Journal Article

Germline HPF1 retrogene insertion in RB1 gene involved in cancer predisposition

Pacquement, Hélène, Vacher, Sophie, Lumbroso-Le Rouic, Livia, Bieche, Ivan, Radvanyi, François, Boutte, Matteo, Dehainault, Catherine, Caputo, Sandrine M, Houdayer, Claude, Golmard, Lisa, Petitalot, Ambre, Gauthier Villars, Marion, Le Gall, Jessica, Doz, François, Lallemand, François, Stoppa-Lyonnet, Dominique, Courtois, Laura

2024

Overview

About half of the human genome is composed of repeated sequences derived from mobile elements, mainly retrotransposons, generally without pathogenic effect. Familial forms of retinoblastoma are caused by germline pathogenic variants in RB1 gene. Here, we describe a family with retinoblastoma affecting a father and his son. No pathogenic variant was identified after DNA analysis of RB1 gene coding sequence and exon-intron junctions. However, RB1 mRNA analysis showed a chimeric transcript with insertion of 114 nucleotides from HPF1 gene inside RB1 gene. This chimeric transcript led to an insertion of 38 amino acids in functional domain of retinoblastoma protein. Subsequent DNA analysis in RB1 intron 17 revealed the presence of a full-length HPF1 retrogene insertion in opposite orientation. Functional assay shows that this insertion has a deleterious impact on retinoblastoma protein function. This is the first report of a full-length retrogene insertion involved in human Mendelian disease leading to a chimeric transcript and a non-functional chimeric protein. Some retrogene insertions may be missed by standard diagnostic genetic testing, so contribution of retrogene insertions to human disease may be underestimated. The increasing use of whole genome sequencing in diagnostic settings will help to get a more comprehensive view of retrogenes.

• Publisher: BMJ Publishing Group Ltd,BMJ Publishing Group LTD
• Subject: Amino acids / Cancer genetics / Carrier Proteins - genetics / Cell cycle / Disease Susceptibility / DNA / DNA Mutational Analysis / Genes, Retinoblastoma / genetic phenomena / genetic predisposition to disease / Genetic screening / genetic variation / Genomes / Humans / Insertion / Mutagenesis / Nuclear Proteins - genetics / Nucleotide sequence / Nucleotides / Proteins / Retinal Neoplasms - diagnosis / Retinal Neoplasms - genetics / Retinal Neoplasms - pathology / Retinoblastoma / Retinoblastoma - diagnosis / Retinoblastoma - genetics / Retinoblastoma - pathology / Retinoblastoma Binding Proteins - genetics / Retinoblastoma protein / Retinoblastoma Protein - genetics / sequence analysis / Ubiquitin-Protein Ligases - genetics / Whole genome sequencing