Evolution and development in Spiralia: Early progeny of the mesodermal lineage in the leech Helobdella sp. (Austin)

One of the major questions in evolutionary biology is, how changes in development over time result in diversity of adult body plans. Spiralia are a highly diverse group of protostome taxa, in terms of their adult body plans, but which nonetheless share a highly conserved pattern of early cell divisions, called spiral cleavage. Thus, in the early embryos of spiralian taxa, homologous blastomeres are identifiable on the basis of their embryonic origins and their subsequent fates in later development. One of the best-known examples of such homologous blastomeres are the precursors of left and right mesoderm, which arise from the bilateral division of a cell classically known as micromere 4d. Given the dramatic differences among body plans of various spiralian species (consider the mesoderm of an unsegmented mollusk and that of a segmented annelid, such as the leech, for example), it is obvious that the 4d lineages must diverge at some point in development of different species. In the leech Helobdella, a clitellate annelid, the homolog of the cell 4d is called DM" and its bilateral division gives rise to two large stem cells (M teloblasts) whose iterated divisions yield precursors (m blast cells) of segmental mesoderm. In this work I present new plasmid driven high-resolution cell lineage tracing techniques. Using high-resolution tracers in conjunction with standard tracers, I have been able to study the early progeny of the M teloblasts in great detail. I have found that each M teloblast produces six precursors of non-segmental mesoderm, prior to initiating the production of purely segmental blast cells. While all segmental blast cells undergo identical stereotyped early divisions and give rise to homologous definitive pattern elements, the early clonal distributions of the first six cells, as well as their definitive contributions differ from each other and from the segmental blast cells. The early mesodermal progeny make major contributions to anterior non-segmental mesoderm especially throughout the head and the muscular proboscis, an eversible, specialized feeding apparatus. Collaborative work with Ayaki Nakamoto on more detailed analysis of the 4d lineage in the oligochaete Tubifex revealed that, in this annelid too, the 4d lineage makes contributions to anterior non-segmental mesoderm. However, unlike Helobdella, Tubifex ingest sediments and are filter feeders, and thus have different head and foregut morphology. In accord with these differences, I find that the anterior contributions of the M lineage differ between these two annelids. These differences illustrate that the 4d lineage exhibits evolutionary plasticity and that potentially small changes in the developmental program of the M teloblasts can result in a diversity of adult body plans

Developmental Mechanisms Linking Form and Function During Jaw Evolution

How does form arise during development and change during evolution? How does form relate to function, and what enables embryonic structures to presage their later use in adults? To address these questions, we leverage the distinct functional morphology of the jaw in duck, chick, and quail. In connection with their specialized mode of feeding, duck develop a secondary cartilage at the tendon insertion of their jaw adductor muscle on the mandible. An equivalent cartilage is absent in chick and quail. We hypothesize that species-specific jaw architecture and mechanical forces promote secondary cartilage in duck through the differential regulation of FGF and TGFβ signaling. First, we perform transplants between chick and duck embryos and demonstrate that the ability of neural crest mesenchyme (NCM) to direct the species-specific insertion of muscle and the formation of secondary cartilage depends upon the amount and spatial distribution of NCM-derived connective tissues. Second, we quantify motility and build finite element models of the jaw complex in duck and quail, which reveals a link between species-specific jaw architecture and the predicted mechanical force environment. Third, we investigate the extent to which mechanical load mediates FGF and TGFβ signaling in the duck jaw adductor insertion, and discover that both pathways are mechano-responsive and required for secondary cartilage formation. Additionally, we find that FGF and TGFβ signaling can also induce secondary cartilage in the absence of mechanical force or in the adductor insertion of quail embryos. Thus, our results provide novel insights on molecular, cellular, and biomechanical mechanisms that couple musculoskeletal form and function during development and evolution

FGF and TGFβ signaling link form and function during jaw development and evolution.

How does form arise during development and change during evolution? How does form relate to function, and what enables embryonic structures to presage their later use in adults? To address these questions, we leverage the distinct functional morphology of the jaw in duck, chick, and quail. In connection with their specialized mode of feeding, duck develop a secondary cartilage at the tendon insertion of their jaw adductor muscle on the mandible. An equivalent cartilage is absent in chick and quail. We hypothesize that species-specific jaw architecture and mechanical forces promote secondary cartilage in duck through the differential regulation of FGF and TGFβ signaling. First, we perform transplants between chick and duck embryos and demonstrate that the ability of neural crest mesenchyme (NCM) to direct the species-specific insertion of muscle and the formation of secondary cartilage depends upon the amount and spatial distribution of NCM-derived connective tissues. Second, we quantify motility and build finite element models of the jaw complex in duck and quail, which reveals a link between species-specific jaw architecture and the predicted mechanical force environment. Third, we investigate the extent to which mechanical load mediates FGF and TGFβ signaling in the duck jaw adductor insertion, and discover that both pathways are mechano-responsive and required for secondary cartilage formation. Additionally, we find that FGF and TGFβ signaling can also induce secondary cartilage in the absence of mechanical force or in the adductor insertion of quail embryos. Thus, our results provide novel insights on molecular, cellular, and biomechanical mechanisms that couple musculoskeletal form and function during development and evolution

A clinically validated human saliva metatranscriptomic test for global systems biology studies

The authors report here the development of a high-throughput, automated, inexpensive and clinically validated saliva metatranscriptome test that requires less than 100 μl of saliva. RNA is preserved at the time of sample collection, allowing for ambient-temperature transportation and storage for up to 28 days. Critically, the RNA preservative is also able to inactivate pathogenic microorganisms, rendering the samples noninfectious and allowing for safe and easy shipping. Given the unique set of convenience, low cost, safety and technical performance, this saliva metatranscriptomic test can be integrated into longitudinal, global-scale systems biology studies that will lead to an accelerated development of precision medicine, diagnostic and therapeutic tools

The salivary metatranscriptome as an accurate diagnostic indicator of oral cancer

Despite advances in cancer treatment, the 5-year mortality rate for oral cancers (OC) is 40%, mainly due to the lack of early diagnostics. To advance early diagnostics for high-risk and average-risk populations, we developed and evaluated machine-learning (ML) classifiers using metatranscriptomic data from saliva samples (n = 433) collected from oral premalignant disorders (OPMD), OC patients (n = 71) and normal controls (n = 171). Our diagnostic classifiers yielded a receiver operating characteristics (ROC) area under the curve (AUC) up to 0.9, sensitivity up to 83% (92.3% for stage 1 cancer) and specificity up to 97.9%. Our metatranscriptomic signature incorporates both taxonomic and functional microbiome features, and reveals a number of taxa and functional pathways associated with OC. We demonstrate the potential clinical utility of an AI/ML model for diagnosing OC early, opening a new era of non-invasive diagnostics, enabling early intervention and improved patient outcomes.</p