CHM13

CHM13 refers to a human cell line used as the basis for a high-quality reference human genome assembly. It derives from a hydatidiform mole (CHM) and is immortalized with the human telomerase reverse transcriptase gene (hTERT), producing the designation CHM13hTERT. Because the line is haploid, it contains only a paternal genome and minimal heterozygosity, simplifying genome sequencing and assembly.

The Telomere-to-Telomere (T2T) consortium used CHM13 to produce the T2T-CHM13 assembly, the first near-complete human genome sequence, including most repetitive regions previously missing from reference genomes, such as centromeres and parts of pericentromeric sequences, telomeres, and ribosomal DNA arrays. The project combined long-read sequencing (PacBio HiFi and/or Oxford Nanopore), high-resolution optical mapping, and chromosome conformation capture to close gaps and validate structure.

Impact and features: The CHM13-based assembly reveals previously unresolved structures and provides a more complete map of structural variation. It is intended as a supplement to the standard reference genome (GRCh38/GRCh38.p13) and is not a representation of human genetic diversity, being based on a single haploid genome. Researchers use it to study genome architecture, repetitive regions, and genome instability.

Access and usage: The T2T-CHM13 genome is publicly available for download and analysis, with versions released by the T2T project and archived in major genomic databases. It has influenced revisions to genome annotation and comparative studies.

Ethical considerations: CHM13 represents a single individual and is not a population reference; data usage follows typical guidelines for human genomic research and privacy.