C. elegans LIN-28 controls temporal cell fate progression by regulating LIN-46 expression via the 5' UTR of lin-46 mRNA

LIN28 upregulation in primary human T cells impaired CAR T antitumoral activity

LIN28, a highly conserved RNA-binding protein that acts as a posttranscriptional modulator, plays a vital role in the regulation of T-cell development, reprogramming, and immune activity in infectious diseases and T-cell-based immunotherapies. LIN28 inhibit the expression of let-7 miRNAs, the most prevalent family of miRNAs in lymphocytes. Recently it has been suggested that let-7 enhances murine anti-tumor immune responses. Here, we investigated the impact of LIN28 upregulation on human T cell functions, focusing on its influence on CAR T cell therapy. LIN28 lentiviral transduction of human T cells led to a stable expression of LIN28 that significantly downregulated the let-7 miRNA family without affecting cell viability or expansion potential. LIN28 overexpression maintained human T cell phenotype markers and functionality but impaired the antitumoral cytotoxicity of NKG2D-CAR T cells both in vitro and in vivo. These findings highlight the intricate relationship between LIN28/let-7 axis and human T cell functionality, including in CAR T cell therapy.

A temporal sequence of heterochronic gene activities promotes stage-specific developmental events in Caenorhabditis elegans

The heterochronic genes of the nematode Caenorhabditis elegans control the succession of postembryonic developmental events. The 4 core heterochronic genes lin-14, lin-28, hbl-1, and lin-41 act in a sequence to specify cell fates specific to each of the 4 larval stages. It was previously shown that lin-14 has 2 activities separated in time that promote L1 and L2 developmental events, respectively. Using the auxin-inducible degron system, we find that lin-28 and hbl-1 each have 2 activities that control L2 and L3 events which are also separated in time. Relative to events they control, both lin-28 and hbl-1 appear to act just prior to or concurrently with events of the L2. Relative to each other, lin-28 and hbl-1 appear to act simultaneously. By contrast, the lin-14 activity controlling L2 events precedes those of lin-28 and hbl-1 controlling the same events, suggesting that lin-14's regulation of lin-28 is responsible for the delay. Likewise, the activities of lin-28 and hbl-1 controlling L3 fates act well in advance of those fates, suggesting a similar regulatory gap. lin-41 acts early in the L3 to affect fates of the L4, although it was not possible to determine whether it too has 2 temporally separated activities. We also uncovered a feedback phenomenon that prevents the reactivation of heterochronic gene activity late in development after it has been downregulated. This study places the heterochronic gene activities into a timeline of postembryonic development relative to one another and to the developmental events whose timing they control.

Orthologs of the Caenorhabditis elegans heterochronic genes have divergent functions in Caenorhabditis briggsae

The heterochronic genes of Caenorhabditis elegans comprise the best-studied pathway controlling the timing of tissue and organ formation in an animal. To begin to understand the evolution of this pathway and the significance of the relationships among its components, we characterized 11 Caenorhabditis briggsae orthologs of C. elegans heterochronic genes. Using CRISPR/Cas9, we made a variety of alleles and found that several mutant phenotypes differ in significant ways from those of C. elegans. Although most mutant orthologs displayed defects in developmental timing, their phenotypes could differ in which stages were affected, the penetrance and expressivity of the phenotypes, or by having additional pleiotropies that were not obviously connected to developmental timing. However, when examining pairwise epistasis and synergistic relationships, we found those paralleled the known relationships between their C. elegans orthologs, suggesting that the arrangements of these genes in functional modules are conserved, but the modules' relationships to each other and/or to their targets has drifted since the time of the species' last common ancestor. Furthermore, our investigation has revealed a relationship between this pathway to other aspects of the animal's growth and development, including gonad development, which is relevant to both species.