El libro humana genoma, sequence of the two X chromosomes and autosomes from the female tissue derived cell line has been completed. This includes the 8% of the genoma, sequence that was missing in the original draft that was released in 2001.
El libro humana genoma, sequence of the entire 3.055 billion base pairs has been revealed by the Telomere-to-Telomere (T2T) Consortium. This represents the largest improvement to the humana referencia genoma, released in 2001 by Celera Genomics and the International Personas Genoma Sequencing Consortium. That genoma, sequence covered most of the euchromatic regions while either leaving out the heterochromatin regions or erroneous representation. These regions comprise 8% of the humana genoma, that has finally been revealed. The new T2T-CHM13 reference1 incluye la secuencia completa para los 22 autosomas más el cromosoma X. Esta nueva secuencia de referencia también ha corregido numerosos errores y ha agregado aproximadamente 200 millones de pb de nuevas secuencias que contienen 2,226 copias de genes, de las cuales se prevé que 115 sean codificantes de proteínas.
The current GRCh38.p13 reference genome has been as a result of two major updates, one in 2013 and the other one on 2019 on the 2001 Celera genome sequence. However, it still had 151 million base pairs of unknown sequence distributed throughout the genoma,, including pericentromeric and sub telomeric regions, duplications, gene and ribosomal DNA (rDNA) arrays, all of which are necessary for fundamental cellular processes. The new reference has been named as T2T-CHM13 as it comes from sequencing the DNA from CHM13 (Complete Hydatiform Mole) cell line and is performed by T2T consortium. The cell line is derived from abnormal fertilized egg or an overgrowth of tissue from the placenta in which women appears to be pregnant (false pregnancy), hence the sequence represents only of the two X chromosomes and autosomes of the female. Multiple sequence technologies have been put to use such as PacBio, Oxford Nanopore, 100X and 70X Illumina sequencers to name a few. The technological advances in sequencing have led to the sequencing of the remaining 8% as mentioned above.
La única limitación de la secuencia T2T-CHM13 es la falta de un cromosoma Y. Esta secuenciación está actualmente en curso, utilizando el ADN de la línea celular HG002, que tiene un 46 (23 pares) con un cariotipo XY. Luego, la secuencia se ensamblará utilizando los mismos métodos desarrollados para el genoma homocigótico de CHM13.
La disponibilidad de T2T-CHM13 como nueva referencia genoma, representa un gran avance que ayudará a comprender el papel de las regiones de heterocromatina y ayudará a comprender sus efectos en los procesos celulares con mayor detalle. Hasta que se complete la secuenciación del cromosoma Y, este servirá como genoma de referencia para futuros estudios en la comprensión de los procesos y funciones celulares.
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Referencias
- Nurk S, Koren S, Rhie A, Rautiainen M, Bzikadze A V, Mikheenko A et al. The complete sequence of a humana genome bioRxiv 2021.05.26.445798; DOI: https://doi.org/10.1101/2021.05.26.445798
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