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Houston, J.

Publications and source records attributed to Houston, J..

6 recordsLinked to original sources

Identifying and ranking species that need urgent management action to achieve Target 4 of the Global Biodiversity Framework

Target 4 of the Kunming-Montreal Global Biodiversity Framework (KMGBF) calls for urgent management actions to halt humaninduced extinctions and enable species recovery. However, most Parties face substantial challenges in determining which species require urgent management actions. Here, we present a transparent, standardised protocol that identifies and ranks species most likely to need urgent management actions at the national level, using globally available data from the IUCN Red List of Threatened Species. The protocol integrates four criteria aligned with Target 4: global extinction risk, rate of decline, population or range restriction, and endemism, to generate a national ranked list of species. Species scoring highly on these four criteria, and therefore most in need of urgent management action, are ranked most highly. We applied this method to all 250 countries and territories listed in the IUCN Red List and pilottested national rankings with participants from eight diverse countries. Across pilots, participants reported that the ranked lists were scientifically robust, timesaving, and valuable starting points for national prioritysetting, while stating the importance of national context, and the need for additional technical and financial support for implementation. Our results demonstrate that a sciencebased approach can meaningfully support Parties in identifying species requiring urgent action under Target 4, in a standardised way. With 2030 approaching rapidly, this protocol provides an immediate, practical tool to accelerate progress toward halting extinctions and advancing species recovery.

ecology↗

Unraveling the Folding Dynamics of DNA Origami Structures

Achieving high folding yield remains a major challenge in DNA origami, particularly as structures increase in complexity and scale. Here, we investigate how DNA origami design influences folding yield and kinetics using a combination of real-time fluorometry, gel electrophoresis, electron microscopy, and theoretical analysis. Results reveal a balance of the free energy changes from loop formation and hybridization that govern nucleation of nanostructure assembly, while the extent of cooperativity determines the overall assembly behavior. We measure the effect of structural complexity, staple design, and scaffold design on each energetic parameter, folding yield, and kinetics. We show that the scaffold crossover pattern determines the extent of cooperativity and subsequent folding kinetics, where fewer scaffold crossovers result in more cooperative folding. We also demonstrate that limiting the number of crossovers per staple should be prioritized over extending staple binding domains. The entropic penalty dominates the lower energy binding, disrupting folding. Finally, we demonstrate a 1-2 hour focused annealing ramp strategy that can increase yield up to 17% relative to traditional multi-day ramps. Optimizing energy changes and the contribution of cooperativity through design can significantly enhance folding yield and assembly time, particularly for complex structures, aiding the design and assembly of large-scale materials. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=101 SRC="FIGDIR/small/664431v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@6d6eb9org.highwire.dtl.DTLVardef@80641dorg.highwire.dtl.DTLVardef@12cde70org.highwire.dtl.DTLVardef@bfb9d3_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

Phospho-KNL-1 recognition by a TPR domain targets the BUB-1/BUB-3 complex to C. elegans kinetochores

During mitosis, the Bub1-Bub3 complex concentrates at kinetochores, the microtubule-coupling interfaces on chromosomes, where it contributes to spindle checkpoint activation, kinetochore-spindle microtubule interactions, and protection of centromeric cohesion. Bub1 has a conserved N-terminal tetratricopeptide (TPR) domain followed by a binding motif for its conserved interactor Bub3. The current model for Bub1-Bub3 localization to kinetochores is that Bub3, along with its bound motif from Bub1, recognizes phosphorylated "MELT" motifs in the kinetochore scaffold protein Knl1. Motivated by the greater phenotypic severity of BUB-1 versus BUB-3 loss in C. elegans, we show that the BUB-1 TPR domain directly recognizes a distinct class of phosphorylated motifs in KNL-1 and that this interaction is essential for BUB-1-BUB-3 localization and function. BUB-3 recognition of phospho-MELT motifs additively contributes to drive super-stoichiometric accumulation of BUB-1-BUB-3 on its KNL-1 scaffold during mitotic entry. Bub1s TPR domain interacts with Knl1 in other species, suggesting that collaboration of TPR-dependent and Bub3-dependent interfaces in Bub1-Bub3 localization and functions may be conserved.

cell biology↗

PLK-1 tethered on BUB-1 directs CDC-20 kinetochore recruitment to ensure timelyembryonic mitoses

