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 Drosophila egg chamber is a powerful model in which to study the relative growth rates of subcellular structures. The egg chamber contains a cluster of 16 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 that different strategies could be used to alter final egg size.

Subungual melanoma with cartilaginous differentiation: Molecular insights.

Melanoma's rare capacity to undergo heterologous differentiation can create significant diagnostic challenges. The molecular mechanisms underlying this phenomenon are not well understood. We present an unusual case of subungual melanoma exhibiting extensive cartilaginous differentiation and provide insights into its molecular and cytogenomic features. Histopathologically, the tumor was predominantly composed of nodules of malignant cartilage in association with a smaller population of nested epithelioid to rhabdoid cells. Immunohistochemically, the tumor cells in both components were positive for S100, SOX10, and PRAME, and were negative for Melan-A and HMB-45. Molecular analysis by whole exome DNA sequence did not detect any pathogenic variants in genes commonly implicated in melanoma. Additional analysis by SNP chromosomal microarray revealed a complex genome characterized by numerous chromosomal losses and gains, including a homozygous deletion of the CDKN2A locus and a heterozygous deletion of the locus containing EXT2, a tumor suppressor implicated in hereditary multiple osteochondromas and secondary chondrosarcomas. This case underscores the importance of recognizing cartilaginous differentiation as a rare manifestation of melanoma, particularly at subungual sites, and suggests that at least some of these melanomas may be driven by non-canonical molecular pathways.

Visual Learning Equity Initiative Enhances Preclinical Dermatologic Image Representation: A Cross-Sectional Study.

Despite growing diversity in the United States population, studies show that medical education lacks representation of conditions in darker skin tones. Given that medical conditions present differently in different skin tones, limited exposure to images of darker tones in medical training may contribute to incorrect or delayed diagnoses, perpetuating health inequities. This study examines the preclinical curriculum at the Georgetown University School of Medicine (GUSOM) to report on its image representation with respect to skin tone and to assess the impact of a student-driven initiative in achieving visual learning equity (VLE). Of 1050 preclinical images, 58.2% depicted conditions in light/white skin tones, 31.3% in medium/brown, and 10.5% in dark/black. The microbiology and pathology courses had the highest percentages of dark/black and medium/brown images. Infectious disease images made up 36.3% of all images with 54.6% light/white, 31.5% medium/brown, and 13.9% dark/black. Overall, the first images representing conditions were 63.5% light/white, 30.0% medium/brown, and 6.6% dark/black. When dark/black images were presented first, 64.3% were of infectious diseases, compared to 35.1% for medium/brown and only 28.4% for white/light first images that were infectious diseases. A significant increase in images of conditions in darker skin tones was observed in the IRD course 2022 compared to the IRD course 2020 (P<.001). Our study highlights an underrepresentation of darker skin tones compared to lighter skin tones in the GUSOM preclinical curriculum. A student-led initiative significantly increased the representation of darker skin tones in dermatologic images, demonstrating the potential impact of such efforts in achieving VLE in medical education.J Drugs Dermatol. 2024;23(7):519-524.  doi:10.36849/JDD.7992.

Lineage-based scaling of germline intercellular bridges during oogenesis.

The size of subcellular structures must be tightly controlled to maintain normal cell function; this is especially important when cells are part of developing tissues or organs. Despite its importance, few studies have determined how the size of organelles or other structures is maintained during tissue growth, 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 germ cells, which are connected through intercellular bridges called ring canals. Ring canals are formed following incomplete cytokinesis after each of four germ cell divisions. As the egg chamber grows, the nurse cells and the ring canals that connect them increase in size. Here, we demonstrate that ring canal size scaling is related to their lineage; the largest, "first born" ring canals grow 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 if the germ cells go through an additional mitotic division. Further, we propose that changes in ring canal scaling could provide a mechanism to alter egg size.