Koo, H. J. | Search bioRxiv

bioRxiv2023

Radial glia control microglial differentiation via integrin avb8-dependent trans-activation of TGFB1

Microglia diversity emerges from interactions between intrinsic genetic programs and environment-derived signals, but how these processes unfold and interact in the developing brain remains unclear. Here, we show that radial glia-expressed integrin beta 8 (ITGB8) expressed in radial glia progenitors activates microglia-expressed TGF{beta}1, permitting microglial development. Domain-restricted deletion of Itgb8 in these progenitors establishes complementary regions with developmentally arrested "dysmature" microglia that persist into adulthood. In the absence of autocrine TGF{beta}1 signaling, we find that microglia adopt a similar dysmature phenotype, leading to neuromotor symptoms almost identical to Itgb8 mutant mice. In contrast, microglia lacking the TGF{beta} signal transducers Smad2 and Smad3 have a less polarized dysmature phenotype and correspondingly less severe neuromotor dysfunction. Finally, we show that non-canonical (Smad-independent) signaling partially suppresses disease and development associated gene expression, providing compelling evidence for the adoption of microglial developmental signaling pathways in the context of injury or disease.

immunology↗

bioRxiv2017

Quantifying the thermostability landscape separating plant sesquiterpene synthase orthologs using Maximum Entropy

As global temperatures rise due to climate change, crops are becoming increasingly vulnerable to failure. We tested the accessibility of thermodynamic phenotypic diversity within limited positional changes using 29=512 mutants of a terpene synthase (TPS), Tobacco 5-epi-Aristolchene synthase. First, we measured the thermal unfolding curves of each mutant and found that mutations shifted the Tms both higher and lower, including a cohort of mutants that failed to fold. The low correlation coefficient between the Tms of these mutants and the proportions of each terpene product output by the enzymes revealed that thermostability and product output are independent traits. Maximum Noise Entropy analyses were used to analyze the impact of the 9 mutational positions on thermostability, revealing that three of these positions were mainly responsible for the trait of increased Tm. These positions form a functional network as measured by the nonlinearity of their combined effects on thermostability. Unexpectedly, the strongly destabilizing positions combine nonlinearly to ameliorate each others deleterious effects resulting in a synergistic dampening. Taken together, our study shows the high potential for specialized metabolic enzyme engineering but also reveals a complex interconnected system of amino acids that will continue to evade perfect predictability.

bioengineering↗