During mitosis chromosomes assemble kinetochores in order to dynamically couple with spindle microtubules (Cheeseman, 2014; Musacchio & Desai, 2017). Kinetochores also function as signaling hubs directing mitotic progression by recruiting and controlling the fate of the Anaphase Promoting Complex/Cyclosome (APC/C) activator CDC-20 (Lara-Gonzalez et al., 2017; Lara-Gonzalez, Pines, et al., 2021; Musacchio, 2015). Kinetochores either incorporate CDC-20 into checkpoint complexes that inhibit the APC/C or dephosphorylate CDC-20, which allows it to interact with and activate the APC/C (Kim et al., 2017; Lara-Gonzalez et al., 2017). The importance of these two CDC-20 fates likely depends on biological context. In somatic cells the major mechanism controlling mitotic progression is the spindle checkpoint. By contrast, progression through mitosis during the cell cycles of early embryos is largely checkpoint-independent (Clute & Masui, 1995; Duro & Nilsson, 2021; Gerhart et al., 1984; Zhang et al., 2015). Here, by manipulating CDC-20 phosphorylation status, we show that CDC-20 phosphoregulation controls mitotic duration in the C. elegans embryo and defines a checkpoint-independent temporal mitotic optimum for robust embryogenesis. Flux of CDC-20 through kinetochores for local dephosphorylation requires an ABBA motif on BUB-1 that directly interfaces with the structured WD40 domain of CDC-20 (Di Fiore et al., 2015; Diaz-Martinez et al., 2015; He et al., 2013; Kim et al., 2017). We show that a conserved "STP" motif in BUB-1 that docks the mitotic kinase PLK-1 (Qi et al., 2006) is also necessary to recruit CDC-20 to kinetochores and for timely mitotic progression. The kinase activity of PLK-1 is required for CDC-20 to localize to kinetochores and targets a site within the CDC-20-binding ABBA motif of BUB-1; phosphorylation of this site promotes BUB-1-CDC-20 interaction and mitotic progression. Thus, the BUB-1-bound pool of PLK-1 ensures timely mitosis during embryonic cell cycles by promoting CDC-20 recruitment to the vicinity of kinetochore-localized phosphatase activity.

cell biology↗

The N-terminal Tail of C. elegans CENP-A Interacts with KNL-2 and is Essential for Centromeric Chromatin Assembly

Centromeres are epigenetically defined by the presence of the centromere-specific histone H3 variant CENP-A. A specialized loading machinery, including the histone chaperone HJURP/Scm3, participates in CENP-A nucleosome assembly. However, Scm3/HJURP is missing from multiple lineages, including nematodes, which rely on a CENP-A-dependent centromere. Here, we show that the extended N-terminal tail of C. elegans CENP-A contains a predicted structured region that is essential for centromeric chromatin assembly. Removal of this region of the CENP-A N-Tail prevents loading, resulting in failure of kinetochore assembly and defective chromosome condensation. By contrast, the N-Tail mutant CENP-A localizes normally in the presence of endogenous CENP-A. The portion of the N-Tail containing the predicted structured region binds to KNL-2, a conserved SANTA and Myb domain-containing protein (referred to as M18BP1 in vertebrates), that is specifically involved in CENP-A chromatin assembly. This direct interaction is conserved in the related nematode C. briggsae, despite divergence of the N-Tail and KNL-2 primary sequences. Thus, the extended N-Tail of CENP-A is essential for CENP-A chromatin assembly in C. elegans and partially substitutes for the function of Scm3/HJURP, in that it mediates an interaction of the specialized histone fold of CENP-A with KNL-2. These results highlight an evolutionary variation on centromeric chromatin assembly in the absence of a dedicated CENP-A-specific chaperone/targeting factor of the Scm3/HJURP family.

cell biology↗

EGFR confers exquisite specificity of Wnt9a-Fzd9b signaling in hematopoietic stem cell development

The mechanisms of Wnt-Frizzled (Fzd) signaling selectivity and their biological implications remain unclear. We demonstrate for the first time that the epidermal growth factor receptor (EGFR) is required as a co-factor for Wnt signaling. Using genetic studies in zebrafish, paired with in vitro cell biology and biochemistry, we have determined that Fzd9b signals specifically with Wnt9a in vivo and in vitro to elicit {beta}-catenin dependent Wnt signals that regulate hematopoietic stem and progenitor cell (HSPC) development in the dorsal aorta. This requirement is conserved in the derivation of HSPCs from human embryonic stem cells. Wnt9a-Fzd9b specificity requires two intracellular domains in Fzd9b, which interact with EGFR as a required co-factor to promote signal transduction. EGFR phosphorylates one tyrosine residue on Fzd9b, a requirement for the Wnt signal. These findings indicate that Wnt signaling interactions can be exquisitely specific and inform protocols for derivation of HSPCs in vitro.\n\nHighlightsO_LIAn in vitro signaling screen identifies Fzd9b as a Wnt9a-specific receptor.\nC_LIO_LIFzd9b and Wnt9a regulate hematopoietic stem cell development as a cognate pair.\nC_LIO_LIWNT9A and FZD9 are required for HSPC derivation from human pluripotent cells in vitro.\nC_LIO_LIEGFR confers specificity to Wnt9a-Fzd9b signaling in zebrafish and human cells.\nC_LI

developmental biology↗