The CCDS project (42) is identifying consistently annotated, high-quality protein-coding variants for the human genome. CCDS variants are annotated only when there is agreement between the three main public annotation resources (GENCODE/Ensembl, NCBI and UCSC). Although the CCDS project can annotate any number of variants for a gene, many genes have a single CCDS variant, a variant agreed upon by all annotation resources. A single CCDS variant is the closest thing to an APPRIS principal variant, therefore, we should expect to see high agreement between the APPRIS constitutional isoforms and the CCDS variants.
