Weekly Advanced Technologies〔68〕丨"NyuWa" Map Reveals Genomic Polymorphism and Deepens the Understanding of Gene Regulation; The "Anti-breathing" Marvel: New Discoveries of Active Galactic Nuclei

More than half of the region of the human genome consists of repetitive sequences. These repetitive sequences are highly variable during human evolution and enrich the genetic diversity of the genome. Variable number of tandem repeats can increase the risk of disease through length expansion, and changes in its repeat motifs have independent pathogenic effects. However, limited by sample size, sequencing depth, population diversity, and identification algorithms, the genetic research on variable number of tandem repeats has been insufficient in the existing population - scale genome sequencing projects. Consequently, the human genome lacks some genetic power. In response to this situation, the research team of the Chinese Academy of Sciences has carried out relevant explorations.

The ultraviolet and optical spectra of active galactic nuclei are characterised by the presence of a large number of broad emission lines with widths exceeding 1,000 kilometres per second. The radiation area of the broad emission lines is called the broad line region. The high gas velocities in the broad line region produce broad emission lines in response to photo-ionisation by high-energy photons from the central accretion disk. 

Studying the structural and dynamical properties of the broad line region can help scientists measure the mass of the central supermassive black hole and can shed light on the physical processes inside active galactic nuclei. And the complex kinematics and spatial distribution of the broad line region are not entirely clear. Recently, a breakthrough was made by researchers at Yunnan Observatory of the Chinese Academy of Sciences and collaborators.

Based on the weekly diary of technology provided by the daily list of the NCSTI online service platform, we launch the column "Weekly Advanced Technologies" at the hotlist of sci-tech innovation. Today, let's check out No.68.

1. Cell Genomics丨"NyuWa" Map Reveals Genomic Polymorphism and Deepens the Understanding of Gene Regulation

Graphical abstract of study resolves small-satellite polymorphism mapping of the human genome

More than half of the region of the human genome consists of repetitive sequences. These repetitive sequences have been highly variable during human evolution and have enriched the genetic diversity of the genome. Variable Number of Tandem Repeats (VNTRs), also known as minisatellite DNA, are a class of DNA tandem sequences with a repeating motif of more than 6 bp and a number of repeats usually ranging from 10 to 60. It has been found that VNTRs can increase the risk of disease through length expansion, and that changes in the repeat motifs of VNTRs have independent pathogenic effects. 

However, due to factors such as sample size, sequencing depth, population diversity and identification algorithms, the genetic study of VNTRs has been insufficient in existing population-scale genome sequencing projects, resulting in a partial lack of heritability in the human genome.

Recently, the team of Xu Tao, academician of CAS and researcher at the Institute of Biophysics, CAS, and the team of He Shunmin, researcher of the Institute of Biophysics, CAS, have developed a genetic map of VNTR polymorphisms in the global population by using the data from the high-depth whole-genome sequencing of 8,222 cases in more than 140 countries and regions - the ‘NyuWa’ VNTR polymorphism map. The ‘NyuWa’ VNTR polymorphism map was constructed to analyse the functional characteristics of VNTR, especially the regulatory role of VNTR in gene expression.

The "NyuWa" VNTR polymorphism map has completed the full coverage of major repetitive sequence elements in the human genome by the "NyuWa" genome resource. It has provided an important reference for analyzing the variation of repetitive sequence elements. This achievement has expanded the scale of repetitive sequence element variation in existing genetic research, providing a new perspective for exploring the role of repetitive sequence elements in gene regulation. It has also offered references for future clinical research and genotype-phenotype association studies.

2. The Astrophysical Journal丨The "Anti-breathing" Marvel: New Discoveries of Active Galactic Nuclei

The ultraviolet and optical spectra of active galactic nuclei are marked by the existence of a large number of broad emission lines whose widths are more than 1,000 kilometres per second. The area where the broad emission lines are radiated is known as the broad-line region. The high gas velocities in the region generate broad emission lines in response to photo-ionization by high-energy photons from the central accretion disk. Studying the structural and dynamical properties of the broad-line region can assist scientists in measuring the mass of the central supermassive black hole and can also clarify the physical processes within active galactic nuclei. The complex kinematics and spatial distribution of the broad-line region are not fully understood.

Recently, researchers from the Yunnan Observatory of the Chinese Academy of Sciences, in collaboration with others, carried out a four-year reaction-mapping observation of the changing-look active galactic nucleus NGC 4151 by using the 2.4-metre telescope at the Lijiang Astronomical Observatory. The results indicate that there is a significant stratification of multiple broad emission lines in NGC 4151. In other words, different emission lines originate from different radial ranges in the broad-line region. At the same time, it has been discovered that there is an anomalous anti-breathing phenomenon in NGC 4151.

According to traditional theories, when the brightness of an active galactic nucleus increases, the radius of the broad-line region should expand accordingly, resulting in an increase in the time delay of broad emission lines, namely the "anti-breathing" phenomenon. However, the observational results of NGC 4151 show that the time delay of broad emission lines shortens as the brightness increases. This phenomenon may be related to the time delay between the ultraviolet-optical variability of active galactic nuclei. 

Further research through velocity-resolved time-delay analysis has found that the geometric structure and dynamic properties of the broad-line region in NGC 4151 have changed significantly on a time scale of less than one year. Such rapid changes cannot be simply explained by the inhomogeneous distribution of the broad-line region, changes in radiation pressure, or changes in the ionizing radiation field, indicating that the physical properties of the broad-line region are more complex than previously thought, or are jointly driven by multiple mechanisms.

The above-mentioned results have enhanced scientists' understanding of the dynamics and geometrical evolution within broad-line regions, thus providing a reference for future investigations into the internal structure of active galactic nuclei through long-time-scale and multi-band observations. In the future, the research team will further analyze the interaction between the broad-line region and the accretion disc by combining high-time-resolution observation data, with the aim of uncovering the physical mechanism underlying its dynamical evolution.

Columnist: Li Xiaoxiao

Translator: Liu Kaiyuan