Establishing an atlas of LAD morphologies and its relationship with cellular function

Objective

The three-dimensional organization of the genome is emerging as a critical regulator of nuclear functions. But we are only beginning to define the diverse nuclear morphologies of different cell types and understand their cell-specific functions. To address this issue, I will focus on Lamina-Associated Domains (LAD), which are large heterochromatic domains anchored to the nuclear lamina. LADs help partition silent heterochromatin from active euchromatin enabling the tridimensional organization of the genome. These domains are crucial for gene silencing, cell signaling, and protecting DNA from UV damage, and their loss often leads to cellular dysfunction, for example in cancer or aging. Studies have shown that LAD morphologies vary considerably in different cell types. I propose to leverage the stereotyped development of C. elegans to generate an atlas of LAD morphologies through embryogenesis. In Aim 1, I will use an automated cell identification AI-based algorithm (ceSCALE, recently developed in the Mango lab) coupled with super-resolution microscopy to extract temporally evolving heterochromatin features across time and space, with a special focus on lamina-associated heterochromatin. I will complement this by defining cell-specific components near the lamina (TurboID, DamID) to uncover some of the governing rules that dictate the formation of specific LAD morphologies. In Aim 2, I will focus on a specific cell type that our preliminary data show contains unusual LADs: gut cells. I will relocate heterochromatin to the nuclear periphery of gut cells through ectopic tethering to determine whether changing gut LAD morphology affects its function. I hypothesize that the almost complete localization of heterochromatin in the interior of the nucleus of gut cells enables effective nuclear export and appropriated response to environmental cues. Altogether, MorphoLADs will define cell-specific LAD morphologies and open an avenue to explore their cellular functions.