Biology subjects

Applewhite, D. A.

Publications and source records attributed to Applewhite, D. A..

4 recordsLinked to original sources

bioRxiv2025

The Drosophila SPECC1L homolog, Split Discs, co-localizes with non-muscle myosin II and regulates focal adhesion dynamics.

Allelic variations of Sperm antigen with calponin homology and Coiled-Coil domains 1 Like (SPECC1L) have been associated with a spectrum of cranial-facial pathologies including Teebi hypertelorism and Opitz G/BBB syndrome which manifest as clefting of the palate, wide-eyes, and incomplete closure of the esophagus among others. These pathologies may be indicative of improper cranial neural crest cell (CNCC) delamination and migration. SPECC1L is hypothesized to be an actin-microtubule cross-linking protein as it co-localizes with both microtubules and actin in tissue culture cells. Further, it has been shown to immunoprecipitate with a protein phosphatase complex-1{beta} (PP1{beta}) member, MYPT1, as well as being involved in the PI3K-AKT signaling axis. In this study we sought to investigate the SPECC1L Drosophila homolog Spdi and despite sharing close homology with its mammalian counterpart we found that Spdi is associated with both non-muscle myosin-II and actin. RNAi depletion of Spdi led to an increase in focal adhesion dynamics and when we introduced conserved point mutations to Spdi that are analogous to those associated with human disease we observed a further increase in focal adhesion dynamics above that of depletion alone. Collectively, our findings suggest that Spdi is a non-muscle myosin II (NMII) binding protein that likely affects focal adhesion dynamics through this association. Our results also suggest that some of the pathologies associated with allelic variants of SPECC1L may be the result of aberrant cell-matrix adhesion.

cell biology↗

bioRxiv2025

LGBTQ+ realities in the biological sciences

While scientific environments have been described as unwelcoming to the LGBTQ+ community, and fields such as physics have systematically documented these challenges, the climate in biology workplaces has not been assessed. We conducted the largest survey to date of LGBTQ+ biologists to examine how their sense of belonging and perception of climate in the biology workplace and professional societies compare to that of their straight and cis peers. We surveyed 1419 biologists across five professional societies, with 486 identifying as LGBTQ+. Trans and gender non-conforming (TGNC) biologists reported lower belonging and morale within the workplace, professional societies, and the biology community compared to cis, straight biologists. They also reported being less comfortable with the climate of various professional biology environments. While LGBTQ+ biologists report that their workplaces are moderately inclusive, over 20% of all LGBTQ+ biologists and nearly 40% of TGNC biologists experience exclusionary behavior at work. This landmark survey provides the first comprehensive analysis of the LGBTQ+ climate in biology, revealing specific challenges faced by TGNC scientists and identifying interventions to enhance inclusivity for scientists. Significance StatementThis landmark study includes the largest known sample of LGBTQ+ biologists and offers the first comprehensive description of the LGBTQ+ climate in biology, differentiating between the experiences of cisgender lesbian, gay, bisexual, and queer (LGBQ) biologists and transgender and gender non-conforming (TGNC) biologists. The study found that compared to non-LGBTQ+ biologists, TGNC participants report lower belonging, morale and comfort with the climate across biology workplaces, professional societies, and the biology community. While on average LGBTQ+ participants reported that their workplaces are moderately inclusive, over 20% of all LGBTQ+ biologists and nearly 40% of TGNC biologists report experiencing exclusionary behaviors at work. The study offers immediate implications for institutional policies and professional development in the biological sciences.

scientific communication and education↗

bioRxiv2018

Ena/VASP processive elongation is modulated by avidity on actin filaments bundled by the filopodia crosslinker fascin

Ena/VASP are tetrameric assembly factors that bind F-actin barbed ends continuously while increasing their elongation rate within dynamic bundled networks such as filopodia. We used single-molecule TIRFM and developed a kinetic model to dissect Ena/VASPs processive mechanism on bundled filaments. Notably, Ena/VASPs processive run length increases with the number of both bundled filaments and Ena arms, revealing avidity facilitates enhanced processivity. Moreover, Ena tetramers form more filopodia than mutant dimer and trimers in Drosophila culture cells. Finally, enhanced processivity on trailing barbed ends of bundled filaments is an evolutionarily conserved property of Ena/VASP homologs and is specific to fascin-bundled filaments. These results demonstrate that Ena tetramers are tailored for enhanced processivity on fascin bundles and avidity of multiple arms associating with multiple filaments is critical for this process. Furthermore, we discovered a novel regulatory mechanism whereby bundle size and bundling protein specificity control activities of a processive assembly factor.

cell biology↗

bioRxiv2018

The Drosophila Cortactin Binding Protein 2 homolog, Nausicaa, regulates lamellipodial actin dynamics in a Cortactin-dependent manner.

Drosophila CG10915 is an uncharacterized protein coding gene with sequence similarity to human Cortactin Binding Protein 2 (CTTNBP2) and Cortactin Binding Protein 2 N-terminal like (CTTNBP2NL). We have named this gene Nausicaa (naus) and characterize it through a combination of quantitative live-cell total internal reflection fluorescence (TIRF) microscopy, electron microscopy, RNAi depletion, and genetics. We found that Naus co-localizes with F-actin and Cortactin in the lamellipodia of Drosophila S2R+ and D25c2 cells and this localization is lost following Cortactin or Arp2/3 depletion or by mutations that disrupt a conserved proline patch found in its mammalian homologs. Using Permeabilization Activated Reduction in Fluorescence (PARF) and Fluorescence Recovery after Photo-bleaching (FRAP), we find that depletion of Cortactin alters Naus dynamics leading to a decrease in its half-life. Furthermore, we discovered that Naus depletion in S2R+ cells led to a decrease in actin retrograde flow and a lamellipodia characterized by long, unbranched filaments. We demonstrate that these alterations to the dynamics and underlying actin architecture also affect D25c2 cell migration and decrease arborization in Drosophila neurons. We present the novel hypothesis that Naus functions to slow Cortactins disassociation from Arp2/3 nucleated branch junctions, thereby increasing both branch nucleation and junction stability.

cell biology↗