FS-HI-C -- TECHNIQUE CAPABLE OF EFFICIENTLY CAPTURING THREE-DIMENSIONAL CHROMOSOME CONFORMATION OF FROZEN BIOLOGICAL SAMPLE

摘要

A sample pretreatment method applicable to Hi-C high throughput sequencing and library construction, comprising: freezing a test biological sample and fixing same by cross-linking. The freeze substitution Hi-C technique (FS-Hi-C) provided by said method is applicable not only to a fresh sample but also to a frozen sample stored in liquid nitrogen. Said method uses a freeze substitution (FS) technique to prepare an Hi-C sample of a liquid nitrogen (LN2) frozen sample, so as to prevent sample from changing in the three-dimensional structure in a temperature rising process after being removed from a liquid nitrogen solution, solving a biological problem of how to use a sample frozen and stored in a low-temperature to study a three-dimensional chromosome structure thereof. Said method is evaluated in Drosophila, cotton, soybeans, and radish, and by means of observation by a high-voltage frozen transmission electron microscope, it is found that a freeze substitution (FS) sample and a fresh sample have highly similar three-dimensional chromatin structures, and the data quality of Hi-C libraries of cotton and Drosophila can be improved. FS-Hi-C exhibits a high degree of consistency in terms of chromatin interaction, A/B compartment, and TAD compared to conventional Hi-C pretreatment methods. Moreover, the library constructed by the FS-Hi-C method has a better quality, increased library capacity, greater amount of effectively interacting data, and reduced repeated data generated by PCR amplification. Said method reduces the requirements for the timeliness of a sample, and facilitates acquisition and storage of a sample. Said method overcomes the limitation for an Hi-C experimental sample, can efficiently capture a three-dimensional chromosome conformation of a frozen biological sample, improves the data quality of biological Hi-C, and provides an improved method for the application of Hi-C in research.