Biosensing of chromatin packing in live cells

为了将包含有机体遗传密码的两米长的DNA分子打包成几微米大小的细胞核，该分子被压缩成一种称为染色质的致密结构。染色质的一些部分显示出一种更开放的形式，称为常染色质，这是高基因表达的特征，而另一些部分则显示出一种更密集的染色质，称为异染色质。目前，还没有生物传感技术能够实时检测异染色质到常染色质的转换，这是了解细胞如何功能和人类基因组如何调控的关键问题。因此，本项目的目标是开发一种在活细胞中动态生物传感染色质包装的方法，并实现这一点，而不使用可能影响细胞功能的外部标记，从而不影响染色质动态。这将通过使用散射光的特性来实现，散射光携带着关于它被散射的物体的信息，即使该物体的结构如此微小，以至于普通显微镜无法分辨它。该项目的一个重要部分将是一个教育推广计划，与代表人数不足的群体和K-12学生分享这项技术。这一推广计划旨在接触到来自以少数民族为主的当地社区的K-12教育贫困学生。在这项申请中提出的用于动态生物传感活细胞中染色质包装的新型无标签技术将解决遗传学和表观遗传学中尚未解决的根本问题。它应该有助于回答一个知之甚少的问题，即信号转导途径如何直接与染色质沟通，以改变表观遗传格局。它还可以促进一种新的合成生物生物传感方法，因为染色质可以作为早期发育过程中代谢变化的传感器。它还应该对公共卫生有重要的影响，包括癌症中的染色质变化或表观遗传学在传染病中的作用。这一方法将促进工程科学和生命科学的发展，并将基于分形传感原理的组合，因为众所周知，活细胞中的染色质是以分形的形式组织的，其异染色质和常染色质区域表现出不同的分维，以及相干共聚焦光吸收和散射光谱显微镜。提出的方法是基于新的基本见解，即染色质分形的自相似属性反映在染色质光散射光谱中，这些光谱可以连续快速地记录，从而在多种空间和时间尺度上创建染色质的3D动态地图。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In order to pack a two-meter-long DNA molecule that contains the genetic code of an organism into a several-micron sized nucleus, the molecule compacts into a dense structure called chromatin. Some parts of chromatin display a more open form called euchromatin, which is characteristic of high gene expression, while others exhibit a more densely packed chromatin called heterochromatin. Currently, there is no biosensing technology capable of sensing the conversion from heterochromatin to euchromatin and back in real time, which is a critically important question for understanding how cells function and how the human genome is regulated. Thus, the goal of this project is to develop a method for dynamic biosensing of chromatin packing in live cells and to achieve this without employing external markers that can affect cell function and, as a result, chromatin dynamics. This will be achieved by using properties of scattered light, which carries information about the object it is scattered by, even if the structure of the object is so tiny that regular microscopes cannot resolve it. An important part of this project will be an educational outreach program to share the technology with underrepresented groups and K-12 students. This outreach program is designed to reach K-12 educationally disadvantaged students from local neighborhoods with predominantly ethnic-minority student populations.The novel label-free technology for dynamic biosensing of chromatin packing in live cells, proposed in this application will address fundamental unsolved problems in genetics and epigenetics. It should help to answer a poorly understood question of how signal transduction pathways directly communicate with chromatin to change the epigenetic landscape. It can also facilitate a novel synthetic biology biosensing approach as chromatin can serve as a sensor of metabolic changes during early development. It should also have important implications in public health, including chromatin changes in cancer or the role of epigenetics in infectious diseases. The approach will advance both engineering and life sciences and will be based on a combination of the principles of fractal sensing, since it is known that chromatin in live cells is organized as a fractal with heterochromatin and euchromatin domains exhibiting different fractal dimensions, and coherent confocal light absorption and scattering spectroscopic microscopy. The proposed approach is motivated by the new fundamental insights that self-similar properties of the chromatin fractal are reflected in the chromatin light scattering spectra, and these spectra can be continuously and rapidly recorded creating a 3D dynamic map of chromatin on a multitude of spatial and temporal scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.