New RDEB intermediate variant with in-frame partial exon skipping in FN III-like domain of type VII collagen

Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a debilitating genodermatosis caused by pathogenic mutations in the COL7A1 gene, which induce absence or reduction in the number of anchoring fibrils. The severity of RDEB depends on the mutation type and localization, but many aspects of this dependence remain to be elucidated. Here, we report a novel variant of RDEB Intermediate in two unrelated patients. Their disease manifestation includes early skin and oral mucosa blistering and is associated with localized atrophic scarring. According to the exome and Sanger sequencing results, both investigated Probands are the carriers of complex heterozygosity in the COL7A1 gene with the same deletion in intron 19 of the COL7A1 gene. RT-PCR followed by sequence analysis revealed skipping of the part of exon19, as well as the rescue of the open reading frame (ORF) of COL7A1 in both Probands. We hypothesize that the mutation in the acceptor splice site leads to the activation of the cryptic donor splice site, resulting in the truncated but partially functional protein and the milder phenotype of intermediate RDEB. This rare type of mutation expands our understanding of RDEB etiology and invites further investigation. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by grant no. 075-15-2019-1789 from the Ministry of Science and Higher Education of the Russian Federation, allocated to the Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Pirogov Russian National Research Medical University Russia. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics Committee of Pirogov Russian National Medical University gave ethical approval for this work. (Protocol No. 219 of 2 June 2022) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available within the manuscript and supplementary materials or from the corresponding author on reasonable request.