Talks by Matthias TITEUX and Shana DELFOSSE

Matthias TITEUX
Laboratory of cellular and molecular mechanisms of hematological disorders and therapeutic implications, U1163-CEREMAST, Foundation IMAGINE - Eric Allemand’s lab

Title:
Splice Modulation strategies for the treatment of Recessive Dystrophic Epidermolysis Bullosa

Abstract:
Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a rare genodermatose characterized by detachment of skin and mucous membranes, caused by loss-of-function variants in COL7A1 encoding type VII collagen (C7), the major component of anchoring fibrils (AFs). We have identified deep intronic variants inducing splice defects (intron retention or pseudoexon incorporation) that were rescued in vitro by antisense oligonucleotides (ASOs), leading to the expression of up to 50% of the normal levels of wild-type COL7A1 mRNA and protein. In addition, the excision of the frequently mutated exon 73 of COL7A1 using ASOs is a promising approach to treat RDEB. We have developed a novel palmitoylated tricyclo-DNA ASO that induced efficient exon skipping and C7 re-expression ex vivo in RDEB patient primary cells. We then demonstrated exon 73 skipping, C7 expression (up to 38% of the normal amount) and AFs formation in relevant tissues (skin, eyes, and oesophagus) in RDEB murine models following subcutaneous and intravenous injections. Preliminary toxicological studies on human plasma and in vivo in mice and in non-human primates demonstrated a safe profile of the ASO. These results paves the way for the development of a systemic treatment for RDEB patients.

Shana DELFOSSE
Unité RNA Biology of Fungal Pathogens – Mycology Department - Institut Pasteur - Jessie Colin’s lab

Title:
Alternative polyadenylation site use in Cryptococcus neoformans

Abstract:
Transcriptome modifications can be either quantitative or qualitative, affecting transcript properties such as length, informational content, and subcellular localization. Among other processes, these changes largely rely on the use of alternative polyadenylation (APA) sites. We used complementary massive sequencing approaches to map and quantify the use of APA sites in the opportunistic pathogenic fungus Cryptococcus neoformans. We found that, in this species, most of the coding genes display APA sites. A striking example of APA-driven regulation is found at the ARG5,6 gene. In most fungi, this gene encodes a single long precursor protein that is post-translationally cleaved into two enzymes of the arginine biosynthesis pathway: a kinase (Arg6) and a reductase (Arg5). In C. neoformans, this gene carries an internal intronic APA site. Its use is tightly regulated by specific conditions, allowing the production of only one of the two enzymes. Our genetic dissection of the ARG5,6 locus suggests that the intronic APA site is involved in regulating the production of two virulence factors: urease and the capsule. These data suggest that APA is not only a regulatory layer but a key driver of transcriptomic diversity in Cryptococcus neoformans, with direct implications for its pathogenicity.