Development of Novel Gene Technology for Treating Epidermolysis Bullosa Simplex (EBS) and Recessive Dystrophic Epidermolysis Bullosa (RDEB)

Short lay summary

About 70% of Epidermolysis Bullosa (EB) cases are classified as EB Simplex (EBS), which is caused by mutations (mistakes) in the genes that manufacture proteins called keratin 5 and keratin 14 (KRT5 and KRT14). Keratins are vital to ensure a strong and healthy skin. There are no effective treatments for EBS, which is characterised by persistent blistering and poor healing of the skin both internally and externally. Genes are inherited, one copy from each parent. Only one copy of the gene needs to contain a mutation to cause EBS – these are called dominant genes. By selectively suppressing the expression of the faulty copy of the gene, this allows the normal copy of the gene to work properly, a strategy that is believed could be developed into an appropriate therapy for EBS.

The initial goal of this project was to develop a novel technology for therapeutic gene silencing in EBS. When the genetic or DNA sequence of a gene is read, akin to a recipe, it is eventually translated through an intermediate stage (messenger RNA) into the production of protein – in this case the keratins found in the top layer of the skin, the epidermis.  New developments in gene technology mean that it is now possible to synthesise a small piece of nucleic acid that will bind to the messenger RNA and inactivate it. This is termed gene silencing technology. Antisense oligonucleotides (ASOs) are small pieces of nucleic acid that can be designed to specifically bind to messenger RNA copies of a certain gene in order to destroy these.

The Clinical Research Fellow was tasked with developing this new gene silencing technology to the point where it could be taken into the clinic. The team in Dundee have been working with the pharmaceutical company WAVE Life Sciences on this project and have identified several ASOs that can silence the KRT14 messenger RNA in human skin cells grown in the laboratory.

Using ASOs for Recessive Dystrophic Epidermolysis Bullosa (a more severe form of EB) is equally challenging. Recessive dystrophic epidermolysis bullosa (RDEB) is caused by faults in the COL7A1 gene, the genetic recipe for the protein collagen type 7. Everybody carries two COL7A1 copies, but, in contrast to EBS, there needs to be a mutation on both copies of the gene to exhibit the symptoms of RDEB – these are recessive genes. The approach to destroy the faulty messenger RNA will not work here. However, a different class of ASOs can be used which can trick the cells into removing the part of the messenger RNA where the mutation is located. This approach is called ‘exon skipping’ and although this will lead to a slightly shorter messenger RNA, it can still be used to produce active (but shorter) type 7 collagen. In a literature study, the Fellow found that people in whom exon skipping occurs naturally (without the use of ASOs but rather due to an additional DNA variation) still have a form of DEB, but this is milder than usual. This emphasizes that exon skipping is a promising therapeutic strategy. The team in Dundee have designed several ASOs that can induce exon skipping of COL7A1 in human skin cells grown in the laboratory.

Novel antisense technology for EB - advancing exon skipping in human skin

(Years 3 & 4)

DEBRA UK has now granted further funding towards the DEBRA Clinical Research Fellow Dr Peter van den Akker for a further year and funding for Dr Aileen Sandilands in the first instance where they will further develop this novel antisense technology.

The major aim is now to study whether the functional ASOs can induce exon skipping of the COL7A1 gene and silencing of the mutant KRT14 RNA copy when applied to human skin (using leftover skin from surgical procedures). This involves studying ways to deliver these ASOs to the right location in the skin. Therefore, the Fellow is working closely with the team of Dr Hickerson.

 The major aims of the clinical research fellowship moving forward are to;

• Induce “knockdown” of the mutant KRT14 mRNA to treat EBS (to work on eliminating the keratin messenger RNA that carries the mutation).
• Skip exons that contain mutations in the COL7A1 gene to treat RDEB (to trick the body’s cells into removing or not reading the part of the gene where the mutation is located).

You can find out more about this project here.

 *Please note: The costs shown are not indicative of salary and include various other costs associated with the provision of the service outlined.