How splicing, the process of intron removal in pre-messenger RNA (mRNA), is carried out with such fidelity in human cells is still not understood, although some general rules are being proposed mainly by in vitro experiments. These rules are currently being redefined by analysis of splicing mechanisms in patients presenting splicing defects. We analysed material of a patient suffering from junctional epidermolysis bullosa, a heritable blistering skin disease. Absence of laminin-5 protein together with hypoplastic hemidesmosomes at the dermo-epidermal junction in the patient's skin was shown by immunohistochemical analysis and immunoelectron microscopy. Subsequent DNA analysis revealed heterozygosity for the mutations R635X and 3009C-T in the LAMB3 gene. The latter did not alter codon translation, but introduced an exonic splice site in exon 20. Interestingly, this exonic splice site, which presented a splice score of only 68.6, was preferentially used by the spliceosome over the wild-type splice site at the exon 20-intron 20 border, which showed a splice score of 92.2. LAMB3 mRNA was still detectable in RT-PCR analysis although the aberrantly spliced mRNA leads to a stop codon in exon 21, 5 0 of the commonly assumed 3 0 border for nonsense-mediated mRNA decay. These results describe an exception to the proposed rules of pre-mRNA splicing and RNA degradation. Keywords: epidermolysis bullosa; laminin-5; nonsense-mediated mRNA decay; skin disease; splicing Splicing of pre-messenger RNA (mRNA) describes the mechanism of intron removal and exon ligation leading to formation of mature mRNA. This process critically depends on accurate recognition of correct splice sites by spliceosomes. The position of a splice site is indicated by a highly conserved sequence at the exon-intron border, which usually is a sequence of eight nucleotides for the 5 0 splice-site and a sequence of four nucleotides, preceded by a pyrimidine-rich region for the 3 0 splice site. Nevertheless, a splice site sequence of neighbouring nucleotides can deviate more or less from the consensus, resulting in a 'weaker' or a 'stronger' splice site. The latter is more tightly bound by splicing factors and therefore used preferentially. 1,2 The strength of a splice site can be described by a splice site score with an optimum of 100 for a very strong splice site. 3 Recently, splice site selection has been shown to be modulated by serine/arginine-rich proteins and heterogeneous nuclear riboproteins, which in turn activate/repress U1 small nuclear ribonucleoproteins responsible for selection of 5 0 splice sites. 4 Mutations changing the consensus sequence can inactivate a splice site. As a result, sequences similar to consensus sequences in exons or introns are targeted by the spliceosome instead. This process called 'cryptic splicing' often leads to the loss of coding sequences, inclusion of noncoding sequences, frameshifts and premature termination codons (PTC), what either results in truncated protein products or activates nonsense-mediated mRNA decay (NMD...

Das Rad der Forschung und Entwicklung in der Medizin dreht sich schnell. Viele neue Arzneimittel und Therapieverfahren drängen jedes Jahr auf den Markt. Woher aber wissen Therapeut, Arzt oder Patient, welche dieser Therapien wirksam sind und welche nicht? „Health Technology Assessment“ heißt die Methode, die medizinische Technologien unter die Lupe nimmt.

Physiotherapeuten, die Prävention für Rückenschmerzen anbieten, müssen sich warm anziehen, denn die Konkurrenz am Präventionsmarkt wird immer größer. Seit kurzem nascht sogar eine Krankenkasse am „Präventionskuchen“ mit und bietet Präventionstraining in hauseigenen Rückenstudios an – und das kostenlos! Müssen Physiotherapeuten um ihre Patienten bangen?