lin-28 Controls the Succession of Cell Fate Choices via Two Distinct Activities

lin-28 is a conserved regulator of cell fate succession in animals. In Caenorhabditis elegans, it is a component of the heterochronic gene pathway that governs larval developmental timing, while its vertebrate homologs promote pluripotency and control differentiation in diverse tissues. The RNA binding protein encoded by lin-28 can directly inhibit let-7 microRNA processing by a novel mechanism that is conserved from worms to humans. We found that C. elegans LIN-28 protein can interact with four distinct let-7 family pre-microRNAs, but in vivo inhibits the premature accumulation of only let-7. Surprisingly, however, lin-28 does not require let-7 or its relatives for its characteristic promotion of second larval stage cell fates. In other words, we find that the premature accumulation of mature let-7 does not account for lin-28's precocious phenotype. To explain let-7's role in lin-28 activity, we provide evidence that lin-28 acts in two steps: first, the let-7–independent positive regulation of hbl-1 through its 3′UTR to control L2 stage-specific cell fates; and second, a let-7–dependent step that controls subsequent fates via repression of lin-41. Our evidence also indicates that let-7 functions one stage earlier in C. elegans development than previously thought. Importantly, lin-28's two-step mechanism resembles that of the heterochronic gene lin-14, and the overlap of their activities suggests a clockwork mechanism for developmental timing. Furthermore, this model explains the previous observation that mammalian Lin28 has two genetically separable activities. Thus, lin-28's two-step mechanism may be an essential feature of its evolutionarily conserved role in cell fate succession

Sub-sewershed Monitoring to Elucidate Down-the-Drain Pesticide Sources

Pesticides have been reported in treated wastewater effluent at concentrations that exceed aquatic toxicity thresholds, indicating that treatment may be insufficient to adequately address potential pesticide impacts on aquatic life. Gaining a better understanding of the relative contribution from specific use patterns, transport pathways, and flow characteristics is an essential first step to informing source control measures. The results of this study are the first of their kind, reporting pesticide concentrations at sub-sewershed sites within a single sewer catchment to provide information on the relative contribution from various urban sources. Seven monitoring events were collected from influent, effluent, and seven sub-sewershed sites to capture seasonal variability. In addition, samples were collected from sites with the potential for relatively large mass fluxes of pesticides (pet grooming operations, pest control operators, and laundromats). Fipronil and imidacloprid were detected in most samples (>70%). Pyrethroids were detected in >50% of all influent and lateral samples. There were significant removals of pyrethroids from the aqueous process stream within the facility to below reporting limits. Imidacloprid and fiproles were the only pesticides that were detected above reporting limits in effluent, highlighting the importance of source identification and control for the more hydrophilic compounds. Single source monitoring revealed large contributions of fipronil, imidacloprid, and permethrin originating from a pet groomer, with elevated levels of cypermethrin at a commercial laundry location. The results provide important information needed to prioritize future monitoring efforts, calibrate down-the-drain models, and identify potential mitigation strategies at the site of pesticide use to prevent introduction to sewersheds

A comparison of cognitive performances based on differing rates of DNA methylation GrimAge acceleration among older men and women

•The DNAm GrimAge clock can be used to parse age from sex effects on cognition.•Rates of aging differ among men and women of similar chronological ages.•Cognition, mood, and education levels varied by age rate.•Sex differences in some cognitive abilities were explained by rates of aging.•However, women maintained a verbal memory advantage regardless of age rate. Cognitive heterogeneity increases with age rendering sex differences difficult to identify. Given established sex differences in biological aging, we examined whether comparisons of men and women on neuropsychological test performances differed as a function of age rate. Data were obtained from 1921 adults enrolled in the 2016 wave of the Health and Retirement Study. The residual from regressing the DNA methylation GrimAge clock on chronological age was used as the measure of aging rate. Slow and fast age rates were predefined as 1 standard deviation below or above the sex-specific mean rates, respectively. ANCOVAs were used to test group differences in test performances. Pairwise comparisons revealed that slow aging men outperformed fast aging women (and vice versa) on measures of executive function/speed, visual memory and semantic fluency; however, when groups were matched by aging rates, no significant differences remained. In contrast, women, regardless of their aging rates, education or depressive symptoms maintained their advantage on verbal learning and memory. Implications for research on sex differences in cognitive aging are discussed

Creating an Equal Opportunity High School

: Target audience to include any administrators, teachers, guidance counselors who work directly with at risk/minority students. The objective will be to demonstrate tools, strategies and programs that build positive relationships, reduce suspension rates, and assist students in meeting challenging academic goals to become college and career read

<i>lin-28</i> mutants can be two stages precocious due to <i>let-7</i> activity.

