What is an in-frame activating fusion?
This is explained in the linked article.


  We found several recurrent translocations of likely pathogenic significance, including an intra-chromosomal translocation on chromosome 4 involving FGFR3 and TACC3 (n=3). The breakpoints were in intron 16 (2 cases) or exon 17 (1 case) of FGFR3 and intron 10 of TACC3 (confirmed by DNA sequencing and RNA-seq). All three lead to fusion mRNA products whose predicted proteins include the N-terminal 758 amino acids of FGFR3 fused with the C-terminal 191 amino acids of TACC3 (Fig. 2a). Based on the structure of the FGFR3-TACC3 fusion protein, we predict that it can auto-dimerize, leading to constitutive activation of the kinase domain of FGFR3. FGFR3-TACC3 fusion, which was recently described in both glioblastoma21 and bladder cancer7,8, represents a promising therapeutic target. 


FGFR3 is a member of the fibroblast growth factor receptor family. It is a transmembrane kinase that is normally activated upon ligand binding which triggers dimerisation. TACC3 is a protein that can dimerise through a coiled-coil domain. 

The FGFR3-TACC3 gene fusion that is generated by the reported intra-chromosomal translocations thus generates a version of the receptor that is predicted to be constitutively active because it can dimerise in the absence of the growth factor. 

Recurrent means occurring frequently.