Biology subjects

Lewellyn, L.

Publications and source records attributed to Lewellyn, L..

4 recordsLinked to original sources

bioRxiv2025

Complementary Volume Electron Microscopy-based approaches reveal ultrastructural changes in germline intercellular bridges of D. melanogaster

Intercellular bridges are essential to connect developing germline cells. The Drosophila melanogaster egg chamber is a powerful model system to study germline intercellular bridges, or ring canals (RCs). RCs connect the developing oocyte to supporting nurse cells, and defects in their stability or growth lead to infertility. Despite their importance, it has been technically difficult to use electron microscopy-based approaches to monitor changes in RC structure during oogenesis. Here, we describe the application of a complementary set of volume EM-based approaches to visualize ultrastructural changes in the germline RCs. The combination of array tomography (AT) and focused ion beam (FIB) scanning electron microscopy (SEM) has allowed us to gain insight into previously unappreciated aspects of RC structure. We were able to quantify differences in RC size and thickness within and between germ cell clusters at different developmental stages. Within a cluster, RC size correlates with lineage; the largest RCs were formed during the first division, and the smallest RCs were formed during the fourth mitotic division. We observed the formation of membrane interdigitations in the vicinity of RCs much earlier than previously reported, and reconstruction of a RC from a mid-stage EC provided insight into the 3D orientation of these extensive cell-cell contacts. Our imaging also revealed a novel membrane structure that appeared to line the interior of the RC lumen. Although the focus was on ultrastructural changes in the germline RCs, our dataset contains valuable details of additional cell types and structures, including the fusome, the germline stem cells and their niche, and the migrating border cells. This imaging framework could be applied to other tissues or samples that face similar technical challenges, where the small structure of interest is located within a large sample volume.

developmental biology↗

bioRxiv2024

Effectiveness of a network Open House model to recruit trainees to post-baccalaureate STEM programs

Post-baccalaureate (post-bac) programs can be instrumental in strengthening science training and expanding STEM career opportunities for junior trainees. Many of these sponsored programs are designed to increase research exposure for underrepresented minorities, including African American, Hispanic, Native American, and first-generation college students, among others. Recruiting trainees to post-bac programs can be challenging for reasons including a lack of awareness about available programs. To address this gap, an Open House event was created with the goal of raising awareness and generating interest among potential students for future post-bac programs. Students were recruited from partnering Minority Serving Institutions (MSIs) to attend a two-day event at a Primarily Undergraduate Institution (PUI) and a Research-Intensive (R1) institution. During the visit, students toured both campuses, learned about various post-bac programs and research opportunities, and interacted with faculty, current graduate students, and a former post-bac scholar. Transportation, lodging, and meals were provided. Participants completed voluntary pre- and post-surveys. Results indicated that attendees, the majority of whom were underrepresented minorities in STEM, left with a stronger understanding of post-bac programs and how these experiences could support their future careers in STEM and that students attendance at the event made it more likely they would apply to available post-bac programs. Mentor and MSI faculty survey responses highlighted their strong support for participating in future recruitment events. These findings demonstrate that in-person Open House events, built on collaborative partnerships across institutions, are an effective strategy for increasing awareness and encouraging participation in post-bac training programs-- particularly among underrepresented student populations.

scientific communication and education↗

bioRxiv2023

Lineage-based scaling of germline intercellular bridges during oogenesis

The size of subcellular structures must be tightly controlled to maintain normal cell function. Despite its importance, few studies have determined how the size of organelles or other structures is maintained during development, when cells are growing, dividing, and rearranging. The developing egg chamber is a powerful model in which to study the relative growth rates of subcellular structures. The egg chamber contains a cluster of sixteen germline cells, which are connected through intercellular bridges called ring canals. As the egg chamber grows, the germline cells and the ring canals that connect them increase in size. Here, we demonstrate that ring canal size scaling is related to lineage; the largest, "first born" ring canals increase in size at a relatively slower rate than ring canals derived from subsequent mitotic divisions. This lineage-based scaling relationship is maintained even if directed transport is reduced, ring canal size is altered, or in egg chambers with twice as many germline cells. Analysis of lines that produce larger or smaller mature eggs reveals different strategies could be used to alter final egg size. Summary StatementUsing the fruit fly egg chamber as a model, this study demonstrates that the size and scaling of germline intercellular bridges vary based on lineage.

developmental biology↗

bioRxiv2019

The Arp2/3 complex and the formin, Diaphanous, are both required to regulate the size of germline ring canals in the developing egg chamber

Intercellular bridges are an essential structural feature found in both germline and somatic cells throughout the animal kingdom. Because of their large size, the germline intercellular bridges, or ring canals, in the developing fruit fly egg chamber are an excellent model to study the formation, stabilization, and expansion of these structures. Within the egg chamber, the germline ring canals connect 15 supporting nurse cells to the developing oocyte, facilitating the transfer of materials required for successful oogenesis. The ring canals are derived from a stalled actomyosin contractile ring; once formed, additional actin and actin-binding proteins are recruited to the ring to support the 20-fold expansion that accompanies oogenesis. These behaviors provide a unique model system to study the actin regulators that control incomplete cytokinesis, intercellular bridge formation, and expansion. By temporally controlling their expression in the germline, we have demonstrated that the Arp2/3 complex and the formin, Diaphanous (Dia), coordinately regulate ring canal size and expansion throughout oogenesis. Dia is required for successful incomplete cytokinesis and the initial stabilization of the germline ring canals. Once the ring canals have formed, the Arp2/3 complex and Dia cooperate to determine ring canal size and maintain their stability. Our data suggest that the nurse cells must maintain a precise balance between the activity of these two nucleators during oogenesis.

developmental biology↗