1<p>All strains are homozygous for null alleles of the genes indicated and carry an integrated transgene of the seam cell marker <i>wIs78(scm::GFP; ajm-1::GFP)</i>. All alleles are null.</p>2<p>Percentage of seam cells synthesizing adult alae by early L3.</p>3<p>n = number of seam cells scored.</p

A model for the two sequential activities of LIN-28 in specifying cell fates.

<p>Top, Genetic formalisms depicting the two <i>lin-28</i> pathways that regulate the L2-to-L3 and the L3-to-L4 fate transitions. Bottom, A schematic time course depicting the regulatory dynamics during the first three larval stages. LIN-14, LIN-28, HBL-1 and LIN-41 are expressed at the start of larval development and are eventually repressed by the microRNAs lin-4, let-7 and the three let-7 family members miR-48, miR-84, and miR-241 (3 let-7s). The approximate times of LIN-14's two activities are indicated with boxed letters. The relevant times of LIN-28's two activities that correspond to the pathways above are depicted with black lines and circled letters.</p

<i>lin-28</i> positively regulates <i>hbl-1</i> reporter expression.

<p>Nomarski and fluorescence micrographs of <i>hbl-1::GFP::hbl-1 3′UTR</i> reporter expression. Early stages are late L1 or early L2. Late stages are L4 or age-matched post-L3 molt <i>lin-28</i> animals. A, wild type. B, <i>mir-48 mir-241; mir-84 (3 let-7s)</i>. C, <i>lin-28; mir-48 mir-241; mir-84 (lin-28; 3 let-7s)</i>. D, a <i>hbl-1::GFP::unc-54 3′UTR</i> reporter in <i>lin-28; mir-48 mir-241; mir-84 (lin-28; 3 let-7s)</i>. Se, seam nuclei. hyp, hyp7 nuclei. All fluorescence images were captured with a 2 sec. exposure time. Scale bar, 10 microns.</p

Relative contribution of <i>hbl-1</i> and <i>lin-41</i> for the <i>let-7</i> retarded phenotype.

1<p>The <i>let-7</i> mutants were identified by Unc phenotype due to the <i>unc-3</i> mutation.</p>2<p>The precocious alae were assessed at the end of L3–L4 molt or in the early L4 stage of development.</p>3<p>As previously noted, <i>hbl-1(RNAi)</i> causes a proliferation defect in the late L4 which is not interpreted as heterochronic <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002588#pgen.1002588-Lin2" target="_blank">[53]</a>. These divisions were not scored.</p><p>ND, not determined.</p

Seam cell lineages of animals with altered <i>lin-28</i> activity.

<p>Lineage patterns characteristic of lateral hypodermal seam cells V1, V2, V3, V4 and V6. Left to right: Wild type <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002588#pgen.1002588-Sulston1" target="_blank">[56]</a>. Animals lacking <i>mir-48</i>, <i>mir-84</i>, and <i>mir-241</i> (<i>3 let-7s</i>), or animals carrying a transgene constitutively expressing <i>lin-28</i> (<i>lin-28(gf)</i>) <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002588#pgen.1002588-Moss3" target="_blank">[62]</a>. <i>let-7</i> null mutants, whose defect in these lineages is first visible in the late L4 stage. Two types of seam cell lineages observed in <i>lin-28</i> null mutants <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002588#pgen.1002588-Ambros1" target="_blank">[1]</a>. Seam cell lineages that skip L2 fates in <i>lin-28(low RNAi)</i> animals (see text). Three horizontal lines indicate the time of adult alae formation. Dashed lines indicate variable lineage patterns in <i>lin-28(gf)</i> animals.</p