCAG3′ and Ex6R 5′TCAGGA-GACTCTTTTATATTTTCTCCA3′.…”

Lichenifikation der großen Beugen, Tetraspastik und mentale Retardierung

“…[3,6]. Eine Korrelation zwischen klinischem Ausprägungsgrad und Art der Mutation (in unserem Fall vergleichsweise milde Ausprägung bei genetischer Compound-Heterozygotie) konnte bislang nicht gefunden werden [6].…”