Biology subjects

Giersch, R. M.

Publications and source records attributed to Giersch, R. M..

3 recordsLinked to original sources

bioRxiv2023

Multiple lineages of transmissible neoplasia in the basket cockle (Clinocardium nuttallii) with repeated horizontal transfer of mitochondrial DNA

Transmissible cancers are clonal lineages of neoplastic cells able to infect multiple hosts, spreading through populations in the environment as an infectious disease. Transmissible cancers have been identified in Tasmanian devils, dogs, and bivalves. Several lineages of bivalve transmissible neoplasias (BTN) have been identified in multiple bivalve species. In 2019 in Puget Sound, Washington, USA, disseminated neoplasia was observed in basket cockles (Clinocardium nuttallii), a species that is important to the culture and diet of the Suquamish Tribe as well as other tribes with traditional access to the species. To test whether disseminated neoplasia in cockles is a previously unknown lineage of BTN, a nuclear locus was amplified from cockles from Agate Pass, Washington, and sequences revealed evidence of transmissible cancer in several individuals. We used a combination of cytology and quantitative PCR to screen collections of cockles from eleven locations in Puget Sound and along the Washington coastline to identify the extent of contagious cancer spread in this species. Two BTN lineages were identified in these cockles, with one of those lineages (CnuBTN1) being the most prevalent and geographically widespread. Within the CnuBTN1 lineage, multiple nuclear loci support the conclusion that all cancer samples form a single clonal lineage. However, the mitochondrial alleles in each cockle with CnuBTN1 are different from each other, suggesting mitochondrial genomes of this cancer have been replaced multiple times during its evolution, through horizontal transmission. The identification and analysis of these BTNs are critical for broodstock selection, management practices, and repopulation of declining cockle populations, which will enable continued cultural connection and dietary use of the cockles by Coast Salish Tribes.

cancer biology↗

bioRxiv2022

Centuries of genome instability and evolution in soft-shell clam transmissible cancer

Transmissible cancers are infectious parasitic clones of malignant cells that metastasize to new hosts, living past the death of the founder animal in which the cancer initiated. Several lineages of transmissible cancer have recently been identified in bivalves, including one that has spread through the soft-shell clam (Mya arenaria) population along the east coast of North America. To investigate the evolutionary history of this transmissible cancer lineage, we assembled a highly contiguous 1.2 Gb soft-shell clam reference genome and characterized somatic mutations from cancer sequences. We show that all cancer cases observed descend from a single founder and cluster into two geographically distinct sub-lineages. We discover a previously unreported clock-like mutational signature that predicts the cancer lineage to be 344 to 877 years old, indicating that it spread undetected long before it was first observed in the 1970s. We observe high mutation density, widespread copy number gain, structural rearrangement, loss of heterozygosity, variable telomere lengths, mitochondrial genome expansion, and transposable element activity, all indicative of an unstable cancer genome. Our study reveals the ability for an invertebrate cancer lineage to survive for centuries while its genome continues to structurally mutate, likely contributing to the ability of this lineage to adapt as a parasitic cancer. SUMMARYThe genome of a contagious cancer in clams reveals structural instability of multiple types throughout the [~]500 years since its origin.

cancer biology↗

bioRxiv2021

Survival and detection of bivalve transmissible neoplasia from the soft-shell clam Mya arenaria (MarBTN) in seawater

Many pathogens can cause cancer, but cancer itself does not normally act as an infectious agent. However, transmissible cancers have been found in a few cases in nature: in Tasmanian devils, dogs, and several bivalve species. The transmissible cancers in dogs and devils are known to spread through direct physical contact, but the exact route of transmission of bivalve transmissible neoplasia (BTN) has not yet been confirmed. It has been hypothesized that cancer cells could be released by diseased animals and spread through the water column to infect/engraft into other animals. To test the feasibility of this proposed mechanism of transmission, we tested the ability of BTN cells from the soft-shell clam (Mya arenaria BTN, or MarBTN) to survive in artificial seawater. We found that BTN cells are highly sensitive to salinity, with acute toxicity at salinity levels lower than those found in their environment. BTN cells also survive longer at lower temperatures, with >48% of cells surviving a week in seawater at temperatures from 4{degrees}C to 16{degrees}C, and 49% surviving for more than two weeks at 4{degrees}C. With one clam donor, living cells were observed for more than eight weeks at 4{degrees}C. We also used qPCR of environmental DNA (eDNA) to detect the presence of BTN-specific DNA in the environment. We observed release of BTN-specific DNA into the water of aquaria from tanks with highly BTN-positive clams, and we detected BTN-specific DNA in seawater samples collected from BTN-endemic areas, although the level detected was much lower. Overall, these data show that BTN cells can survive well in seawater, and they are released into the water by diseased animals, supporting the hypothesis that BTN is spread from animal-to-animal by cells through seawater.

cancer biology↗